| Message ID | 1614774618-22410-3-git-send-email-sergei.shtepa@veeam.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block-layer interposer | expand |
> +static blk_qc_t __submit_bio_interposed(struct bio *bio) > +{ > + struct bio_list bio_list[2] = { }; > + blk_qc_t ret = BLK_QC_T_NONE; > + > + current->bio_list = bio_list; > + if (likely(bio_queue_enter(bio) == 0)) { > + struct block_device *bdev = bio->bi_bdev; > + > + if (likely(bdev_has_interposer(bdev))) { > + bio_set_flag(bio, BIO_INTERPOSED); > + bdev->bd_interposer->ip_submit_bio(bio); > + } else { > + /* interposer was removed */ > + bio_list_add(¤t->bio_list[0], bio); > + } > + > + blk_queue_exit(bdev->bd_disk->queue); > + } > + current->bio_list = NULL; > + > + /* Resubmit remaining bios */ > + while ((bio = bio_list_pop(&bio_list[0]))) > + ret = submit_bio_noacct(bio); > + > + return ret; > +} > + > /** > * submit_bio_noacct - re-submit a bio to the block device layer for I/O > * @bio: The bio describing the location in memory and on the device. > @@ -1043,6 +1071,14 @@ blk_qc_t submit_bio_noacct(struct bio *bio) > return BLK_QC_T_NONE; > } > > + /* > + * Checking the BIO_INTERPOSED flag is necessary so that the bio > + * created by the bdev_interposer do not get to it for processing. > + */ > + if (bdev_has_interposer(bio->bi_bdev) && > + !bio_flagged(bio, BIO_INTERPOSED)) > + return __submit_bio_interposed(bio); > + > if (!bio->bi_bdev->bd_disk->fops->submit_bio) > return __submit_bio_noacct_mq(bio); > return __submit_bio_noacct(bio); > diff --git a/block/genhd.c b/block/genhd.c > index fcc530164b5a..1ae8516643c8 100644 > --- a/block/genhd.c > +++ b/block/genhd.c > @@ -30,6 +30,11 @@ > static struct kobject *block_depr; > > DECLARE_RWSEM(bdev_lookup_sem); > +/* > + * Prevents different block-layer interposers from attaching or detaching > + * to the block device at the same time. > + */ > +DEFINE_MUTEX(bdev_interposer_attach_lock); This one can and should be marked static. > +int bdev_interposer_attach(struct block_device *bdev, struct bdev_interposer *interposer, Please avoid the overly long line. > + int ret = 0; > + > + if (WARN_ON(!interposer)) WARN_ON_ONCE? > + return -EINVAL; > + > + if (!blk_mq_is_queue_frozen(bdev->bd_disk->queue)) > + return -EPERM; This probly should be a WARN_ON_ONCE() as well. > + > + mutex_lock(&bdev_interposer_attach_lock); > + if (bdev_has_interposer(bdev)) { > + if (bdev->bd_interposer->ip_submit_bio == ip_submit_bio) > + ret = -EALREADY; > + else > + ret = -EBUSY; > + goto out; > + } Do we really need the two different error codes here? > + > + interposer->ip_submit_bio = ip_submit_bio; I'd rather let the caller initialize the field instead of passing the submit function separately. > +void bdev_interposer_detach(struct bdev_interposer *interposer, > + const ip_submit_bio_t ip_submit_bio) > +{ > + /* Check if it is really our interposer. */ > + if (WARN_ON(bdev->bd_interposer->ip_submit_bio != ip_submit_bio)) > + goto out; I don't really see any need to pass ip_submit_bio just for this check. > + struct bdev_interposer * bd_interposer; The * goes just before the member name. > +/* > + * block layer interposers structure and functions > + */ > +typedef void (*ip_submit_bio_t) (struct bio *bio); > + > +struct bdev_interposer { > + ip_submit_bio_t ip_submit_bio; > + struct block_device *bdev; Do we need the ip_ prefix here? Also we probably don't really the the typedef for the function pointer. > +#define bdev_has_interposer(bd) ((bd)->bd_interposer != NULL) And inline function would be nice here.
Thank you, Christoph, for the review. I will correct all except two points. The 03/09/2021 20:27, Christoph Hellwig wrote: > > +static blk_qc_t __submit_bio_interposed(struct bio *bio) > > +{ > > + struct bio_list bio_list[2] = { }; > > + blk_qc_t ret = BLK_QC_T_NONE; > > + > > + current->bio_list = bio_list; > > + if (likely(bio_queue_enter(bio) == 0)) { > > + struct block_device *bdev = bio->bi_bdev; > > + > > + if (likely(bdev_has_interposer(bdev))) { > > + bio_set_flag(bio, BIO_INTERPOSED); > > + bdev->bd_interposer->ip_submit_bio(bio); > > + } else { > > + /* interposer was removed */ > > + bio_list_add(¤t->bio_list[0], bio); > > + } > > + > > + blk_queue_exit(bdev->bd_disk->queue); > > + } > > + current->bio_list = NULL; > > + > > + /* Resubmit remaining bios */ > > + while ((bio = bio_list_pop(&bio_list[0]))) > > + ret = submit_bio_noacct(bio); > > + > > + return ret; > > +} > > + > > /** > > * submit_bio_noacct - re-submit a bio to the block device layer for I/O > > * @bio: The bio describing the location in memory and on the device. > > @@ -1043,6 +1071,14 @@ blk_qc_t submit_bio_noacct(struct bio *bio) > > return BLK_QC_T_NONE; > > } > > > > + /* > > + * Checking the BIO_INTERPOSED flag is necessary so that the bio > > + * created by the bdev_interposer do not get to it for processing. > > + */ > > + if (bdev_has_interposer(bio->bi_bdev) && > > + !bio_flagged(bio, BIO_INTERPOSED)) > > + return __submit_bio_interposed(bio); > > + > > if (!bio->bi_bdev->bd_disk->fops->submit_bio) > > return __submit_bio_noacct_mq(bio); > > return __submit_bio_noacct(bio); > > diff --git a/block/genhd.c b/block/genhd.c > > index fcc530164b5a..1ae8516643c8 100644 > > --- a/block/genhd.c > > +++ b/block/genhd.c > > @@ -30,6 +30,11 @@ > > static struct kobject *block_depr; > > > > DECLARE_RWSEM(bdev_lookup_sem); > > +/* > > + * Prevents different block-layer interposers from attaching or detaching > > + * to the block device at the same time. > > + */ > > +DEFINE_MUTEX(bdev_interposer_attach_lock); > > This one can and should be marked static. > > > +int bdev_interposer_attach(struct block_device *bdev, struct bdev_interposer *interposer, > > Please avoid the overly long line. > > > + int ret = 0; > > + > > + if (WARN_ON(!interposer)) > > WARN_ON_ONCE? This function should be called quite rarely, and the absence of the interposer parameter indicates that the function is being used incorrectly. I would like to see this warning every time. > > > + return -EINVAL; > > + > > + if (!blk_mq_is_queue_frozen(bdev->bd_disk->queue)) > > + return -EPERM; > > This probly should be a WARN_ON_ONCE() as well. I think it's better to apply WARN_ON here. > > > + > > + mutex_lock(&bdev_interposer_attach_lock); > > + if (bdev_has_interposer(bdev)) { > > + if (bdev->bd_interposer->ip_submit_bio == ip_submit_bio) > > + ret = -EALREADY; > > + else > > + ret = -EBUSY; > > + goto out; > > + } > > Do we really need the two different error codes here? I think I need it. If we try to initialize the interposer again, the reason for this error is most likely in the logic of the module itself. If the interposer is occupied by someone else, then we need to let know about it. > > > + > > + interposer->ip_submit_bio = ip_submit_bio; > > I'd rather let the caller initialize the field instead of passing the > submit function separately. Yes, I think so. This will allow to keep only one parameter of the function. > > > +void bdev_interposer_detach(struct bdev_interposer *interposer, > > + const ip_submit_bio_t ip_submit_bio) > > +{ > > > + /* Check if it is really our interposer. */ > > + if (WARN_ON(bdev->bd_interposer->ip_submit_bio != ip_submit_bio)) > > + goto out; > > I don't really see any need to pass ip_submit_bio just for this check. > > > + struct bdev_interposer * bd_interposer; > > The * goes just before the member name. > > > +/* > > + * block layer interposers structure and functions > > + */ > > +typedef void (*ip_submit_bio_t) (struct bio *bio); > > + > > +struct bdev_interposer { > > + ip_submit_bio_t ip_submit_bio; > > + struct block_device *bdev; > > Do we need the ip_ prefix here? Also we probably don't really the > the typedef for the function pointer. Ok. Maybe submit_bio_hook would be better? or submit_bio_interposer. > > > +#define bdev_has_interposer(bd) ((bd)->bd_interposer != NULL) > > And inline function would be nice here.
On Wed, Mar 10, 2021 at 07:53:13AM +0300, Sergei Shtepa wrote: > > Please avoid the overly long line. > > > > > + int ret = 0; > > > + > > > + if (WARN_ON(!interposer)) > > > > WARN_ON_ONCE? > > This function should be called quite rarely, and the absence of the interposer > parameter indicates that the function is being used incorrectly. > I would like to see this warning every time. Yes. Most kernel code would in fact just remove the check entirely and let the kernel crash to indicate this. Maybe that is an even better option for such a grave API usage mistake. > > > +struct bdev_interposer { > > > + ip_submit_bio_t ip_submit_bio; > > > + struct block_device *bdev; > > > > Do we need the ip_ prefix here? Also we probably don't really the > > the typedef for the function pointer. > > Ok. Maybe submit_bio_hook would be better? or submit_bio_interposer. Or interpose_bio?
diff --git a/block/bio.c b/block/bio.c index a1c4d2900c7a..0bfbf06475ee 100644 --- a/block/bio.c +++ b/block/bio.c @@ -640,6 +640,8 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src) bio_set_flag(bio, BIO_THROTTLED); if (bio_flagged(bio_src, BIO_REMAPPED)) bio_set_flag(bio, BIO_REMAPPED); + if (bio_flagged(bio_src, BIO_INTERPOSED)) + bio_set_flag(bio, BIO_INTERPOSED); bio->bi_opf = bio_src->bi_opf; bio->bi_ioprio = bio_src->bi_ioprio; bio->bi_write_hint = bio_src->bi_write_hint; diff --git a/block/blk-core.c b/block/blk-core.c index fc60ff208497..e749507cadd3 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1018,6 +1018,34 @@ static blk_qc_t __submit_bio_noacct_mq(struct bio *bio) return ret; } +static blk_qc_t __submit_bio_interposed(struct bio *bio) +{ + struct bio_list bio_list[2] = { }; + blk_qc_t ret = BLK_QC_T_NONE; + + current->bio_list = bio_list; + if (likely(bio_queue_enter(bio) == 0)) { + struct block_device *bdev = bio->bi_bdev; + + if (likely(bdev_has_interposer(bdev))) { + bio_set_flag(bio, BIO_INTERPOSED); + bdev->bd_interposer->ip_submit_bio(bio); + } else { + /* interposer was removed */ + bio_list_add(¤t->bio_list[0], bio); + } + + blk_queue_exit(bdev->bd_disk->queue); + } + current->bio_list = NULL; + + /* Resubmit remaining bios */ + while ((bio = bio_list_pop(&bio_list[0]))) + ret = submit_bio_noacct(bio); + + return ret; +} + /** * submit_bio_noacct - re-submit a bio to the block device layer for I/O * @bio: The bio describing the location in memory and on the device. @@ -1043,6 +1071,14 @@ blk_qc_t submit_bio_noacct(struct bio *bio) return BLK_QC_T_NONE; } + /* + * Checking the BIO_INTERPOSED flag is necessary so that the bio + * created by the bdev_interposer do not get to it for processing. + */ + if (bdev_has_interposer(bio->bi_bdev) && + !bio_flagged(bio, BIO_INTERPOSED)) + return __submit_bio_interposed(bio); + if (!bio->bi_bdev->bd_disk->fops->submit_bio) return __submit_bio_noacct_mq(bio); return __submit_bio_noacct(bio); diff --git a/block/genhd.c b/block/genhd.c index fcc530164b5a..1ae8516643c8 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -30,6 +30,11 @@ static struct kobject *block_depr; DECLARE_RWSEM(bdev_lookup_sem); +/* + * Prevents different block-layer interposers from attaching or detaching + * to the block device at the same time. + */ +DEFINE_MUTEX(bdev_interposer_attach_lock); /* for extended dynamic devt allocation, currently only one major is used */ #define NR_EXT_DEVT (1 << MINORBITS) @@ -1941,3 +1946,91 @@ static void disk_release_events(struct gendisk *disk) WARN_ON_ONCE(disk->ev && disk->ev->block != 1); kfree(disk->ev); } + +/** + * bdev_interposer_attach - Attach interposer to block device + * @bdev: target block device + * @interposer: block device interposer + * @ip_submit_bio: hook for submit_bio() + * + * Returns: + * -EINVAL if @interposer is NULL. + * -EPERM if queue is not frozen. + * -EBUSY if the block device already has @interposer. + * -EALREADY if the block device already has @interposer with same callback. + * -ENODEV if the block device cannot be referenced. + * + * Disk must be frozen by blk_mq_freeze_queue(). + */ +int bdev_interposer_attach(struct block_device *bdev, struct bdev_interposer *interposer, + const ip_submit_bio_t ip_submit_bio) +{ + int ret = 0; + + if (WARN_ON(!interposer)) + return -EINVAL; + + if (!blk_mq_is_queue_frozen(bdev->bd_disk->queue)) + return -EPERM; + + mutex_lock(&bdev_interposer_attach_lock); + if (bdev_has_interposer(bdev)) { + if (bdev->bd_interposer->ip_submit_bio == ip_submit_bio) + ret = -EALREADY; + else + ret = -EBUSY; + goto out; + } + + interposer->ip_submit_bio = ip_submit_bio; + + interposer->bdev = bdgrab(bdev); + if (!interposer->bdev) { + ret = -ENODEV; + goto out; + } + + bdev->bd_interposer = interposer; +out: + mutex_unlock(&bdev_interposer_attach_lock); + + return ret; +} +EXPORT_SYMBOL_GPL(bdev_interposer_attach); + +/** + * bdev_interposer_detach - Detach interposer from block device + * @interposer: block device interposer + * @ip_submit_bio: hook for submit_bio() + * + * Disk must be frozen by blk_mq_freeze_queue(). + */ +void bdev_interposer_detach(struct bdev_interposer *interposer, + const ip_submit_bio_t ip_submit_bio) +{ + struct block_device *bdev; + + if (WARN_ON(!interposer)) + return; + + mutex_lock(&bdev_interposer_attach_lock); + + /* Check if the interposer is still active. */ + bdev = interposer->bdev; + if (WARN_ON(!bdev)) + goto out; + + if (WARN_ON(!blk_mq_is_queue_frozen(bdev->bd_disk->queue))) + goto out; + + /* Check if it is really our interposer. */ + if (WARN_ON(bdev->bd_interposer->ip_submit_bio != ip_submit_bio)) + goto out; + + bdev->bd_interposer = NULL; + interposer->bdev = NULL; + bdput(bdev); +out: + mutex_unlock(&bdev_interposer_attach_lock); +} +EXPORT_SYMBOL_GPL(bdev_interposer_detach); diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index db026b6ec15a..2b43f65bb356 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -19,6 +19,7 @@ struct io_context; struct cgroup_subsys_state; typedef void (bio_end_io_t) (struct bio *); struct bio_crypt_ctx; +struct bdev_interposer; struct block_device { sector_t bd_start_sect; @@ -46,6 +47,7 @@ struct block_device { spinlock_t bd_size_lock; /* for bd_inode->i_size updates */ struct gendisk * bd_disk; struct backing_dev_info *bd_bdi; + struct bdev_interposer * bd_interposer; /* The counter of freeze processes */ int bd_fsfreeze_count; @@ -304,6 +306,8 @@ enum { BIO_CGROUP_ACCT, /* has been accounted to a cgroup */ BIO_TRACKED, /* set if bio goes through the rq_qos path */ BIO_REMAPPED, + BIO_INTERPOSED, /* bio has been interposed and can be moved to + * a different block device */ BIO_FLAG_LAST }; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index c032cfe133c7..82f8515fa3c8 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -2033,4 +2033,21 @@ int fsync_bdev(struct block_device *bdev); int freeze_bdev(struct block_device *bdev); int thaw_bdev(struct block_device *bdev); +/* + * block layer interposers structure and functions + */ +typedef void (*ip_submit_bio_t) (struct bio *bio); + +struct bdev_interposer { + ip_submit_bio_t ip_submit_bio; + struct block_device *bdev; +}; + +#define bdev_has_interposer(bd) ((bd)->bd_interposer != NULL) + +int bdev_interposer_attach(struct block_device *bdev, struct bdev_interposer *interposer, + const ip_submit_bio_t ip_submit_bio); +void bdev_interposer_detach(struct bdev_interposer *interposer, + const ip_submit_bio_t ip_submit_bio); + #endif /* _LINUX_BLKDEV_H */
blk_interposer allows to intercept bio requests, remap bio to another devices or add new bios. Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com> --- block/bio.c | 2 + block/blk-core.c | 36 +++++++++++++++ block/genhd.c | 93 +++++++++++++++++++++++++++++++++++++++ include/linux/blk_types.h | 4 ++ include/linux/blkdev.h | 17 +++++++ 5 files changed, 152 insertions(+)