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

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: [PATCH] xfs: enforce imax_pct when we have per-cpu SB accounting
From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Date: Tue, 5 May 2015 15:02:08 -0700
Cc: xfs <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
User-agent: Mutt/1.5.21 (2010-09-15)
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@xxxxxxxxxx>
---
 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;

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