| Message ID | 1614774618-22410-5-git-send-email-sergei.shtepa@veeam.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block-layer interposer | expand |
On Wed, Mar 03, 2021 at 03:30:18PM +0300, Sergei Shtepa wrote: > DM_INTERPOSED_FLAG allow to create dm targets on "the fly". > Underlying block device opens without a flag FMODE_EXCL. > Dm target receives bio from the original device via > blk_interposer. > > Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com> > --- > drivers/md/dm-core.h | 6 ++ > drivers/md/dm-ioctl.c | 9 +++ > drivers/md/dm-table.c | 115 +++++++++++++++++++++++++++++++--- > drivers/md/dm.c | 38 +++++++---- > include/linux/device-mapper.h | 1 + > include/uapi/linux/dm-ioctl.h | 6 ++ > 6 files changed, 154 insertions(+), 21 deletions(-) > > diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h > index 5953ff2bd260..e5c845f9b1df 100644 > --- a/drivers/md/dm-core.h > +++ b/drivers/md/dm-core.h > @@ -21,6 +21,8 @@ > > #define DM_RESERVED_MAX_IOS 1024 > > +struct dm_interposed_dev; > + > struct dm_kobject_holder { > struct kobject kobj; > struct completion completion; > @@ -114,6 +116,10 @@ struct mapped_device { > bool init_tio_pdu:1; > > struct srcu_struct io_barrier; > + > + /* for interposers logic */ > + bool is_interposed; > + struct dm_interposed_dev *ip_dev; > }; > > void disable_discard(struct mapped_device *md); > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c > index 5e306bba4375..2bcb316144a1 100644 > --- a/drivers/md/dm-ioctl.c > +++ b/drivers/md/dm-ioctl.c > @@ -1267,6 +1267,11 @@ static inline fmode_t get_mode(struct dm_ioctl *param) > return mode; > } > > +static inline bool get_interposer_flag(struct dm_ioctl *param) > +{ > + return (param->flags & DM_INTERPOSED_FLAG); > +} > + > static int next_target(struct dm_target_spec *last, uint32_t next, void *end, > struct dm_target_spec **spec, char **target_params) > { > @@ -1338,6 +1343,8 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si > if (!md) > return -ENXIO; > > + md->is_interposed = get_interposer_flag(param); > + > r = dm_table_create(&t, get_mode(param), param->target_count, md); > if (r) > goto err; > @@ -2098,6 +2105,8 @@ int __init dm_early_create(struct dm_ioctl *dmi, > if (r) > goto err_hash_remove; > > + md->is_interposed = get_interposer_flag(dmi); > + > /* add targets */ > for (i = 0; i < dmi->target_count; i++) { > r = dm_table_add_target(t, spec_array[i]->target_type, > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c > index 95391f78b8d5..0b2f9b66ade5 100644 > --- a/drivers/md/dm-table.c > +++ b/drivers/md/dm-table.c > @@ -6,6 +6,7 @@ > */ > > #include "dm-core.h" > +#include "dm-interposer.h" > > #include <linux/module.h> > #include <linux/vmalloc.h> > @@ -225,12 +226,13 @@ void dm_table_destroy(struct dm_table *t) > /* > * See if we've already got a device in the list. > */ > -static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev) > +static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev, bool is_interposed) > { > struct dm_dev_internal *dd; > > list_for_each_entry (dd, l, list) > - if (dd->dm_dev->bdev->bd_dev == dev) > + if ((dd->dm_dev->bdev->bd_dev == dev) && > + (dd->dm_dev->is_interposed == is_interposed)) > return dd; > > return NULL; > @@ -358,6 +360,90 @@ dev_t dm_get_dev_t(const char *path) > } > EXPORT_SYMBOL_GPL(dm_get_dev_t); > > +/* > + * Redirect bio from interposed device to dm device > + */ > +static void dm_interpose_fn(struct dm_interposed_dev *ip_dev, struct bio *bio) > +{ > + struct mapped_device *md = ip_dev->private; > + > + if (bio_flagged(bio, BIO_REMAPPED)) { > + /* > + * Since bio has already been remapped, we need to subtract > + * the block device offset from the beginning of the disk. > + */ > + bio->bi_iter.bi_sector -= get_start_sect(bio->bi_bdev); > + > + bio_clear_flag(bio, BIO_REMAPPED); > + } So instead of doing this shoudn't the imposer just always submit to the whole device? But if we keep it, the logic in this funtion should go into a block layer helper, passing a block device instead of the dm_interposed_dev. This avoids having such fragile logic in drivers. > + if ((ofs + len) > bdev_nr_sectors(bdev)) { > + DMERR("The specified range of sectors exceeds of the size of the block device."); > + return -ERANGE; > + } > + > + md->ip_dev = kzalloc(sizeof(struct dm_interposed_dev), GFP_KERNEL); > + if (!md->ip_dev) > + return -ENOMEM; > + > + if ((ofs == 0) && (len == 0)) Lots of superflous inner braces.
The 03/09/2021 20:35, Christoph Hellwig wrote: > On Wed, Mar 03, 2021 at 03:30:18PM +0300, Sergei Shtepa wrote: > > DM_INTERPOSED_FLAG allow to create dm targets on "the fly". > > Underlying block device opens without a flag FMODE_EXCL. > > Dm target receives bio from the original device via > > blk_interposer. > > > > Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com> > > --- > > drivers/md/dm-core.h | 6 ++ > > drivers/md/dm-ioctl.c | 9 +++ > > drivers/md/dm-table.c | 115 +++++++++++++++++++++++++++++++--- > > drivers/md/dm.c | 38 +++++++---- > > include/linux/device-mapper.h | 1 + > > include/uapi/linux/dm-ioctl.h | 6 ++ > > 6 files changed, 154 insertions(+), 21 deletions(-) > > > > diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h > > index 5953ff2bd260..e5c845f9b1df 100644 > > --- a/drivers/md/dm-core.h > > +++ b/drivers/md/dm-core.h > > @@ -21,6 +21,8 @@ > > > > #define DM_RESERVED_MAX_IOS 1024 > > > > +struct dm_interposed_dev; > > + > > struct dm_kobject_holder { > > struct kobject kobj; > > struct completion completion; > > @@ -114,6 +116,10 @@ struct mapped_device { > > bool init_tio_pdu:1; > > > > struct srcu_struct io_barrier; > > + > > + /* for interposers logic */ > > + bool is_interposed; > > + struct dm_interposed_dev *ip_dev; > > }; > > > > void disable_discard(struct mapped_device *md); > > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c > > index 5e306bba4375..2bcb316144a1 100644 > > --- a/drivers/md/dm-ioctl.c > > +++ b/drivers/md/dm-ioctl.c > > @@ -1267,6 +1267,11 @@ static inline fmode_t get_mode(struct dm_ioctl *param) > > return mode; > > } > > > > +static inline bool get_interposer_flag(struct dm_ioctl *param) > > +{ > > + return (param->flags & DM_INTERPOSED_FLAG); > > +} > > + > > static int next_target(struct dm_target_spec *last, uint32_t next, void *end, > > struct dm_target_spec **spec, char **target_params) > > { > > @@ -1338,6 +1343,8 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si > > if (!md) > > return -ENXIO; > > > > + md->is_interposed = get_interposer_flag(param); > > + > > r = dm_table_create(&t, get_mode(param), param->target_count, md); > > if (r) > > goto err; > > @@ -2098,6 +2105,8 @@ int __init dm_early_create(struct dm_ioctl *dmi, > > if (r) > > goto err_hash_remove; > > > > + md->is_interposed = get_interposer_flag(dmi); > > + > > /* add targets */ > > for (i = 0; i < dmi->target_count; i++) { > > r = dm_table_add_target(t, spec_array[i]->target_type, > > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c > > index 95391f78b8d5..0b2f9b66ade5 100644 > > --- a/drivers/md/dm-table.c > > +++ b/drivers/md/dm-table.c > > @@ -6,6 +6,7 @@ > > */ > > > > #include "dm-core.h" > > +#include "dm-interposer.h" > > > > #include <linux/module.h> > > #include <linux/vmalloc.h> > > @@ -225,12 +226,13 @@ void dm_table_destroy(struct dm_table *t) > > /* > > * See if we've already got a device in the list. > > */ > > -static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev) > > +static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev, bool is_interposed) > > { > > struct dm_dev_internal *dd; > > > > list_for_each_entry (dd, l, list) > > - if (dd->dm_dev->bdev->bd_dev == dev) > > + if ((dd->dm_dev->bdev->bd_dev == dev) && > > + (dd->dm_dev->is_interposed == is_interposed)) > > return dd; > > > > return NULL; > > @@ -358,6 +360,90 @@ dev_t dm_get_dev_t(const char *path) > > } > > EXPORT_SYMBOL_GPL(dm_get_dev_t); > > > > +/* > > + * Redirect bio from interposed device to dm device > > + */ > > +static void dm_interpose_fn(struct dm_interposed_dev *ip_dev, struct bio *bio) > > +{ > > + struct mapped_device *md = ip_dev->private; > > + > > + if (bio_flagged(bio, BIO_REMAPPED)) { > > + /* > > + * Since bio has already been remapped, we need to subtract > > + * the block device offset from the beginning of the disk. > > + */ > > + bio->bi_iter.bi_sector -= get_start_sect(bio->bi_bdev); > > + > > + bio_clear_flag(bio, BIO_REMAPPED); > > + } > > So instead of doing this shoudn't the imposer just always submit to the > whole device? But if we keep it, the logic in this funtion should go > into a block layer helper, passing a block device instead of the > dm_interposed_dev. This avoids having such fragile logic in drivers. device-mapper allows to create devices of any size using only part of the underlying device. Therefore, it is not possible to apply the interposer to the whole block device. Perhaps it makes sense to put the blk_partition_unremap() function in the block layer? I'm not sure that's a good thing. > > > + if ((ofs + len) > bdev_nr_sectors(bdev)) { > > + DMERR("The specified range of sectors exceeds of the size of the block device."); > > + return -ERANGE; > > + } > > + > > + md->ip_dev = kzalloc(sizeof(struct dm_interposed_dev), GFP_KERNEL); > > + if (!md->ip_dev) > > + return -ENOMEM; > > + > > + if ((ofs == 0) && (len == 0)) > > Lots of superflous inner braces.
On Wed, Mar 10, 2021 at 08:28:12AM +0300, Sergei Shtepa wrote: > > So instead of doing this shoudn't the interposer just always submit to the > > whole device? But if we keep it, the logic in this funtion should go > > into a block layer helper, passing a block device instead of the > > device-mapper allows to create devices of any size using only part of > the underlying device. Therefore, it is not possible to apply the > interposer to the whole block device. > Perhaps it makes sense to put the blk_partition_unremap() function in the > block layer? I'm not sure that's a good thing. I suspect the answer is to not remap bios that are going to be handled by the interposer. In fact much of submit_bio_checks as-is is a bad idea for interposed devices. I think what we need to do instead is to pass an explicit bdev to submit_bio_checks and use that everywhere, including in the subfunctions. With that we might also be able to remove the separate interpose hook and thus struct bdev_interposer entirely as now ->submit_bio of the interposer could do all the work: static noinline blk_qc_t submit_bio_interposed(struct bio *bio) { struct block_device *orig_bdev = bio->bi_bdev, *interposer; struct bio_list bio_list[2] = { }; blk_qc_t ret = BLK_QC_T_NONE; if (current->bio_list) { bio_list_add(¤t->bio_list[0], bio); return BLK_QC_T_NONE; } if (unlikely(bio_queue_enter(bio))) return BLK_QC_T_NONE; interposer = orig_bdev->bd_interposer; if (unlikely(!interposer)) { /* interposer was removed */ bio_list_add(¤t->bio_list[0], bio); goto queue_exit; } if (!submit_bio_checks(bio, interposer)) goto queue_exit; bio_set_flag(bio, BIO_INTERPOSED); current->bio_list = bio_list; ret = interposer->bd_disk->fops->submit_bio(bio); current->bio_list = NULL; queue_exit: blk_queue_exit(bdev->bd_disk->queue); /* Resubmit remaining bios */ while ((bio = bio_list_pop(&bio_list[0]))) ret = submit_bio_noacct(bio); return ret; } blk_qc_t submit_bio_noacct(struct bio *bio) { if (bio->bi_bdev->bd_interposer && !bio_flagged(bio, BIO_INTERPOSED) return submit_bio_interposed(bio); ... } Note that both with this and your original code the interposer must never resubmit I/O to itself. Is that actually the case for DM? I'm trying to think of a good debug check for that, but right now I can't think of something that doesn't cause any overhead for n
The 03/10/2021 15:34, Christoph Hellwig wrote: > On Wed, Mar 10, 2021 at 08:28:12AM +0300, Sergei Shtepa wrote: > > > So instead of doing this shoudn't the interposer just always submit to the > > > whole device? But if we keep it, the logic in this funtion should go > > > into a block layer helper, passing a block device instead of the > > > > > device-mapper allows to create devices of any size using only part of > > the underlying device. Therefore, it is not possible to apply the > > interposer to the whole block device. > > Perhaps it makes sense to put the blk_partition_unremap() function in the > > block layer? I'm not sure that's a good thing. > > I suspect the answer is to not remap bios that are going to be handled > by the interposer. In fact much of submit_bio_checks as-is is a bad > idea for interposed devices. I think what we need to do instead is to > pass an explicit bdev to submit_bio_checks and use that everywhere, > including in the subfunctions. > > With that we might also be able to remove the separate interpose hook > and thus struct bdev_interposer entirely as now ->submit_bio of the > interposer could do all the work: > > static noinline blk_qc_t submit_bio_interposed(struct bio *bio) > { > struct block_device *orig_bdev = bio->bi_bdev, *interposer; > struct bio_list bio_list[2] = { }; > blk_qc_t ret = BLK_QC_T_NONE; > > if (current->bio_list) { > bio_list_add(¤t->bio_list[0], bio); > return BLK_QC_T_NONE; > } > > if (unlikely(bio_queue_enter(bio))) > return BLK_QC_T_NONE; > > interposer = orig_bdev->bd_interposer; > if (unlikely(!interposer)) { > /* interposer was removed */ > bio_list_add(¤t->bio_list[0], bio); > goto queue_exit; > } > if (!submit_bio_checks(bio, interposer)) > goto queue_exit; > > bio_set_flag(bio, BIO_INTERPOSED); > > current->bio_list = bio_list; > ret = interposer->bd_disk->fops->submit_bio(bio); > current->bio_list = NULL; > > queue_exit: > blk_queue_exit(bdev->bd_disk->queue); > > /* Resubmit remaining bios */ > while ((bio = bio_list_pop(&bio_list[0]))) > ret = submit_bio_noacct(bio); > return ret; > } > > blk_qc_t submit_bio_noacct(struct bio *bio) > { > if (bio->bi_bdev->bd_interposer && !bio_flagged(bio, BIO_INTERPOSED) > return submit_bio_interposed(bio); > > ... > } Your point of view is very interesting. I like. I will try to implement it and check how it works. So far, I see the problem in that the interposer device has to intercept all bio requests from the original device. It will not be possible to implement an interception of some part. Device mapper can create its own target for a part of the block device. But maybe it's a good thing. First, there is little real benefit from being able to intercept bio requests from a part of the block device. In real use, this may not be necessary. Secondly, it will get rid of the problem when part of the bio needs to be intercepted, and part does not. I'd like to know Mike's opinion on this issue. > > Note that both with this and your original code the interposer must > never resubmit I/O to itself. Is that actually the case for DM? I'm > trying to think of a good debug check for that, but right now I can't > think of something that doesn't cause any overhead for n I believe that the BIO_INTERPOSED flag is quite good at solving this problem. When cloning a bio, the flag is passed, which means that bio cannot be called twice. Thank you again. Because of you, I will have to rewrite some code again ;) But it's all for the best.
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 5953ff2bd260..e5c845f9b1df 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -21,6 +21,8 @@ #define DM_RESERVED_MAX_IOS 1024 +struct dm_interposed_dev; + struct dm_kobject_holder { struct kobject kobj; struct completion completion; @@ -114,6 +116,10 @@ struct mapped_device { bool init_tio_pdu:1; struct srcu_struct io_barrier; + + /* for interposers logic */ + bool is_interposed; + struct dm_interposed_dev *ip_dev; }; void disable_discard(struct mapped_device *md); diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 5e306bba4375..2bcb316144a1 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1267,6 +1267,11 @@ static inline fmode_t get_mode(struct dm_ioctl *param) return mode; } +static inline bool get_interposer_flag(struct dm_ioctl *param) +{ + return (param->flags & DM_INTERPOSED_FLAG); +} + static int next_target(struct dm_target_spec *last, uint32_t next, void *end, struct dm_target_spec **spec, char **target_params) { @@ -1338,6 +1343,8 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si if (!md) return -ENXIO; + md->is_interposed = get_interposer_flag(param); + r = dm_table_create(&t, get_mode(param), param->target_count, md); if (r) goto err; @@ -2098,6 +2105,8 @@ int __init dm_early_create(struct dm_ioctl *dmi, if (r) goto err_hash_remove; + md->is_interposed = get_interposer_flag(dmi); + /* add targets */ for (i = 0; i < dmi->target_count; i++) { r = dm_table_add_target(t, spec_array[i]->target_type, diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 95391f78b8d5..0b2f9b66ade5 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -6,6 +6,7 @@ */ #include "dm-core.h" +#include "dm-interposer.h" #include <linux/module.h> #include <linux/vmalloc.h> @@ -225,12 +226,13 @@ void dm_table_destroy(struct dm_table *t) /* * See if we've already got a device in the list. */ -static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev) +static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev, bool is_interposed) { struct dm_dev_internal *dd; list_for_each_entry (dd, l, list) - if (dd->dm_dev->bdev->bd_dev == dev) + if ((dd->dm_dev->bdev->bd_dev == dev) && + (dd->dm_dev->is_interposed == is_interposed)) return dd; return NULL; @@ -358,6 +360,90 @@ dev_t dm_get_dev_t(const char *path) } EXPORT_SYMBOL_GPL(dm_get_dev_t); +/* + * Redirect bio from interposed device to dm device + */ +static void dm_interpose_fn(struct dm_interposed_dev *ip_dev, struct bio *bio) +{ + struct mapped_device *md = ip_dev->private; + + if (bio_flagged(bio, BIO_REMAPPED)) { + /* + * Since bio has already been remapped, we need to subtract + * the block device offset from the beginning of the disk. + */ + bio->bi_iter.bi_sector -= get_start_sect(bio->bi_bdev); + + bio_clear_flag(bio, BIO_REMAPPED); + } + + /* + * Set acceptor device. + * It is quite convenient that device mapper creates + * one disk for one block device. + */ + bio->bi_bdev = md->disk->part0; + + /* + * Bio should be resubmitted. + * The bio will be checked again and placed in current->bio_list. + */ + submit_bio_noacct(bio); +} + +static int _interposer_dev_create(struct block_device *bdev, sector_t ofs, sector_t len, + struct mapped_device *md) +{ + int ret; + + DMDEBUG("Create dm interposer."); + + if (md->ip_dev) { + DMERR("The dm interposer device already in use."); + return -EALREADY; + } + + if ((ofs + len) > bdev_nr_sectors(bdev)) { + DMERR("The specified range of sectors exceeds of the size of the block device."); + return -ERANGE; + } + + md->ip_dev = kzalloc(sizeof(struct dm_interposed_dev), GFP_KERNEL); + if (!md->ip_dev) + return -ENOMEM; + + if ((ofs == 0) && (len == 0)) + DMDEBUG("Whole block device should be interposed."); + + dm_interposer_dev_init(md->ip_dev, + ofs, len, + md, dm_interpose_fn); + + ret = dm_interposer_dev_attach(bdev, md->ip_dev); + if (ret) { + DMERR("Cannot attach dm interposer device."); + kfree(md->ip_dev); + md->ip_dev = NULL; + } + + return ret; +} + +static void _interposer_dev_remove(struct block_device *bdev, struct mapped_device *md) +{ + if (!md->ip_dev) + return; + + DMDEBUG("Remove dm interposer. %llu bios was interposed.", + atomic64_read(&md->ip_dev->ip_cnt)); + + if (dm_interposer_detach_dev(bdev, md->ip_dev)) + DMERR("Failed to detach dm interposer."); + + kfree(md->ip_dev); + md->ip_dev = NULL; +} + /* * Add a device to the list, or just increment the usage count if * it's already present. @@ -385,7 +471,7 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, return -ENODEV; } - dd = find_device(&t->devices, dev); + dd = find_device(&t->devices, dev, t->md->is_interposed); if (!dd) { dd = kmalloc(sizeof(*dd), GFP_KERNEL); if (!dd) @@ -398,15 +484,22 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, refcount_set(&dd->count, 1); list_add(&dd->list, &t->devices); - goto out; - } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) { r = upgrade_mode(dd, mode, t->md); if (r) return r; + refcount_inc(&dd->count); } - refcount_inc(&dd->count); -out: + + if (t->md->is_interposed) { + r = _interposer_dev_create(dd->dm_dev->bdev, ti->begin, ti->len, t->md); + if (r) { + dm_put_device(ti, dd->dm_dev); + DMERR("Failed to attach dm interposer."); + return r; + } + } + *result = dd->dm_dev; return 0; } @@ -446,6 +539,7 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d) { int found = 0; struct list_head *devices = &ti->table->devices; + struct mapped_device *md = ti->table->md; struct dm_dev_internal *dd; list_for_each_entry(dd, devices, list) { @@ -456,11 +550,14 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d) } if (!found) { DMWARN("%s: device %s not in table devices list", - dm_device_name(ti->table->md), d->name); + dm_device_name(md), d->name); return; } + if (md->is_interposed) + _interposer_dev_remove(d->bdev, md); + if (refcount_dec_and_test(&dd->count)) { - dm_put_table_device(ti->table->md, d); + dm_put_table_device(md, d); list_del(&dd->list); kfree(dd); } diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 50b693d776d6..466bf70a66b0 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -762,16 +762,24 @@ static int open_table_device(struct table_device *td, dev_t dev, BUG_ON(td->dm_dev.bdev); - bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _dm_claim_ptr); - if (IS_ERR(bdev)) - return PTR_ERR(bdev); + if (md->is_interposed) { - r = bd_link_disk_holder(bdev, dm_disk(md)); - if (r) { - blkdev_put(bdev, td->dm_dev.mode | FMODE_EXCL); - return r; + bdev = blkdev_get_by_dev(dev, td->dm_dev.mode, NULL); + if (IS_ERR(bdev)) + return PTR_ERR(bdev); + } else { + bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _dm_claim_ptr); + if (IS_ERR(bdev)) + return PTR_ERR(bdev); + + r = bd_link_disk_holder(bdev, dm_disk(md)); + if (r) { + blkdev_put(bdev, td->dm_dev.mode | FMODE_EXCL); + return r; + } } + td->dm_dev.is_interposed = md->is_interposed; td->dm_dev.bdev = bdev; td->dm_dev.dax_dev = dax_get_by_host(bdev->bd_disk->disk_name); return 0; @@ -785,20 +793,26 @@ static void close_table_device(struct table_device *td, struct mapped_device *md if (!td->dm_dev.bdev) return; - bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md)); - blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL); + if (td->dm_dev.is_interposed) + blkdev_put(td->dm_dev.bdev, td->dm_dev.mode); + else { + bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md)); + blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL); + } put_dax(td->dm_dev.dax_dev); td->dm_dev.bdev = NULL; td->dm_dev.dax_dev = NULL; } static struct table_device *find_table_device(struct list_head *l, dev_t dev, - fmode_t mode) + fmode_t mode, bool is_interposed) { struct table_device *td; list_for_each_entry(td, l, list) - if (td->dm_dev.bdev->bd_dev == dev && td->dm_dev.mode == mode) + if (td->dm_dev.bdev->bd_dev == dev && + td->dm_dev.mode == mode && + td->dm_dev.is_interposed == is_interposed) return td; return NULL; @@ -811,7 +825,7 @@ int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode, struct table_device *td; mutex_lock(&md->table_devices_lock); - td = find_table_device(&md->table_devices, dev, mode); + td = find_table_device(&md->table_devices, dev, mode, md->is_interposed); if (!td) { td = kmalloc_node(sizeof(*td), GFP_KERNEL, md->numa_node_id); if (!td) { diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 7f4ac87c0b32..76a6dfb1cb29 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -159,6 +159,7 @@ struct dm_dev { struct block_device *bdev; struct dax_device *dax_dev; fmode_t mode; + bool is_interposed; char name[16]; }; diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index fcff6669137b..fc4d06bb3dbb 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -362,4 +362,10 @@ enum { */ #define DM_INTERNAL_SUSPEND_FLAG (1 << 18) /* Out */ +/* + * If set, the underlying device should open without FMODE_EXCL + * and attach mapped device via bdev_interposer. + */ +#define DM_INTERPOSED_FLAG (1 << 19) /* In */ + #endif /* _LINUX_DM_IOCTL_H */
DM_INTERPOSED_FLAG allow to create dm targets on "the fly". Underlying block device opens without a flag FMODE_EXCL. Dm target receives bio from the original device via blk_interposer. Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com> --- drivers/md/dm-core.h | 6 ++ drivers/md/dm-ioctl.c | 9 +++ drivers/md/dm-table.c | 115 +++++++++++++++++++++++++++++++--- drivers/md/dm.c | 38 +++++++---- include/linux/device-mapper.h | 1 + include/uapi/linux/dm-ioctl.h | 6 ++ 6 files changed, 154 insertions(+), 21 deletions(-)