[09/10] loop: document why loop_clear_limits updates queue limits without freezing

Commit Message

Christoph Hellwig Jan. 6, 2025, 10:06 a.m. UTC

Signed-off-by: Christoph Hellwig <[e-mail]>
---
 drivers/block/loop.c | 7 +++++++
 1 file changed, 7 insertions(+)

Patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 836a53eef4b4..84b007b9c38c 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -311,6 +311,13 @@  static void loop_clear_limits(struct loop_device *lo, int mode)
 		lim.discard_granularity = 0;
 	}
 
+	/*
+	 * XXX: this updates the queue limits without freezing the queue, which
+	 * is against the locking protocol and dangerous.  But we can't just
+	 * freeze the queue as we're inside the ->queue_rq method here.  So this
+	 * should move out into a workqueue unless we get the file operations to
+	 * advertise if they support specific fallocate operations.
+	 */
 	queue_limits_commit_update(lo->lo_queue, &lim);
 }