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GFS2: Fix glock deallocation race

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This patch fixes a race in deallocating glocks which was introduced
in the RCU glock patch. We need to ensure that the glock count is
kept correct even in the case that there is a race to add a new
glock into the hash table. Also, to avoid having to wait for an
RCU grace period, the glock counter can be decremented before
call_rcu() is called.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
This commit is contained in:
Steven Whitehouse 2011-03-09 10:58:04 +00:00
parent 662e3a551b
commit fc0e38dae6
4 changed files with 12 additions and 11 deletions
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10
fs/gfs2/glock.c
View file

@ -103,16 +103,21 @@ static inline void spin_unlock_bucket(unsigned int hash)
__bit_spin_unlock(0, (unsigned long *)bl);
}
void gfs2_glock_free(struct rcu_head *rcu)
static void gfs2_glock_dealloc(struct rcu_head *rcu)
{
struct gfs2_glock *gl = container_of(rcu, struct gfs2_glock, gl_rcu);
struct gfs2_sbd *sdp = gl->gl_sbd;
if (gl->gl_ops->go_flags & GLOF_ASPACE)
kmem_cache_free(gfs2_glock_aspace_cachep, gl);
else
kmem_cache_free(gfs2_glock_cachep, gl);
}
void gfs2_glock_free(struct gfs2_glock *gl)
{
struct gfs2_sbd *sdp = gl->gl_sbd;
call_rcu(&gl->gl_rcu, gfs2_glock_dealloc);
if (atomic_dec_and_test(&sdp->sd_glock_disposal))
wake_up(&sdp->sd_glock_wait);
}
@ -760,6 +765,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
if (tmp) {
spin_unlock_bucket(hash);
kmem_cache_free(cachep, gl);
atomic_dec(&sdp->sd_glock_disposal);
gl = tmp;
} else {
hlist_bl_add_head_rcu(&gl->gl_list, &gl_hash_table[hash]);

2
fs/gfs2/glock.h
View file

@ -230,7 +230,7 @@ extern void gfs2_gl_hash_clear(struct gfs2_sbd *sdp);
extern void gfs2_glock_finish_truncate(struct gfs2_inode *ip);
extern void gfs2_glock_thaw(struct gfs2_sbd *sdp);
extern void gfs2_glock_schedule_for_reclaim(struct gfs2_glock *gl);
extern void gfs2_glock_free(struct rcu_head *rcu);
extern void gfs2_glock_free(struct gfs2_glock *gl);
extern int __init gfs2_glock_init(void);
extern void gfs2_glock_exit(void);

4
fs/gfs2/lock_dlm.c
View file

@ -30,7 +30,7 @@ static void gdlm_ast(void *arg)
switch (gl->gl_lksb.sb_status) {
case -DLM_EUNLOCK: /* Unlocked, so glock can be freed */
call_rcu(&gl->gl_rcu, gfs2_glock_free);
gfs2_glock_free(gl);
return;
case -DLM_ECANCEL: /* Cancel while getting lock */
ret |= LM_OUT_CANCELED;
@ -165,7 +165,7 @@ static void gdlm_put_lock(struct gfs2_glock *gl)
int error;
if (gl->gl_lksb.sb_lkid == 0) {
call_rcu(&gl->gl_rcu, gfs2_glock_free);
gfs2_glock_free(gl);
return;
}

7
fs/gfs2/ops_fstype.c
View file

@ -928,14 +928,9 @@ static const match_table_t nolock_tokens = {
{ Opt_err, NULL },
};
static void nolock_put_lock(struct gfs2_glock *gl)
{
call_rcu(&gl->gl_rcu, gfs2_glock_free);
}
static const struct lm_lockops nolock_ops = {
.lm_proto_name = "lock_nolock",
.lm_put_lock = nolock_put_lock,
.lm_put_lock = gfs2_glock_free,
.lm_tokens = &nolock_tokens,
};