| Message ID | 20220630091406.19624-2-kch@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: add support for REQ_OP_VERIFY | expand |
On Thu, Jun 30, 2022 at 02:14:01AM -0700, Chaitanya Kulkarni wrote: > This adds a new block layer operation to offload verifying a range of > LBAs. This support is needed in order to provide file systems and > fabrics, kernel components to offload LBA verification when it is > supported by the hardware controller. In case hardware offloading is > not supported then we provide API to emulate the same. The prominent > example of that is SCSI and NVMe Verify command. We also provide > an emulation of the same operation that can be used in case H/W does > not support verify. This is still useful when block device is remotely > attached e.g. using NVMeOF. > > Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com> > --- > Documentation/ABI/stable/sysfs-block | 12 +++ > block/blk-core.c | 5 + > block/blk-lib.c | 155 +++++++++++++++++++++++++++ > block/blk-merge.c | 18 ++++ > block/blk-settings.c | 17 +++ > block/blk-sysfs.c | 8 ++ > block/blk.h | 4 + > block/ioctl.c | 35 ++++++ > include/linux/bio.h | 9 +- > include/linux/blk_types.h | 2 + > include/linux/blkdev.h | 22 ++++ > include/uapi/linux/fs.h | 1 + > 12 files changed, 285 insertions(+), 3 deletions(-) > > diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block > index e8797cd09aff..a71d9c41cf8b 100644 > --- a/Documentation/ABI/stable/sysfs-block > +++ b/Documentation/ABI/stable/sysfs-block > @@ -657,6 +657,18 @@ Description: > in a single write zeroes command. If write_zeroes_max_bytes is > 0, write zeroes is not supported by the device. > > +What: /sys/block/<disk>/queue/verify_max_bytes > +Date: April 2022 > +Contact: Chaitanya Kulkarni <kch@nvidia.com> > +Description: > + Devices that support verify operation in which a single > + request can be issued to verify the range of the contiguous > + blocks on the storage without any payload in the request. > + This can be used to optimize verifying LBAs on the device > + without reading by offloading functionality. verify_max_bytes > + indicates how many bytes can be written in a single verify > + command. If verify_max_bytes is 0, verify operation is not > + supported by the device. > > What: /sys/block/<disk>/queue/zone_append_max_bytes > Date: May 2020 > diff --git a/block/blk-core.c b/block/blk-core.c > index 06ff5bbfe8f6..9ad52247dcdf 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -123,6 +123,7 @@ static const char *const blk_op_name[] = { > REQ_OP_NAME(ZONE_FINISH), > REQ_OP_NAME(ZONE_APPEND), > REQ_OP_NAME(WRITE_ZEROES), > + REQ_OP_NAME(VERIFY), > REQ_OP_NAME(DRV_IN), > REQ_OP_NAME(DRV_OUT), > }; > @@ -842,6 +843,10 @@ void submit_bio_noacct(struct bio *bio) > if (!q->limits.max_write_zeroes_sectors) > goto not_supported; > break; > + case REQ_OP_VERIFY: > + if (!q->limits.max_verify_sectors) > + goto not_supported; > + break; > default: > break; > } > diff --git a/block/blk-lib.c b/block/blk-lib.c > index 09b7e1200c0f..4624d68bb3cb 100644 > --- a/block/blk-lib.c > +++ b/block/blk-lib.c > @@ -340,3 +340,158 @@ int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector, > return ret; > } > EXPORT_SYMBOL(blkdev_issue_secure_erase); > + > +/** > + * __blkdev_emulate_verify - emulate number of verify operations > + * asynchronously > + * @bdev: blockdev to issue > + * @sector: start sector > + * @nr_sects: number of sectors to verify > + * @gfp_mask: memory allocation flags (for bio_alloc) > + * @biop: pointer to anchor bio > + * @buf: data buffer to mapped on bio > + * > + * Description: > + * Verify a block range by emulating REQ_OP_VERIFY into REQ_OP_READ, > + * use this when H/W offloading is not supported asynchronously. > + * Caller is responsible to handle anchored bio. > + */ > +static int __blkdev_emulate_verify(struct block_device *bdev, sector_t sector, > + sector_t nr_sects, gfp_t gfp_mask, struct bio **biop, char *buf) > +{ > + struct bio *bio = *biop; > + unsigned int sz; > + int bi_size; > + > + while (nr_sects != 0) { > + bio = blk_next_bio(bio, bdev, > + __blkdev_sectors_to_bio_pages(nr_sects), > + REQ_OP_READ, gfp_mask); > + bio->bi_iter.bi_sector = sector; > + > + while (nr_sects != 0) { > + bool is_vaddr = is_vmalloc_addr(buf); > + struct page *p; > + > + p = is_vaddr ? vmalloc_to_page(buf) : virt_to_page(buf); > + sz = min((sector_t) PAGE_SIZE, nr_sects << 9); > + > + bi_size = bio_add_page(bio, p, sz, offset_in_page(buf)); > + if (bi_size < sz) > + return -EIO; > + > + nr_sects -= bi_size >> 9; > + sector += bi_size >> 9; > + buf += bi_size; > + } > + cond_resched(); > + } > + > + *biop = bio; > + return 0; > +} > + > +/** > + * __blkdev_issue_verify - generate number of verify operations > + * @bdev: blockdev to issue > + * @sector: start sector > + * @nr_sects: number of sectors to verify > + * @gfp_mask: memory allocation flags (for bio_alloc()) > + * @biop: pointer to anchor bio > + * > + * Description: > + * Verify a block range using hardware offload. > + * > + * The function will emulate verify operation if no explicit hardware > + * offloading for verifying is provided. > + */ > +int __blkdev_issue_verify(struct block_device *bdev, sector_t sector, > + sector_t nr_sects, gfp_t gfp_mask, struct bio **biop) > +{ > + unsigned int max_verify_sectors = bdev_verify_sectors(bdev); > + sector_t min_io_sect = (BIO_MAX_VECS << PAGE_SHIFT) >> 9; > + struct bio *bio = *biop; > + sector_t curr_sects; > + char *buf; > + > + if (!max_verify_sectors) { > + int ret = 0; > + > + buf = kzalloc(min_io_sect << 9, GFP_KERNEL); k*z*alloc? I don't think you need to zero a buffer that we're reading into, right? --D > + if (!buf) > + return -ENOMEM; > + > + while (nr_sects > 0) { > + curr_sects = min_t(sector_t, nr_sects, min_io_sect); > + ret = __blkdev_emulate_verify(bdev, sector, curr_sects, > + gfp_mask, &bio, buf); > + if (ret) > + break; > + > + if (bio) { > + ret = submit_bio_wait(bio); > + bio_put(bio); > + bio = NULL; > + } > + > + nr_sects -= curr_sects; > + sector += curr_sects; > + > + } > + /* set the biop to NULL since we have alrady completed above */ > + *biop = NULL; > + kfree(buf); > + return ret; > + } > + > + while (nr_sects) { > + bio = blk_next_bio(bio, bdev, 0, REQ_OP_VERIFY, gfp_mask); > + bio->bi_iter.bi_sector = sector; > + > + if (nr_sects > max_verify_sectors) { > + bio->bi_iter.bi_size = max_verify_sectors << 9; > + nr_sects -= max_verify_sectors; > + sector += max_verify_sectors; > + } else { > + bio->bi_iter.bi_size = nr_sects << 9; > + nr_sects = 0; > + } > + cond_resched(); > + } > + *biop = bio; > + return 0; > +} > +EXPORT_SYMBOL_GPL(__blkdev_issue_verify); > + > +/** > + * blkdev_issue_verify - verify a block range > + * @bdev: blockdev to verify > + * @sector: start sector > + * @nr_sects: number of sectors to verify > + * @gfp_mask: memory allocation flags (for bio_alloc) > + * > + * Description: > + * Verify a block range using hardware offload. > + */ > +int blkdev_issue_verify(struct block_device *bdev, sector_t sector, > + sector_t nr_sects, gfp_t gfp_mask) > +{ > + sector_t bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1; > + struct bio *bio = NULL; > + struct blk_plug plug; > + int ret = 0; > + > + if ((sector | nr_sects) & bs_mask) > + return -EINVAL; > + > + blk_start_plug(&plug); > + ret = __blkdev_issue_verify(bdev, sector, nr_sects, gfp_mask, &bio); > + if (ret == 0 && bio) { > + ret = submit_bio_wait(bio); > + bio_put(bio); > + } > + blk_finish_plug(&plug); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(blkdev_issue_verify); > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 7771dacc99cb..8ff305377b5a 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -153,6 +153,20 @@ static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, > return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); > } > > +static struct bio *blk_bio_verify_split(struct request_queue *q, > + struct bio *bio, struct bio_set *bs, unsigned *nsegs) > +{ > + *nsegs = 0; > + > + if (!q->limits.max_verify_sectors) > + return NULL; > + > + if (bio_sectors(bio) <= q->limits.max_verify_sectors) > + return NULL; > + > + return bio_split(bio, q->limits.max_verify_sectors, GFP_NOIO, bs); > +} > + > /* > * Return the maximum number of sectors from the start of a bio that may be > * submitted as a single request to a block device. If enough sectors remain, > @@ -336,6 +350,10 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio, > split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, > nr_segs); > break; > + case REQ_OP_VERIFY: > + split = blk_bio_verify_split(q, *bio, &q->bio_split, > + nr_segs); > + break; > default: > split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs); > break; > diff --git a/block/blk-settings.c b/block/blk-settings.c > index 6ccceb421ed2..c77697290bc5 100644 > --- a/block/blk-settings.c > +++ b/block/blk-settings.c > @@ -43,6 +43,7 @@ void blk_set_default_limits(struct queue_limits *lim) > lim->max_dev_sectors = 0; > lim->chunk_sectors = 0; > lim->max_write_zeroes_sectors = 0; > + lim->max_verify_sectors = 0; > lim->max_zone_append_sectors = 0; > lim->max_discard_sectors = 0; > lim->max_hw_discard_sectors = 0; > @@ -80,6 +81,7 @@ void blk_set_stacking_limits(struct queue_limits *lim) > lim->max_sectors = UINT_MAX; > lim->max_dev_sectors = UINT_MAX; > lim->max_write_zeroes_sectors = UINT_MAX; > + lim->max_verify_sectors = UINT_MAX; > lim->max_zone_append_sectors = UINT_MAX; > } > EXPORT_SYMBOL(blk_set_stacking_limits); > @@ -202,6 +204,19 @@ void blk_queue_max_write_zeroes_sectors(struct request_queue *q, > } > EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors); > > +/** > + * blk_queue_max_verify_sectors - set max sectors for a single verify > + * > + * @q: the request queue for the device > + * @max_verify_sectors: maximum number of sectors to verify per command > + **/ > +void blk_queue_max_verify_sectors(struct request_queue *q, > + unsigned int max_verify_sectors) > +{ > + q->limits.max_verify_sectors = max_verify_sectors; > +} > +EXPORT_SYMBOL(blk_queue_max_verify_sectors); > + > /** > * blk_queue_max_zone_append_sectors - set max sectors for a single zone append > * @q: the request queue for the device > @@ -554,6 +569,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, > t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors); > t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors, > b->max_write_zeroes_sectors); > + t->max_verify_sectors = min(t->max_verify_sectors, > + b->max_verify_sectors); > t->max_zone_append_sectors = min(t->max_zone_append_sectors, > b->max_zone_append_sectors); > t->bounce = max(t->bounce, b->bounce); > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index 88bd41d4cb59..4fb6a731acad 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -113,6 +113,12 @@ queue_ra_store(struct request_queue *q, const char *page, size_t count) > return ret; > } > > +static ssize_t queue_verify_max_show(struct request_queue *q, char *page) > +{ > + return sprintf(page, "%llu\n", > + (unsigned long long)q->limits.max_verify_sectors << 9); > +} > + > static ssize_t queue_max_sectors_show(struct request_queue *q, char *page) > { > int max_sectors_kb = queue_max_sectors(q) >> 1; > @@ -588,6 +594,7 @@ QUEUE_RO_ENTRY(queue_discard_zeroes_data, "discard_zeroes_data"); > > QUEUE_RO_ENTRY(queue_write_same_max, "write_same_max_bytes"); > QUEUE_RO_ENTRY(queue_write_zeroes_max, "write_zeroes_max_bytes"); > +QUEUE_RO_ENTRY(queue_verify_max, "verify_max_bytes"); > QUEUE_RO_ENTRY(queue_zone_append_max, "zone_append_max_bytes"); > QUEUE_RO_ENTRY(queue_zone_write_granularity, "zone_write_granularity"); > > @@ -644,6 +651,7 @@ static struct attribute *queue_attrs[] = { > &queue_discard_zeroes_data_entry.attr, > &queue_write_same_max_entry.attr, > &queue_write_zeroes_max_entry.attr, > + &queue_verify_max_entry.attr, > &queue_zone_append_max_entry.attr, > &queue_zone_write_granularity_entry.attr, > &queue_nonrot_entry.attr, > diff --git a/block/blk.h b/block/blk.h > index 434017701403..63a0e3aca7e0 100644 > --- a/block/blk.h > +++ b/block/blk.h > @@ -132,6 +132,9 @@ static inline bool rq_mergeable(struct request *rq) > if (req_op(rq) == REQ_OP_WRITE_ZEROES) > return false; > > + if (req_op(rq) == REQ_OP_VERIFY) > + return false; > + > if (req_op(rq) == REQ_OP_ZONE_APPEND) > return false; > > @@ -286,6 +289,7 @@ static inline bool blk_may_split(struct request_queue *q, struct bio *bio) > case REQ_OP_DISCARD: > case REQ_OP_SECURE_ERASE: > case REQ_OP_WRITE_ZEROES: > + case REQ_OP_VERIFY: > return true; /* non-trivial splitting decisions */ > default: > break; > diff --git a/block/ioctl.c b/block/ioctl.c > index 46949f1b0dba..60a48e24b82d 100644 > --- a/block/ioctl.c > +++ b/block/ioctl.c > @@ -192,6 +192,39 @@ static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode, > return err; > } > > +static int blk_ioctl_verify(struct block_device *bdev, fmode_t mode, > + unsigned long arg) > +{ > + uint64_t range[2]; > + struct address_space *mapping; > + uint64_t start, end, len; > + > + if (!(mode & FMODE_READ)) > + return -EBADF; > + > + if (copy_from_user(range, (void __user *)arg, sizeof(range))) > + return -EFAULT; > + > + start = range[0]; > + len = range[1]; > + end = start + len - 1; > + > + if (start & 511) > + return -EINVAL; > + if (len & 511) > + return -EINVAL; > + if (end >= (uint64_t)i_size_read(bdev->bd_inode)) > + return -EINVAL; > + if (end < start) > + return -EINVAL; > + > + /* Invalidate the page cache, including dirty pages */ > + mapping = bdev->bd_inode->i_mapping; > + truncate_inode_pages_range(mapping, start, end); You might want to write any dirty pagecache contents to disk before you invalidate them all... > + > + return blkdev_issue_verify(bdev, start >> 9, len >> 9, GFP_KERNEL); > +} > + > static int put_ushort(unsigned short __user *argp, unsigned short val) > { > return put_user(val, argp); > @@ -483,6 +516,8 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode, > return blk_ioctl_secure_erase(bdev, mode, argp); > case BLKZEROOUT: > return blk_ioctl_zeroout(bdev, mode, arg); > + case BLKVERIFY: > + return blk_ioctl_verify(bdev, mode, arg); > case BLKGETDISKSEQ: > return put_u64(argp, bdev->bd_disk->diskseq); > case BLKREPORTZONE: > diff --git a/include/linux/bio.h b/include/linux/bio.h > index 1cf3738ef1ea..3dfafe1da098 100644 > --- a/include/linux/bio.h > +++ b/include/linux/bio.h > @@ -55,7 +55,8 @@ static inline bool bio_has_data(struct bio *bio) > bio->bi_iter.bi_size && > bio_op(bio) != REQ_OP_DISCARD && > bio_op(bio) != REQ_OP_SECURE_ERASE && > - bio_op(bio) != REQ_OP_WRITE_ZEROES) > + bio_op(bio) != REQ_OP_WRITE_ZEROES && > + bio_op(bio) != REQ_OP_VERIFY) > return true; > > return false; > @@ -65,7 +66,8 @@ static inline bool bio_no_advance_iter(const struct bio *bio) > { > return bio_op(bio) == REQ_OP_DISCARD || > bio_op(bio) == REQ_OP_SECURE_ERASE || > - bio_op(bio) == REQ_OP_WRITE_ZEROES; > + bio_op(bio) == REQ_OP_WRITE_ZEROES || > + bio_op(bio) == REQ_OP_VERIFY; > } > > static inline void *bio_data(struct bio *bio) > @@ -176,7 +178,7 @@ static inline unsigned bio_segments(struct bio *bio) > struct bvec_iter iter; > > /* > - * We special case discard/write same/write zeroes, because they > + * We special case discard/write same/write zeroes/verify, because they > * interpret bi_size differently: > */ > > @@ -184,6 +186,7 @@ static inline unsigned bio_segments(struct bio *bio) > case REQ_OP_DISCARD: > case REQ_OP_SECURE_ERASE: > case REQ_OP_WRITE_ZEROES: > + case REQ_OP_VERIFY: > return 0; > default: > break; > diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h > index a24d4078fb21..0d5383fc84ed 100644 > --- a/include/linux/blk_types.h > +++ b/include/linux/blk_types.h > @@ -363,6 +363,8 @@ enum req_opf { > REQ_OP_FLUSH = 2, > /* discard sectors */ > REQ_OP_DISCARD = 3, > + /* Verify the sectors */ > + REQ_OP_VERIFY = 6, > /* securely erase sectors */ > REQ_OP_SECURE_ERASE = 5, > /* write the zero filled sector many times */ > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 608d577734c2..78fd6c5530d7 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -266,6 +266,7 @@ struct queue_limits { > unsigned int max_hw_discard_sectors; > unsigned int max_secure_erase_sectors; > unsigned int max_write_zeroes_sectors; > + unsigned int max_verify_sectors; > unsigned int max_zone_append_sectors; > unsigned int discard_granularity; > unsigned int discard_alignment; > @@ -925,6 +926,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q, > if (unlikely(op == REQ_OP_WRITE_ZEROES)) > return q->limits.max_write_zeroes_sectors; > > + if (unlikely(op == REQ_OP_VERIFY)) > + return q->limits.max_verify_sectors; > + > return q->limits.max_sectors; > } > > @@ -968,6 +972,8 @@ extern void blk_queue_max_discard_sectors(struct request_queue *q, > unsigned int max_discard_sectors); > extern void blk_queue_max_write_zeroes_sectors(struct request_queue *q, > unsigned int max_write_same_sectors); > +extern void blk_queue_max_verify_sectors(struct request_queue *q, > + unsigned int max_verify_sectors); > extern void blk_queue_logical_block_size(struct request_queue *, unsigned int); > extern void blk_queue_max_zone_append_sectors(struct request_queue *q, > unsigned int max_zone_append_sectors); > @@ -1119,6 +1125,12 @@ extern int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, > extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, > sector_t nr_sects, gfp_t gfp_mask, unsigned flags); > > +extern int __blkdev_issue_verify(struct block_device *bdev, > + sector_t sector, sector_t nr_sects, gfp_t gfp_mask, > + struct bio **biop); > +extern int blkdev_issue_verify(struct block_device *bdev, sector_t sector, > + sector_t nr_sects, gfp_t gfp_mask); > + > static inline int sb_issue_discard(struct super_block *sb, sector_t block, > sector_t nr_blocks, gfp_t gfp_mask, unsigned long flags) > { > @@ -1293,6 +1305,16 @@ static inline unsigned int bdev_write_zeroes_sectors(struct block_device *bdev) > return 0; > } > > +static inline unsigned int bdev_verify_sectors(struct block_device *bdev) > +{ > + struct request_queue *q = bdev_get_queue(bdev); > + > + if (q) > + return q->limits.max_verify_sectors; > + > + return 0; > +} > + > static inline bool bdev_nonrot(struct block_device *bdev) > { > return blk_queue_nonrot(bdev_get_queue(bdev)); > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index bdf7b404b3e7..ad0e5cb5cac4 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -185,6 +185,7 @@ struct fsxattr { > #define BLKROTATIONAL _IO(0x12,126) > #define BLKZEROOUT _IO(0x12,127) > #define BLKGETDISKSEQ _IOR(0x12,128,__u64) > +#define BLKVERIFY _IO(0x12,129) > /* > * A jump here: 130-136 are reserved for zoned block devices > * (see uapi/linux/blkzoned.h) > -- > 2.29.0 >
On Thu, Jun 30, 2022 at 02:14:01AM -0700, Chaitanya Kulkarni wrote: > This adds a new block layer operation to offload verifying a range of > LBAs. This support is needed in order to provide file systems and > fabrics, kernel components to offload LBA verification when it is > supported by the hardware controller. In case hardware offloading is > not supported then we provide API to emulate the same. The prominent > example of that is SCSI and NVMe Verify command. We also provide > an emulation of the same operation that can be used in case H/W does > not support verify. This is still useful when block device is remotely > attached e.g. using NVMeOF. What is the point of providing the offload?
Darrik, Thanks for the reply. >> + >> +/** >> + * __blkdev_issue_verify - generate number of verify operations >> + * @bdev: blockdev to issue >> + * @sector: start sector >> + * @nr_sects: number of sectors to verify >> + * @gfp_mask: memory allocation flags (for bio_alloc()) >> + * @biop: pointer to anchor bio >> + * >> + * Description: >> + * Verify a block range using hardware offload. >> + * >> + * The function will emulate verify operation if no explicit hardware >> + * offloading for verifying is provided. >> + */ >> +int __blkdev_issue_verify(struct block_device *bdev, sector_t sector, >> + sector_t nr_sects, gfp_t gfp_mask, struct bio **biop) >> +{ >> + unsigned int max_verify_sectors = bdev_verify_sectors(bdev); >> + sector_t min_io_sect = (BIO_MAX_VECS << PAGE_SHIFT) >> 9; >> + struct bio *bio = *biop; >> + sector_t curr_sects; >> + char *buf; >> + >> + if (!max_verify_sectors) { >> + int ret = 0; >> + >> + buf = kzalloc(min_io_sect << 9, GFP_KERNEL); > > k*z*alloc? I don't think you need to zero a buffer that we're reading > into, right? > > --D we don't need to but I guess it is just a habit to make sure alloced buffer is zeored, should I remove it for any particular reason ? -ck
On Tue, Jul 05, 2022 at 04:50:33PM +0000, Chaitanya Kulkarni wrote: > Darrik, > > Thanks for the reply. > > >> + > >> +/** > >> + * __blkdev_issue_verify - generate number of verify operations > >> + * @bdev: blockdev to issue > >> + * @sector: start sector > >> + * @nr_sects: number of sectors to verify > >> + * @gfp_mask: memory allocation flags (for bio_alloc()) > >> + * @biop: pointer to anchor bio > >> + * > >> + * Description: > >> + * Verify a block range using hardware offload. > >> + * > >> + * The function will emulate verify operation if no explicit hardware > >> + * offloading for verifying is provided. > >> + */ > >> +int __blkdev_issue_verify(struct block_device *bdev, sector_t sector, > >> + sector_t nr_sects, gfp_t gfp_mask, struct bio **biop) > >> +{ > >> + unsigned int max_verify_sectors = bdev_verify_sectors(bdev); > >> + sector_t min_io_sect = (BIO_MAX_VECS << PAGE_SHIFT) >> 9; > >> + struct bio *bio = *biop; > >> + sector_t curr_sects; > >> + char *buf; > >> + > >> + if (!max_verify_sectors) { > >> + int ret = 0; > >> + > >> + buf = kzalloc(min_io_sect << 9, GFP_KERNEL); > > > > k*z*alloc? I don't think you need to zero a buffer that we're reading > > into, right? > > > > --D > > we don't need to but I guess it is just a habit to make sure alloced > buffer is zeored, should I remove it for any particular reason ? What's the point in wasting CPU time zeroing a buffer if you're just going to DMA into it? --D > -ck > >
On 7/5/22 01:34, Christoph Hellwig wrote: > On Thu, Jun 30, 2022 at 02:14:01AM -0700, Chaitanya Kulkarni wrote: >> This adds a new block layer operation to offload verifying a range of >> LBAs. This support is needed in order to provide file systems and >> fabrics, kernel components to offload LBA verification when it is >> supported by the hardware controller. In case hardware offloading is >> not supported then we provide API to emulate the same. The prominent >> example of that is SCSI and NVMe Verify command. We also provide >> an emulation of the same operation that can be used in case H/W does >> not support verify. This is still useful when block device is remotely >> attached e.g. using NVMeOF. > > What is the point of providing the offload? Data block verification is done at the time of file-scrubbing e.g. see [1], having support to offload the verify command will :- 1. Reduce the DMA transfer at the time of scrubbing :- In the absense of verify command user has to send the read command that will trigger same behaviour as verify command, but with the DMA traffic with operating system storage stack overhead of REQ_OP_READ. This overhead gets duplicated for the fabrics controller where host and target now has to issue REQ_OP_READ leading to significant DMA transfer as compare to REQ_OP_VERIFY for each protocol SCSI/NVMe etc. This makes it possible to do a low-level scrub of the stored data without being bottlenecked by the host interface bandwidth. 2. Allow us to use to unify interface for applications :- Currently in linux there is no unified interface to issue verify command so each application will have to duplicate the code for the discovering controllers protocol type, opencoding device passthru ioctl for protocol spefcific verify command and issuing verify read emulation if it is not supported, see [1]. 3. Allow us to use controller's internal bandwidth :- For some controllers offloading the verify command can reault in decrease in data block verification time, since their internal bandwidth can be higher than host DMA transfer + OS storage stack overhead of the read command. 4. Pro-actively avoiding unrecoverable read errors:- Verify command does everything a normal read command does, except for returning the data to the host system. This makes it possible to do a low-level scrub of the stored data without being bottlenecked by the host interface bandwidth. Please note that analyzing controller verify command performance for common protocols (SCSI/NVMe) is out of scope for REQ_OP_VERIFY. -ck [1] xfs_scrub issueing the verify command :- xfs-progs/scrub/disk.c 340: disk_read_verify()->disk_scsi_verify()
>>>> +int __blkdev_issue_verify(struct block_device *bdev, sector_t sector, >>>> + sector_t nr_sects, gfp_t gfp_mask, struct bio **biop) >>>> +{ >>>> + unsigned int max_verify_sectors = bdev_verify_sectors(bdev); >>>> + sector_t min_io_sect = (BIO_MAX_VECS << PAGE_SHIFT) >> 9; >>>> + struct bio *bio = *biop; >>>> + sector_t curr_sects; >>>> + char *buf; >>>> + >>>> + if (!max_verify_sectors) { >>>> + int ret = 0; >>>> + >>>> + buf = kzalloc(min_io_sect << 9, GFP_KERNEL); >>> >>> k*z*alloc? I don't think you need to zero a buffer that we're reading >>> into, right? >>> >>> --D >> >> we don't need to but I guess it is just a habit to make sure alloced >> buffer is zeored, should I remove it for any particular reason ? > > What's the point in wasting CPU time zeroing a buffer if you're just > going to DMA into it? > > --D > true, will remove it ... >> -ck >> >>
diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block index e8797cd09aff..a71d9c41cf8b 100644 --- a/Documentation/ABI/stable/sysfs-block +++ b/Documentation/ABI/stable/sysfs-block @@ -657,6 +657,18 @@ Description: in a single write zeroes command. If write_zeroes_max_bytes is 0, write zeroes is not supported by the device. +What: /sys/block/<disk>/queue/verify_max_bytes +Date: April 2022 +Contact: Chaitanya Kulkarni <kch@nvidia.com> +Description: + Devices that support verify operation in which a single + request can be issued to verify the range of the contiguous + blocks on the storage without any payload in the request. + This can be used to optimize verifying LBAs on the device + without reading by offloading functionality. verify_max_bytes + indicates how many bytes can be written in a single verify + command. If verify_max_bytes is 0, verify operation is not + supported by the device. What: /sys/block/<disk>/queue/zone_append_max_bytes Date: May 2020 diff --git a/block/blk-core.c b/block/blk-core.c index 06ff5bbfe8f6..9ad52247dcdf 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -123,6 +123,7 @@ static const char *const blk_op_name[] = { REQ_OP_NAME(ZONE_FINISH), REQ_OP_NAME(ZONE_APPEND), REQ_OP_NAME(WRITE_ZEROES), + REQ_OP_NAME(VERIFY), REQ_OP_NAME(DRV_IN), REQ_OP_NAME(DRV_OUT), }; @@ -842,6 +843,10 @@ void submit_bio_noacct(struct bio *bio) if (!q->limits.max_write_zeroes_sectors) goto not_supported; break; + case REQ_OP_VERIFY: + if (!q->limits.max_verify_sectors) + goto not_supported; + break; default: break; } diff --git a/block/blk-lib.c b/block/blk-lib.c index 09b7e1200c0f..4624d68bb3cb 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -340,3 +340,158 @@ int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector, return ret; } EXPORT_SYMBOL(blkdev_issue_secure_erase); + +/** + * __blkdev_emulate_verify - emulate number of verify operations + * asynchronously + * @bdev: blockdev to issue + * @sector: start sector + * @nr_sects: number of sectors to verify + * @gfp_mask: memory allocation flags (for bio_alloc) + * @biop: pointer to anchor bio + * @buf: data buffer to mapped on bio + * + * Description: + * Verify a block range by emulating REQ_OP_VERIFY into REQ_OP_READ, + * use this when H/W offloading is not supported asynchronously. + * Caller is responsible to handle anchored bio. + */ +static int __blkdev_emulate_verify(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, struct bio **biop, char *buf) +{ + struct bio *bio = *biop; + unsigned int sz; + int bi_size; + + while (nr_sects != 0) { + bio = blk_next_bio(bio, bdev, + __blkdev_sectors_to_bio_pages(nr_sects), + REQ_OP_READ, gfp_mask); + bio->bi_iter.bi_sector = sector; + + while (nr_sects != 0) { + bool is_vaddr = is_vmalloc_addr(buf); + struct page *p; + + p = is_vaddr ? vmalloc_to_page(buf) : virt_to_page(buf); + sz = min((sector_t) PAGE_SIZE, nr_sects << 9); + + bi_size = bio_add_page(bio, p, sz, offset_in_page(buf)); + if (bi_size < sz) + return -EIO; + + nr_sects -= bi_size >> 9; + sector += bi_size >> 9; + buf += bi_size; + } + cond_resched(); + } + + *biop = bio; + return 0; +} + +/** + * __blkdev_issue_verify - generate number of verify operations + * @bdev: blockdev to issue + * @sector: start sector + * @nr_sects: number of sectors to verify + * @gfp_mask: memory allocation flags (for bio_alloc()) + * @biop: pointer to anchor bio + * + * Description: + * Verify a block range using hardware offload. + * + * The function will emulate verify operation if no explicit hardware + * offloading for verifying is provided. + */ +int __blkdev_issue_verify(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, struct bio **biop) +{ + unsigned int max_verify_sectors = bdev_verify_sectors(bdev); + sector_t min_io_sect = (BIO_MAX_VECS << PAGE_SHIFT) >> 9; + struct bio *bio = *biop; + sector_t curr_sects; + char *buf; + + if (!max_verify_sectors) { + int ret = 0; + + buf = kzalloc(min_io_sect << 9, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + while (nr_sects > 0) { + curr_sects = min_t(sector_t, nr_sects, min_io_sect); + ret = __blkdev_emulate_verify(bdev, sector, curr_sects, + gfp_mask, &bio, buf); + if (ret) + break; + + if (bio) { + ret = submit_bio_wait(bio); + bio_put(bio); + bio = NULL; + } + + nr_sects -= curr_sects; + sector += curr_sects; + + } + /* set the biop to NULL since we have alrady completed above */ + *biop = NULL; + kfree(buf); + return ret; + } + + while (nr_sects) { + bio = blk_next_bio(bio, bdev, 0, REQ_OP_VERIFY, gfp_mask); + bio->bi_iter.bi_sector = sector; + + if (nr_sects > max_verify_sectors) { + bio->bi_iter.bi_size = max_verify_sectors << 9; + nr_sects -= max_verify_sectors; + sector += max_verify_sectors; + } else { + bio->bi_iter.bi_size = nr_sects << 9; + nr_sects = 0; + } + cond_resched(); + } + *biop = bio; + return 0; +} +EXPORT_SYMBOL_GPL(__blkdev_issue_verify); + +/** + * blkdev_issue_verify - verify a block range + * @bdev: blockdev to verify + * @sector: start sector + * @nr_sects: number of sectors to verify + * @gfp_mask: memory allocation flags (for bio_alloc) + * + * Description: + * Verify a block range using hardware offload. + */ +int blkdev_issue_verify(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask) +{ + sector_t bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1; + struct bio *bio = NULL; + struct blk_plug plug; + int ret = 0; + + if ((sector | nr_sects) & bs_mask) + return -EINVAL; + + blk_start_plug(&plug); + ret = __blkdev_issue_verify(bdev, sector, nr_sects, gfp_mask, &bio); + if (ret == 0 && bio) { + ret = submit_bio_wait(bio); + bio_put(bio); + } + blk_finish_plug(&plug); + + return ret; +} +EXPORT_SYMBOL_GPL(blkdev_issue_verify); diff --git a/block/blk-merge.c b/block/blk-merge.c index 7771dacc99cb..8ff305377b5a 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -153,6 +153,20 @@ static struct bio *blk_bio_write_zeroes_split(struct request_queue *q, return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs); } +static struct bio *blk_bio_verify_split(struct request_queue *q, + struct bio *bio, struct bio_set *bs, unsigned *nsegs) +{ + *nsegs = 0; + + if (!q->limits.max_verify_sectors) + return NULL; + + if (bio_sectors(bio) <= q->limits.max_verify_sectors) + return NULL; + + return bio_split(bio, q->limits.max_verify_sectors, GFP_NOIO, bs); +} + /* * Return the maximum number of sectors from the start of a bio that may be * submitted as a single request to a block device. If enough sectors remain, @@ -336,6 +350,10 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio, split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, nr_segs); break; + case REQ_OP_VERIFY: + split = blk_bio_verify_split(q, *bio, &q->bio_split, + nr_segs); + break; default: split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs); break; diff --git a/block/blk-settings.c b/block/blk-settings.c index 6ccceb421ed2..c77697290bc5 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -43,6 +43,7 @@ void blk_set_default_limits(struct queue_limits *lim) lim->max_dev_sectors = 0; lim->chunk_sectors = 0; lim->max_write_zeroes_sectors = 0; + lim->max_verify_sectors = 0; lim->max_zone_append_sectors = 0; lim->max_discard_sectors = 0; lim->max_hw_discard_sectors = 0; @@ -80,6 +81,7 @@ void blk_set_stacking_limits(struct queue_limits *lim) lim->max_sectors = UINT_MAX; lim->max_dev_sectors = UINT_MAX; lim->max_write_zeroes_sectors = UINT_MAX; + lim->max_verify_sectors = UINT_MAX; lim->max_zone_append_sectors = UINT_MAX; } EXPORT_SYMBOL(blk_set_stacking_limits); @@ -202,6 +204,19 @@ void blk_queue_max_write_zeroes_sectors(struct request_queue *q, } EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors); +/** + * blk_queue_max_verify_sectors - set max sectors for a single verify + * + * @q: the request queue for the device + * @max_verify_sectors: maximum number of sectors to verify per command + **/ +void blk_queue_max_verify_sectors(struct request_queue *q, + unsigned int max_verify_sectors) +{ + q->limits.max_verify_sectors = max_verify_sectors; +} +EXPORT_SYMBOL(blk_queue_max_verify_sectors); + /** * blk_queue_max_zone_append_sectors - set max sectors for a single zone append * @q: the request queue for the device @@ -554,6 +569,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors); t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors, b->max_write_zeroes_sectors); + t->max_verify_sectors = min(t->max_verify_sectors, + b->max_verify_sectors); t->max_zone_append_sectors = min(t->max_zone_append_sectors, b->max_zone_append_sectors); t->bounce = max(t->bounce, b->bounce); diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 88bd41d4cb59..4fb6a731acad 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -113,6 +113,12 @@ queue_ra_store(struct request_queue *q, const char *page, size_t count) return ret; } +static ssize_t queue_verify_max_show(struct request_queue *q, char *page) +{ + return sprintf(page, "%llu\n", + (unsigned long long)q->limits.max_verify_sectors << 9); +} + static ssize_t queue_max_sectors_show(struct request_queue *q, char *page) { int max_sectors_kb = queue_max_sectors(q) >> 1; @@ -588,6 +594,7 @@ QUEUE_RO_ENTRY(queue_discard_zeroes_data, "discard_zeroes_data"); QUEUE_RO_ENTRY(queue_write_same_max, "write_same_max_bytes"); QUEUE_RO_ENTRY(queue_write_zeroes_max, "write_zeroes_max_bytes"); +QUEUE_RO_ENTRY(queue_verify_max, "verify_max_bytes"); QUEUE_RO_ENTRY(queue_zone_append_max, "zone_append_max_bytes"); QUEUE_RO_ENTRY(queue_zone_write_granularity, "zone_write_granularity"); @@ -644,6 +651,7 @@ static struct attribute *queue_attrs[] = { &queue_discard_zeroes_data_entry.attr, &queue_write_same_max_entry.attr, &queue_write_zeroes_max_entry.attr, + &queue_verify_max_entry.attr, &queue_zone_append_max_entry.attr, &queue_zone_write_granularity_entry.attr, &queue_nonrot_entry.attr, diff --git a/block/blk.h b/block/blk.h index 434017701403..63a0e3aca7e0 100644 --- a/block/blk.h +++ b/block/blk.h @@ -132,6 +132,9 @@ static inline bool rq_mergeable(struct request *rq) if (req_op(rq) == REQ_OP_WRITE_ZEROES) return false; + if (req_op(rq) == REQ_OP_VERIFY) + return false; + if (req_op(rq) == REQ_OP_ZONE_APPEND) return false; @@ -286,6 +289,7 @@ static inline bool blk_may_split(struct request_queue *q, struct bio *bio) case REQ_OP_DISCARD: case REQ_OP_SECURE_ERASE: case REQ_OP_WRITE_ZEROES: + case REQ_OP_VERIFY: return true; /* non-trivial splitting decisions */ default: break; diff --git a/block/ioctl.c b/block/ioctl.c index 46949f1b0dba..60a48e24b82d 100644 --- a/block/ioctl.c +++ b/block/ioctl.c @@ -192,6 +192,39 @@ static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode, return err; } +static int blk_ioctl_verify(struct block_device *bdev, fmode_t mode, + unsigned long arg) +{ + uint64_t range[2]; + struct address_space *mapping; + uint64_t start, end, len; + + if (!(mode & FMODE_READ)) + return -EBADF; + + if (copy_from_user(range, (void __user *)arg, sizeof(range))) + return -EFAULT; + + start = range[0]; + len = range[1]; + end = start + len - 1; + + if (start & 511) + return -EINVAL; + if (len & 511) + return -EINVAL; + if (end >= (uint64_t)i_size_read(bdev->bd_inode)) + return -EINVAL; + if (end < start) + return -EINVAL; + + /* Invalidate the page cache, including dirty pages */ + mapping = bdev->bd_inode->i_mapping; + truncate_inode_pages_range(mapping, start, end); + + return blkdev_issue_verify(bdev, start >> 9, len >> 9, GFP_KERNEL); +} + static int put_ushort(unsigned short __user *argp, unsigned short val) { return put_user(val, argp); @@ -483,6 +516,8 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode, return blk_ioctl_secure_erase(bdev, mode, argp); case BLKZEROOUT: return blk_ioctl_zeroout(bdev, mode, arg); + case BLKVERIFY: + return blk_ioctl_verify(bdev, mode, arg); case BLKGETDISKSEQ: return put_u64(argp, bdev->bd_disk->diskseq); case BLKREPORTZONE: diff --git a/include/linux/bio.h b/include/linux/bio.h index 1cf3738ef1ea..3dfafe1da098 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -55,7 +55,8 @@ static inline bool bio_has_data(struct bio *bio) bio->bi_iter.bi_size && bio_op(bio) != REQ_OP_DISCARD && bio_op(bio) != REQ_OP_SECURE_ERASE && - bio_op(bio) != REQ_OP_WRITE_ZEROES) + bio_op(bio) != REQ_OP_WRITE_ZEROES && + bio_op(bio) != REQ_OP_VERIFY) return true; return false; @@ -65,7 +66,8 @@ static inline bool bio_no_advance_iter(const struct bio *bio) { return bio_op(bio) == REQ_OP_DISCARD || bio_op(bio) == REQ_OP_SECURE_ERASE || - bio_op(bio) == REQ_OP_WRITE_ZEROES; + bio_op(bio) == REQ_OP_WRITE_ZEROES || + bio_op(bio) == REQ_OP_VERIFY; } static inline void *bio_data(struct bio *bio) @@ -176,7 +178,7 @@ static inline unsigned bio_segments(struct bio *bio) struct bvec_iter iter; /* - * We special case discard/write same/write zeroes, because they + * We special case discard/write same/write zeroes/verify, because they * interpret bi_size differently: */ @@ -184,6 +186,7 @@ static inline unsigned bio_segments(struct bio *bio) case REQ_OP_DISCARD: case REQ_OP_SECURE_ERASE: case REQ_OP_WRITE_ZEROES: + case REQ_OP_VERIFY: return 0; default: break; diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index a24d4078fb21..0d5383fc84ed 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -363,6 +363,8 @@ enum req_opf { REQ_OP_FLUSH = 2, /* discard sectors */ REQ_OP_DISCARD = 3, + /* Verify the sectors */ + REQ_OP_VERIFY = 6, /* securely erase sectors */ REQ_OP_SECURE_ERASE = 5, /* write the zero filled sector many times */ diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 608d577734c2..78fd6c5530d7 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -266,6 +266,7 @@ struct queue_limits { unsigned int max_hw_discard_sectors; unsigned int max_secure_erase_sectors; unsigned int max_write_zeroes_sectors; + unsigned int max_verify_sectors; unsigned int max_zone_append_sectors; unsigned int discard_granularity; unsigned int discard_alignment; @@ -925,6 +926,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q, if (unlikely(op == REQ_OP_WRITE_ZEROES)) return q->limits.max_write_zeroes_sectors; + if (unlikely(op == REQ_OP_VERIFY)) + return q->limits.max_verify_sectors; + return q->limits.max_sectors; } @@ -968,6 +972,8 @@ extern void blk_queue_max_discard_sectors(struct request_queue *q, unsigned int max_discard_sectors); extern void blk_queue_max_write_zeroes_sectors(struct request_queue *q, unsigned int max_write_same_sectors); +extern void blk_queue_max_verify_sectors(struct request_queue *q, + unsigned int max_verify_sectors); extern void blk_queue_logical_block_size(struct request_queue *, unsigned int); extern void blk_queue_max_zone_append_sectors(struct request_queue *q, unsigned int max_zone_append_sectors); @@ -1119,6 +1125,12 @@ extern int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, sector_t nr_sects, gfp_t gfp_mask, unsigned flags); +extern int __blkdev_issue_verify(struct block_device *bdev, + sector_t sector, sector_t nr_sects, gfp_t gfp_mask, + struct bio **biop); +extern int blkdev_issue_verify(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask); + static inline int sb_issue_discard(struct super_block *sb, sector_t block, sector_t nr_blocks, gfp_t gfp_mask, unsigned long flags) { @@ -1293,6 +1305,16 @@ static inline unsigned int bdev_write_zeroes_sectors(struct block_device *bdev) return 0; } +static inline unsigned int bdev_verify_sectors(struct block_device *bdev) +{ + struct request_queue *q = bdev_get_queue(bdev); + + if (q) + return q->limits.max_verify_sectors; + + return 0; +} + static inline bool bdev_nonrot(struct block_device *bdev) { return blk_queue_nonrot(bdev_get_queue(bdev)); diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index bdf7b404b3e7..ad0e5cb5cac4 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -185,6 +185,7 @@ struct fsxattr { #define BLKROTATIONAL _IO(0x12,126) #define BLKZEROOUT _IO(0x12,127) #define BLKGETDISKSEQ _IOR(0x12,128,__u64) +#define BLKVERIFY _IO(0x12,129) /* * A jump here: 130-136 are reserved for zoned block devices * (see uapi/linux/blkzoned.h)
This adds a new block layer operation to offload verifying a range of LBAs. This support is needed in order to provide file systems and fabrics, kernel components to offload LBA verification when it is supported by the hardware controller. In case hardware offloading is not supported then we provide API to emulate the same. The prominent example of that is SCSI and NVMe Verify command. We also provide an emulation of the same operation that can be used in case H/W does not support verify. This is still useful when block device is remotely attached e.g. using NVMeOF. Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com> --- Documentation/ABI/stable/sysfs-block | 12 +++ block/blk-core.c | 5 + block/blk-lib.c | 155 +++++++++++++++++++++++++++ block/blk-merge.c | 18 ++++ block/blk-settings.c | 17 +++ block/blk-sysfs.c | 8 ++ block/blk.h | 4 + block/ioctl.c | 35 ++++++ include/linux/bio.h | 9 +- include/linux/blk_types.h | 2 + include/linux/blkdev.h | 22 ++++ include/uapi/linux/fs.h | 1 + 12 files changed, 285 insertions(+), 3 deletions(-)