xfs: enable buffer deadlock postmortem diagnosis via ftrace
Create a second buf_trylock tracepoint so that we can distinguish
between a successful and a failed trylock. With this piece, we can
use a script to look at the ftrace output to detect buffer deadlocks.
[dchinner: update to if/else as per hch's suggestion]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index e71cfbd..f14daeb 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -944,10 +944,12 @@
int locked;
locked = down_trylock(&bp->b_sema) == 0;
- if (locked)
+ if (locked) {
XB_SET_OWNER(bp);
-
- trace_xfs_buf_trylock(bp, _RET_IP_);
+ trace_xfs_buf_trylock(bp, _RET_IP_);
+ } else {
+ trace_xfs_buf_trylock_fail(bp, _RET_IP_);
+ }
return locked;
}
