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UPSTREAM: block: fix queue freeze vs limits lock order in sysfs store methods

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queue_attr_store() always freezes a device queue before calling the
attribute store operation. For attributes that control queue limits, the
store operation will also lock the queue limits with a call to
queue_limits_start_update(). However, some drivers (e.g. SCSI sd) may
need to issue commands to a device to obtain limit values from the
hardware with the queue limits locked. This creates a potential ABBA
deadlock situation if a user attempts to modify a limit (thus freezing
the device queue) while the device driver starts a revalidation of the
device queue limits.

Avoid such deadlock by not freezing the queue before calling the
->store_limit() method in struct queue_sysfs_entry and instead use the
queue_limits_commit_update_frozen helper to freeze the queue after taking
the limits lock.

This also removes taking the sysfs lock for the store_limit method as
it doesn't protect anything here, but creates even more nesting.
Hopefully it will go away from the actual sysfs methods entirely soon.

(commit log adapted from a similar patch from  Damien Le Moal)

Fixes: ff956a3be9 ("block: use queue_limits_commit_update in queue_discard_max_store")
Fixes: 0327ca9d53 ("block: use queue_limits_commit_update in queue_max_sectors_store")
Change-Id: I333037c1af6516b24675832799d910529642eb44
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20250110054726.1499538-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(cherry picked from commit c99f66e4084a62a2cc401c4704a84328aeddc9ec)
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Christoph Hellwig
2025-01-10 06:47:14 +01:00
committed by Bart Van Assche
parent e4eb47a3ec
commit 32ab5e2dd9
1 changed files with 10 additions and 8 deletions
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18
block/blk-sysfs.c
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@@ -684,22 +684,24 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
return res;
}
mutex_lock(&q->sysfs_lock);
blk_mq_freeze_queue(q);
if (entry->store_limit) {
struct queue_limits lim = queue_limits_start_update(q);
res = entry->store_limit(disk, page, length, &lim);
if (res < 0) {
queue_limits_cancel_update(q);
} else {
res = queue_limits_commit_update(q, &lim);
if (!res)
res = length;
return res;
}
} else {
res = entry->store(disk, page, length);
res = queue_limits_commit_update_frozen(q, &lim);
if (res)
return res;
return length;
}
mutex_lock(&q->sysfs_lock);
blk_mq_freeze_queue(q);
res = entry->store(disk, page, length);
blk_mq_unfreeze_queue(q);
mutex_unlock(&q->sysfs_lock);
return res;