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>
diff --git a/libxfs/libxfs_priv.h b/libxfs/libxfs_priv.h
index 25f7508..ffc3e45 100644
--- a/libxfs/libxfs_priv.h
+++ b/libxfs/libxfs_priv.h
@@ -173,8 +173,9 @@
#define rcu_read_unlock() ((void) 0)
#define WARN_ON_ONCE(expr) ((void) 0)
-#define percpu_counter_read(x) (*x)
-#define percpu_counter_sum(x) (*x)
+#define percpu_counter_read(x) (*x)
+#define percpu_counter_read_positive(x) ((*x) > 0 ? (*x) : 0)
+#define percpu_counter_sum(x) (*x)
/*
* prandom_u32 is used for di_gen inode allocation, it must be zero for libxfs
diff --git a/libxfs/xfs_ialloc.c b/libxfs/xfs_ialloc.c
index 5e512be..b57f89a 100644
--- a/libxfs/xfs_ialloc.c
+++ b/libxfs/xfs_ialloc.c
@@ -621,7 +621,7 @@
*/
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;
@@ -1699,10 +1699,13 @@
* 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;
}
