kernel.git/drivers/md/dm.c, branch linux-6.16.y

dm: Check for forbidden splitting of zone write operations

2025-08-28T14:34:12Z

commit 409f9287dab3b53bffe8d28d883a529028aa6a42 upstream. DM targets must not split zone append and write operations using dm_accept_partial_bio() as doing so is forbidden for zone append BIOs, breaks zone append emulation using regular write BIOs and potentially creates deadlock situations with queue freeze operations. Modify dm_accept_partial_bio() to add missing BUG_ON() checks for all these cases, that is, check that the BIO is a write or write zeroes operation. This change packs all the zone related checks together under a static_branch_unlikely(&zoned_enabled) and done only if the target is a zoned device. Fixes: f211268ed1f9 ("dm: Use the block layer zone append emulation") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Reviewed-by: Mikulas Patocka Link: https://lore.kernel.org/r/20250625093327.548866-6-dlemoal@kernel.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

dm: split write BIOs on zone boundaries when zone append is not emulated

2025-08-20T16:41:44Z

commit 675f940576351bb049f5677615140b9d0a7712d0 upstream. Commit 2df7168717b7 ("dm: Always split write BIOs to zoned device limits") updates the device-mapper driver to perform splits for the write BIOs. However, it did not address the cases where DM targets do not emulate zone append, such as in the cases of dm-linear or dm-flakey. For these targets, when the write BIOs span across zone boundaries, they trigger WARN_ON_ONCE(bio_straddles_zones(bio)) in blk_zone_wplug_handle_write(). This results in I/O errors. The errors are reproduced by running blktests test case zbd/004 using zoned dm-linear or dm-flakey devices. To avoid the I/O errors, handle the write BIOs regardless whether DM targets emulate zone append or not, so that all write BIOs are split at zone boundaries. For that purpose, drop the check for zone append emulation in dm_zone_bio_needs_split(). Its argument 'md' is no longer used then drop it also. Fixes: 2df7168717b7 ("dm: Always split write BIOs to zoned device limits") Signed-off-by: Shin'ichiro Kawasaki Reviewed-by: Damien Le Moal Reviewed-by: Mikulas Patocka Link: https://lore.kernel.org/r/20250717103539.37279-1-shinichiro.kawasaki@wdc.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

dm: Always split write BIOs to zoned device limits

2025-08-20T16:41:35Z

commit 2df7168717b7d2d32bcf017c68be16e4aae9dd13 upstream. Any zoned DM target that requires zone append emulation will use the block layer zone write plugging. In such case, DM target drivers must not split BIOs using dm_accept_partial_bio() as doing so can potentially lead to deadlocks with queue freeze operations. Regular write operations used to emulate zone append operations also cannot be split by the target driver as that would result in an invalid writen sector value return using the BIO sector. In order for zoned DM target drivers to avoid such incorrect BIO splitting, we must ensure that large BIOs are split before being passed to the map() function of the target, thus guaranteeing that the limits for the mapped device are not exceeded. dm-crypt and dm-flakey are the only target drivers supporting zoned devices and using dm_accept_partial_bio(). In the case of dm-crypt, this function is used to split BIOs to the internal max_write_size limit (which will be suppressed in a different patch). However, since crypt_alloc_buffer() uses a bioset allowing only up to BIO_MAX_VECS (256) vectors in a BIO. The dm-crypt device max_segments limit, which is not set and so default to BLK_MAX_SEGMENTS (128), must thus be respected and write BIOs split accordingly. In the case of dm-flakey, since zone append emulation is not required, the block layer zone write plugging is not used and no splitting of BIOs required. Modify the function dm_zone_bio_needs_split() to use the block layer helper function bio_needs_zone_write_plugging() to force a call to bio_split_to_limits() in dm_split_and_process_bio(). This allows DM target drivers to avoid using dm_accept_partial_bio() for write operations on zoned DM devices. Fixes: f211268ed1f9 ("dm: Use the block layer zone append emulation") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Reviewed-by: Mikulas Patocka Reviewed-by: Johannes Thumshirn Link: https://lore.kernel.org/r/20250625093327.548866-4-dlemoal@kernel.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: Introduce bio_needs_zone_write_plugging()

2025-08-20T16:41:35Z

commit f70291411ba20d50008db90a6f0731efac27872c upstream. In preparation for fixing device mapper zone write handling, introduce the inline helper function bio_needs_zone_write_plugging() to test if a BIO requires handling through zone write plugging using the function blk_zone_plug_bio(). This function returns true for any write (op_is_write(bio) == true) operation directed at a zoned block device using zone write plugging, that is, a block device with a disk that has a zone write plug hash table. This helper allows simplifying the check on entry to blk_zone_plug_bio() and used in to protect calls to it for blk-mq devices and DM devices. Fixes: f211268ed1f9 ("dm: Use the block layer zone append emulation") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20250625093327.548866-3-dlemoal@kernel.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

dm: Allow .prepare_ioctl to handle ioctls directly

2025-05-04T09:35:05Z

This adds a 'bool *forward' parameter to .prepare_ioctl, which allows device mapper targets to accept ioctls to themselves instead of the underlying device. If the target already fully handled the ioctl, it sets *forward to false and device mapper won't forward it to the underlying device any more. In order for targets to actually know what the ioctl is about and how to handle it, pass also cmd and arg. As long as targets restrict themselves to interpreting ioctls of type DM_IOCTL, this is a backwards compatible change because previously, any such ioctl would have been passed down through all device mapper layers until it reached a device that can't understand the ioctl and would return an error. Signed-off-by: Kevin Wolf Reviewed-by: Benjamin Marzinski Signed-off-by: Mikulas Patocka

dm: use generic functions instead of disable_discard and disable_write_zeroes

2025-05-04T09:35:05Z

A small code cleanup: use blk_queue_disable_discard and blk_queue_disable_write_zeroes instead of disable_discard and disable_write_zeroes. Signed-off-by: Mikulas Patocka

dm: limit swapping tables for devices with zone write plugs

2025-05-04T09:35:05Z

dm_revalidate_zones() only allowed new or previously unzoned devices to call blk_revalidate_disk_zones(). If the device was already zoned, disk->nr_zones would always equal md->nr_zones, so dm_revalidate_zones() returned without doing any work. This would make the zoned settings for the device not match the new table. If the device had zone write plug resources, it could run into errors like bdev_zone_is_seq() reading invalid memory because disk->conv_zones_bitmap was the wrong size. If the device doesn't have any zone write plug resources, calling blk_revalidate_disk_zones() will always correctly update device. If blk_revalidate_disk_zones() fails, it can still overwrite or clear the current disk->nr_zones value. In this case, DM must restore the previous value of disk->nr_zones, so that the zoned settings will continue to match the previous value that it fell back to. If the device already has zone write plug resources, blk_revalidate_disk_zones() will not correctly update them, if it is called for arbitrary zoned device changes. Since there is not much need for this ability, the easiest solution is to disallow any table reloads that change the zoned settings, for devices that already have zone plug resources. Specifically, if a device already has zone plug resources allocated, it can only switch to another zoned table that also emulates zone append. Also, it cannot change the device size or the zone size. A device can switch to an error target. Fixes: bb37d77239af2 ("dm: introduce zone append emulation") Reviewed-by: Damien Le Moal Tested-by: Damien Le Moal Signed-off-by: Benjamin Marzinski Signed-off-by: Mikulas Patocka

dm: free table mempools if not used in __bind

2025-04-11T11:38:50Z

With request-based dm, the mempools don't need reloading when switching tables, but the unused table mempools are not freed until the active table is finally freed. Free them immediately if they are not needed. Fixes: 29dec90a0f1d9 ("dm: fix bio_set allocation") Reviewed-by: Damien Le Moal Tested-by: Damien Le Moal Signed-off-by: Benjamin Marzinski Signed-off-by: Mikulas Patocka

dm: don't change md if dm_table_set_restrictions() fails

2025-04-11T11:38:39Z

__bind was changing the disk capacity, geometry and mempools of the mapped device before calling dm_table_set_restrictions() which could fail, forcing dm to drop the new table. Failing here would leave the device using the old table but with the wrong capacity and mempools. Move dm_table_set_restrictions() earlier in __bind(). Since it needs the capacity to be set, save the old version and restore it on failure. Fixes: bb37d77239af2 ("dm: introduce zone append emulation") Reviewed-by: Damien Le Moal Tested-by: Damien Le Moal Signed-off-by: Benjamin Marzinski Signed-off-by: Mikulas Patocka

dm: fix unconditional IO throttle caused by REQ_PREFLUSH

2025-02-24T11:09:44Z

When a bio with REQ_PREFLUSH is submitted to dm, __send_empty_flush() generates a flush_bio with REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC, which causes the flush_bio to be throttled by wbt_wait(). An example from v5.4, similar problem also exists in upstream: crash> bt 2091206 PID: 2091206 TASK: ffff2050df92a300 CPU: 109 COMMAND: "kworker/u260:0" #0 [ffff800084a2f7f0] __switch_to at ffff80004008aeb8 #1 [ffff800084a2f820] __schedule at ffff800040bfa0c4 #2 [ffff800084a2f880] schedule at ffff800040bfa4b4 #3 [ffff800084a2f8a0] io_schedule at ffff800040bfa9c4 #4 [ffff800084a2f8c0] rq_qos_wait at ffff8000405925bc #5 [ffff800084a2f940] wbt_wait at ffff8000405bb3a0 #6 [ffff800084a2f9a0] __rq_qos_throttle at ffff800040592254 #7 [ffff800084a2f9c0] blk_mq_make_request at ffff80004057cf38 #8 [ffff800084a2fa60] generic_make_request at ffff800040570138 #9 [ffff800084a2fae0] submit_bio at ffff8000405703b4 #10 [ffff800084a2fb50] xlog_write_iclog at ffff800001280834 [xfs] #11 [ffff800084a2fbb0] xlog_sync at ffff800001280c3c [xfs] #12 [ffff800084a2fbf0] xlog_state_release_iclog at ffff800001280df4 [xfs] #13 [ffff800084a2fc10] xlog_write at ffff80000128203c [xfs] #14 [ffff800084a2fcd0] xlog_cil_push at ffff8000012846dc [xfs] #15 [ffff800084a2fda0] xlog_cil_push_work at ffff800001284a2c [xfs] #16 [ffff800084a2fdb0] process_one_work at ffff800040111d08 #17 [ffff800084a2fe00] worker_thread at ffff8000401121cc #18 [ffff800084a2fe70] kthread at ffff800040118de4 After commit 2def2845cc33 ("xfs: don't allow log IO to be throttled"), the metadata submitted by xlog_write_iclog() should not be throttled. But due to the existence of the dm layer, throttling flush_bio indirectly causes the metadata bio to be throttled. Fix this by conditionally adding REQ_IDLE to flush_bio.bi_opf, which makes wbt_should_throttle() return false to avoid wbt_wait(). Signed-off-by: Jinliang Zheng Reviewed-by: Tianxiang Peng Reviewed-by: Hao Peng Signed-off-by: Mikulas Patocka