xfs: per-filesystem stats in sysfs

This patch implements per-filesystem stats objects in sysfs. It
depends on the application of the previous patch series that
develops the infrastructure to support both xfs global stats and
xfs per-fs stats in sysfs.

Stats objects are instantiated when an xfs filesystem is mounted
and deleted on unmount. With this patch, the stats directory is
created and populated with the familiar stats and stats_clear files.
Example:
        /sys/fs/xfs/sda9/stats/stats
        /sys/fs/xfs/sda9/stats/stats_clear

With this patch, the individual counts within the new per-fs
stats file(s) remain at zero. Functions that use the the macros
to increment, decrement, and add-to the per-fs stats counts will
be covered in a separate new patch to follow this one. Note that
the counts within the global stats file (/sys/fs/xfs/stats/stats)
advance normally and can be cleared as it was prior to this patch.

[dchinner: move setup/teardown to xfs_fs_{fill|put}_super() so
it is down before/after any path that uses the per-mount stats. ]

Signed-off-by: Bill O'Donnell <billodo@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_mount.c

@@ -693,10 +693,15 @@ xfs_mountfs(
 	if (error)
 		goto out;
 
-	error = xfs_uuid_mount(mp);
+	error = xfs_sysfs_init(&mp->m_stats.xs_kobj, &xfs_stats_ktype,
+			       &mp->m_kobj, "stats");
 	if (error)
 		goto out_remove_sysfs;
 
+	error = xfs_uuid_mount(mp);
+	if (error)
+		goto out_del_stats;
+
 	/*
 	 * Set the minimum read and write sizes
 	 */
@@ -971,6 +976,8 @@ xfs_mountfs(
 	xfs_da_unmount(mp);
  out_remove_uuid:
 	xfs_uuid_unmount(mp);
+ out_del_stats:
+	xfs_sysfs_del(&mp->m_stats.xs_kobj);
  out_remove_sysfs:
 	xfs_sysfs_del(&mp->m_kobj);
  out:
@@ -1047,6 +1054,7 @@ xfs_unmountfs(
 		xfs_warn(mp, "Unable to update superblock counters. "
 				"Freespace may not be correct on next mount.");
 
+
 	xfs_log_unmount(mp);
 	xfs_da_unmount(mp);
 	xfs_uuid_unmount(mp);
@@ -1056,6 +1064,7 @@ xfs_unmountfs(
 #endif
 	xfs_free_perag(mp);
 
+	xfs_sysfs_del(&mp->m_stats.xs_kobj);
 	xfs_sysfs_del(&mp->m_kobj);
 }
 

fs/xfs/xfs_mount.h

@@ -127,6 +127,7 @@ typedef struct xfs_mount {
 	int64_t			m_low_space[XFS_LOWSP_MAX];
 						/* low free space thresholds */
 	struct xfs_kobj		m_kobj;
+	struct xstats		m_stats;	/* per-fs stats */
 
 	struct workqueue_struct *m_buf_workqueue;
 	struct workqueue_struct	*m_data_workqueue;

fs/xfs/xfs_super.c

@@ -1474,9 +1474,16 @@ xfs_fs_fill_super(
 	if (error)
 		goto out_destroy_workqueues;
 
+	/* Allocate stats memory before we do operations that might use it */
+	mp->m_stats.xs_stats = alloc_percpu(struct xfsstats);
+	if (!mp->m_stats.xs_stats) {
+		error = PTR_ERR(mp->m_stats.xs_stats);
+		goto out_destroy_counters;
+	}
+
 	error = xfs_readsb(mp, flags);
 	if (error)
-		goto out_destroy_counters;
+		goto out_free_stats;
 
 	error = xfs_finish_flags(mp);
 	if (error)
@@ -1545,9 +1552,11 @@ xfs_fs_fill_super(
 	xfs_filestream_unmount(mp);
  out_free_sb:
 	xfs_freesb(mp);
+ out_free_stats:
+	free_percpu(mp->m_stats.xs_stats);
  out_destroy_counters:
 	xfs_destroy_percpu_counters(mp);
-out_destroy_workqueues:
+ out_destroy_workqueues:
 	xfs_destroy_mount_workqueues(mp);
  out_close_devices:
 	xfs_close_devices(mp);
@@ -1574,6 +1583,7 @@ xfs_fs_put_super(
 	xfs_unmountfs(mp);
 
 	xfs_freesb(mp);
+	free_percpu(mp->m_stats.xs_stats);
 	xfs_destroy_percpu_counters(mp);
 	xfs_destroy_mount_workqueues(mp);
 	xfs_close_devices(mp);