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| /openbmc/linux/drivers/md/ |
| H A D | dm-rq.c | diff 9360d077d3197f895f34cb8e6ae1b599278abf9d Fri Sep 13 08:05:18 CDT 2024 Mikulas Patocka <mpatocka@redhat.com> Revert "dm: requeue IO if mapping table not yet available"
[ Upstream commit c8691cd0fc11197515ed148de0780d927bfca38b ]
This reverts commit fa247089de9936a46e290d4724cb5f0b845600f5.
The following sequence of commands causes a livelock - there will be
workqueue process looping and consuming 100% CPU:
dmsetup create --notable test
truncate -s 1MiB testdata
losetup /dev/loop0 testdata
dmsetup load test --table '0 2048 linear /dev/loop0 0'
dd if=/dev/zero of=/dev/dm-0 bs=16k count=1 conv=fdatasync
The livelock is caused by the commit fa247089de99. The commit claims that
it fixes a race condition, however, it is unknown what the actual race
condition is and what program is involved in the race condition.
When the inactive table is loaded, the nodes /dev/dm-0 and
/sys/block/dm-0 are created. /dev/dm-0 has zero size at this point. When
the device is suspended and resumed, the nodes /dev/mapper/test and
/dev/disk/* are created.
If some program opens a block device before it is created by dmsetup or
lvm, the program is buggy, so dm could just report an error as it used to
do before.
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: fa247089de99 ("dm: requeue IO if mapping table not yet available")
Signed-off-by: Sasha Levin <sashal@kernel.org>
|
| H A D | dm.c | diff 9360d077d3197f895f34cb8e6ae1b599278abf9d Fri Sep 13 08:05:18 CDT 2024 Mikulas Patocka <mpatocka@redhat.com> Revert "dm: requeue IO if mapping table not yet available"
[ Upstream commit c8691cd0fc11197515ed148de0780d927bfca38b ]
This reverts commit fa247089de9936a46e290d4724cb5f0b845600f5.
The following sequence of commands causes a livelock - there will be
workqueue process looping and consuming 100% CPU:
dmsetup create --notable test
truncate -s 1MiB testdata
losetup /dev/loop0 testdata
dmsetup load test --table '0 2048 linear /dev/loop0 0'
dd if=/dev/zero of=/dev/dm-0 bs=16k count=1 conv=fdatasync
The livelock is caused by the commit fa247089de99. The commit claims that
it fixes a race condition, however, it is unknown what the actual race
condition is and what program is involved in the race condition.
When the inactive table is loaded, the nodes /dev/dm-0 and
/sys/block/dm-0 are created. /dev/dm-0 has zero size at this point. When
the device is suspended and resumed, the nodes /dev/mapper/test and
/dev/disk/* are created.
If some program opens a block device before it is created by dmsetup or
lvm, the program is buggy, so dm could just report an error as it used to
do before.
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: fa247089de99 ("dm: requeue IO if mapping table not yet available")
Signed-off-by: Sasha Levin <sashal@kernel.org>
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