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GFS2: Fix race between lru_list and glock ref count

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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>
This commit is contained in:
Steven Whitehouse 2012-01-16 15:46:21 +00:00
parent 586c6e7013
commit 4043b886b0
1 changed files with 10 additions and 4 deletions
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14
fs/gfs2/glock.c
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@ -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);