gfs2: Minor run_queue fixes

Provide a better description of why the GLF_DEMOTE_IN_PROGRESS flag
cannot be set.

Function do_xmote() may block, so make sure it isn't called when
nonblock is true.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Andrew Price <anprice@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 1eba27bb5f3cf754f2b736230ec2b9bd094d36fa..747ee7ca44e2fe38961c42f1687f919433b48730 100644 (file)
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -832,7 +832,12 @@ __acquires(&gl->gl_lockref.lock)
                return;
        set_bit(GLF_LOCK, &gl->gl_flags);
 
-       /* While a demote is in progress, the GLF_LOCK flag must be set. */
+       /*
+        * The GLF_DEMOTE_IN_PROGRESS flag is only set intermittently during
+        * locking operations.  We have just started a locking operation by
+        * setting the GLF_LOCK flag, so the GLF_DEMOTE_IN_PROGRESS flag must
+        * be cleared.
+        */
        GLOCK_BUG_ON(gl, test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags));
 
        if (test_bit(GLF_DEMOTE, &gl->gl_flags)) {
@@ -859,6 +864,8 @@ promote:
        gh = find_first_waiter(gl);
        if (!gh)
                goto out_unlock;
+       if (nonblock)
+               goto out_sched;
        gl->gl_target = gh->gh_state;
        if (!(gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)))
                do_error(gl, 0); /* Fail queued try locks */