xfs: use percpu_counter_read_positive for mp->m_icount

Function percpu_counter_read just return the current counter, which can be
negative. This will cause the checking of "allocated inode
counts <= m_maxicount" false positive. Use percpu_counter_read_positive can
solve this problem, and be consistent with the purpose to introduce percpu
mechanism to xfs.

Signed-off-by: George Wang <xuw2015@gmail.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 07349a183a11..1c9e75521250 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -376,7 +376,7 @@ xfs_ialloc_ag_alloc(
          */
         newlen = args.mp->m_ialloc_inos;
         if (args.mp->m_maxicount &&
-            percpu_counter_read(&args.mp->m_icount) + newlen >
+            percpu_counter_read_positive(&args.mp->m_icount) + newlen >
                                                         args.mp->m_maxicount)
                 return -ENOSPC;
         args.minlen = args.maxlen = args.mp->m_ialloc_blks;
@@ -1339,10 +1339,13 @@ xfs_dialloc(
          * If we have already hit the ceiling of inode blocks then clear
          * okalloc so we scan all available agi structures for a free
          * inode.
+         *
+         * Read rough value of mp->m_icount by percpu_counter_read_positive,
+         * which will sacrifice the preciseness but improve the performance.
          */
         if (mp->m_maxicount &&
-            percpu_counter_read(&mp->m_icount) + mp->m_ialloc_inos >
-                                                        mp->m_maxicount) {
+            percpu_counter_read_positive(&mp->m_icount) + mp->m_ialloc_inos
+                                                        > mp->m_maxicount) {
                 noroom = 1;
                 okalloc = 0;
         }