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[PATCH RFC 1/2] xfs: conditionally force log on trylock failure of pinne

To: xfs@xxxxxxxxxxx
Subject: [PATCH RFC 1/2] xfs: conditionally force log on trylock failure of pinned/stale buf
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue, 29 Jan 2013 15:42:36 -0500
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1359492157-30521-1-git-send-email-bfoster@xxxxxxxxxx>
References: <1359492157-30521-1-git-send-email-bfoster@xxxxxxxxxx>
xfs_force_log() is not safe from all contexts. Add a flag parameter
to xfs_buf_trylock() to specify when the force is appropriate and
create a macro to preserve current behavior.

Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
---
 fs/xfs/xfs_buf.c |    8 +++++---
 fs/xfs/xfs_buf.h |    3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index fbbb9eb..2e04a44 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -943,15 +943,17 @@ xfs_buf_rele(
  *     to push on stale inode buffers.
  */
 int
-xfs_buf_trylock(
-       struct xfs_buf          *bp)
+__xfs_buf_trylock(
+       struct xfs_buf          *bp,
+       bool                    force_log)
 {
        int                     locked;
 
        locked = down_trylock(&bp->b_sema) == 0;
        if (locked)
                XB_SET_OWNER(bp);
-       else if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
+       else if (force_log &&
+                atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
                xfs_log_force(bp->b_target->bt_mount, 0);
 
        trace_xfs_buf_trylock(bp, _RET_IP_);
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 433a12e..667b723 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -258,7 +258,8 @@ extern void xfs_buf_free(xfs_buf_t *);
 extern void xfs_buf_rele(xfs_buf_t *);
 
 /* Locking and Unlocking Buffers */
-extern int xfs_buf_trylock(xfs_buf_t *);
+#define xfs_buf_trylock(bp) __xfs_buf_trylock(bp, true)
+extern int __xfs_buf_trylock(xfs_buf_t *, bool);
 extern void xfs_buf_lock(xfs_buf_t *);
 extern void xfs_buf_unlock(xfs_buf_t *);
 #define xfs_buf_islocked(bp) \
-- 
1.7.7.6

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