[RFC,v5,2/4] block: add simple copy support

Commit Message

SelvaKumar S Feb. 19, 2021, 12:45 p.m. UTC

Add new BLKCOPY ioctl that offloads copying of one or more sources
ranges to a destination in the device. Accepts a 'copy_range' structure
that contains destination (in sectors), no of sources and pointer to the
array of source ranges. Each source range is represented by 'range_entry'
that contains start and length of source ranges (in sectors).

Introduce REQ_OP_COPY, a no-merge copy offload operation. Create
bio with control information as payload and submit to the device.
REQ_OP_COPY(19) is a write op and takes zone_write_lock when submitted
to zoned device.

If the device doesn't support copy or copy offload is disabled, then
copy operation is emulated by default. However, the copy-emulation is an
opt-in feature. Caller can choose not to use the copy-emulation by
specifying a flag 'BLKDEV_COPY_NOEMULATION'.

Copy-emulation is implemented by allocating memory of total copy size.
The source ranges are read into memory by chaining bio for each source
ranges and submitting them async and the last bio waits for completion.
After data is read, it is written to the destination.

bio_map_kern() is used to allocate bio and add pages of copy buffer to
bio. As bio->bi_private and bio->bi_end_io are needed for chaining the
bio and gets over-written, invalidate_kernel_vmap_range() for read is
called in the caller.

Introduce queue limits for simple copy and other helper functions.
Add device limits as sysfs entries.
	- copy_offload
	- max_copy_sectors
	- max_copy_ranges_sectors
	- max_copy_nr_ranges

copy_offload(= 0) is disabled by default. This needs to be enabled if
copy-offload needs to be used.
max_copy_sectors = 0 indicates the device doesn't support native copy.

Native copy offload is not supported for stacked devices and is done via
copy emulation.

Signed-off-by: SelvaKumar S <[e-mail]>
Signed-off-by: Kanchan Joshi <[e-mail]>
Signed-off-by: Nitesh Shetty <[e-mail]>
Signed-off-by: Javier González <[e-mail]>
Signed-off-by: Chaitanya Kulkarni <[e-mail]>
---
 block/blk-core.c          | 102 ++++++++++++++++--
 block/blk-lib.c           | 222 ++++++++++++++++++++++++++++++++++++++
 block/blk-merge.c         |   2 +
 block/blk-settings.c      |  10 ++
 block/blk-sysfs.c         |  47 ++++++++
 block/blk-zoned.c         |   1 +
 block/bounce.c            |   1 +
 block/ioctl.c             |  33 ++++++
 include/linux/bio.h       |   1 +
 include/linux/blk_types.h |  14 +++
 include/linux/blkdev.h    |  15 +++
 include/uapi/linux/fs.h   |  13 +++
 12 files changed, 453 insertions(+), 8 deletions(-)

Comments

Damien Le Moal Feb. 20, 2021, 4:59 a.m. UTC | #1

On 2021/02/20 11:01, SelvaKumar S wrote:
> Add new BLKCOPY ioctl that offloads copying of one or more sources
> ranges to a destination in the device. Accepts a 'copy_range' structure
> that contains destination (in sectors), no of sources and pointer to the
> array of source ranges. Each source range is represented by 'range_entry'
> that contains start and length of source ranges (in sectors).
> 
> Introduce REQ_OP_COPY, a no-merge copy offload operation. Create
> bio with control information as payload and submit to the device.
> REQ_OP_COPY(19) is a write op and takes zone_write_lock when submitted
> to zoned device.
> 
> If the device doesn't support copy or copy offload is disabled, then
> copy operation is emulated by default. However, the copy-emulation is an
> opt-in feature. Caller can choose not to use the copy-emulation by
> specifying a flag 'BLKDEV_COPY_NOEMULATION'.
> 
> Copy-emulation is implemented by allocating memory of total copy size.
> The source ranges are read into memory by chaining bio for each source
> ranges and submitting them async and the last bio waits for completion.
> After data is read, it is written to the destination.
> 
> bio_map_kern() is used to allocate bio and add pages of copy buffer to
> bio. As bio->bi_private and bio->bi_end_io are needed for chaining the
> bio and gets over-written, invalidate_kernel_vmap_range() for read is
> called in the caller.
> 
> Introduce queue limits for simple copy and other helper functions.
> Add device limits as sysfs entries.
> 	- copy_offload
> 	- max_copy_sectors
> 	- max_copy_ranges_sectors
> 	- max_copy_nr_ranges
> 
> copy_offload(= 0) is disabled by default. This needs to be enabled if
> copy-offload needs to be used.
> max_copy_sectors = 0 indicates the device doesn't support native copy.
> 
> Native copy offload is not supported for stacked devices and is done via
> copy emulation.
> 
> Signed-off-by: SelvaKumar S <[e-mail]>
> Signed-off-by: Kanchan Joshi <[e-mail]>
> Signed-off-by: Nitesh Shetty <[e-mail]>
> Signed-off-by: Javier González <[e-mail]>
> Signed-off-by: Chaitanya Kulkarni <[e-mail]>
> ---
>  block/blk-core.c          | 102 ++++++++++++++++--
>  block/blk-lib.c           | 222 ++++++++++++++++++++++++++++++++++++++
>  block/blk-merge.c         |   2 +
>  block/blk-settings.c      |  10 ++
>  block/blk-sysfs.c         |  47 ++++++++
>  block/blk-zoned.c         |   1 +
>  block/bounce.c            |   1 +
>  block/ioctl.c             |  33 ++++++
>  include/linux/bio.h       |   1 +
>  include/linux/blk_types.h |  14 +++
>  include/linux/blkdev.h    |  15 +++
>  include/uapi/linux/fs.h   |  13 +++
>  12 files changed, 453 insertions(+), 8 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 7663a9b94b80..23e646e5ae43 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -720,6 +720,17 @@ static noinline int should_fail_bio(struct bio *bio)
>  }
>  ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);
>  
> +static inline int bio_check_copy_eod(struct bio *bio, sector_t start,
> +		sector_t nr_sectors, sector_t max_sect)
> +{
> +	if (nr_sectors && max_sect &&
> +	    (nr_sectors > max_sect || start > max_sect - nr_sectors)) {
> +		handle_bad_sector(bio, max_sect);
> +		return -EIO;
> +	}
> +	return 0;
> +}
> +
>  /*
>   * Check whether this bio extends beyond the end of the device or partition.
>   * This may well happen - the kernel calls bread() without checking the size of
> @@ -738,6 +749,75 @@ static inline int bio_check_eod(struct bio *bio, sector_t maxsector)
>  	return 0;
>  }
>  
> +/*
> + * Check for copy limits and remap source ranges if needed.
> + */
> +static int blk_check_copy(struct bio *bio)
> +{
> +	struct blk_copy_payload *payload = bio_data(bio);
> +	struct request_queue *q = bio->bi_disk->queue;
> +	sector_t max_sect, start_sect, copy_size = 0;
> +	sector_t src_max_sect, src_start_sect;
> +	struct block_device *bd_part;
> +	int i, ret = -EIO;
> +
> +	rcu_read_lock();
> +
> +	bd_part = __disk_get_part(bio->bi_disk, bio->bi_partno);
> +	if (unlikely(!bd_part)) {
> +		rcu_read_unlock();
> +		goto out;
> +	}
> +
> +	max_sect =  bdev_nr_sectors(bd_part);
> +	start_sect = bd_part->bd_start_sect;
> +
> +	src_max_sect = bdev_nr_sectors(payload->src_bdev);
> +	src_start_sect = payload->src_bdev->bd_start_sect;
> +
> +	if (unlikely(should_fail_request(bd_part, bio->bi_iter.bi_size)))
> +		goto out;
> +
> +	if (unlikely(bio_check_ro(bio, bd_part)))
> +		goto out;

There is no rcu_unlock() in that out label. Did you test ?

> +
> +	rcu_read_unlock();
> +
> +	/* cannot handle copy crossing nr_ranges limit */
> +	if (payload->copy_nr_ranges > q->limits.max_copy_nr_ranges)
> +		goto out;
> +
> +	for (i = 0; i < payload->copy_nr_ranges; i++) {
> +		ret = bio_check_copy_eod(bio, payload->range[i].src,
> +				payload->range[i].len, src_max_sect);
> +		if (unlikely(ret))
> +			goto out;
> +
> +		/* single source range length limit */
> +		if (payload->range[i].len > q->limits.max_copy_range_sectors)
> +			goto out;

ret is not set. You will return success with this.

> +
> +		payload->range[i].src += src_start_sect;
> +		copy_size += payload->range[i].len;
> +	}
> +
> +	/* check if copy length crosses eod */
> +	ret = bio_check_copy_eod(bio, bio->bi_iter.bi_sector,
> +				copy_size, max_sect);
> +	if (unlikely(ret))
> +		goto out;
> +
> +	/* cannot handle copy more than copy limits */
> +	if (copy_size > q->limits.max_copy_sectors)
> +		goto out;

Again ret is not set... No error return ?

> +
> +	bio->bi_iter.bi_sector += start_sect;
> +	bio->bi_partno = 0;
> +	ret = 0;
> +out:
> +	return ret;
> +}
> +
>  /*
>   * Remap block n of partition p to block n+start(p) of the disk.
>   */
> @@ -827,14 +907,16 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
>  	if (should_fail_bio(bio))
>  		goto end_io;
>  
> -	if (bio->bi_partno) {
> -		if (unlikely(blk_partition_remap(bio)))
> -			goto end_io;
> -	} else {
> -		if (unlikely(bio_check_ro(bio, bio->bi_disk->part0)))
> -			goto end_io;
> -		if (unlikely(bio_check_eod(bio, get_capacity(bio->bi_disk))))
> -			goto end_io;
> +	if (likely(!op_is_copy(bio->bi_opf))) {
> +		if (bio->bi_partno) {
> +			if (unlikely(blk_partition_remap(bio)))
> +				goto end_io;
> +		} else {
> +			if (unlikely(bio_check_ro(bio, bio->bi_disk->part0)))
> +				goto end_io;
> +			if (unlikely(bio_check_eod(bio, get_capacity(bio->bi_disk))))
> +				goto end_io;
> +		}
>  	}
>  
>  	/*
> @@ -858,6 +940,10 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
>  		if (!blk_queue_discard(q))
>  			goto not_supported;
>  		break;
> +	case REQ_OP_COPY:
> +		if (unlikely(blk_check_copy(bio)))
> +			goto end_io;
> +		break;
>  	case REQ_OP_SECURE_ERASE:
>  		if (!blk_queue_secure_erase(q))
>  			goto not_supported;
> diff --git a/block/blk-lib.c b/block/blk-lib.c
> index 752f9c722062..97ba58d8d9a1 100644
> --- a/block/blk-lib.c
> +++ b/block/blk-lib.c
> @@ -150,6 +150,228 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
>  }
>  EXPORT_SYMBOL(blkdev_issue_discard);
>  
> +int blk_copy_offload(struct block_device *dest_bdev, struct blk_copy_payload *payload,
> +		sector_t dest, gfp_t gfp_mask)

Simple copy is only over the same device, right ? So the name "dest_bdev" is a
little strange.

> +{
> +	struct request_queue *q = bdev_get_queue(dest_bdev);
> +	struct bio *bio;
> +	int ret, payload_size;
> +
> +	payload_size = struct_size(payload, range, payload->copy_nr_ranges);
> +	bio = bio_map_kern(q, payload, payload_size, gfp_mask);
> +	if (IS_ERR(bio)) {
> +		ret = PTR_ERR(bio);
> +		goto err;

This will do a bio_put() on a non existent bio...

> +	}
> +
> +	bio->bi_iter.bi_sector = dest;
> +	bio->bi_opf = REQ_OP_COPY | REQ_NOMERGE;
> +	bio_set_dev(bio, dest_bdev);
> +
> +	ret = submit_bio_wait(bio);
> +err:
> +	bio_put(bio);
> +	return ret;
> +}
> +
> +int blk_read_to_buf(struct block_device *src_bdev, struct blk_copy_payload *payload,
> +		gfp_t gfp_mask, sector_t copy_size, void **buf_p)
> +{
> +	struct request_queue *q = bdev_get_queue(src_bdev);
> +	struct bio *bio, *parent = NULL;
> +	void *buf = NULL;
> +	int copy_len = copy_size << SECTOR_SHIFT;
> +	int i, nr_srcs, ret, cur_size, t_len = 0;
> +	bool is_vmalloc;
> +
> +	nr_srcs = payload->copy_nr_ranges;
> +
> +	buf = kvmalloc(copy_len, gfp_mask);
> +	if (!buf)
> +		return -ENOMEM;
> +	is_vmalloc = is_vmalloc_addr(buf);
> +
> +	for (i = 0; i < nr_srcs; i++) {
> +		cur_size = payload->range[i].len << SECTOR_SHIFT;
> +
> +		bio = bio_map_kern(q, buf + t_len, cur_size, gfp_mask);
> +		if (IS_ERR(bio)) {
> +			ret = PTR_ERR(bio);
> +			goto out;
> +		}
> +
> +		bio->bi_iter.bi_sector = payload->range[i].src;
> +		bio->bi_opf = REQ_OP_READ;
> +		bio_set_dev(bio, src_bdev);
> +		bio->bi_end_io = NULL;
> +		bio->bi_private = NULL;
> +
> +		if (parent) {
> +			bio_chain(parent, bio);
> +			submit_bio(parent);
> +		}
> +
> +		parent = bio;
> +		t_len += cur_size;
> +	}
> +
> +	ret = submit_bio_wait(bio);
> +	bio_put(bio);
> +	if (is_vmalloc)
> +		invalidate_kernel_vmap_range(buf, copy_len);

But blk_write_from_buf() will use the buffer right after this.. Is this really OK ?

> +	if (ret)
> +		goto out;
> +
> +	*buf_p = buf;
> +	return 0;
> +out:
> +	kvfree(buf);
> +	return ret;
> +}
> +
> +int blk_write_from_buf(struct block_device *dest_bdev, void *buf, sector_t dest,
> +		sector_t copy_size, gfp_t gfp_mask)
> +{
> +	struct request_queue *q = bdev_get_queue(dest_bdev);
> +	struct bio *bio;
> +	int ret, copy_len = copy_size << SECTOR_SHIFT;
> +
> +	bio = bio_map_kern(q, buf, copy_len, gfp_mask);
> +	if (IS_ERR(bio)) {
> +		ret = PTR_ERR(bio);
> +		goto out;
> +	}
> +	bio_set_dev(bio, dest_bdev);
> +	bio->bi_opf = REQ_OP_WRITE;
> +	bio->bi_iter.bi_sector = dest;
> +
> +	bio->bi_end_io = NULL;
> +	ret = submit_bio_wait(bio);
> +	bio_put(bio);
> +out:
> +	return ret;
> +}
> +
> +int blk_prepare_payload(struct block_device *src_bdev, int nr_srcs, struct range_entry *rlist,
> +		gfp_t gfp_mask, struct blk_copy_payload **payload_p, sector_t *copy_size)
> +{
> +
> +	struct request_queue *q = bdev_get_queue(src_bdev);
> +	struct blk_copy_payload *payload;
> +	sector_t bs_mask, total_len = 0;
> +	int i, ret, payload_size;
> +
> +	if (!q)
> +		return -ENXIO;
> +
> +	if (!nr_srcs)
> +		return -EINVAL;
> +
> +	if (bdev_read_only(src_bdev))
> +		return -EPERM;
> +
> +	bs_mask = (bdev_logical_block_size(src_bdev) >> 9) - 1;
> +
> +	payload_size = struct_size(payload, range, nr_srcs);
> +	payload = kmalloc(payload_size, gfp_mask);
> +	if (!payload)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < nr_srcs; i++) {
> +		if (rlist[i].src & bs_mask || rlist[i].len & bs_mask) {
> +			ret = -EINVAL;
> +			goto err;
> +		}
> +
> +		payload->range[i].src = rlist[i].src;
> +		payload->range[i].len = rlist[i].len;
> +
> +		total_len += rlist[i].len;
> +	}
> +
> +	payload->copy_nr_ranges = i;
> +	payload->src_bdev = src_bdev;
> +	*copy_size = total_len;
> +
> +	*payload_p = payload;
> +	return 0;
> +err:
> +	kfree(payload);
> +	return ret;
> +}
> +
> +int blk_copy_emulate(struct block_device *src_bdev, struct blk_copy_payload *payload,
> +			struct block_device *dest_bdev, sector_t dest,
> +			sector_t copy_size, gfp_t gfp_mask)
> +{
> +	void *buf = NULL;
> +	int ret;
> +
> +	ret = blk_read_to_buf(src_bdev, payload, gfp_mask, copy_size, &buf);
> +	if (ret)
> +		goto out;
> +
> +	ret = blk_write_from_buf(dest_bdev, buf, dest, copy_size, gfp_mask);
> +	if (buf)
> +		kvfree(buf);
> +out:
> +	return ret;
> +}

I already commented that this should better use the dm-kcopyd design, which
would be far more efficient than this. This will be slow...

Your function blkdev_issue_copy() below should deal only with issuing simple
copy (amd later scsi xcopy) for devices that support it. Bring the dm-kcopyd
interface in the block layer as a generic interface for hadling emulation.
Otherwise you are repeating what dm does, but not as efficiently.

> +
> +/**
> + * blkdev_issue_copy - queue a copy
> + * @src_bdev:	source block device
> + * @nr_srcs:	number of source ranges to copy
> + * @rlist:	array of source ranges in sector
> + * @dest_bdev:	destination block device
> + * @dest:	destination in sector
> + * @gfp_mask:   memory allocation flags (for bio_alloc)
> + * @flags:	BLKDEV_COPY_* flags to control behaviour
> + *
> + * Description:
> + *	Copy array of source ranges from source block device to
> + *	destination block devcie. All source must belong to same bdev and
> + *	length of a source range cannot be zero.
> + */
> +
> +int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
> +		struct range_entry *src_rlist, struct block_device *dest_bdev,
> +		sector_t dest, gfp_t gfp_mask, int flags)
> +{
> +	struct request_queue *q = bdev_get_queue(src_bdev);
> +	struct request_queue *dest_q = bdev_get_queue(dest_bdev);
> +	struct blk_copy_payload *payload;
> +	sector_t bs_mask, copy_size;
> +	int ret;
> +
> +	ret = blk_prepare_payload(src_bdev, nr_srcs, src_rlist, gfp_mask,
> +			&payload, &copy_size);
> +	if (ret)
> +		return ret;
> +
> +	bs_mask = (bdev_logical_block_size(dest_bdev) >> 9) - 1;
> +	if (dest & bs_mask) {
> +		return -EINVAL;
> +		goto out;
> +	}
> +
> +	if (q == dest_q && q->limits.copy_offload) {
> +		ret = blk_copy_offload(src_bdev, payload, dest, gfp_mask);
> +		if (ret)
> +			goto out;
> +	} else if (flags & BLKDEV_COPY_NOEMULATION) {

Why ? whoever calls blkdev_issue_copy() wants a copy to be done. Why would that
user say "Fail on me if the device does not support copy" ??? This is a weird
interface in my opinion.

> +		ret = -EIO;
> +		goto out;
> +	} else

Missing braces. By you do not need all these else after the gotos anyway.

> +		ret = blk_copy_emulate(src_bdev, payload, dest_bdev, dest,
> +				copy_size, gfp_mask);
> +
> +out:
> +	kvfree(payload);
> +	return ret;
> +}
> +EXPORT_SYMBOL(blkdev_issue_copy);
> +
>  /**
>   * __blkdev_issue_write_same - generate number of bios with same page
>   * @bdev:	target blockdev
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 808768f6b174..4e04f24e13c1 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -309,6 +309,8 @@ void __blk_queue_split(struct bio **bio, unsigned int *nr_segs)
>  	struct bio *split = NULL;
>  
>  	switch (bio_op(*bio)) {
> +	case REQ_OP_COPY:
> +			break;

Why would this even be called ? Copy BIOs cannot be split, right ?

>  	case REQ_OP_DISCARD:
>  	case REQ_OP_SECURE_ERASE:
>  		split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs);
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 43990b1d148b..93c15ba45a69 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -60,6 +60,10 @@ void blk_set_default_limits(struct queue_limits *lim)
>  	lim->io_opt = 0;
>  	lim->misaligned = 0;
>  	lim->zoned = BLK_ZONED_NONE;
> +	lim->copy_offload = 0;
> +	lim->max_copy_sectors = 0;
> +	lim->max_copy_nr_ranges = 0;
> +	lim->max_copy_range_sectors = 0;
>  }
>  EXPORT_SYMBOL(blk_set_default_limits);
>  
> @@ -565,6 +569,12 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
>  	if (b->chunk_sectors)
>  		t->chunk_sectors = gcd(t->chunk_sectors, b->chunk_sectors);
>  
> +	/* simple copy not supported in stacked devices */
> +	t->copy_offload = 0;
> +	t->max_copy_sectors = 0;
> +	t->max_copy_range_sectors = 0;
> +	t->max_copy_nr_ranges = 0;

You do not need this. Limits not explicitely initialized are 0 already.
But I do not see why you can't support copy on stacked devices. That should be
feasible taking the min() for each of the above limit.

> +
>  	/* Physical block size a multiple of the logical block size? */
>  	if (t->physical_block_size & (t->logical_block_size - 1)) {
>  		t->physical_block_size = t->logical_block_size;
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index b513f1683af0..625a72541263 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -166,6 +166,44 @@ static ssize_t queue_discard_granularity_show(struct request_queue *q, char *pag
>  	return queue_var_show(q->limits.discard_granularity, page);
>  }
>  
> +static ssize_t queue_copy_offload_show(struct request_queue *q, char *page)
> +{
> +	return queue_var_show(q->limits.copy_offload, page);
> +}
> +
> +static ssize_t queue_copy_offload_store(struct request_queue *q,
> +				       const char *page, size_t count)
> +{
> +	unsigned long copy_offload;
> +	ssize_t ret = queue_var_store(&copy_offload, page, count);
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	if (copy_offload && q->limits.max_copy_sectors == 0)
> +		return -EINVAL;
> +
> +	q->limits.copy_offload = copy_offload;
> +	return ret;
> +}

This is weird. If you want to allow a user to disable copy offload, then use
max_copy_sectors. This one should be read-only and only indicate if the device
supports it or not. I also would actually change this one into
max_copy_hw_sectors, immutable, indicating the max copy sectors that the device
supports, and 0 for no support. That would allow an easy implementation of
max_copy_sectors being red/write for controlling enable/disable.

> +
> +static ssize_t queue_max_copy_sectors_show(struct request_queue *q, char *page)
> +{
> +	return queue_var_show(q->limits.max_copy_sectors, page);
> +}
> +
> +static ssize_t queue_max_copy_range_sectors_show(struct request_queue *q,
> +		char *page)
> +{
> +	return queue_var_show(q->limits.max_copy_range_sectors, page);
> +}
> +
> +static ssize_t queue_max_copy_nr_ranges_show(struct request_queue *q,
> +		char *page)
> +{
> +	return queue_var_show(q->limits.max_copy_nr_ranges, page);
> +}
> +
>  static ssize_t queue_discard_max_hw_show(struct request_queue *q, char *page)
>  {
>  
> @@ -591,6 +629,11 @@ QUEUE_RO_ENTRY(queue_nr_zones, "nr_zones");
>  QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones");
>  QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones");
>  
> +QUEUE_RW_ENTRY(queue_copy_offload, "copy_offload");
> +QUEUE_RO_ENTRY(queue_max_copy_sectors, "max_copy_sectors");
> +QUEUE_RO_ENTRY(queue_max_copy_range_sectors, "max_copy_range_sectors");
> +QUEUE_RO_ENTRY(queue_max_copy_nr_ranges, "max_copy_nr_ranges");
> +
>  QUEUE_RW_ENTRY(queue_nomerges, "nomerges");
>  QUEUE_RW_ENTRY(queue_rq_affinity, "rq_affinity");
>  QUEUE_RW_ENTRY(queue_poll, "io_poll");
> @@ -636,6 +679,10 @@ static struct attribute *queue_attrs[] = {
>  	&queue_discard_max_entry.attr,
>  	&queue_discard_max_hw_entry.attr,
>  	&queue_discard_zeroes_data_entry.attr,
> +	&queue_copy_offload_entry.attr,
> +	&queue_max_copy_sectors_entry.attr,
> +	&queue_max_copy_range_sectors_entry.attr,
> +	&queue_max_copy_nr_ranges_entry.attr,
>  	&queue_write_same_max_entry.attr,
>  	&queue_write_zeroes_max_entry.attr,
>  	&queue_zone_append_max_entry.attr,
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 7a68b6e4300c..02069178d51e 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -75,6 +75,7 @@ bool blk_req_needs_zone_write_lock(struct request *rq)
>  	case REQ_OP_WRITE_ZEROES:
>  	case REQ_OP_WRITE_SAME:
>  	case REQ_OP_WRITE:
> +	case REQ_OP_COPY:
>  		return blk_rq_zone_is_seq(rq);
>  	default:
>  		return false;
> diff --git a/block/bounce.c b/block/bounce.c
> index d3f51acd6e3b..5e052afe8691 100644
> --- a/block/bounce.c
> +++ b/block/bounce.c
> @@ -254,6 +254,7 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
>  	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
>  
>  	switch (bio_op(bio)) {
> +	case REQ_OP_COPY:
>  	case REQ_OP_DISCARD:
>  	case REQ_OP_SECURE_ERASE:
>  	case REQ_OP_WRITE_ZEROES:
> diff --git a/block/ioctl.c b/block/ioctl.c
> index d61d652078f4..0e52181657a4 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -133,6 +133,37 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
>  				    GFP_KERNEL, flags);
>  }
>  
> +static int blk_ioctl_copy(struct block_device *bdev, fmode_t mode,
> +		unsigned long arg, unsigned long flags)
> +{
> +	struct copy_range crange;
> +	struct range_entry *rlist;
> +	int ret;
> +
> +	if (!(mode & FMODE_WRITE))
> +		return -EBADF;
> +
> +	if (copy_from_user(&crange, (void __user *)arg, sizeof(crange)))
> +		return -EFAULT;
> +
> +	rlist = kmalloc_array(crange.nr_range, sizeof(*rlist),
> +			GFP_KERNEL);
> +	if (!rlist)
> +		return -ENOMEM;
> +
> +	if (copy_from_user(rlist, (void __user *)crange.range_list,
> +				sizeof(*rlist) * crange.nr_range)) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	ret = blkdev_issue_copy(bdev, crange.nr_range, rlist, bdev, crange.dest,
> +			GFP_KERNEL, flags);
> +out:
> +	kfree(rlist);
> +	return ret;
> +}
> +
>  static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode,
>  		unsigned long arg)
>  {
> @@ -458,6 +489,8 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
>  	case BLKSECDISCARD:
>  		return blk_ioctl_discard(bdev, mode, arg,
>  				BLKDEV_DISCARD_SECURE);
> +	case BLKCOPY:
> +		return blk_ioctl_copy(bdev, mode, arg, 0);
>  	case BLKZEROOUT:
>  		return blk_ioctl_zeroout(bdev, mode, arg);
>  	case BLKREPORTZONE:
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 1edda614f7ce..164313bdfb35 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -71,6 +71,7 @@ static inline bool bio_has_data(struct bio *bio)
>  static inline bool bio_no_advance_iter(const struct bio *bio)
>  {
>  	return bio_op(bio) == REQ_OP_DISCARD ||
> +	       bio_op(bio) == REQ_OP_COPY ||
>  	       bio_op(bio) == REQ_OP_SECURE_ERASE ||
>  	       bio_op(bio) == REQ_OP_WRITE_SAME ||
>  	       bio_op(bio) == REQ_OP_WRITE_ZEROES;
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 866f74261b3b..5a35c02ac0a8 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -380,6 +380,8 @@ enum req_opf {
>  	REQ_OP_ZONE_RESET	= 15,
>  	/* reset all the zone present on the device */
>  	REQ_OP_ZONE_RESET_ALL	= 17,
> +	/* copy ranges within device */
> +	REQ_OP_COPY		= 19,
>  
>  	/* SCSI passthrough using struct scsi_request */
>  	REQ_OP_SCSI_IN		= 32,
> @@ -506,6 +508,11 @@ static inline bool op_is_discard(unsigned int op)
>  	return (op & REQ_OP_MASK) == REQ_OP_DISCARD;
>  }
>  
> +static inline bool op_is_copy(unsigned int op)
> +{
> +	return (op & REQ_OP_MASK) == REQ_OP_COPY;
> +}
> +
>  /*
>   * Check if a bio or request operation is a zone management operation, with
>   * the exception of REQ_OP_ZONE_RESET_ALL which is treated as a special case
> @@ -565,4 +572,11 @@ struct blk_rq_stat {
>  	u64 batch;
>  };
>  
> +struct blk_copy_payload {
> +	sector_t	dest;
> +	int		copy_nr_ranges;
> +	struct block_device *src_bdev;
> +	struct	range_entry	range[];
> +};
> +
>  #endif /* __LINUX_BLK_TYPES_H */
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 699ace6b25ff..2bb4513d4bb8 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -337,10 +337,14 @@ struct queue_limits {
>  	unsigned int		max_zone_append_sectors;
>  	unsigned int		discard_granularity;
>  	unsigned int		discard_alignment;
> +	unsigned int		copy_offload;
> +	unsigned int		max_copy_sectors;
>  
>  	unsigned short		max_segments;
>  	unsigned short		max_integrity_segments;
>  	unsigned short		max_discard_segments;
> +	unsigned short		max_copy_range_sectors;
> +	unsigned short		max_copy_nr_ranges;
>  
>  	unsigned char		misaligned;
>  	unsigned char		discard_misaligned;
> @@ -621,6 +625,7 @@ struct request_queue {
>  #define QUEUE_FLAG_RQ_ALLOC_TIME 27	/* record rq->alloc_time_ns */
>  #define QUEUE_FLAG_HCTX_ACTIVE	28	/* at least one blk-mq hctx is active */
>  #define QUEUE_FLAG_NOWAIT       29	/* device supports NOWAIT */
> +#define QUEUE_FLAG_SIMPLE_COPY	30	/* supports simple copy */
>  
>  #define QUEUE_FLAG_MQ_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
>  				 (1 << QUEUE_FLAG_SAME_COMP) |		\
> @@ -643,6 +648,7 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
>  #define blk_queue_io_stat(q)	test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
>  #define blk_queue_add_random(q)	test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
>  #define blk_queue_discard(q)	test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
> +#define blk_queue_copy(q)	test_bit(QUEUE_FLAG_SIMPLE_COPY, &(q)->queue_flags)
>  #define blk_queue_zone_resetall(q)	\
>  	test_bit(QUEUE_FLAG_ZONE_RESETALL, &(q)->queue_flags)
>  #define blk_queue_secure_erase(q) \
> @@ -1069,6 +1075,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
>  		return min(q->limits.max_discard_sectors,
>  			   UINT_MAX >> SECTOR_SHIFT);
>  
> +	if (unlikely(op == REQ_OP_COPY))
> +		return q->limits.max_copy_sectors;
> +

I would agreee with this if a copy BIO was always a single range, but that is
not the case. So I am not sure this makes sense at all.

>  	if (unlikely(op == REQ_OP_WRITE_SAME))
>  		return q->limits.max_write_same_sectors;
>  
> @@ -1343,6 +1352,12 @@ extern int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
>  		sector_t nr_sects, gfp_t gfp_mask, int flags,
>  		struct bio **biop);
>  
> +#define BLKDEV_COPY_NOEMULATION	(1 << 0)	/* do not emulate if copy offload not supported */
> +
> +extern int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
> +		struct range_entry *src_rlist, struct block_device *dest_bdev,
> +		sector_t dest, gfp_t gfp_mask, int flags);

No need for extern.

> +
>  #define BLKDEV_ZERO_NOUNMAP	(1 << 0)  /* do not free blocks */
>  #define BLKDEV_ZERO_NOFALLBACK	(1 << 1)  /* don't write explicit zeroes */
>  
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index f44eb0a04afd..5cadb176317a 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -64,6 +64,18 @@ struct fstrim_range {
>  	__u64 minlen;
>  };
>  
> +struct range_entry {
> +	__u64 src;
> +	__u64 len;
> +};
> +
> +struct copy_range {
> +	__u64 dest;
> +	__u64 nr_range;
> +	__u64 range_list;
> +	__u64 rsvd;
> +};
> +
>  /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
>  #define FILE_DEDUPE_RANGE_SAME		0
>  #define FILE_DEDUPE_RANGE_DIFFERS	1
> @@ -184,6 +196,7 @@ struct fsxattr {
>  #define BLKSECDISCARD _IO(0x12,125)
>  #define BLKROTATIONAL _IO(0x12,126)
>  #define BLKZEROOUT _IO(0x12,127)
> +#define BLKCOPY _IOWR(0x12, 128, struct copy_range)
>  /*
>   * A jump here: 130-131 are reserved for zoned block devices
>   * (see uapi/linux/blkzoned.h)
> 

Please test your code more thoroughly. It is full of problems that you should
have detected with better testing including RO devices, partitions and error
path coverage.

Selva Jove April 7, 2021, 11:32 a.m. UTC | #2

Initially I started moving the dm-kcopyd interface to the block layer
as a generic interface.
Once I dig deeper in dm-kcopyd code, I figured that dm-kcopyd is
tightly coupled with dm_io()

To move dm-kcopyd to block layer, it would also require dm_io code to
be moved to block layer.
It would cause havoc in dm layer, as it is the backbone of the
dm-layer and needs complete
rewriting of dm-layer. Do you see any other way of doing this without
having to move dm_io code
or to have redundant code ?


On Sat, Feb 20, 2021 at 10:29 AM Damien Le Moal <[e-mail]> wrote:
>
> On 2021/02/20 11:01, SelvaKumar S wrote:
> > Add new BLKCOPY ioctl that offloads copying of one or more sources
> > ranges to a destination in the device. Accepts a 'copy_range' structure
> > that contains destination (in sectors), no of sources and pointer to the
> > array of source ranges. Each source range is represented by 'range_entry'
> > that contains start and length of source ranges (in sectors).
> >
> > Introduce REQ_OP_COPY, a no-merge copy offload operation. Create
> > bio with control information as payload and submit to the device.
> > REQ_OP_COPY(19) is a write op and takes zone_write_lock when submitted
> > to zoned device.
> >
> > If the device doesn't support copy or copy offload is disabled, then
> > copy operation is emulated by default. However, the copy-emulation is an
> > opt-in feature. Caller can choose not to use the copy-emulation by
> > specifying a flag 'BLKDEV_COPY_NOEMULATION'.
> >
> > Copy-emulation is implemented by allocating memory of total copy size.
> > The source ranges are read into memory by chaining bio for each source
> > ranges and submitting them async and the last bio waits for completion.
> > After data is read, it is written to the destination.
> >
> > bio_map_kern() is used to allocate bio and add pages of copy buffer to
> > bio. As bio->bi_private and bio->bi_end_io are needed for chaining the
> > bio and gets over-written, invalidate_kernel_vmap_range() for read is
> > called in the caller.
> >
> > Introduce queue limits for simple copy and other helper functions.
> > Add device limits as sysfs entries.
> >       - copy_offload
> >       - max_copy_sectors
> >       - max_copy_ranges_sectors
> >       - max_copy_nr_ranges
> >
> > copy_offload(= 0) is disabled by default. This needs to be enabled if
> > copy-offload needs to be used.
> > max_copy_sectors = 0 indicates the device doesn't support native copy.
> >
> > Native copy offload is not supported for stacked devices and is done via
> > copy emulation.
> >
> > Signed-off-by: SelvaKumar S <[e-mail]>
> > Signed-off-by: Kanchan Joshi <[e-mail]>
> > Signed-off-by: Nitesh Shetty <[e-mail]>
> > Signed-off-by: Javier González <[e-mail]>
> > Signed-off-by: Chaitanya Kulkarni <[e-mail]>
> > ---
> >  block/blk-core.c          | 102 ++++++++++++++++--
> >  block/blk-lib.c           | 222 ++++++++++++++++++++++++++++++++++++++
> >  block/blk-merge.c         |   2 +
> >  block/blk-settings.c      |  10 ++
> >  block/blk-sysfs.c         |  47 ++++++++
> >  block/blk-zoned.c         |   1 +
> >  block/bounce.c            |   1 +
> >  block/ioctl.c             |  33 ++++++
> >  include/linux/bio.h       |   1 +
> >  include/linux/blk_types.h |  14 +++
> >  include/linux/blkdev.h    |  15 +++
> >  include/uapi/linux/fs.h   |  13 +++
> >  12 files changed, 453 insertions(+), 8 deletions(-)
> >
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index 7663a9b94b80..23e646e5ae43 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -720,6 +720,17 @@ static noinline int should_fail_bio(struct bio *bio)
> >  }
> >  ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);
> >
> > +static inline int bio_check_copy_eod(struct bio *bio, sector_t start,
> > +             sector_t nr_sectors, sector_t max_sect)
> > +{
> > +     if (nr_sectors && max_sect &&
> > +         (nr_sectors > max_sect || start > max_sect - nr_sectors)) {
> > +             handle_bad_sector(bio, max_sect);
> > +             return -EIO;
> > +     }
> > +     return 0;
> > +}
> > +
> >  /*
> >   * Check whether this bio extends beyond the end of the device or partition.
> >   * This may well happen - the kernel calls bread() without checking the size of
> > @@ -738,6 +749,75 @@ static inline int bio_check_eod(struct bio *bio, sector_t maxsector)
> >       return 0;
> >  }
> >
> > +/*
> > + * Check for copy limits and remap source ranges if needed.
> > + */
> > +static int blk_check_copy(struct bio *bio)
> > +{
> > +     struct blk_copy_payload *payload = bio_data(bio);
> > +     struct request_queue *q = bio->bi_disk->queue;
> > +     sector_t max_sect, start_sect, copy_size = 0;
> > +     sector_t src_max_sect, src_start_sect;
> > +     struct block_device *bd_part;
> > +     int i, ret = -EIO;
> > +
> > +     rcu_read_lock();
> > +
> > +     bd_part = __disk_get_part(bio->bi_disk, bio->bi_partno);
> > +     if (unlikely(!bd_part)) {
> > +             rcu_read_unlock();
> > +             goto out;
> > +     }
> > +
> > +     max_sect =  bdev_nr_sectors(bd_part);
> > +     start_sect = bd_part->bd_start_sect;
> > +
> > +     src_max_sect = bdev_nr_sectors(payload->src_bdev);
> > +     src_start_sect = payload->src_bdev->bd_start_sect;
> > +
> > +     if (unlikely(should_fail_request(bd_part, bio->bi_iter.bi_size)))
> > +             goto out;
> > +
> > +     if (unlikely(bio_check_ro(bio, bd_part)))
> > +             goto out;
>
> There is no rcu_unlock() in that out label. Did you test ?
>
> > +
> > +     rcu_read_unlock();
> > +
> > +     /* cannot handle copy crossing nr_ranges limit */
> > +     if (payload->copy_nr_ranges > q->limits.max_copy_nr_ranges)
> > +             goto out;
> > +
> > +     for (i = 0; i < payload->copy_nr_ranges; i++) {
> > +             ret = bio_check_copy_eod(bio, payload->range[i].src,
> > +                             payload->range[i].len, src_max_sect);
> > +             if (unlikely(ret))
> > +                     goto out;
> > +
> > +             /* single source range length limit */
> > +             if (payload->range[i].len > q->limits.max_copy_range_sectors)
> > +                     goto out;
>
> ret is not set. You will return success with this.
>
> > +
> > +             payload->range[i].src += src_start_sect;
> > +             copy_size += payload->range[i].len;
> > +     }
> > +
> > +     /* check if copy length crosses eod */
> > +     ret = bio_check_copy_eod(bio, bio->bi_iter.bi_sector,
> > +                             copy_size, max_sect);
> > +     if (unlikely(ret))
> > +             goto out;
> > +
> > +     /* cannot handle copy more than copy limits */
> > +     if (copy_size > q->limits.max_copy_sectors)
> > +             goto out;
>
> Again ret is not set... No error return ?
>
> > +
> > +     bio->bi_iter.bi_sector += start_sect;
> > +     bio->bi_partno = 0;
> > +     ret = 0;
> > +out:
> > +     return ret;
> > +}
> > +
> >  /*
> >   * Remap block n of partition p to block n+start(p) of the disk.
> >   */
> > @@ -827,14 +907,16 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
> >       if (should_fail_bio(bio))
> >               goto end_io;
> >
> > -     if (bio->bi_partno) {
> > -             if (unlikely(blk_partition_remap(bio)))
> > -                     goto end_io;
> > -     } else {
> > -             if (unlikely(bio_check_ro(bio, bio->bi_disk->part0)))
> > -                     goto end_io;
> > -             if (unlikely(bio_check_eod(bio, get_capacity(bio->bi_disk))))
> > -                     goto end_io;
> > +     if (likely(!op_is_copy(bio->bi_opf))) {
> > +             if (bio->bi_partno) {
> > +                     if (unlikely(blk_partition_remap(bio)))
> > +                             goto end_io;
> > +             } else {
> > +                     if (unlikely(bio_check_ro(bio, bio->bi_disk->part0)))
> > +                             goto end_io;
> > +                     if (unlikely(bio_check_eod(bio, get_capacity(bio->bi_disk))))
> > +                             goto end_io;
> > +             }
> >       }
> >
> >       /*
> > @@ -858,6 +940,10 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
> >               if (!blk_queue_discard(q))
> >                       goto not_supported;
> >               break;
> > +     case REQ_OP_COPY:
> > +             if (unlikely(blk_check_copy(bio)))
> > +                     goto end_io;
> > +             break;
> >       case REQ_OP_SECURE_ERASE:
> >               if (!blk_queue_secure_erase(q))
> >                       goto not_supported;
> > diff --git a/block/blk-lib.c b/block/blk-lib.c
> > index 752f9c722062..97ba58d8d9a1 100644
> > --- a/block/blk-lib.c
> > +++ b/block/blk-lib.c
> > @@ -150,6 +150,228 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
> >  }
> >  EXPORT_SYMBOL(blkdev_issue_discard);
> >
> > +int blk_copy_offload(struct block_device *dest_bdev, struct blk_copy_payload *payload,
> > +             sector_t dest, gfp_t gfp_mask)
>
> Simple copy is only over the same device, right ? So the name "dest_bdev" is a
> little strange.
>
> > +{
> > +     struct request_queue *q = bdev_get_queue(dest_bdev);
> > +     struct bio *bio;
> > +     int ret, payload_size;
> > +
> > +     payload_size = struct_size(payload, range, payload->copy_nr_ranges);
> > +     bio = bio_map_kern(q, payload, payload_size, gfp_mask);
> > +     if (IS_ERR(bio)) {
> > +             ret = PTR_ERR(bio);
> > +             goto err;
>
> This will do a bio_put() on a non existent bio...
>
> > +     }
> > +
> > +     bio->bi_iter.bi_sector = dest;
> > +     bio->bi_opf = REQ_OP_COPY | REQ_NOMERGE;
> > +     bio_set_dev(bio, dest_bdev);
> > +
> > +     ret = submit_bio_wait(bio);
> > +err:
> > +     bio_put(bio);
> > +     return ret;
> > +}
> > +
> > +int blk_read_to_buf(struct block_device *src_bdev, struct blk_copy_payload *payload,
> > +             gfp_t gfp_mask, sector_t copy_size, void **buf_p)
> > +{
> > +     struct request_queue *q = bdev_get_queue(src_bdev);
> > +     struct bio *bio, *parent = NULL;
> > +     void *buf = NULL;
> > +     int copy_len = copy_size << SECTOR_SHIFT;
> > +     int i, nr_srcs, ret, cur_size, t_len = 0;
> > +     bool is_vmalloc;
> > +
> > +     nr_srcs = payload->copy_nr_ranges;
> > +
> > +     buf = kvmalloc(copy_len, gfp_mask);
> > +     if (!buf)
> > +             return -ENOMEM;
> > +     is_vmalloc = is_vmalloc_addr(buf);
> > +
> > +     for (i = 0; i < nr_srcs; i++) {
> > +             cur_size = payload->range[i].len << SECTOR_SHIFT;
> > +
> > +             bio = bio_map_kern(q, buf + t_len, cur_size, gfp_mask);
> > +             if (IS_ERR(bio)) {
> > +                     ret = PTR_ERR(bio);
> > +                     goto out;
> > +             }
> > +
> > +             bio->bi_iter.bi_sector = payload->range[i].src;
> > +             bio->bi_opf = REQ_OP_READ;
> > +             bio_set_dev(bio, src_bdev);
> > +             bio->bi_end_io = NULL;
> > +             bio->bi_private = NULL;
> > +
> > +             if (parent) {
> > +                     bio_chain(parent, bio);
> > +                     submit_bio(parent);
> > +             }
> > +
> > +             parent = bio;
> > +             t_len += cur_size;
> > +     }
> > +
> > +     ret = submit_bio_wait(bio);
> > +     bio_put(bio);
> > +     if (is_vmalloc)
> > +             invalidate_kernel_vmap_range(buf, copy_len);
>
> But blk_write_from_buf() will use the buffer right after this.. Is this really OK ?
>

As we are over-writing bio->private adn bi->bi_endio during
submit_bio_wait(), the original
bio_map_kern_endio() can't be used to invalidate_kernel_vmap_range().
So we are doing it
here explicitly. invalidate_kernel_vmap_range() is only necessary for
data reads and the buf
is safe to be used in blk_write_from_buf().

>
> > +     if (ret)
> > +             goto out;
> > +
> > +     *buf_p = buf;
> > +     return 0;
> > +out:
> > +     kvfree(buf);
> > +     return ret;
> > +}
> > +
> > +int blk_write_from_buf(struct block_device *dest_bdev, void *buf, sector_t dest,
> > +             sector_t copy_size, gfp_t gfp_mask)
> > +{
> > +     struct request_queue *q = bdev_get_queue(dest_bdev);
> > +     struct bio *bio;
> > +     int ret, copy_len = copy_size << SECTOR_SHIFT;
> > +
> > +     bio = bio_map_kern(q, buf, copy_len, gfp_mask);
> > +     if (IS_ERR(bio)) {
> > +             ret = PTR_ERR(bio);
> > +             goto out;
> > +     }
> > +     bio_set_dev(bio, dest_bdev);
> > +     bio->bi_opf = REQ_OP_WRITE;
> > +     bio->bi_iter.bi_sector = dest;
> > +
> > +     bio->bi_end_io = NULL;
> > +     ret = submit_bio_wait(bio);
> > +     bio_put(bio);
> > +out:
> > +     return ret;
> > +}
> > +
> > +int blk_prepare_payload(struct block_device *src_bdev, int nr_srcs, struct range_entry *rlist,
> > +             gfp_t gfp_mask, struct blk_copy_payload **payload_p, sector_t *copy_size)
> > +{
> > +
> > +     struct request_queue *q = bdev_get_queue(src_bdev);
> > +     struct blk_copy_payload *payload;
> > +     sector_t bs_mask, total_len = 0;
> > +     int i, ret, payload_size;
> > +
> > +     if (!q)
> > +             return -ENXIO;
> > +
> > +     if (!nr_srcs)
> > +             return -EINVAL;
> > +
> > +     if (bdev_read_only(src_bdev))
> > +             return -EPERM;
> > +
> > +     bs_mask = (bdev_logical_block_size(src_bdev) >> 9) - 1;
> > +
> > +     payload_size = struct_size(payload, range, nr_srcs);
> > +     payload = kmalloc(payload_size, gfp_mask);
> > +     if (!payload)
> > +             return -ENOMEM;
> > +
> > +     for (i = 0; i < nr_srcs; i++) {
> > +             if (rlist[i].src & bs_mask || rlist[i].len & bs_mask) {
> > +                     ret = -EINVAL;
> > +                     goto err;
> > +             }
> > +
> > +             payload->range[i].src = rlist[i].src;
> > +             payload->range[i].len = rlist[i].len;
> > +
> > +             total_len += rlist[i].len;
> > +     }
> > +
> > +     payload->copy_nr_ranges = i;
> > +     payload->src_bdev = src_bdev;
> > +     *copy_size = total_len;
> > +
> > +     *payload_p = payload;
> > +     return 0;
> > +err:
> > +     kfree(payload);
> > +     return ret;
> > +}
> > +
> > +int blk_copy_emulate(struct block_device *src_bdev, struct blk_copy_payload *payload,
> > +                     struct block_device *dest_bdev, sector_t dest,
> > +                     sector_t copy_size, gfp_t gfp_mask)
> > +{
> > +     void *buf = NULL;
> > +     int ret;
> > +
> > +     ret = blk_read_to_buf(src_bdev, payload, gfp_mask, copy_size, &buf);
> > +     if (ret)
> > +             goto out;
> > +
> > +     ret = blk_write_from_buf(dest_bdev, buf, dest, copy_size, gfp_mask);
> > +     if (buf)
> > +             kvfree(buf);
> > +out:
> > +     return ret;
> > +}
>
> I already commented that this should better use the dm-kcopyd design, which
> would be far more efficient than this. This will be slow...
>
> Your function blkdev_issue_copy() below should deal only with issuing simple
> copy (amd later scsi xcopy) for devices that support it. Bring the dm-kcopyd
> interface in the block layer as a generic interface for hadling emulation.
> Otherwise you are repeating what dm does, but not as efficiently.
>
> > +
> > +/**
> > + * blkdev_issue_copy - queue a copy
> > + * @src_bdev:        source block device
> > + * @nr_srcs: number of source ranges to copy
> > + * @rlist:   array of source ranges in sector
> > + * @dest_bdev:       destination block device
> > + * @dest:    destination in sector
> > + * @gfp_mask:   memory allocation flags (for bio_alloc)
> > + * @flags:   BLKDEV_COPY_* flags to control behaviour
> > + *
> > + * Description:
> > + *   Copy array of source ranges from source block device to
> > + *   destination block devcie. All source must belong to same bdev and
> > + *   length of a source range cannot be zero.
> > + */
> > +
> > +int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
> > +             struct range_entry *src_rlist, struct block_device *dest_bdev,
> > +             sector_t dest, gfp_t gfp_mask, int flags)
> > +{
> > +     struct request_queue *q = bdev_get_queue(src_bdev);
> > +     struct request_queue *dest_q = bdev_get_queue(dest_bdev);
> > +     struct blk_copy_payload *payload;
> > +     sector_t bs_mask, copy_size;
> > +     int ret;
> > +
> > +     ret = blk_prepare_payload(src_bdev, nr_srcs, src_rlist, gfp_mask,
> > +                     &payload, &copy_size);
> > +     if (ret)
> > +             return ret;
> > +
> > +     bs_mask = (bdev_logical_block_size(dest_bdev) >> 9) - 1;
> > +     if (dest & bs_mask) {
> > +             return -EINVAL;
> > +             goto out;
> > +     }
> > +
> > +     if (q == dest_q && q->limits.copy_offload) {
> > +             ret = blk_copy_offload(src_bdev, payload, dest, gfp_mask);
> > +             if (ret)
> > +                     goto out;
> > +     } else if (flags & BLKDEV_COPY_NOEMULATION) {
>
> Why ? whoever calls blkdev_issue_copy() wants a copy to be done. Why would that
> user say "Fail on me if the device does not support copy" ??? This is a weird
> interface in my opinion.
>

BLKDEV_COPY_NOEMULATION flag was introduced to allow blkdev_issue_copy() callers
to use their native copying method instead of the emulated copy that I
added. This way we
ensure that dm uses the hw-assisted copy and if that is not present,
it falls back to existing
copy method.

The other users who don't have their native emulation can use this
emulated-copy implementation.

>
> > +             ret = -EIO;
> > +             goto out;
> > +     } else
>
> Missing braces. By you do not need all these else after the gotos anyway.
>
> > +             ret = blk_copy_emulate(src_bdev, payload, dest_bdev, dest,
> > +                             copy_size, gfp_mask);
> > +
> > +out:
> > +     kvfree(payload);
> > +     return ret;
> > +}
> > +EXPORT_SYMBOL(blkdev_issue_copy);
> > +
> >  /**
> >   * __blkdev_issue_write_same - generate number of bios with same page
> >   * @bdev:    target blockdev
> > diff --git a/block/blk-merge.c b/block/blk-merge.c
> > index 808768f6b174..4e04f24e13c1 100644
> > --- a/block/blk-merge.c
> > +++ b/block/blk-merge.c
> > @@ -309,6 +309,8 @@ void __blk_queue_split(struct bio **bio, unsigned int *nr_segs)
> >       struct bio *split = NULL;
> >
> >       switch (bio_op(*bio)) {
> > +     case REQ_OP_COPY:
> > +                     break;
>
> Why would this even be called ? Copy BIOs cannot be split, right ?
>
> >       case REQ_OP_DISCARD:
> >       case REQ_OP_SECURE_ERASE:
> >               split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs);
> > diff --git a/block/blk-settings.c b/block/blk-settings.c
> > index 43990b1d148b..93c15ba45a69 100644
> > --- a/block/blk-settings.c
> > +++ b/block/blk-settings.c
> > @@ -60,6 +60,10 @@ void blk_set_default_limits(struct queue_limits *lim)
> >       lim->io_opt = 0;
> >       lim->misaligned = 0;
> >       lim->zoned = BLK_ZONED_NONE;
> > +     lim->copy_offload = 0;
> > +     lim->max_copy_sectors = 0;
> > +     lim->max_copy_nr_ranges = 0;
> > +     lim->max_copy_range_sectors = 0;
> >  }
> >  EXPORT_SYMBOL(blk_set_default_limits);
> >
> > @@ -565,6 +569,12 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
> >       if (b->chunk_sectors)
> >               t->chunk_sectors = gcd(t->chunk_sectors, b->chunk_sectors);
> >
> > +     /* simple copy not supported in stacked devices */
> > +     t->copy_offload = 0;
> > +     t->max_copy_sectors = 0;
> > +     t->max_copy_range_sectors = 0;
> > +     t->max_copy_nr_ranges = 0;
>
> You do not need this. Limits not explicitely initialized are 0 already.
> But I do not see why you can't support copy on stacked devices. That should be
> feasible taking the min() for each of the above limit.
>

Disabling stacked device support was feedback from v2.

https://patchwork.kernel.org/project/linux-block/patch/[e-mail]/

>
> > +
> >       /* Physical block size a multiple of the logical block size? */
> >       if (t->physical_block_size & (t->logical_block_size - 1)) {
> >               t->physical_block_size = t->logical_block_size;
> > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> > index b513f1683af0..625a72541263 100644
> > --- a/block/blk-sysfs.c
> > +++ b/block/blk-sysfs.c
> > @@ -166,6 +166,44 @@ static ssize_t queue_discard_granularity_show(struct request_queue *q, char *pag
> >       return queue_var_show(q->limits.discard_granularity, page);
> >  }
> >
> > +static ssize_t queue_copy_offload_show(struct request_queue *q, char *page)
> > +{
> > +     return queue_var_show(q->limits.copy_offload, page);
> > +}
> > +
> > +static ssize_t queue_copy_offload_store(struct request_queue *q,
> > +                                    const char *page, size_t count)
> > +{
> > +     unsigned long copy_offload;
> > +     ssize_t ret = queue_var_store(&copy_offload, page, count);
> > +
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     if (copy_offload && q->limits.max_copy_sectors == 0)
> > +             return -EINVAL;
> > +
> > +     q->limits.copy_offload = copy_offload;
> > +     return ret;
> > +}
>
> This is weird. If you want to allow a user to disable copy offload, then use
> max_copy_sectors. This one should be read-only and only indicate if the device
> supports it or not. I also would actually change this one into
> max_copy_hw_sectors, immutable, indicating the max copy sectors that the device
> supports, and 0 for no support. That would allow an easy implementation of
> max_copy_sectors being red/write for controlling enable/disable.
>
> > +
> > +static ssize_t queue_max_copy_sectors_show(struct request_queue *q, char *page)
> > +{
> > +     return queue_var_show(q->limits.max_copy_sectors, page);
> > +}
> > +
> > +static ssize_t queue_max_copy_range_sectors_show(struct request_queue *q,
> > +             char *page)
> > +{
> > +     return queue_var_show(q->limits.max_copy_range_sectors, page);
> > +}
> > +
> > +static ssize_t queue_max_copy_nr_ranges_show(struct request_queue *q,
> > +             char *page)
> > +{
> > +     return queue_var_show(q->limits.max_copy_nr_ranges, page);
> > +}
> > +
> >  static ssize_t queue_discard_max_hw_show(struct request_queue *q, char *page)
> >  {
> >
> > @@ -591,6 +629,11 @@ QUEUE_RO_ENTRY(queue_nr_zones, "nr_zones");
> >  QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones");
> >  QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones");
> >
> > +QUEUE_RW_ENTRY(queue_copy_offload, "copy_offload");
> > +QUEUE_RO_ENTRY(queue_max_copy_sectors, "max_copy_sectors");
> > +QUEUE_RO_ENTRY(queue_max_copy_range_sectors, "max_copy_range_sectors");
> > +QUEUE_RO_ENTRY(queue_max_copy_nr_ranges, "max_copy_nr_ranges");
> > +
> >  QUEUE_RW_ENTRY(queue_nomerges, "nomerges");
> >  QUEUE_RW_ENTRY(queue_rq_affinity, "rq_affinity");
> >  QUEUE_RW_ENTRY(queue_poll, "io_poll");
> > @@ -636,6 +679,10 @@ static struct attribute *queue_attrs[] = {
> >       &queue_discard_max_entry.attr,
> >       &queue_discard_max_hw_entry.attr,
> >       &queue_discard_zeroes_data_entry.attr,
> > +     &queue_copy_offload_entry.attr,
> > +     &queue_max_copy_sectors_entry.attr,
> > +     &queue_max_copy_range_sectors_entry.attr,
> > +     &queue_max_copy_nr_ranges_entry.attr,
> >       &queue_write_same_max_entry.attr,
> >       &queue_write_zeroes_max_entry.attr,
> >       &queue_zone_append_max_entry.attr,
> > diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> > index 7a68b6e4300c..02069178d51e 100644
> > --- a/block/blk-zoned.c
> > +++ b/block/blk-zoned.c
> > @@ -75,6 +75,7 @@ bool blk_req_needs_zone_write_lock(struct request *rq)
> >       case REQ_OP_WRITE_ZEROES:
> >       case REQ_OP_WRITE_SAME:
> >       case REQ_OP_WRITE:
> > +     case REQ_OP_COPY:
> >               return blk_rq_zone_is_seq(rq);
> >       default:
> >               return false;
> > diff --git a/block/bounce.c b/block/bounce.c
> > index d3f51acd6e3b..5e052afe8691 100644
> > --- a/block/bounce.c
> > +++ b/block/bounce.c
> > @@ -254,6 +254,7 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
> >       bio->bi_iter.bi_size    = bio_src->bi_iter.bi_size;
> >
> >       switch (bio_op(bio)) {
> > +     case REQ_OP_COPY:
> >       case REQ_OP_DISCARD:
> >       case REQ_OP_SECURE_ERASE:
> >       case REQ_OP_WRITE_ZEROES:
> > diff --git a/block/ioctl.c b/block/ioctl.c
> > index d61d652078f4..0e52181657a4 100644
> > --- a/block/ioctl.c
> > +++ b/block/ioctl.c
> > @@ -133,6 +133,37 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
> >                                   GFP_KERNEL, flags);
> >  }
> >
> > +static int blk_ioctl_copy(struct block_device *bdev, fmode_t mode,
> > +             unsigned long arg, unsigned long flags)
> > +{
> > +     struct copy_range crange;
> > +     struct range_entry *rlist;
> > +     int ret;
> > +
> > +     if (!(mode & FMODE_WRITE))
> > +             return -EBADF;
> > +
> > +     if (copy_from_user(&crange, (void __user *)arg, sizeof(crange)))
> > +             return -EFAULT;
> > +
> > +     rlist = kmalloc_array(crange.nr_range, sizeof(*rlist),
> > +                     GFP_KERNEL);
> > +     if (!rlist)
> > +             return -ENOMEM;
> > +
> > +     if (copy_from_user(rlist, (void __user *)crange.range_list,
> > +                             sizeof(*rlist) * crange.nr_range)) {
> > +             ret = -EFAULT;
> > +             goto out;
> > +     }
> > +
> > +     ret = blkdev_issue_copy(bdev, crange.nr_range, rlist, bdev, crange.dest,
> > +                     GFP_KERNEL, flags);
> > +out:
> > +     kfree(rlist);
> > +     return ret;
> > +}
> > +
> >  static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode,
> >               unsigned long arg)
> >  {
> > @@ -458,6 +489,8 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
> >       case BLKSECDISCARD:
> >               return blk_ioctl_discard(bdev, mode, arg,
> >                               BLKDEV_DISCARD_SECURE);
> > +     case BLKCOPY:
> > +             return blk_ioctl_copy(bdev, mode, arg, 0);
> >       case BLKZEROOUT:
> >               return blk_ioctl_zeroout(bdev, mode, arg);
> >       case BLKREPORTZONE:
> > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > index 1edda614f7ce..164313bdfb35 100644
> > --- a/include/linux/bio.h
> > +++ b/include/linux/bio.h
> > @@ -71,6 +71,7 @@ static inline bool bio_has_data(struct bio *bio)
> >  static inline bool bio_no_advance_iter(const struct bio *bio)
> >  {
> >       return bio_op(bio) == REQ_OP_DISCARD ||
> > +            bio_op(bio) == REQ_OP_COPY ||
> >              bio_op(bio) == REQ_OP_SECURE_ERASE ||
> >              bio_op(bio) == REQ_OP_WRITE_SAME ||
> >              bio_op(bio) == REQ_OP_WRITE_ZEROES;
> > diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> > index 866f74261b3b..5a35c02ac0a8 100644
> > --- a/include/linux/blk_types.h
> > +++ b/include/linux/blk_types.h
> > @@ -380,6 +380,8 @@ enum req_opf {
> >       REQ_OP_ZONE_RESET       = 15,
> >       /* reset all the zone present on the device */
> >       REQ_OP_ZONE_RESET_ALL   = 17,
> > +     /* copy ranges within device */
> > +     REQ_OP_COPY             = 19,
> >
> >       /* SCSI passthrough using struct scsi_request */
> >       REQ_OP_SCSI_IN          = 32,
> > @@ -506,6 +508,11 @@ static inline bool op_is_discard(unsigned int op)
> >       return (op & REQ_OP_MASK) == REQ_OP_DISCARD;
> >  }
> >
> > +static inline bool op_is_copy(unsigned int op)
> > +{
> > +     return (op & REQ_OP_MASK) == REQ_OP_COPY;
> > +}
> > +
> >  /*
> >   * Check if a bio or request operation is a zone management operation, with
> >   * the exception of REQ_OP_ZONE_RESET_ALL which is treated as a special case
> > @@ -565,4 +572,11 @@ struct blk_rq_stat {
> >       u64 batch;
> >  };
> >
> > +struct blk_copy_payload {
> > +     sector_t        dest;
> > +     int             copy_nr_ranges;
> > +     struct block_device *src_bdev;
> > +     struct  range_entry     range[];
> > +};
> > +
> >  #endif /* __LINUX_BLK_TYPES_H */
> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > index 699ace6b25ff..2bb4513d4bb8 100644
> > --- a/include/linux/blkdev.h
> > +++ b/include/linux/blkdev.h
> > @@ -337,10 +337,14 @@ struct queue_limits {
> >       unsigned int            max_zone_append_sectors;
> >       unsigned int            discard_granularity;
> >       unsigned int            discard_alignment;
> > +     unsigned int            copy_offload;
> > +     unsigned int            max_copy_sectors;
> >
> >       unsigned short          max_segments;
> >       unsigned short          max_integrity_segments;
> >       unsigned short          max_discard_segments;
> > +     unsigned short          max_copy_range_sectors;
> > +     unsigned short          max_copy_nr_ranges;
> >
> >       unsigned char           misaligned;
> >       unsigned char           discard_misaligned;
> > @@ -621,6 +625,7 @@ struct request_queue {
> >  #define QUEUE_FLAG_RQ_ALLOC_TIME 27  /* record rq->alloc_time_ns */
> >  #define QUEUE_FLAG_HCTX_ACTIVE       28      /* at least one blk-mq hctx is active */
> >  #define QUEUE_FLAG_NOWAIT       29   /* device supports NOWAIT */
> > +#define QUEUE_FLAG_SIMPLE_COPY       30      /* supports simple copy */
> >
> >  #define QUEUE_FLAG_MQ_DEFAULT        ((1 << QUEUE_FLAG_IO_STAT) |            \
> >                                (1 << QUEUE_FLAG_SAME_COMP) |          \
> > @@ -643,6 +648,7 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
> >  #define blk_queue_io_stat(q) test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
> >  #define blk_queue_add_random(q)      test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
> >  #define blk_queue_discard(q) test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
> > +#define blk_queue_copy(q)    test_bit(QUEUE_FLAG_SIMPLE_COPY, &(q)->queue_flags)
> >  #define blk_queue_zone_resetall(q)   \
> >       test_bit(QUEUE_FLAG_ZONE_RESETALL, &(q)->queue_flags)
> >  #define blk_queue_secure_erase(q) \
> > @@ -1069,6 +1075,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
> >               return min(q->limits.max_discard_sectors,
> >                          UINT_MAX >> SECTOR_SHIFT);
> >
> > +     if (unlikely(op == REQ_OP_COPY))
> > +             return q->limits.max_copy_sectors;
> > +
>
> I would agreee with this if a copy BIO was always a single range, but that is
> not the case. So I am not sure this makes sense at all.
>
> >       if (unlikely(op == REQ_OP_WRITE_SAME))
> >               return q->limits.max_write_same_sectors;
> >
> > @@ -1343,6 +1352,12 @@ extern int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
> >               sector_t nr_sects, gfp_t gfp_mask, int flags,
> >               struct bio **biop);
> >
> > +#define BLKDEV_COPY_NOEMULATION      (1 << 0)        /* do not emulate if copy offload not supported */
> > +
> > +extern int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
> > +             struct range_entry *src_rlist, struct block_device *dest_bdev,
> > +             sector_t dest, gfp_t gfp_mask, int flags);
>
> No need for extern.
>
> > +
> >  #define BLKDEV_ZERO_NOUNMAP  (1 << 0)  /* do not free blocks */
> >  #define BLKDEV_ZERO_NOFALLBACK       (1 << 1)  /* don't write explicit zeroes */
> >
> > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> > index f44eb0a04afd..5cadb176317a 100644
> > --- a/include/uapi/linux/fs.h
> > +++ b/include/uapi/linux/fs.h
> > @@ -64,6 +64,18 @@ struct fstrim_range {
> >       __u64 minlen;
> >  };
> >
> > +struct range_entry {
> > +     __u64 src;
> > +     __u64 len;
> > +};
> > +
> > +struct copy_range {
> > +     __u64 dest;
> > +     __u64 nr_range;
> > +     __u64 range_list;
> > +     __u64 rsvd;
> > +};
> > +
> >  /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
> >  #define FILE_DEDUPE_RANGE_SAME               0
> >  #define FILE_DEDUPE_RANGE_DIFFERS    1
> > @@ -184,6 +196,7 @@ struct fsxattr {
> >  #define BLKSECDISCARD _IO(0x12,125)
> >  #define BLKROTATIONAL _IO(0x12,126)
> >  #define BLKZEROOUT _IO(0x12,127)
> > +#define BLKCOPY _IOWR(0x12, 128, struct copy_range)
> >  /*
> >   * A jump here: 130-131 are reserved for zoned block devices
> >   * (see uapi/linux/blkzoned.h)
> >
>
> Please test your code more thoroughly. It is full of problems that you should
> have detected with better testing including RO devices, partitions and error
> path coverage.
>
> --
> Damien Le Moal
> Western Digital Research

Damien Le Moal April 12, 2021, 12:24 a.m. UTC | #3

On 2021/04/07 20:33, Selva Jove wrote:
> Initially I started moving the dm-kcopyd interface to the block layer
> as a generic interface.
> Once I dig deeper in dm-kcopyd code, I figured that dm-kcopyd is
> tightly coupled with dm_io()
> 
> To move dm-kcopyd to block layer, it would also require dm_io code to
> be moved to block layer.
> It would cause havoc in dm layer, as it is the backbone of the
> dm-layer and needs complete
> rewriting of dm-layer. Do you see any other way of doing this without
> having to move dm_io code
> or to have redundant code ?

Right. Missed that. So reusing dm-kcopyd and making it a common interface will
take some more efforts. OK, then. For the first round of commits, let's forget
about this. But I still think that your emulation could be a lot better than a
loop doing blocking writes after blocking reads.

[...]
>>> +int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
>>> +             struct range_entry *src_rlist, struct block_device *dest_bdev,
>>> +             sector_t dest, gfp_t gfp_mask, int flags)
>>> +{
>>> +     struct request_queue *q = bdev_get_queue(src_bdev);
>>> +     struct request_queue *dest_q = bdev_get_queue(dest_bdev);
>>> +     struct blk_copy_payload *payload;
>>> +     sector_t bs_mask, copy_size;
>>> +     int ret;
>>> +
>>> +     ret = blk_prepare_payload(src_bdev, nr_srcs, src_rlist, gfp_mask,
>>> +                     &payload, &copy_size);
>>> +     if (ret)
>>> +             return ret;
>>> +
>>> +     bs_mask = (bdev_logical_block_size(dest_bdev) >> 9) - 1;
>>> +     if (dest & bs_mask) {
>>> +             return -EINVAL;
>>> +             goto out;
>>> +     }
>>> +
>>> +     if (q == dest_q && q->limits.copy_offload) {
>>> +             ret = blk_copy_offload(src_bdev, payload, dest, gfp_mask);
>>> +             if (ret)
>>> +                     goto out;
>>> +     } else if (flags & BLKDEV_COPY_NOEMULATION) {
>>
>> Why ? whoever calls blkdev_issue_copy() wants a copy to be done. Why would that
>> user say "Fail on me if the device does not support copy" ??? This is a weird
>> interface in my opinion.
>>
> 
> BLKDEV_COPY_NOEMULATION flag was introduced to allow blkdev_issue_copy() callers
> to use their native copying method instead of the emulated copy that I
> added. This way we
> ensure that dm uses the hw-assisted copy and if that is not present,
> it falls back to existing
> copy method.
> 
> The other users who don't have their native emulation can use this
> emulated-copy implementation.

I do not understand. Emulation or not should be entirely driven by the device
reporting support for simple copy (or not). It does not matter which component
is issuing the simple copy call: an FS to a real device, and FS to a DM device
or a DM target driver. If the underlying device reported support for simple
copy, use that. Otherwise, emulate with read/write. What am I missing here ?

[...]
>>> @@ -565,6 +569,12 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
>>>       if (b->chunk_sectors)
>>>               t->chunk_sectors = gcd(t->chunk_sectors, b->chunk_sectors);
>>>
>>> +     /* simple copy not supported in stacked devices */
>>> +     t->copy_offload = 0;
>>> +     t->max_copy_sectors = 0;
>>> +     t->max_copy_range_sectors = 0;
>>> +     t->max_copy_nr_ranges = 0;
>>
>> You do not need this. Limits not explicitely initialized are 0 already.
>> But I do not see why you can't support copy on stacked devices. That should be
>> feasible taking the min() for each of the above limit.
>>
> 
> Disabling stacked device support was feedback from v2.
> 
> https://patchwork.kernel.org/project/linux-block/patch/[e-mail]/

Right. But the initialization to 0 is still not needed. The fields are already
initialized to 0.

Selva Jove April 12, 2021, 2:34 p.m. UTC | #4

On Mon, Apr 12, 2021 at 5:55 AM Damien Le Moal <[e-mail]> wrote:
>
> On 2021/04/07 20:33, Selva Jove wrote:
> > Initially I started moving the dm-kcopyd interface to the block layer
> > as a generic interface.
> > Once I dig deeper in dm-kcopyd code, I figured that dm-kcopyd is
> > tightly coupled with dm_io()
> >
> > To move dm-kcopyd to block layer, it would also require dm_io code to
> > be moved to block layer.
> > It would cause havoc in dm layer, as it is the backbone of the
> > dm-layer and needs complete
> > rewriting of dm-layer. Do you see any other way of doing this without
> > having to move dm_io code
> > or to have redundant code ?
>
> Right. Missed that. So reusing dm-kcopyd and making it a common interface will
> take some more efforts. OK, then. For the first round of commits, let's forget
> about this. But I still think that your emulation could be a lot better than a
> loop doing blocking writes after blocking reads.
>

Current implementation issues read asynchronously and once all the reads are
completed, then the write is issued as whole to reduce the IO traffic
in the queue.
I agree that things can be better. Will explore another approach of
sending writes
immediately once reads are completed and with  plugging to increase the chances
of merging.

> [...]
> >>> +int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
> >>> +             struct range_entry *src_rlist, struct block_device *dest_bdev,
> >>> +             sector_t dest, gfp_t gfp_mask, int flags)
> >>> +{
> >>> +     struct request_queue *q = bdev_get_queue(src_bdev);
> >>> +     struct request_queue *dest_q = bdev_get_queue(dest_bdev);
> >>> +     struct blk_copy_payload *payload;
> >>> +     sector_t bs_mask, copy_size;
> >>> +     int ret;
> >>> +
> >>> +     ret = blk_prepare_payload(src_bdev, nr_srcs, src_rlist, gfp_mask,
> >>> +                     &payload, &copy_size);
> >>> +     if (ret)
> >>> +             return ret;
> >>> +
> >>> +     bs_mask = (bdev_logical_block_size(dest_bdev) >> 9) - 1;
> >>> +     if (dest & bs_mask) {
> >>> +             return -EINVAL;
> >>> +             goto out;
> >>> +     }
> >>> +
> >>> +     if (q == dest_q && q->limits.copy_offload) {
> >>> +             ret = blk_copy_offload(src_bdev, payload, dest, gfp_mask);
> >>> +             if (ret)
> >>> +                     goto out;
> >>> +     } else if (flags & BLKDEV_COPY_NOEMULATION) {
> >>
> >> Why ? whoever calls blkdev_issue_copy() wants a copy to be done. Why would that
> >> user say "Fail on me if the device does not support copy" ??? This is a weird
> >> interface in my opinion.
> >>
> >
> > BLKDEV_COPY_NOEMULATION flag was introduced to allow blkdev_issue_copy() callers
> > to use their native copying method instead of the emulated copy that I
> > added. This way we
> > ensure that dm uses the hw-assisted copy and if that is not present,
> > it falls back to existing
> > copy method.
> >
> > The other users who don't have their native emulation can use this
> > emulated-copy implementation.
>
> I do not understand. Emulation or not should be entirely driven by the device
> reporting support for simple copy (or not). It does not matter which component
> is issuing the simple copy call: an FS to a real device, and FS to a DM device
> or a DM target driver. If the underlying device reported support for simple
> copy, use that. Otherwise, emulate with read/write. What am I missing here ?
>

blkdev_issue_copy() api will generally complete the copy-operation,
either by using
offloaded-copy or by using emulated-copy. The caller of the api is not
required to
figure the type of support. However, it can opt out of emulated-copy
by specifying
the flag BLKDEV_NOEMULATION. This is helpful for the case when the
caller already
has got a sophisticated emulation (e.g. dm-kcopyd users).

>
> [...]
> >>> @@ -565,6 +569,12 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
> >>>       if (b->chunk_sectors)
> >>>               t->chunk_sectors = gcd(t->chunk_sectors, b->chunk_sectors);
> >>>
> >>> +     /* simple copy not supported in stacked devices */
> >>> +     t->copy_offload = 0;
> >>> +     t->max_copy_sectors = 0;
> >>> +     t->max_copy_range_sectors = 0;
> >>> +     t->max_copy_nr_ranges = 0;
> >>
> >> You do not need this. Limits not explicitely initialized are 0 already.
> >> But I do not see why you can't support copy on stacked devices. That should be
> >> feasible taking the min() for each of the above limit.
> >>
> >
> > Disabling stacked device support was feedback from v2.
> >
> > https://patchwork.kernel.org/project/linux-block/patch/[e-mail]/
>
> Right. But the initialization to 0 is still not needed. The fields are already
> initialized to 0.
>
>
> --
> Damien Le Moal
> Western Digital Research

Damien Le Moal April 13, 2021, 12:32 a.m. UTC | #5

On 2021/04/12 23:35, Selva Jove wrote:
> On Mon, Apr 12, 2021 at 5:55 AM Damien Le Moal <[e-mail]> wrote:
>>
>> On 2021/04/07 20:33, Selva Jove wrote:
>>> Initially I started moving the dm-kcopyd interface to the block layer
>>> as a generic interface.
>>> Once I dig deeper in dm-kcopyd code, I figured that dm-kcopyd is
>>> tightly coupled with dm_io()
>>>
>>> To move dm-kcopyd to block layer, it would also require dm_io code to
>>> be moved to block layer.
>>> It would cause havoc in dm layer, as it is the backbone of the
>>> dm-layer and needs complete
>>> rewriting of dm-layer. Do you see any other way of doing this without
>>> having to move dm_io code
>>> or to have redundant code ?
>>
>> Right. Missed that. So reusing dm-kcopyd and making it a common interface will
>> take some more efforts. OK, then. For the first round of commits, let's forget
>> about this. But I still think that your emulation could be a lot better than a
>> loop doing blocking writes after blocking reads.
>>
> 
> Current implementation issues read asynchronously and once all the reads are
> completed, then the write is issued as whole to reduce the IO traffic
> in the queue.
> I agree that things can be better. Will explore another approach of
> sending writes
> immediately once reads are completed and with  plugging to increase the chances
> of merging.
> 
>> [...]
>>>>> +int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
>>>>> +             struct range_entry *src_rlist, struct block_device *dest_bdev,
>>>>> +             sector_t dest, gfp_t gfp_mask, int flags)
>>>>> +{
>>>>> +     struct request_queue *q = bdev_get_queue(src_bdev);
>>>>> +     struct request_queue *dest_q = bdev_get_queue(dest_bdev);
>>>>> +     struct blk_copy_payload *payload;
>>>>> +     sector_t bs_mask, copy_size;
>>>>> +     int ret;
>>>>> +
>>>>> +     ret = blk_prepare_payload(src_bdev, nr_srcs, src_rlist, gfp_mask,
>>>>> +                     &payload, &copy_size);
>>>>> +     if (ret)
>>>>> +             return ret;
>>>>> +
>>>>> +     bs_mask = (bdev_logical_block_size(dest_bdev) >> 9) - 1;
>>>>> +     if (dest & bs_mask) {
>>>>> +             return -EINVAL;
>>>>> +             goto out;
>>>>> +     }
>>>>> +
>>>>> +     if (q == dest_q && q->limits.copy_offload) {
>>>>> +             ret = blk_copy_offload(src_bdev, payload, dest, gfp_mask);
>>>>> +             if (ret)
>>>>> +                     goto out;
>>>>> +     } else if (flags & BLKDEV_COPY_NOEMULATION) {
>>>>
>>>> Why ? whoever calls blkdev_issue_copy() wants a copy to be done. Why would that
>>>> user say "Fail on me if the device does not support copy" ??? This is a weird
>>>> interface in my opinion.
>>>>
>>>
>>> BLKDEV_COPY_NOEMULATION flag was introduced to allow blkdev_issue_copy() callers
>>> to use their native copying method instead of the emulated copy that I
>>> added. This way we
>>> ensure that dm uses the hw-assisted copy and if that is not present,
>>> it falls back to existing
>>> copy method.
>>>
>>> The other users who don't have their native emulation can use this
>>> emulated-copy implementation.
>>
>> I do not understand. Emulation or not should be entirely driven by the device
>> reporting support for simple copy (or not). It does not matter which component
>> is issuing the simple copy call: an FS to a real device, and FS to a DM device
>> or a DM target driver. If the underlying device reported support for simple
>> copy, use that. Otherwise, emulate with read/write. What am I missing here ?
>>
> 
> blkdev_issue_copy() api will generally complete the copy-operation,
> either by using
> offloaded-copy or by using emulated-copy. The caller of the api is not
> required to
> figure the type of support. However, it can opt out of emulated-copy
> by specifying
> the flag BLKDEV_NOEMULATION. This is helpful for the case when the
> caller already
> has got a sophisticated emulation (e.g. dm-kcopyd users).

This does not make any sense to me. If the user has already another mean of
doing copies, then that user will not call blkdev_issue_copy(). So I really do
not understand what the "opting out of emulated copy" would be useful for. That
user can check the simple copy support glag in the device request queue and act
accordingly: use its own block copy code when simple copy is not supported or
use blkdev_issue_copy() when the device has simple copy. Adding that
BLKDEV_COPY_NOEMULATION does not serve any purpose at all.

Selva Jove April 14, 2021, 6:58 a.m. UTC | #6

I agree with you. Will remove BLKDEV_COPY_NOEMULATION.

On Tue, Apr 13, 2021 at 6:03 AM Damien Le Moal <[e-mail]> wrote:
>
> On 2021/04/12 23:35, Selva Jove wrote:
> > On Mon, Apr 12, 2021 at 5:55 AM Damien Le Moal <[e-mail]> wrote:
> >>
> >> On 2021/04/07 20:33, Selva Jove wrote:
> >>> Initially I started moving the dm-kcopyd interface to the block layer
> >>> as a generic interface.
> >>> Once I dig deeper in dm-kcopyd code, I figured that dm-kcopyd is
> >>> tightly coupled with dm_io()
> >>>
> >>> To move dm-kcopyd to block layer, it would also require dm_io code to
> >>> be moved to block layer.
> >>> It would cause havoc in dm layer, as it is the backbone of the
> >>> dm-layer and needs complete
> >>> rewriting of dm-layer. Do you see any other way of doing this without
> >>> having to move dm_io code
> >>> or to have redundant code ?
> >>
> >> Right. Missed that. So reusing dm-kcopyd and making it a common interface will
> >> take some more efforts. OK, then. For the first round of commits, let's forget
> >> about this. But I still think that your emulation could be a lot better than a
> >> loop doing blocking writes after blocking reads.
> >>
> >
> > Current implementation issues read asynchronously and once all the reads are
> > completed, then the write is issued as whole to reduce the IO traffic
> > in the queue.
> > I agree that things can be better. Will explore another approach of
> > sending writes
> > immediately once reads are completed and with  plugging to increase the chances
> > of merging.
> >
> >> [...]
> >>>>> +int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
> >>>>> +             struct range_entry *src_rlist, struct block_device *dest_bdev,
> >>>>> +             sector_t dest, gfp_t gfp_mask, int flags)
> >>>>> +{
> >>>>> +     struct request_queue *q = bdev_get_queue(src_bdev);
> >>>>> +     struct request_queue *dest_q = bdev_get_queue(dest_bdev);
> >>>>> +     struct blk_copy_payload *payload;
> >>>>> +     sector_t bs_mask, copy_size;
> >>>>> +     int ret;
> >>>>> +
> >>>>> +     ret = blk_prepare_payload(src_bdev, nr_srcs, src_rlist, gfp_mask,
> >>>>> +                     &payload, &copy_size);
> >>>>> +     if (ret)
> >>>>> +             return ret;
> >>>>> +
> >>>>> +     bs_mask = (bdev_logical_block_size(dest_bdev) >> 9) - 1;
> >>>>> +     if (dest & bs_mask) {
> >>>>> +             return -EINVAL;
> >>>>> +             goto out;
> >>>>> +     }
> >>>>> +
> >>>>> +     if (q == dest_q && q->limits.copy_offload) {
> >>>>> +             ret = blk_copy_offload(src_bdev, payload, dest, gfp_mask);
> >>>>> +             if (ret)
> >>>>> +                     goto out;
> >>>>> +     } else if (flags & BLKDEV_COPY_NOEMULATION) {
> >>>>
> >>>> Why ? whoever calls blkdev_issue_copy() wants a copy to be done. Why would that
> >>>> user say "Fail on me if the device does not support copy" ??? This is a weird
> >>>> interface in my opinion.
> >>>>
> >>>
> >>> BLKDEV_COPY_NOEMULATION flag was introduced to allow blkdev_issue_copy() callers
> >>> to use their native copying method instead of the emulated copy that I
> >>> added. This way we
> >>> ensure that dm uses the hw-assisted copy and if that is not present,
> >>> it falls back to existing
> >>> copy method.
> >>>
> >>> The other users who don't have their native emulation can use this
> >>> emulated-copy implementation.
> >>
> >> I do not understand. Emulation or not should be entirely driven by the device
> >> reporting support for simple copy (or not). It does not matter which component
> >> is issuing the simple copy call: an FS to a real device, and FS to a DM device
> >> or a DM target driver. If the underlying device reported support for simple
> >> copy, use that. Otherwise, emulate with read/write. What am I missing here ?
> >>
> >
> > blkdev_issue_copy() api will generally complete the copy-operation,
> > either by using
> > offloaded-copy or by using emulated-copy. The caller of the api is not
> > required to
> > figure the type of support. However, it can opt out of emulated-copy
> > by specifying
> > the flag BLKDEV_NOEMULATION. This is helpful for the case when the
> > caller already
> > has got a sophisticated emulation (e.g. dm-kcopyd users).
>
> This does not make any sense to me. If the user has already another mean of
> doing copies, then that user will not call blkdev_issue_copy(). So I really do
> not understand what the "opting out of emulated copy" would be useful for. That
> user can check the simple copy support glag in the device request queue and act
> accordingly: use its own block copy code when simple copy is not supported or
> use blkdev_issue_copy() when the device has simple copy. Adding that
> BLKDEV_COPY_NOEMULATION does not serve any purpose at all.
>
>
>
> --
> Damien Le Moal
> Western Digital Research

Patch

diff --git a/block/blk-core.c b/block/blk-core.c
index 7663a9b94b80..23e646e5ae43 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -720,6 +720,17 @@  static noinline int should_fail_bio(struct bio *bio)
 }
 ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);
 
+static inline int bio_check_copy_eod(struct bio *bio, sector_t start,
+		sector_t nr_sectors, sector_t max_sect)
+{
+	if (nr_sectors && max_sect &&
+	    (nr_sectors > max_sect || start > max_sect - nr_sectors)) {
+		handle_bad_sector(bio, max_sect);
+		return -EIO;
+	}
+	return 0;
+}
+
 /*
  * Check whether this bio extends beyond the end of the device or partition.
  * This may well happen - the kernel calls bread() without checking the size of
@@ -738,6 +749,75 @@  static inline int bio_check_eod(struct bio *bio, sector_t maxsector)
 	return 0;
 }
 
+/*
+ * Check for copy limits and remap source ranges if needed.
+ */
+static int blk_check_copy(struct bio *bio)
+{
+	struct blk_copy_payload *payload = bio_data(bio);
+	struct request_queue *q = bio->bi_disk->queue;
+	sector_t max_sect, start_sect, copy_size = 0;
+	sector_t src_max_sect, src_start_sect;
+	struct block_device *bd_part;
+	int i, ret = -EIO;
+
+	rcu_read_lock();
+
+	bd_part = __disk_get_part(bio->bi_disk, bio->bi_partno);
+	if (unlikely(!bd_part)) {
+		rcu_read_unlock();
+		goto out;
+	}
+
+	max_sect =  bdev_nr_sectors(bd_part);
+	start_sect = bd_part->bd_start_sect;
+
+	src_max_sect = bdev_nr_sectors(payload->src_bdev);
+	src_start_sect = payload->src_bdev->bd_start_sect;
+
+	if (unlikely(should_fail_request(bd_part, bio->bi_iter.bi_size)))
+		goto out;
+
+	if (unlikely(bio_check_ro(bio, bd_part)))
+		goto out;
+
+	rcu_read_unlock();
+
+	/* cannot handle copy crossing nr_ranges limit */
+	if (payload->copy_nr_ranges > q->limits.max_copy_nr_ranges)
+		goto out;
+
+	for (i = 0; i < payload->copy_nr_ranges; i++) {
+		ret = bio_check_copy_eod(bio, payload->range[i].src,
+				payload->range[i].len, src_max_sect);
+		if (unlikely(ret))
+			goto out;
+
+		/* single source range length limit */
+		if (payload->range[i].len > q->limits.max_copy_range_sectors)
+			goto out;
+
+		payload->range[i].src += src_start_sect;
+		copy_size += payload->range[i].len;
+	}
+
+	/* check if copy length crosses eod */
+	ret = bio_check_copy_eod(bio, bio->bi_iter.bi_sector,
+				copy_size, max_sect);
+	if (unlikely(ret))
+		goto out;
+
+	/* cannot handle copy more than copy limits */
+	if (copy_size > q->limits.max_copy_sectors)
+		goto out;
+
+	bio->bi_iter.bi_sector += start_sect;
+	bio->bi_partno = 0;
+	ret = 0;
+out:
+	return ret;
+}
+
 /*
  * Remap block n of partition p to block n+start(p) of the disk.
  */
@@ -827,14 +907,16 @@  static noinline_for_stack bool submit_bio_checks(struct bio *bio)
 	if (should_fail_bio(bio))
 		goto end_io;
 
-	if (bio->bi_partno) {
-		if (unlikely(blk_partition_remap(bio)))
-			goto end_io;
-	} else {
-		if (unlikely(bio_check_ro(bio, bio->bi_disk->part0)))
-			goto end_io;
-		if (unlikely(bio_check_eod(bio, get_capacity(bio->bi_disk))))
-			goto end_io;
+	if (likely(!op_is_copy(bio->bi_opf))) {
+		if (bio->bi_partno) {
+			if (unlikely(blk_partition_remap(bio)))
+				goto end_io;
+		} else {
+			if (unlikely(bio_check_ro(bio, bio->bi_disk->part0)))
+				goto end_io;
+			if (unlikely(bio_check_eod(bio, get_capacity(bio->bi_disk))))
+				goto end_io;
+		}
 	}
 
 	/*
@@ -858,6 +940,10 @@  static noinline_for_stack bool submit_bio_checks(struct bio *bio)
 		if (!blk_queue_discard(q))
 			goto not_supported;
 		break;
+	case REQ_OP_COPY:
+		if (unlikely(blk_check_copy(bio)))
+			goto end_io;
+		break;
 	case REQ_OP_SECURE_ERASE:
 		if (!blk_queue_secure_erase(q))
 			goto not_supported;
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 752f9c722062..97ba58d8d9a1 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -150,6 +150,228 @@  int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 }
 EXPORT_SYMBOL(blkdev_issue_discard);
 
+int blk_copy_offload(struct block_device *dest_bdev, struct blk_copy_payload *payload,
+		sector_t dest, gfp_t gfp_mask)
+{
+	struct request_queue *q = bdev_get_queue(dest_bdev);
+	struct bio *bio;
+	int ret, payload_size;
+
+	payload_size = struct_size(payload, range, payload->copy_nr_ranges);
+	bio = bio_map_kern(q, payload, payload_size, gfp_mask);
+	if (IS_ERR(bio)) {
+		ret = PTR_ERR(bio);
+		goto err;
+	}
+
+	bio->bi_iter.bi_sector = dest;
+	bio->bi_opf = REQ_OP_COPY | REQ_NOMERGE;
+	bio_set_dev(bio, dest_bdev);
+
+	ret = submit_bio_wait(bio);
+err:
+	bio_put(bio);
+	return ret;
+}
+
+int blk_read_to_buf(struct block_device *src_bdev, struct blk_copy_payload *payload,
+		gfp_t gfp_mask, sector_t copy_size, void **buf_p)
+{
+	struct request_queue *q = bdev_get_queue(src_bdev);
+	struct bio *bio, *parent = NULL;
+	void *buf = NULL;
+	int copy_len = copy_size << SECTOR_SHIFT;
+	int i, nr_srcs, ret, cur_size, t_len = 0;
+	bool is_vmalloc;
+
+	nr_srcs = payload->copy_nr_ranges;
+
+	buf = kvmalloc(copy_len, gfp_mask);
+	if (!buf)
+		return -ENOMEM;
+	is_vmalloc = is_vmalloc_addr(buf);
+
+	for (i = 0; i < nr_srcs; i++) {
+		cur_size = payload->range[i].len << SECTOR_SHIFT;
+
+		bio = bio_map_kern(q, buf + t_len, cur_size, gfp_mask);
+		if (IS_ERR(bio)) {
+			ret = PTR_ERR(bio);
+			goto out;
+		}
+
+		bio->bi_iter.bi_sector = payload->range[i].src;
+		bio->bi_opf = REQ_OP_READ;
+		bio_set_dev(bio, src_bdev);
+		bio->bi_end_io = NULL;
+		bio->bi_private = NULL;
+
+		if (parent) {
+			bio_chain(parent, bio);
+			submit_bio(parent);
+		}
+
+		parent = bio;
+		t_len += cur_size;
+	}
+
+	ret = submit_bio_wait(bio);
+	bio_put(bio);
+	if (is_vmalloc)
+		invalidate_kernel_vmap_range(buf, copy_len);
+	if (ret)
+		goto out;
+
+	*buf_p = buf;
+	return 0;
+out:
+	kvfree(buf);
+	return ret;
+}
+
+int blk_write_from_buf(struct block_device *dest_bdev, void *buf, sector_t dest,
+		sector_t copy_size, gfp_t gfp_mask)
+{
+	struct request_queue *q = bdev_get_queue(dest_bdev);
+	struct bio *bio;
+	int ret, copy_len = copy_size << SECTOR_SHIFT;
+
+	bio = bio_map_kern(q, buf, copy_len, gfp_mask);
+	if (IS_ERR(bio)) {
+		ret = PTR_ERR(bio);
+		goto out;
+	}
+	bio_set_dev(bio, dest_bdev);
+	bio->bi_opf = REQ_OP_WRITE;
+	bio->bi_iter.bi_sector = dest;
+
+	bio->bi_end_io = NULL;
+	ret = submit_bio_wait(bio);
+	bio_put(bio);
+out:
+	return ret;
+}
+
+int blk_prepare_payload(struct block_device *src_bdev, int nr_srcs, struct range_entry *rlist,
+		gfp_t gfp_mask, struct blk_copy_payload **payload_p, sector_t *copy_size)
+{
+
+	struct request_queue *q = bdev_get_queue(src_bdev);
+	struct blk_copy_payload *payload;
+	sector_t bs_mask, total_len = 0;
+	int i, ret, payload_size;
+
+	if (!q)
+		return -ENXIO;
+
+	if (!nr_srcs)
+		return -EINVAL;
+
+	if (bdev_read_only(src_bdev))
+		return -EPERM;
+
+	bs_mask = (bdev_logical_block_size(src_bdev) >> 9) - 1;
+
+	payload_size = struct_size(payload, range, nr_srcs);
+	payload = kmalloc(payload_size, gfp_mask);
+	if (!payload)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_srcs; i++) {
+		if (rlist[i].src & bs_mask || rlist[i].len & bs_mask) {
+			ret = -EINVAL;
+			goto err;
+		}
+
+		payload->range[i].src = rlist[i].src;
+		payload->range[i].len = rlist[i].len;
+
+		total_len += rlist[i].len;
+	}
+
+	payload->copy_nr_ranges = i;
+	payload->src_bdev = src_bdev;
+	*copy_size = total_len;
+
+	*payload_p = payload;
+	return 0;
+err:
+	kfree(payload);
+	return ret;
+}
+
+int blk_copy_emulate(struct block_device *src_bdev, struct blk_copy_payload *payload,
+			struct block_device *dest_bdev, sector_t dest,
+			sector_t copy_size, gfp_t gfp_mask)
+{
+	void *buf = NULL;
+	int ret;
+
+	ret = blk_read_to_buf(src_bdev, payload, gfp_mask, copy_size, &buf);
+	if (ret)
+		goto out;
+
+	ret = blk_write_from_buf(dest_bdev, buf, dest, copy_size, gfp_mask);
+	if (buf)
+		kvfree(buf);
+out:
+	return ret;
+}
+
+/**
+ * blkdev_issue_copy - queue a copy
+ * @src_bdev:	source block device
+ * @nr_srcs:	number of source ranges to copy
+ * @rlist:	array of source ranges in sector
+ * @dest_bdev:	destination block device
+ * @dest:	destination in sector
+ * @gfp_mask:   memory allocation flags (for bio_alloc)
+ * @flags:	BLKDEV_COPY_* flags to control behaviour
+ *
+ * Description:
+ *	Copy array of source ranges from source block device to
+ *	destination block devcie. All source must belong to same bdev and
+ *	length of a source range cannot be zero.
+ */
+
+int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
+		struct range_entry *src_rlist, struct block_device *dest_bdev,
+		sector_t dest, gfp_t gfp_mask, int flags)
+{
+	struct request_queue *q = bdev_get_queue(src_bdev);
+	struct request_queue *dest_q = bdev_get_queue(dest_bdev);
+	struct blk_copy_payload *payload;
+	sector_t bs_mask, copy_size;
+	int ret;
+
+	ret = blk_prepare_payload(src_bdev, nr_srcs, src_rlist, gfp_mask,
+			&payload, &copy_size);
+	if (ret)
+		return ret;
+
+	bs_mask = (bdev_logical_block_size(dest_bdev) >> 9) - 1;
+	if (dest & bs_mask) {
+		return -EINVAL;
+		goto out;
+	}
+
+	if (q == dest_q && q->limits.copy_offload) {
+		ret = blk_copy_offload(src_bdev, payload, dest, gfp_mask);
+		if (ret)
+			goto out;
+	} else if (flags & BLKDEV_COPY_NOEMULATION) {
+		ret = -EIO;
+		goto out;
+	} else
+		ret = blk_copy_emulate(src_bdev, payload, dest_bdev, dest,
+				copy_size, gfp_mask);
+
+out:
+	kvfree(payload);
+	return ret;
+}
+EXPORT_SYMBOL(blkdev_issue_copy);
+
 /**
  * __blkdev_issue_write_same - generate number of bios with same page
  * @bdev:	target blockdev
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 808768f6b174..4e04f24e13c1 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -309,6 +309,8 @@  void __blk_queue_split(struct bio **bio, unsigned int *nr_segs)
 	struct bio *split = NULL;
 
 	switch (bio_op(*bio)) {
+	case REQ_OP_COPY:
+			break;
 	case REQ_OP_DISCARD:
 	case REQ_OP_SECURE_ERASE:
 		split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs);
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 43990b1d148b..93c15ba45a69 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -60,6 +60,10 @@  void blk_set_default_limits(struct queue_limits *lim)
 	lim->io_opt = 0;
 	lim->misaligned = 0;
 	lim->zoned = BLK_ZONED_NONE;
+	lim->copy_offload = 0;
+	lim->max_copy_sectors = 0;
+	lim->max_copy_nr_ranges = 0;
+	lim->max_copy_range_sectors = 0;
 }
 EXPORT_SYMBOL(blk_set_default_limits);
 
@@ -565,6 +569,12 @@  int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 	if (b->chunk_sectors)
 		t->chunk_sectors = gcd(t->chunk_sectors, b->chunk_sectors);
 
+	/* simple copy not supported in stacked devices */
+	t->copy_offload = 0;
+	t->max_copy_sectors = 0;
+	t->max_copy_range_sectors = 0;
+	t->max_copy_nr_ranges = 0;
+
 	/* Physical block size a multiple of the logical block size? */
 	if (t->physical_block_size & (t->logical_block_size - 1)) {
 		t->physical_block_size = t->logical_block_size;
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b513f1683af0..625a72541263 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -166,6 +166,44 @@  static ssize_t queue_discard_granularity_show(struct request_queue *q, char *pag
 	return queue_var_show(q->limits.discard_granularity, page);
 }
 
+static ssize_t queue_copy_offload_show(struct request_queue *q, char *page)
+{
+	return queue_var_show(q->limits.copy_offload, page);
+}
+
+static ssize_t queue_copy_offload_store(struct request_queue *q,
+				       const char *page, size_t count)
+{
+	unsigned long copy_offload;
+	ssize_t ret = queue_var_store(&copy_offload, page, count);
+
+	if (ret < 0)
+		return ret;
+
+	if (copy_offload && q->limits.max_copy_sectors == 0)
+		return -EINVAL;
+
+	q->limits.copy_offload = copy_offload;
+	return ret;
+}
+
+static ssize_t queue_max_copy_sectors_show(struct request_queue *q, char *page)
+{
+	return queue_var_show(q->limits.max_copy_sectors, page);
+}
+
+static ssize_t queue_max_copy_range_sectors_show(struct request_queue *q,
+		char *page)
+{
+	return queue_var_show(q->limits.max_copy_range_sectors, page);
+}
+
+static ssize_t queue_max_copy_nr_ranges_show(struct request_queue *q,
+		char *page)
+{
+	return queue_var_show(q->limits.max_copy_nr_ranges, page);
+}
+
 static ssize_t queue_discard_max_hw_show(struct request_queue *q, char *page)
 {
 
@@ -591,6 +629,11 @@  QUEUE_RO_ENTRY(queue_nr_zones, "nr_zones");
 QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones");
 QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones");
 
+QUEUE_RW_ENTRY(queue_copy_offload, "copy_offload");
+QUEUE_RO_ENTRY(queue_max_copy_sectors, "max_copy_sectors");
+QUEUE_RO_ENTRY(queue_max_copy_range_sectors, "max_copy_range_sectors");
+QUEUE_RO_ENTRY(queue_max_copy_nr_ranges, "max_copy_nr_ranges");
+
 QUEUE_RW_ENTRY(queue_nomerges, "nomerges");
 QUEUE_RW_ENTRY(queue_rq_affinity, "rq_affinity");
 QUEUE_RW_ENTRY(queue_poll, "io_poll");
@@ -636,6 +679,10 @@  static struct attribute *queue_attrs[] = {
 	&queue_discard_max_entry.attr,
 	&queue_discard_max_hw_entry.attr,
 	&queue_discard_zeroes_data_entry.attr,
+	&queue_copy_offload_entry.attr,
+	&queue_max_copy_sectors_entry.attr,
+	&queue_max_copy_range_sectors_entry.attr,
+	&queue_max_copy_nr_ranges_entry.attr,
 	&queue_write_same_max_entry.attr,
 	&queue_write_zeroes_max_entry.attr,
 	&queue_zone_append_max_entry.attr,
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 7a68b6e4300c..02069178d51e 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -75,6 +75,7 @@  bool blk_req_needs_zone_write_lock(struct request *rq)
 	case REQ_OP_WRITE_ZEROES:
 	case REQ_OP_WRITE_SAME:
 	case REQ_OP_WRITE:
+	case REQ_OP_COPY:
 		return blk_rq_zone_is_seq(rq);
 	default:
 		return false;
diff --git a/block/bounce.c b/block/bounce.c
index d3f51acd6e3b..5e052afe8691 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -254,6 +254,7 @@  static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
 
 	switch (bio_op(bio)) {
+	case REQ_OP_COPY:
 	case REQ_OP_DISCARD:
 	case REQ_OP_SECURE_ERASE:
 	case REQ_OP_WRITE_ZEROES:
diff --git a/block/ioctl.c b/block/ioctl.c
index d61d652078f4..0e52181657a4 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -133,6 +133,37 @@  static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
 				    GFP_KERNEL, flags);
 }
 
+static int blk_ioctl_copy(struct block_device *bdev, fmode_t mode,
+		unsigned long arg, unsigned long flags)
+{
+	struct copy_range crange;
+	struct range_entry *rlist;
+	int ret;
+
+	if (!(mode & FMODE_WRITE))
+		return -EBADF;
+
+	if (copy_from_user(&crange, (void __user *)arg, sizeof(crange)))
+		return -EFAULT;
+
+	rlist = kmalloc_array(crange.nr_range, sizeof(*rlist),
+			GFP_KERNEL);
+	if (!rlist)
+		return -ENOMEM;
+
+	if (copy_from_user(rlist, (void __user *)crange.range_list,
+				sizeof(*rlist) * crange.nr_range)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	ret = blkdev_issue_copy(bdev, crange.nr_range, rlist, bdev, crange.dest,
+			GFP_KERNEL, flags);
+out:
+	kfree(rlist);
+	return ret;
+}
+
 static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode,
 		unsigned long arg)
 {
@@ -458,6 +489,8 @@  static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
 	case BLKSECDISCARD:
 		return blk_ioctl_discard(bdev, mode, arg,
 				BLKDEV_DISCARD_SECURE);
+	case BLKCOPY:
+		return blk_ioctl_copy(bdev, mode, arg, 0);
 	case BLKZEROOUT:
 		return blk_ioctl_zeroout(bdev, mode, arg);
 	case BLKREPORTZONE:
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 1edda614f7ce..164313bdfb35 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -71,6 +71,7 @@  static inline bool bio_has_data(struct bio *bio)
 static inline bool bio_no_advance_iter(const struct bio *bio)
 {
 	return bio_op(bio) == REQ_OP_DISCARD ||
+	       bio_op(bio) == REQ_OP_COPY ||
 	       bio_op(bio) == REQ_OP_SECURE_ERASE ||
 	       bio_op(bio) == REQ_OP_WRITE_SAME ||
 	       bio_op(bio) == REQ_OP_WRITE_ZEROES;
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 866f74261b3b..5a35c02ac0a8 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -380,6 +380,8 @@  enum req_opf {
 	REQ_OP_ZONE_RESET	= 15,
 	/* reset all the zone present on the device */
 	REQ_OP_ZONE_RESET_ALL	= 17,
+	/* copy ranges within device */
+	REQ_OP_COPY		= 19,
 
 	/* SCSI passthrough using struct scsi_request */
 	REQ_OP_SCSI_IN		= 32,
@@ -506,6 +508,11 @@  static inline bool op_is_discard(unsigned int op)
 	return (op & REQ_OP_MASK) == REQ_OP_DISCARD;
 }
 
+static inline bool op_is_copy(unsigned int op)
+{
+	return (op & REQ_OP_MASK) == REQ_OP_COPY;
+}
+
 /*
  * Check if a bio or request operation is a zone management operation, with
  * the exception of REQ_OP_ZONE_RESET_ALL which is treated as a special case
@@ -565,4 +572,11 @@  struct blk_rq_stat {
 	u64 batch;
 };
 
+struct blk_copy_payload {
+	sector_t	dest;
+	int		copy_nr_ranges;
+	struct block_device *src_bdev;
+	struct	range_entry	range[];
+};
+
 #endif /* __LINUX_BLK_TYPES_H */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 699ace6b25ff..2bb4513d4bb8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -337,10 +337,14 @@  struct queue_limits {
 	unsigned int		max_zone_append_sectors;
 	unsigned int		discard_granularity;
 	unsigned int		discard_alignment;
+	unsigned int		copy_offload;
+	unsigned int		max_copy_sectors;
 
 	unsigned short		max_segments;
 	unsigned short		max_integrity_segments;
 	unsigned short		max_discard_segments;
+	unsigned short		max_copy_range_sectors;
+	unsigned short		max_copy_nr_ranges;
 
 	unsigned char		misaligned;
 	unsigned char		discard_misaligned;
@@ -621,6 +625,7 @@  struct request_queue {
 #define QUEUE_FLAG_RQ_ALLOC_TIME 27	/* record rq->alloc_time_ns */
 #define QUEUE_FLAG_HCTX_ACTIVE	28	/* at least one blk-mq hctx is active */
 #define QUEUE_FLAG_NOWAIT       29	/* device supports NOWAIT */
+#define QUEUE_FLAG_SIMPLE_COPY	30	/* supports simple copy */
 
 #define QUEUE_FLAG_MQ_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
 				 (1 << QUEUE_FLAG_SAME_COMP) |		\
@@ -643,6 +648,7 @@  bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
 #define blk_queue_io_stat(q)	test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
 #define blk_queue_add_random(q)	test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
 #define blk_queue_discard(q)	test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
+#define blk_queue_copy(q)	test_bit(QUEUE_FLAG_SIMPLE_COPY, &(q)->queue_flags)
 #define blk_queue_zone_resetall(q)	\
 	test_bit(QUEUE_FLAG_ZONE_RESETALL, &(q)->queue_flags)
 #define blk_queue_secure_erase(q) \
@@ -1069,6 +1075,9 @@  static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
 		return min(q->limits.max_discard_sectors,
 			   UINT_MAX >> SECTOR_SHIFT);
 
+	if (unlikely(op == REQ_OP_COPY))
+		return q->limits.max_copy_sectors;
+
 	if (unlikely(op == REQ_OP_WRITE_SAME))
 		return q->limits.max_write_same_sectors;
 
@@ -1343,6 +1352,12 @@  extern int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, int flags,
 		struct bio **biop);
 
+#define BLKDEV_COPY_NOEMULATION	(1 << 0)	/* do not emulate if copy offload not supported */
+
+extern int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs,
+		struct range_entry *src_rlist, struct block_device *dest_bdev,
+		sector_t dest, gfp_t gfp_mask, int flags);
+
 #define BLKDEV_ZERO_NOUNMAP	(1 << 0)  /* do not free blocks */
 #define BLKDEV_ZERO_NOFALLBACK	(1 << 1)  /* don't write explicit zeroes */
 
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index f44eb0a04afd..5cadb176317a 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -64,6 +64,18 @@  struct fstrim_range {
 	__u64 minlen;
 };
 
+struct range_entry {
+	__u64 src;
+	__u64 len;
+};
+
+struct copy_range {
+	__u64 dest;
+	__u64 nr_range;
+	__u64 range_list;
+	__u64 rsvd;
+};
+
 /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
 #define FILE_DEDUPE_RANGE_SAME		0
 #define FILE_DEDUPE_RANGE_DIFFERS	1
@@ -184,6 +196,7 @@  struct fsxattr {
 #define BLKSECDISCARD _IO(0x12,125)
 #define BLKROTATIONAL _IO(0x12,126)
 #define BLKZEROOUT _IO(0x12,127)
+#define BLKCOPY _IOWR(0x12, 128, struct copy_range)
 /*
  * A jump here: 130-131 are reserved for zoned block devices
  * (see uapi/linux/blkzoned.h)