kernel/linux.git/drivers/md/dm-ebs-target.c, branch v6.12.80

dm-ebs: Mark full buffer dirty even on partial write

2026-01-08T09:14:44+00:00

commit 7fa3e7d114abc9cc71cc35d768e116641074ddb4 upstream. When performing a read-modify-write(RMW) operation, any modification to a buffered block must cause the entire buffer to be marked dirty. Marking only a subrange as dirty is incorrect because the underlying device block size(ubs) defines the minimum read/write granularity. A lower device can perform I/O only on regions which are fully aligned and sized to ubs. This change ensures that write-back operations always occur in full ubs-sized chunks, matching the intended emulation semantics of the EBS target. As for user space visible impact, submitting sub-ubs and misaligned I/O for devices which are tuned to ubs sizes only, will reject such requests, therefore it can lead to losing data. Example: 1) Create a 8K nvme device in qemu by adding -device nvme,drive=drv0,serial=foo,logical_block_size=8192,physical_block_size=8192 2) Setup dm-ebs to emulate 512B to 8K mapping urezki@pc638:~/bin$ cat dmsetup.sh lower=/dev/nvme0n1 len=$(blockdev --getsz "$lower") echo "0 $len ebs $lower 0 1 16" | dmsetup create nvme-8k urezki@pc638:~/bin$ offset 0, ebs=1 and ubs=16(in sectors). 3) Create an ext4 filesystem(default 4K block size) urezki@pc638:~/bin$ sudo mkfs.ext4 -F /dev/dm-0 mke2fs 1.47.0 (5-Feb-2023) Discarding device blocks: done Creating filesystem with 2072576 4k blocks and 518144 inodes Filesystem UUID: bd0b6ca6-0506-4e31-86da-8d22c9d50b63 Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 Allocating group tables: done Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: mkfs.ext4: Input/output error while writing out and closing file system urezki@pc638:~/bin$ dmesg [ 1618.875449] buffer_io_error: 1028 callbacks suppressed [ 1618.875456] Buffer I/O error on dev dm-0, logical block 0, lost async page write [ 1618.875527] Buffer I/O error on dev dm-0, logical block 1, lost async page write [ 1618.875602] Buffer I/O error on dev dm-0, logical block 2, lost async page write [ 1618.875620] Buffer I/O error on dev dm-0, logical block 3, lost async page write [ 1618.875639] Buffer I/O error on dev dm-0, logical block 4, lost async page write [ 1618.894316] Buffer I/O error on dev dm-0, logical block 5, lost async page write [ 1618.894358] Buffer I/O error on dev dm-0, logical block 6, lost async page write [ 1618.894380] Buffer I/O error on dev dm-0, logical block 7, lost async page write [ 1618.894405] Buffer I/O error on dev dm-0, logical block 8, lost async page write [ 1618.894427] Buffer I/O error on dev dm-0, logical block 9, lost async page write Many I/O errors because the lower 8K device rejects sub-ubs/misaligned requests. with a patch: urezki@pc638:~/bin$ sudo mkfs.ext4 -F /dev/dm-0 mke2fs 1.47.0 (5-Feb-2023) Discarding device blocks: done Creating filesystem with 2072576 4k blocks and 518144 inodes Filesystem UUID: 9b54f44f-ef55-4bd4-9e40-c8b775a616ac Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 Allocating group tables: done Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: done urezki@pc638:~/bin$ sudo mount /dev/dm-0 /mnt/ urezki@pc638:~/bin$ ls -al /mnt/ total 24 drwxr-xr-x 3 root root 4096 Oct 17 15:13 . drwxr-xr-x 19 root root 4096 Jul 10 19:42 .. drwx------ 2 root root 16384 Oct 17 15:13 lost+found urezki@pc638:~/bin$ After this change: mkfs completes; mount succeeds. Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

dm-ebs: fix prefetch-vs-suspend race

2025-04-20T08:15:53+00:00

commit 9c565428788fb9b49066f94ab7b10efc686a0a4c upstream. There's a possible race condition in dm-ebs - dm bufio prefetch may be in progress while the device is suspended. Fix this by calling dm_bufio_client_reset in the postsuspend hook. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

dm-ebs: don't set the flag DM_TARGET_PASSES_INTEGRITY

2025-01-17T12:40:46+00:00

commit 47f33c27fc9565fb0bc7dfb76be08d445cd3d236 upstream. dm-ebs uses dm-bufio to process requests that are not aligned on logical sector size. dm-bufio doesn't support passing integrity data (and it is unclear how should it do it), so we shouldn't set the DM_TARGET_PASSES_INTEGRITY flag. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Fixes: d3c7b35c20d6 ("dm: add emulated block size target") Signed-off-by: Greg Kroah-Hartman

dm: stop using blk_limits_io_{min,opt}

2024-07-10T11:10:06+00:00

Remove use of the blk_limits_io_{min,opt} and assign the values directly to the queue_limits structure. For the io_opt this is a completely mechanical change, for io_min it removes flooring the limit to the physical and logical block size in the particular caller. But as blk_validate_limits will do the same later when actually applying the limits, there still is no change in overall behavior. Signed-off-by: Christoph Hellwig Signed-off-by: Mikulas Patocka

dm: update relevant MODULE_AUTHOR entries to latest dm-devel mailing list

2024-02-20T19:22:55+00:00

Signed-off-by: Mike Snitzer

dm: add helper macro for simple DM target module init and exit

2023-04-11T16:09:08+00:00

Eliminate duplicate boilerplate code for simple modules that contain a single DM target driver without any additional setup code. Add a new module_dm() macro, which replaces the module_init() and module_exit() with template functions that call dm_register_target() and dm_unregister_target() respectively. Signed-off-by: Yangtao Li Signed-off-by: Mike Snitzer

dm: push error reporting down to dm_register_target()

2023-04-11T16:01:01+00:00

Simplifies each DM target's init method by making dm_register_target() responsible for its error reporting (on behalf of targets). Signed-off-by: Yangtao Li Signed-off-by: Mike Snitzer

dm: avoid spaces before function arguments or in favour of tabs

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm: change "unsigned" to "unsigned int"

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm: add missing SPDX-License-Indentifiers

2023-02-14T19:23:06+00:00

'GPL-2.0-only' is used instead of 'GPL-2.0' because SPDX has deprecated its use. Suggested-by: John Wiele Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer