[PATCH] xfs: enforce imax_pct when we have per-cpu SB accounting

[Darrick J. Wong]

When per-CPU superblock counters are enabled (i.e. SMP=y), we don't
update the in-core superblock's sb_icount value prior to checking if
we're already at maximum inodes.  Therefore, it's possible for a tight
file creation loop (e.g. "for i in {0..100000}; do touch /mnt/$i;
done") to allocate far more inodes than the administrator specified at
mkfs time.  Fix this by synchronizing the counters every time we think
we need to allocate another chunk of inodes.

Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
---
 fs/xfs/libxfs/xfs_ialloc.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 116ef1d..a8aaab6 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -375,6 +375,8 @@ xfs_ialloc_ag_alloc(
 	 * at one time.
 	 */
 	newlen = args.mp->m_ialloc_inos;
+	if (args.mp->m_maxicount)
+		xfs_icsb_sync_counters(args.mp, 0);
 	if (args.mp->m_maxicount &&
 	    args.mp->m_sb.sb_icount + newlen > args.mp->m_maxicount)
 		return -ENOSPC;
@@ -1339,6 +1341,8 @@ xfs_dialloc(
 	 * okalloc so we scan all available agi structures for a free
 	 * inode.
 	 */
+	if (mp->m_maxicount)
+		xfs_icsb_sync_counters(mp, 0);
 	if (mp->m_maxicount &&
 	    mp->m_sb.sb_icount + mp->m_ialloc_inos > mp->m_maxicount) {
 		noroom = 1;