GFS2: Fix recovery stuck bug (try #2)

This is a clean up of the code which deals with LM_FLAG_NOEXP
which aims to remove any possible race conditions by using
gl_spin to cover the gap between testing for the LM_FLAG_NOEXP
and the GL_FROZEN flag.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 39 insertions, 7 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 2b3d8f8a8393..9adf8f924e08 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1063,6 +1063,9 @@ int gfs2_glock_nq(struct gfs2_holder *gh)
 
         spin_lock(&gl->gl_spin);
         add_to_queue(gh);
+        if ((LM_FLAG_NOEXP & gh->gh_flags) &&
+            test_and_clear_bit(GLF_FROZEN, &gl->gl_flags))
+                set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
         run_queue(gl, 1);
         spin_unlock(&gl->gl_spin);
 
@@ -1320,6 +1323,36 @@ void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
 }
 
 /**
+ * gfs2_should_freeze - Figure out if glock should be frozen
+ * @gl: The glock in question
+ *
+ * Glocks are not frozen if (a) the result of the dlm operation is
+ * an error, (b) the locking operation was an unlock operation or
+ * (c) if there is a "noexp" flagged request anywhere in the queue
+ *
+ * Returns: 1 if freezing should occur, 0 otherwise
+ */
+
+static int gfs2_should_freeze(const struct gfs2_glock *gl)
+{
+        const struct gfs2_holder *gh;
+
+        if (gl->gl_reply & ~LM_OUT_ST_MASK)
+                return 0;
+        if (gl->gl_target == LM_ST_UNLOCKED)
+                return 0;
+
+        list_for_each_entry(gh, &gl->gl_holders, gh_list) {
+                if (test_bit(HIF_HOLDER, &gh->gh_iflags))
+                        continue;
+                if (LM_FLAG_NOEXP & gh->gh_flags)
+                        return 0;
+        }
+
+        return 1;
+}
+
+/**
  * gfs2_glock_complete - Callback used by locking
  * @gl: Pointer to the glock
  * @ret: The return value from the dlm
@@ -1329,18 +1362,17 @@ void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
 void gfs2_glock_complete(struct gfs2_glock *gl, int ret)
 {
         struct lm_lockstruct *ls = &gl->gl_sbd->sd_lockstruct;
+
         gl->gl_reply = ret;
+
         if (unlikely(test_bit(DFL_BLOCK_LOCKS, &ls->ls_flags))) {
-                struct gfs2_holder *gh;
                 spin_lock(&gl->gl_spin);
-                gh = find_first_waiter(gl);
-                if ((!(gh && (gh->gh_flags & LM_FLAG_NOEXP)) &&
-                     (gl->gl_target != LM_ST_UNLOCKED)) ||
-                    ((ret & ~LM_OUT_ST_MASK) != 0))
+                if (gfs2_should_freeze(gl)) {
                         set_bit(GLF_FROZEN, &gl->gl_flags);
-                spin_unlock(&gl->gl_spin);
-                if (test_bit(GLF_FROZEN, &gl->gl_flags))
+                        spin_unlock(&gl->gl_spin);
                         return;
+                }
+                spin_unlock(&gl->gl_spin);
         }
         set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
         gfs2_glock_hold(gl);