quota: avoid unnecessary dqget()/dqput() calls

Avoid unnecessary dqget()/dqput() calls in __dquot_initialize(),
that will introduce global lock contention otherwise.
Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/quota/dquot.c

@@ -1402,7 +1402,7 @@ static int dquot_active(const struct inode *inode)
  */
 static void __dquot_initialize(struct inode *inode, int type)
 {
-	int cnt;
+	int cnt, init_needed = 0;
 	struct dquot *got[MAXQUOTAS];
 	struct super_block *sb = inode->i_sb;
 	qsize_t rsv;
@@ -1418,6 +1418,15 @@ static void __dquot_initialize(struct inode *inode, int type)
 		got[cnt] = NULL;
 		if (type != -1 && cnt != type)
 			continue;
+		/*
+		 * The i_dquot should have been initialized in most cases,
+		 * we check it without locking here to avoid unnecessary
+		 * dqget()/dqput() calls.
+		 */
+		if (inode->i_dquot[cnt])
+			continue;
+		init_needed = 1;
+
 		switch (cnt) {
 		case USRQUOTA:
 			qid = make_kqid_uid(inode->i_uid);
@@ -1429,6 +1438,10 @@ static void __dquot_initialize(struct inode *inode, int type)
 		got[cnt] = dqget(sb, qid);
 	}
 
+	/* All required i_dquot has been initialized */
+	if (!init_needed)
+		return;
+
 	down_write(&sb_dqopt(sb)->dqptr_sem);
 	if (IS_NOQUOTA(inode))
 		goto out_err;