xfs: use generic percpu counters for free inode counter

XFS has hand-rolled per-cpu counters for the superblock since before
there was any generic implementation. The free inode counter is not
used for any limit enforcement - the per-AG free inode counters are
used during allocation to determine if there are inode available for
allocation.

Hence we don't need any of the complexity of the hand-rolled
counters and we can simply replace them with generic per-cpu
counters similar to the inode counter.

This version introduces a xfs_mod_ifree() helper function from
Christoph Hellwig.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 76b18c8c58c5..7ce997d43d81 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -84,6 +84,7 @@ typedef struct xfs_mount {
         struct xfs_sb           m_sb;           /* copy of fs superblock */
         spinlock_t              m_sb_lock;      /* sb counter lock */
         struct percpu_counter   m_icount;       /* allocated inodes counter */
+        struct percpu_counter   m_ifree;        /* free inodes counter */
 
         struct xfs_buf          *m_sb_bp;       /* buffer for superblock */
         char                    *m_fsname;      /* filesystem name */
@@ -391,6 +392,7 @@ extern int	xfs_mod_incore_sb(xfs_mount_t *, xfs_sb_field_t, int64_t, int);
 extern int      xfs_mod_incore_sb_batch(xfs_mount_t *, xfs_mod_sb_t *,
                         uint, int);
 extern int      xfs_mod_icount(struct xfs_mount *mp, int64_t delta);
+extern int      xfs_mod_ifree(struct xfs_mount *mp, int64_t delta);
 extern int      xfs_mount_log_sb(xfs_mount_t *);
 extern struct xfs_buf *xfs_getsb(xfs_mount_t *, int);
 extern int      xfs_readsb(xfs_mount_t *, int);