[Cluster-devel] [GFS2 PATCH v2 5/6] gfs2: simplify do_promote and fix promote trace

[Bob Peterson <rpeterso@redhat.com>]

Before this patch, the gfs2_promote kernel trace point would would only
record the "first" flag if the go_lock function was called. This patch
simplifies do_promote by eliminating the redundant code in do_promote
and fixes the trace point by adding a new gfs2_first_holder function.
This will also be used in a future patch.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
 fs/gfs2/glock.c | 19 ++++++++++++-------
 fs/gfs2/glock.h |  7 +++++++
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index b8248ceff3c3..4fcf340603e7 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -394,6 +394,7 @@ __acquires(&gl->gl_lockref.lock)
 {
 	const struct gfs2_glock_operations *glops = gl->gl_ops;
 	struct gfs2_holder *gh, *tmp;
+	int first;
 	int ret;
 
 restart:
@@ -401,8 +402,8 @@ __acquires(&gl->gl_lockref.lock)
 		if (test_bit(HIF_HOLDER, &gh->gh_iflags))
 			continue;
 		if (may_grant(gl, gh)) {
-			if (gh->gh_list.prev == &gl->gl_holders &&
-			    glops->go_lock) {
+			first = gfs2_first_holder(gh);
+			if (first && glops->go_lock) {
 				if (!(gh->gh_flags & GL_SKIP)) {
 					spin_unlock(&gl->gl_lockref.lock);
 					/* FIXME: eliminate this eventually */
@@ -418,14 +419,18 @@ __acquires(&gl->gl_lockref.lock)
 						goto restart;
 					}
 				}
-				set_bit(HIF_HOLDER, &gh->gh_iflags);
-				trace_gfs2_promote(gh, 1);
-				gfs2_holder_wake(gh);
-				goto restart;
 			}
 			set_bit(HIF_HOLDER, &gh->gh_iflags);
-			trace_gfs2_promote(gh, 0);
+			trace_gfs2_promote(gh, first);
 			gfs2_holder_wake(gh);
+			/*
+			 * If this was the first holder, we may have released
+			 * the gl_lockref.lock, so the holders list may have
+			 * changed. For that reason, we start again at the
+			 * start of the holders queue.
+			 */
+			if (first)
+				goto restart;
 			continue;
 		}
 		if (gh->gh_list.prev == &gl->gl_holders)
diff --git a/fs/gfs2/glock.h b/fs/gfs2/glock.h
index 31a8f2f649b5..699c5e95006a 100644
--- a/fs/gfs2/glock.h
+++ b/fs/gfs2/glock.h
@@ -325,6 +325,13 @@ static inline void glock_clear_object(struct gfs2_glock *gl, void *object)
 	spin_unlock(&gl->gl_lockref.lock);
 }
 
+static inline bool gfs2_first_holder(struct gfs2_holder *gh)
+{
+	struct gfs2_glock *gl = gh->gh_gl;
+
+	return (gh->gh_list.prev == &gl->gl_holders);
+}
+
 extern void gfs2_inode_remember_delete(struct gfs2_glock *gl, u64 generation);
 extern bool gfs2_inode_already_deleted(struct gfs2_glock *gl, u64 generation);
 
-- 
2.31.1