This allow us to remove dq_state_lock from dqget quota state test.
synchronize_rcu() in dquot_disable() is a bit strage usage for RCU,
but rcu_read_lock will be used in dqget() more properly later to
get make lookup lock-less.
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
fs/quota/dquot.c | 32 ++++++++++++++++++++++----------
1 files changed, 22 insertions(+), 10 deletions(-)
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 771aaab..0d755ef 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -878,7 +878,7 @@ static struct dquot *get_empty_dquot(struct super_block *sb, int type)
/*
* Get reference to dquot
*
- * Locking is slightly tricky here. We are guarded from parallel quotaoff()
+ * We are guarded from parallel quotaoff() by holding rcu_read_lock
* destroying our dquot by:
* a) checking for quota flags under dq_list_lock and
* b) getting a reference to dquot before we release dq_list_lock
@@ -888,17 +888,15 @@ struct dquot *dqget(struct super_block *sb, unsigned int id, int type)
struct dquot *dquot = NULL, *empty = NULL;
struct quota_info *dqopt = dqopts(sb);
- if (!sb_has_quota_active(sb, type))
- return NULL;
we_slept:
- spin_lock(&dqopt->dq_list_lock);
- spin_lock(&dqopt->dq_state_lock);
+ rcu_read_lock();
if (!sb_has_quota_active(sb, type)) {
- spin_unlock(&dqopt->dq_state_lock);
- spin_unlock(&dqopt->dq_list_lock);
- goto out;
+ rcu_read_unlock();
+ return NULL;
}
- spin_unlock(&dqopt->dq_state_lock);
+ spin_lock(&dqopt->dq_list_lock);
+ /* XXX: Currently RCU used only for synchronization with quotaoff */
+ rcu_read_unlock();
dquot = find_dquot(sb, id, type);
if (!dquot) {
@@ -2113,6 +2111,21 @@ int dquot_disable(struct super_block *sb, int type, unsigned int flags)
if (sb_has_quota_loaded(sb, cnt) && !(flags & DQUOT_SUSPENDED))
continue;
+ toputinode[cnt] = dqopt->files[cnt];
+ }
+ /*
+ * Wait for all dqget() callers to finish.
+ */
+ synchronize_rcu();
+
+ /*
+ * At this moment all quota functions disabled, is is now safe to
+ * perform final cleanup.
+ */
+ for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
+
+ if (!toputinode[cnt])
+ continue;
/* Note: these are blocking operations */
drop_dquot_ref(sb, cnt);
invalidate_dquots(sb, cnt);
@@ -2126,7 +2139,6 @@ int dquot_disable(struct super_block *sb, int type, unsigned int flags)
dqopt->fmt_ops[cnt]->free_file_info(sb, cnt);
put_quota_format(dqopt->info[cnt].dqi_format);
- toputinode[cnt] = dqopt->files[cnt];
if (!sb_has_quota_loaded(sb, cnt))
dqopt->files[cnt] = NULL;
dqopt->info[cnt].dqi_flags = 0;
--
1.6.5.2
--
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