[PATCH v2 1/2] xfs: conditionally force log on trylock failure of pinned/stale buf

[Brian Foster]

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 at redhat.com>
---
 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