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authorSteven Whitehouse <swhiteho@redhat.com>2010-09-03 09:39:20 +0100
committerSteven Whitehouse <swhiteho@redhat.com>2010-09-20 11:19:50 +0100
commit7b5e3d5fcf0d6fce66050bd0313a7dc2ae4abc62 (patch)
tree2121e7587c5bb73faeaba6e438178ea8aff570ee /fs/gfs2/glock.c
parentfe08d5a89726675a920b0e9bbbe849c46b27a6e5 (diff)
GFS2: Don't enforce min hold time when two demotes occur in rapid succession
Due to the design of the VFS, it is quite usual for operations on GFS2 to consist of a lookup (requiring a shared lock) followed by an operation requiring an exclusive lock. If a remote node has cached an exclusive lock, then it will receive two demote events in rapid succession firstly for a shared lock and then to unlocked. The existing min hold time code was triggering in this case, even if the node was otherwise idle since the state change time was being updated by the initial demote. This patch introduces logic to skip the min hold timer in the case that a "double demote" of this kind has occurred. The min hold timer will still be used in all other cases. A new glock flag is introduced which is used to keep track of whether there have been any newly queued holders since the last glock state change. The min hold time is only applied if the flag is set. Signed-off-by: Steven Whitehouse <swhiteho@redhat.com> Tested-by: Abhijith Das <adas@redhat.com>
Diffstat (limited to 'fs/gfs2/glock.c')
-rw-r--r--fs/gfs2/glock.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 9adf8f924e08..8e478e27f1f7 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -441,6 +441,8 @@ static void state_change(struct gfs2_glock *gl, unsigned int new_state)
else
gfs2_glock_put_nolock(gl);
}
+ if (held1 && held2 && list_empty(&gl->gl_holders))
+ clear_bit(GLF_QUEUED, &gl->gl_flags);
gl->gl_state = new_state;
gl->gl_tchange = jiffies;
@@ -1012,6 +1014,7 @@ fail:
if (unlikely((gh->gh_flags & LM_FLAG_PRIORITY) && !insert_pt))
insert_pt = &gh2->gh_list;
}
+ set_bit(GLF_QUEUED, &gl->gl_flags);
if (likely(insert_pt == NULL)) {
list_add_tail(&gh->gh_list, &gl->gl_holders);
if (unlikely(gh->gh_flags & LM_FLAG_PRIORITY))
@@ -1310,10 +1313,12 @@ void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
gfs2_glock_hold(gl);
holdtime = gl->gl_tchange + gl->gl_ops->go_min_hold_time;
- if (time_before(now, holdtime))
- delay = holdtime - now;
- if (test_bit(GLF_REPLY_PENDING, &gl->gl_flags))
- delay = gl->gl_ops->go_min_hold_time;
+ if (test_bit(GLF_QUEUED, &gl->gl_flags)) {
+ if (time_before(now, holdtime))
+ delay = holdtime - now;
+ if (test_bit(GLF_REPLY_PENDING, &gl->gl_flags))
+ delay = gl->gl_ops->go_min_hold_time;
+ }
spin_lock(&gl->gl_spin);
handle_callback(gl, state, delay);
@@ -1660,6 +1665,8 @@ static const char *gflags2str(char *buf, const unsigned long *gflags)
*p++ = 'I';
if (test_bit(GLF_FROZEN, gflags))
*p++ = 'F';
+ if (test_bit(GLF_QUEUED, gflags))
+ *p++ = 'q';
*p = 0;
return buf;
}