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Go Back   Linux Archive > Redhat > Cluster Development

 
 
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Old 02-28-2012, 10:11 AM
Steven Whitehouse
 
Default GFS2: Fix race between lru_list and glock ref count

This patch fixes a narrow race window between the glock ref count
hitting zero and glocks being removed from the lru_list.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 376816f..351a3e7 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -167,14 +167,19 @@ void gfs2_glock_add_to_lru(struct gfs2_glock *gl)
spin_unlock(&lru_lock);
}

-static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
+static void __gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
{
- spin_lock(&lru_lock);
if (!list_empty(&gl->gl_lru)) {
list_del_init(&gl->gl_lru);
atomic_dec(&lru_count);
clear_bit(GLF_LRU, &gl->gl_flags);
}
+}
+
+static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
+{
+ spin_lock(&lru_lock);
+ __gfs2_glock_remove_from_lru(gl);
spin_unlock(&lru_lock);
}

@@ -217,11 +222,12 @@ void gfs2_glock_put(struct gfs2_glock *gl)
struct gfs2_sbd *sdp = gl->gl_sbd;
struct address_space *mapping = gfs2_glock2aspace(gl);

- if (atomic_dec_and_test(&gl->gl_ref)) {
+ if (atomic_dec_and_lock(&gl->gl_ref, &lru_lock)) {
+ __gfs2_glock_remove_from_lru(gl);
+ spin_unlock(&lru_lock);
spin_lock_bucket(gl->gl_hash);
hlist_bl_del_rcu(&gl->gl_list);
spin_unlock_bucket(gl->gl_hash);
- gfs2_glock_remove_from_lru(gl);
GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));
GLOCK_BUG_ON(gl, mapping && mapping->nrpages);
trace_gfs2_glock_put(gl);
--
1.7.4
 

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