linux-kernel - [PATCH 4.19 555/639] Btrfs: fix inode cache waiters hanging on path allocation failure

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Message-Id: <20200124093158.757266300@linuxfoundation.org>
Date:   Fri, 24 Jan 2020 10:32:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nikolay Borisov <nborisov@...e.com>,
        Filipe Manana <fdmanana@...e.com>,
        David Sterba <dsterba@...e.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 555/639] Btrfs: fix inode cache waiters hanging on path allocation failure

From: Filipe Manana <fdmanana@...e.com>

[ Upstream commit 9d123a35d7e97bb2139747b16127c9b22b6a593e ]

If the caching thread fails to allocate a path, it returns without waking
up any cache waiters, leaving them hang forever. Fix this by following the
same approach as when we fail to start the caching thread: print an error
message, disable inode caching and make the wakers fallback to non-caching
mode behaviour (calling btrfs_find_free_objectid()).

Fixes: 581bb050941b4f ("Btrfs: Cache free inode numbers in memory")
Reviewed-by: Nikolay Borisov <nborisov@...e.com>
Signed-off-by: Filipe Manana <fdmanana@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/btrfs/inode-map.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 7c4d0107c6fb9..c7dcb7c521086 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -41,8 +41,10 @@ static int caching_kthread(void *data)
 		return 0;
 
 	path = btrfs_alloc_path();
-	if (!path)
+	if (!path) {
+		fail_caching_thread(root);
 		return -ENOMEM;
+	}
 
 	/* Since the commit root is read-only, we can safely skip locking. */
 	path->skip_locking = 1;
-- 
2.20.1