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-   -   GFS2: Fix potential race in glock code (http://www.linux-archive.org/cluster-development/286017-gfs2-fix-potential-race-glock-code.html)

Steven Whitehouse 11-25-2009 01:22 PM

GFS2: Fix potential race in glock code
 
We need to be careful of the ordering between clearing the
GLF_LOCK bit and scheduling the workqueue.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
---
fs/gfs2/glock.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 8b674b1..a3f90ad 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -672,12 +672,17 @@ out:
return;

out_sched:
+ clear_bit(GLF_LOCK, &gl->gl_flags);
+ smp_mb__after_clear_bit();
gfs2_glock_hold(gl);
if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
gfs2_glock_put_nolock(gl);
+ return;
+
out_unlock:
clear_bit(GLF_LOCK, &gl->gl_flags);
- goto out;
+ smp_mb__after_clear_bit();
+ return;
}

static void delete_work_func(struct work_struct *work)
@@ -1375,10 +1380,11 @@ static int gfs2_shrink_glock_memory(int nr, gfp_t gfp_mask)
handle_callback(gl, LM_ST_UNLOCKED, 0);
nr--;
}
+ clear_bit(GLF_LOCK, &gl->gl_flags);
+ smp_mb__after_clear_bit();
if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
gfs2_glock_put_nolock(gl);
spin_unlock(&gl->gl_spin);
- clear_bit(GLF_LOCK, &gl->gl_flags);
spin_lock(&lru_lock);
continue;
}
--
1.6.2.5


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