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

JIRA: https://issues.redhat.com/browse/RHEL-71345
Upstream Status: for-6.4/block

commit c99f66e
Author: Christoph Hellwig <hch@lst.de>
Date:   Fri Jan 10 06:47:14 2025 +0100

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

    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: ff956a3 ("block: use queue_limits_commit_update in queue_discard_max_store")
    Fixes: 0327ca9 ("block: use queue_limits_commit_update in queue_max_sectors_store")
    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>

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Author: Ming Lei

block/blk-sysfs.c

@@ -681,22 +681,24 @@ 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;