FAILED: patch "[PATCH] xfs: check for dead buffers in xfs_buf_find_insert" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 07eae0fa67ca4bbb199ad85645e0f9dfaef931cd
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025020447-mastiff-cauterize-c488@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 07eae0fa67ca4bbb199ad85645e0f9dfaef931cd Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <[email protected]>
Date: Thu, 16 Jan 2025 07:01:41 +0100
Subject: [PATCH] xfs: check for dead buffers in xfs_buf_find_insert

Commit 32dd4f9c506b ("xfs: remove a superflous hash lookup when inserting new buffers") converted xfs_buf_find_insert to use rhashtable_lookup_get_insert_fast and thus an operation that returns the existing buffer when an insert would duplicate the hash key. But this code path misses the check for a buffer with a reference count of zero, which could lead to reusing an about to be freed buffer. Fix this by using the same atomic_inc_not_zero pattern as xfs_buf_insert.

index d9636bff16ce..183428fbc607 100644
@@ -655,9 +655,8 @@ xfs_buf_find_insert(
 		spin_unlock(&bch->bc_lock);
 		goto out_free_buf;
 	}
-	if (bp) {
+	if (bp && atomic_inc_not_zero(&bp->b_hold)) {
 		/* found an existing buffer */
-		atomic_inc(&bp->b_hold);
 		spin_unlock(&bch->bc_lock);
 		error = xfs_buf_find_lock(bp, flags);
 		if (error)