btrfs: put delayed item hook into inode

Inodes for delayed iput allocate a trivial helper structure, let's place
the list hook directly into the inode and save a kmalloc (killing a
__GFP_NOFAIL as a bonus) at the cost of increasing size of btrfs_inode.

The inode can be put into the delayed_iputs list more than once and we
have to keep the count. This means we can't use the list_splice to
process a bunch of inodes because we'd lost track of the count if the
inode is put into the delayed iputs again while it's processed.

Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 0ef5cc13fae2..61205e3bbefa 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -192,6 +192,10 @@ struct btrfs_inode {
 	/* File creation time. */
 	struct timespec i_otime;
 
+	/* Hook into fs_info->delayed_iputs */
+	struct list_head delayed_iput;
+	long delayed_iput_count;
+
 	struct inode vfs_inode;
 };