FAILED: patch "[PATCH] btrfs: do not BUG_ON() on tree mod log failure at" failed to apply to 5.4-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.4-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 <stable@vger.kernel.org>.

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-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 40b0a749388517de244643c09bdbb98f7dcb6ef1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023071602-oxford-etching-4c52@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

40b0a7493885 ("btrfs: do not BUG_ON() on tree mod log failure at __btrfs_cow_block()")
406808ab2f0b ("btrfs: use booleans where appropriate for the tree mod log functions")
f3a84ccd28d0 ("btrfs: move the tree mod log code into its own file")
dbcc7d57bffc ("btrfs: fix race when cloning extent buffer during rewind of an old root")
cac06d843f25 ("btrfs: introduce the skeleton of btrfs_subpage structure")
1b7ec85ef490 ("btrfs: pass root owner to read_tree_block")
bfb484d922a3 ("btrfs: cleanup extent buffer readahead")
ac5887c8e013 ("btrfs: locking: remove all the blocking helpers")
196d59ab9ccc ("btrfs: switch extent buffer tree lock to rw_semaphore")
bf77467a93bd ("btrfs: introduce BTRFS_NESTING_LEFT/BTRFS_NESTING_RIGHT")
9631e4cc1a03 ("btrfs: introduce BTRFS_NESTING_COW for cow'ing blocks")
fd7ba1c1202d ("btrfs: add nesting tags to the locking helpers")
51899412dd95 ("btrfs: introduce btrfs_path::recurse")
329ced799be8 ("btrfs: rename extent_buffer::lock_nested to extent_buffer::lock_recursed")
d16c702fe4f2 ("btrfs: ctree: check key order before merging tree blocks")
d3beaa253fd6 ("btrfs: set the lockdep class for log tree extent buffers")
ad24466588ab ("btrfs: set the correct lockdep class for new nodes")
d85327b1d8b7 ("btrfs: prefetch chunk tree leaves at mount")
49e5fb46211d ("btrfs: qgroup: export qgroups in sysfs")
5958253cf65d ("btrfs: qgroup: catch reserved space leaks at unmount time")

thanks,

greg k-h

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

From 40b0a749388517de244643c09bdbb98f7dcb6ef1 Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@suse.com>
Date: Thu, 8 Jun 2023 11:27:40 +0100
Subject: [PATCH] btrfs: do not BUG_ON() on tree mod log failure at
 __btrfs_cow_block()

At __btrfs_cow_block(), instead of doing a BUG_ON() in case we fail to
record a tree mod log root insertion operation, do a transaction abort
instead. There's really no need for the BUG_ON(), we can properly
release all resources in this context and turn the filesystem to RO mode
and in an error state instead.

CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 8496535828de..d6c29564ce49 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -584,9 +584,14 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 		    btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
 			parent_start = buf->start;
 
-		atomic_inc(&cow->refs);
 		ret = btrfs_tree_mod_log_insert_root(root->node, cow, true);
-		BUG_ON(ret < 0);
+		if (ret < 0) {
+			btrfs_tree_unlock(cow);
+			free_extent_buffer(cow);
+			btrfs_abort_transaction(trans, ret);
+			return ret;
+		}
+		atomic_inc(&cow->refs);
 		rcu_assign_pointer(root->node, cow);
 
 		btrfs_free_tree_block(trans, btrfs_root_id(root), buf,