This is a note to let you know that I've just added the patch titled

btrfs: fix deadlock when writing out space cache

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: btrfs-fix-deadlock-when-writing-out-space-cache.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Feb 1 14:00:34 CET 2018

From: Josef Bacik jbacik@fb.com Date: Wed, 15 Nov 2017 16:20:52 -0500 Subject: btrfs: fix deadlock when writing out space cache

From: Josef Bacik jbacik@fb.com

[ Upstream commit b77000ed558daa3bef0899d29bf171b8c9b5e6a8 ]

If we fail to prepare our pages for whatever reason (out of memory in our case) we need to make sure to drop the block_group->data_rwsem, otherwise hilarity ensues.

Signed-off-by: Josef Bacik jbacik@fb.com Reviewed-by: Omar Sandoval osandov@fb.com Reviewed-by: Liu Bo bo.li.liu@oracle.com Reviewed-by: David Sterba dsterba@suse.com [ add label and use existing unlocking code ] Signed-off-by: David Sterba dsterba@suse.com

Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/free-space-cache.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -1253,7 +1253,7 @@ static int __btrfs_write_out_cache(struc /* Lock all pages first so we can lock the extent safely. */ ret = io_ctl_prepare_pages(io_ctl, inode, 0); if (ret) - goto out; + goto out_unlock;

lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1, &cached_state); @@ -1346,6 +1346,7 @@ out_nospc_locked: out_nospc: cleanup_write_cache_enospc(inode, io_ctl, &cached_state, &bitmap_list);

+out_unlock: if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA)) up_write(&block_group->data_rwsem);

Patches currently in stable-queue which might be from jbacik@fb.com are

queue-4.9/btrfs-fix-deadlock-when-writing-out-space-cache.patch