linux-ext4 - [PATCH 2/3 v2] quota: avoid unnecessary dqget()/dqput() calls

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Message-ID: <538541A3.2060102@gmail.com>
Date:	Wed, 28 May 2014 09:53:39 +0800
From:	Niu Yawei <yawei.niu@...il.com>
To:	Christoph Hellwig <hch@...radead.org>, jack@...e.cz
CC:	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	yawei.niu@...el.com, andreas.dilger@...el.com, lai.siyao@...el.com
Subject: [PATCH 2/3 v2] 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@...el.com>
Signed-off-by: Niu Yawei <yawei.niu@...el.com>
---
 fs/quota/dquot.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 9cd5f63..dc6f711 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1400,7 +1400,7 @@ static int dquot_active(const struct inode *inode)
  */
 static void __dquot_initialize(struct inode *inode, int type)
 {
-	int cnt;
+	int cnt, dq_get = 0;
 	struct dquot *got[MAXQUOTAS];
 	struct super_block *sb = inode->i_sb;
 	qsize_t rsv;
@@ -1416,6 +1416,13 @@ 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 case,
+		 * we check it without locking here to avoid unnecessary
+		 * dqget()/dqput() calls. */
+		if (inode->i_dquot[cnt])
+			continue;
+		dq_get = 1;
+
 		switch (cnt) {
 		case USRQUOTA:
 			qid = make_kqid_uid(inode->i_uid);
@@ -1427,6 +1434,10 @@ static void __dquot_initialize(struct inode *inode, int type)
 		got[cnt] = dqget(sb, qid);
 	}
 
+	/* all required i_dquot has been initialized */
+	if (!dq_get)
+		return;
+
 	down_write(&sb_dqopt(sb)->dqptr_sem);
 	if (IS_NOQUOTA(inode))
 		goto out_err;
-- 
1.7.1


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