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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
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>
-rw-r--r--fs/gfs2/glock.c15
-rw-r--r--fs/gfs2/incore.h1
-rw-r--r--fs/gfs2/trace_gfs2.h3
3 files changed, 14 insertions, 5 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 9adf8f924e0..8e478e27f1f 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;
}
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 578234bb03f..b12ca10481e 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -196,6 +196,7 @@ enum {
GLF_REPLY_PENDING = 9,
GLF_INITIAL = 10,
GLF_FROZEN = 11,
+ GLF_QUEUED = 12,
};
struct gfs2_glock {
diff --git a/fs/gfs2/trace_gfs2.h b/fs/gfs2/trace_gfs2.h
index 148d55c1417..cedb0bb96d9 100644
--- a/fs/gfs2/trace_gfs2.h
+++ b/fs/gfs2/trace_gfs2.h
@@ -39,7 +39,8 @@
{(1UL << GLF_INVALIDATE_IN_PROGRESS), "i" }, \
{(1UL << GLF_REPLY_PENDING), "r" }, \
{(1UL << GLF_INITIAL), "I" }, \
- {(1UL << GLF_FROZEN), "F" })
+ {(1UL << GLF_FROZEN), "F" }, \
+ {(1UL << GLF_QUEUED), "q" })
#ifndef NUMPTY
#define NUMPTY