[PATCH 21/27] quota: Allow disabling tracking of dirty dquots in a list

[Jan Kara <jack@suse.cz>]

Filesystems that are journalling quotas generally don't need tracking of
dirty dquots in a list since forcing a transaction commit flushes all
quotas anyway. Allow filesystem to say it doesn't want dquots to be
tracked as it reduces contention on the dq_list_lock.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/quota/dquot.c      | 6 ++++++
 include/linux/quota.h | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 57de84ab0ce7..0b3fbf75a5c9 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -344,6 +344,9 @@ int dquot_mark_dquot_dirty(struct dquot *dquot)
 	if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
 		return 0;
 
+	if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NOLIST_DIRTY)
+		return test_and_set_bit(DQ_MOD_B, &dquot->dq_flags);
+
 	/* If quota is dirty already, we don't have to acquire dq_list_lock */
 	if (test_bit(DQ_MOD_B, &dquot->dq_flags))
 		return 1;
@@ -379,6 +382,9 @@ static inline void dqput_all(struct dquot **dquot)
 
 static inline int clear_dquot_dirty(struct dquot *dquot)
 {
+	if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NOLIST_DIRTY)
+		return test_and_clear_bit(DQ_MOD_B, &dquot->dq_flags);
+
 	spin_lock(&dq_list_lock);
 	if (!test_and_clear_bit(DQ_MOD_B, &dquot->dq_flags)) {
 		spin_unlock(&dq_list_lock);
diff --git a/include/linux/quota.h b/include/linux/quota.h
index ad6809f099ac..eccc1cb6274e 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -490,6 +490,9 @@ enum {
 						 */
 #define DQUOT_NEGATIVE_USAGE	(1 << (DQUOT_STATE_LAST + 1))
 					       /* Allow negative quota usage */
+/* Do not track dirty dquots in a list */
+#define DQUOT_NOLIST_DIRTY	(1 << (DQUOT_STATE_LAST + 2))
+
 static inline unsigned int dquot_state_flag(unsigned int flags, int type)
 {
 	return flags << type;
-- 
2.12.3