gfs2: Faster gfs2_upgrade_iopen_glock wakeups

Move function needs_demote() to glock.h and rename it to
glock_needs_demote().  In handle_callback(), wake up the glock when
setting the GLF_PENDING_DEMOTE flag as well.  (Setting the GLF_DEMOTE
flag already triggered a wake-up.)

With that, check for glock_needs_demote() in gfs2_upgrade_iopen_glock()
to wake up when either of those flags is set for the inode glock: the
faster we can react to contention, the better.

The GLF_PENDING_DEMOTE flag is only used for inode glocks (see
gfs2_glock_cb()) so it's okay to only check for the GLF_DEMOTE flag in
gfs2_drop_inode().  Still, using glock_needs_demote() there as well
makes the code a little easier to read.

Signed-off-by: Andreas Gruenbacher <[email protected]>

Author: Andreas Gruenbacher

fs/gfs2/glock.c

@@ -563,11 +563,11 @@ static void state_change(struct gfs2_glock *gl, unsigned int new_state)
 	gl->gl_tchange = jiffies;
 }
 
-static void gfs2_set_demote(struct gfs2_glock *gl)
+static void gfs2_set_demote(int nr, struct gfs2_glock *gl)
 {
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 
-	set_bit(GLF_DEMOTE, &gl->gl_flags);
+	set_bit(nr, &gl->gl_flags);
 	smp_mb();
 	wake_up(&sdp->sd_async_glock_wait);
 }
@@ -1101,7 +1101,7 @@ static void glock_work_func(struct work_struct *work)
 
 		if (!delay) {
 			clear_bit(GLF_PENDING_DEMOTE, &gl->gl_flags);
-			gfs2_set_demote(gl);
+			gfs2_set_demote(GLF_DEMOTE, gl);
 		}
 	}
 	run_queue(gl, 0);
@@ -1443,10 +1443,7 @@ int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs)
 static void request_demote(struct gfs2_glock *gl, unsigned int state,
 			   unsigned long delay, bool remote)
 {
-	if (delay)
-		set_bit(GLF_PENDING_DEMOTE, &gl->gl_flags);
-	else
-		gfs2_set_demote(gl);
+	gfs2_set_demote(delay ? GLF_PENDING_DEMOTE : GLF_DEMOTE, gl);
 	if (gl->gl_demote_state == LM_ST_EXCLUSIVE) {
 		gl->gl_demote_state = state;
 		gl->gl_demote_time = jiffies;
@@ -1636,12 +1633,6 @@ int gfs2_glock_poll(struct gfs2_holder *gh)
 	return test_bit(HIF_WAIT, &gh->gh_iflags) ? 0 : 1;
 }
 
-static inline bool needs_demote(struct gfs2_glock *gl)
-{
-	return (test_bit(GLF_DEMOTE, &gl->gl_flags) ||
-		test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags));
-}
-
 static void __gfs2_glock_dq(struct gfs2_holder *gh)
 {
 	struct gfs2_glock *gl = gh->gh_gl;
@@ -1650,8 +1641,8 @@ static void __gfs2_glock_dq(struct gfs2_holder *gh)
 
 	/*
 	 * This holder should not be cached, so mark it for demote.
-	 * Note: this should be done before the check for needs_demote
-	 * below.
+	 * Note: this should be done before the glock_needs_demote
+	 * check below.
 	 */
 	if (gh->gh_flags & GL_NOCACHE)
 		request_demote(gl, LM_ST_UNLOCKED, 0, false);
@@ -1664,7 +1655,7 @@ static void __gfs2_glock_dq(struct gfs2_holder *gh)
 	 * If there hasn't been a demote request we are done.
 	 * (Let the remaining holders, if any, keep holding it.)
 	 */
-	if (!needs_demote(gl)) {
+	if (!glock_needs_demote(gl)) {
 		if (list_empty(&gl->gl_holders))
 			fast_path = 1;
 	}

fs/gfs2/glock.h

@@ -285,4 +285,10 @@ static inline bool gfs2_holder_queued(struct gfs2_holder *gh)
 void gfs2_inode_remember_delete(struct gfs2_glock *gl, u64 generation);
 bool gfs2_inode_already_deleted(struct gfs2_glock *gl, u64 generation);
 
+static inline bool glock_needs_demote(struct gfs2_glock *gl)
+{
+	return (test_bit(GLF_DEMOTE, &gl->gl_flags) ||
+		test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags));
+}
+
 #endif /* __GLOCK_DOT_H__ */

fs/gfs2/super.c

@@ -1030,7 +1030,7 @@ static int gfs2_drop_inode(struct inode *inode)
 	if (inode->i_nlink &&
 	    gfs2_holder_initialized(&ip->i_iopen_gh)) {
 		struct gfs2_glock *gl = ip->i_iopen_gh.gh_gl;
-		if (test_bit(GLF_DEMOTE, &gl->gl_flags))
+		if (glock_needs_demote(gl))
 			clear_nlink(inode);
 	}
 
@@ -1294,7 +1294,7 @@ static bool gfs2_upgrade_iopen_glock(struct inode *inode)
 
 	wait_event_interruptible_timeout(sdp->sd_async_glock_wait,
 		!test_bit(HIF_WAIT, &gh->gh_iflags) ||
-		test_bit(GLF_DEMOTE, &ip->i_gl->gl_flags),
+		glock_needs_demote(ip->i_gl),
 		5 * HZ);
 	if (!test_bit(HIF_HOLDER, &gh->gh_iflags)) {
 		gfs2_glock_dq(gh);