linux-kernel - [PATCH 14/27] GFS2: Eliminate redundant calls to may

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Date:	Wed, 26 Sep 2012 09:25:35 +0100
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	linux-kernel@...r.kernel.org, cluster-devel@...hat.com
Cc:	Bob Peterson <rpeterso@...hat.com>,
	Steven Whitehouse <swhiteho@...hat.com>
Subject: [PATCH 14/27] GFS2: Eliminate redundant calls to may_grant

From: Bob Peterson <rpeterso@...hat.com>

Function add_to_queue was checking may_grant for the passed-in
holder for every iteration of its gh2 loop. Now it only checks it
once at the beginning to see if a try lock is futile.

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

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index fca6a87..e6c2fd5 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -954,7 +954,7 @@ __acquires(&gl->gl_spin)
 	struct gfs2_sbd *sdp = gl->gl_sbd;
 	struct list_head *insert_pt = NULL;
 	struct gfs2_holder *gh2;
-	int try_lock = 0;
+	int try_futile = 0;
 
 	BUG_ON(gh->gh_owner_pid == NULL);
 	if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags))
@@ -962,7 +962,7 @@ __acquires(&gl->gl_spin)
 
 	if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) {
 		if (test_bit(GLF_LOCK, &gl->gl_flags))
-			try_lock = 1;
+			try_futile = !may_grant(gl, gh);
 		if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags))
 			goto fail;
 	}
@@ -971,9 +971,8 @@ __acquires(&gl->gl_spin)
 		if (unlikely(gh2->gh_owner_pid == gh->gh_owner_pid &&
 		    (gh->gh_gl->gl_ops->go_type != LM_TYPE_FLOCK)))
 			goto trap_recursive;
-		if (try_lock &&
-		    !(gh2->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) &&
-		    !may_grant(gl, gh)) {
+		if (try_futile &&
+		    !(gh2->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
 fail:
 			gh->gh_error = GLR_TRYFAILED;
 			gfs2_holder_wake(gh);
-- 
1.7.4

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