GFS2: Merge glock state fields into a bitfield

We can only merge the fields into a bitfield if the locking
rules for them are the same. In this case gl_spin covers all
of the fields (write side) but a couple of them are used
with GLF_LOCK as the read side lock, which should be ok
since we know that the field in question won't be changing
at the time.

The gl_req setting has to be done earlier (in glock.c) in order
to place it under gl_spin. The gl_reply setting also has to be
brought under gl_spin in order to comply with the new rules.

This saves 4*sizeof(unsigned int) per glock.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Bob Peterson <rpeterso@redhat.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 2dd1d72..08a8beb 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -567,6 +567,7 @@ __acquires(&gl->gl_spin)
 		set_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
 		do_error(gl, 0); /* Fail queued try locks */
 	}
+	gl->gl_req = target;
 	spin_unlock(&gl->gl_spin);
 	if (glops->go_xmote_th)
 		glops->go_xmote_th(gl);
@@ -1353,24 +1354,28 @@ static int gfs2_should_freeze(const struct gfs2_glock *gl)
  * @gl: Pointer to the glock
  * @ret: The return value from the dlm
  *
+ * The gl_reply field is under the gl_spin lock so that it is ok
+ * to use a bitfield shared with other glock state fields.
  */
 
 void gfs2_glock_complete(struct gfs2_glock *gl, int ret)
 {
 	struct lm_lockstruct *ls = &gl->gl_sbd->sd_lockstruct;
 
+	spin_lock(&gl->gl_spin);
 	gl->gl_reply = ret;
 
 	if (unlikely(test_bit(DFL_BLOCK_LOCKS, &ls->ls_flags))) {
-		spin_lock(&gl->gl_spin);
 		if (gfs2_should_freeze(gl)) {
 			set_bit(GLF_FROZEN, &gl->gl_flags);
 			spin_unlock(&gl->gl_spin);
 			return;
 		}
-		spin_unlock(&gl->gl_spin);
 	}
+
+	spin_unlock(&gl->gl_spin);
 	set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
+	smp_wmb();
 	gfs2_glock_hold(gl);
 	if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
 		gfs2_glock_put(gl);