[PATCH v3 3/4] btrfs: set AS_UNCHARGED on the btree_inode

[Boris Burkov <boris@bur.io>]

extent_buffers are global and shared so their pages should not belong to
any particular cgroup (currently whichever cgroups happens to allocate
the extent_buffer).

Btrfs tree operations should not arbitrarily block on cgroup reclaim or
have the shared extent_buffer pages on a cgroup's reclaim lists.

Acked-by: David Sterba <dsterba@suse.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Tested-by: syzbot@syzkaller.appspotmail.com
Signed-off-by: Boris Burkov <boris@bur.io>
---
 fs/btrfs/disk-io.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 70fc4e7cc5a0..24ac4006dfe2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1930,6 +1930,7 @@ static int btrfs_init_btree_inode(struct super_block *sb)
 	BTRFS_I(inode)->root = btrfs_grab_root(fs_info->tree_root);
 	set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
 	__insert_inode_hash(inode, hash);
+	set_bit(AS_UNCHARGED, &inode->i_mapping->flags);
 	fs_info->btree_inode = inode;
 
 	return 0;
-- 
2.50.1