[PATCH] gfs2: harden gfs2_glock_hold

Function gfs2_glock_hold() is expected only to be called when the glock is
held, so use lockref_get_not_zero() instead of lockref_get_not_dead().

In addition, when an asynchronous callback arrives in gfs2_glock_cb(), the
glock can already be dead (from __gfs2_glock_put()), or it can be on the glock
lru list with refcount 0, so we cannot use gfs2_glock_hold() there.

With gfs2_glock_cb() now handling dead glocks, we can remove the racy check in
gdlm_bast().

Signed-off-by: Andreas Gruenbacher <[email protected]>
---
 fs/gfs2/glock.c    | 6 ++++--
 fs/gfs2/lock_dlm.c | 3 ---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 558c8c660a3d..9cf59ee2f443 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -183,7 +183,7 @@ static void gfs2_free_dead_glocks(struct gfs2_sbd *sdp)
 
 struct gfs2_glock *gfs2_glock_hold(struct gfs2_glock *gl)
 {
-	if (!lockref_get_not_dead(&gl->gl_lockref))
+	if (!lockref_get_not_zero(&gl->gl_lockref))
 		GLOCK_BUG_ON(gl, 1);
 	return gl;
 }
@@ -1769,7 +1769,9 @@ void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
 {
 	unsigned long delay = 0;
 
-	gfs2_glock_hold(gl);
+	if (!lockref_get_not_dead(&gl->gl_lockref))
+		return;
+
 	spin_lock(&gl->gl_lockref.lock);
 	if (!list_empty(&gl->gl_holders) &&
 	    glock_type(gl) == LM_TYPE_INODE) {
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index ab7ac8e634bf..babce07b84f1 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -182,9 +182,6 @@ static void gdlm_bast(void *arg, int mode)
 {
 	struct gfs2_glock *gl = arg;
 
-	if (__lockref_is_dead(&gl->gl_lockref))
-		return;
-
 	switch (mode) {
 	case DLM_LOCK_EX:
 		gfs2_glock_cb(gl, LM_ST_UNLOCKED);
-- 
2.55.0