[PATCH 004/119] xfs: enable buffer deadlock postmortem diagnosis via ftrace

Darrick J. Wong
2016-06-17T01:18:27Z

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.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_buf.c | 3 ++-
fs/xfs/xfs_trace.h | 1 +
2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index efa2a73..2333db7 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -947,7 +947,8 @@ xfs_buf_trylock(
if (locked)
XB_SET_OWNER(bp);

- trace_xfs_buf_trylock(bp, _RET_IP_);
+ locked ? trace_xfs_buf_trylock(bp, _RET_IP_) :
+ trace_xfs_buf_trylock_fail(bp, _RET_IP_);
return locked;
}

diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index ea94ee0..68f27f7 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -354,6 +354,7 @@ DEFINE_BUF_EVENT(xfs_buf_submit_wait);
DEFINE_BUF_EVENT(xfs_buf_bawrite);
DEFINE_BUF_EVENT(xfs_buf_lock);
DEFINE_BUF_EVENT(xfs_buf_lock_done);
+DEFINE_BUF_EVENT(xfs_buf_trylock_fail);
DEFINE_BUF_EVENT(xfs_buf_trylock);
DEFINE_BUF_EVENT(xfs_buf_unlock);
DEFINE_BUF_EVENT(xfs_buf_iowait);