6.13-stable review patch. If anyone has any objections, please let me know.
------------------
From: Christoph Hellwig <hch@xxxxxx>
[ Upstream commit c99f66e4084a62a2cc401c4704a84328aeddc9ec ]
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: ff956a3be95b ("block: use queue_limits_commit_update in queue_discard_max_store")
Fixes: 0327ca9d53bf ("block: use queue_limits_commit_update in queue_max_sectors_store")
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Reviewed-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Link: https://lore.kernel.org/r/20250110054726.1499538-7-hch@xxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
block/blk-sysfs.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index d2aa2177e4ba5..e828be777206b 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -694,22 +694,24 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
if (entry->load_module)
entry->load_module(disk, page, length);
- 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;
--
2.39.5
