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[PATCH 2/2] xfs: inode counter needs to use __percpu_counter_compare

To: xfs@xxxxxxxxxxx
Subject: [PATCH 2/2] xfs: inode counter needs to use __percpu_counter_compare
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 6 May 2015 08:01:39 +1000
Cc: linux-kernel@xxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1430863299-9341-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1430863299-9341-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

From: Dave Chinner <dchinner@xxxxxxxxxx>

Because the counter uses a custom batch size, the comparison
function needs to be aware of that batch size otherwise the
comparison does not work correctly. This leads to ASSERT failures
on generic/027 like this:

 XFS: Assertion failed: 0, file: fs/xfs/xfs_mount.c, line: 1099
 ------------[ cut here ]------------
 Call Trace:
  [<ffffffff81522a39>] xfs_mod_icount+0x99/0xc0
  [<ffffffff815285cb>] xfs_trans_unreserve_and_mod_sb+0x28b/0x5b0
  [<ffffffff8152f941>] xfs_log_commit_cil+0x321/0x580
  [<ffffffff81528e17>] xfs_trans_commit+0xb7/0x260
  [<ffffffff81503d4d>] xfs_bmap_finish+0xcd/0x1b0
  [<ffffffff8151da41>] xfs_inactive_ifree+0x1e1/0x250
  [<ffffffff8151dbe0>] xfs_inactive+0x130/0x200
  [<ffffffff81523a21>] xfs_fs_evict_inode+0x91/0xf0
  [<ffffffff811f3958>] evict+0xb8/0x190
  [<ffffffff811f433b>] iput+0x18b/0x1f0
  [<ffffffff811e8853>] do_unlinkat+0x1f3/0x320
  [<ffffffff811d548a>] ? filp_close+0x5a/0x80
  [<ffffffff811e999b>] SyS_unlinkat+0x1b/0x40
  [<ffffffff81e0892e>] system_call_fastpath+0x12/0x71

This is a regression introduced by commit 501ab32 ("xfs: use generic
percpu counters for inode counter").

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
 fs/xfs/xfs_mount.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 02f827f..900f8ce 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1106,8 +1106,9 @@ xfs_mod_icount(
        int64_t                 delta)
        /* deltas are +/-64, hence the large batch size of 128. */
-       __percpu_counter_add(&mp->m_icount, delta, 128);
-       if (percpu_counter_compare(&mp->m_icount, 0) < 0) {
+#define _ICOUNT_BATCH  128
+       __percpu_counter_add(&mp->m_icount, delta, _ICOUNT_BATCH);
+       if (__percpu_counter_compare(&mp->m_icount, 0, _ICOUNT_BATCH) < 0) {
                percpu_counter_add(&mp->m_icount, -delta);
                return -EINVAL;

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