linux-kernel - [patch] skip writing data pages when inode is under I

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Message-Id: <200712031435.59893.qiyong@fc-cn.com>
Date:	Mon, 3 Dec 2007 14:35:56 +0800
From:	Qi Yong <qiyong@...cn.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	nickpiggin@...oo.com.au, akpm@...l.org, a.p.zijlstra@...llo.nl,
	hugh@...itas.com, dhowells@...hat.com, joern@...nheim.fh-wedel.de,
	linux-kernel@...r.kernel.org
Subject: [patch] skip writing data pages when inode is under I_SYNC

Hello,

Since I_SYNC was split out from I_LOCK, the concern in commit 
4b89eed93e0fa40a63e3d7b1796ec1337ea7a3aa is not longer valid.

We should revert to the original behavior: in __writeback_single_inode(),
when we find an I_SYNC-ed inode and we're not doing a data-integrity sync, 
skip writing entirely. Otherwise, we are double calling do_writepages()

Signed-off-by: Qi Yong <qiyong@...cn.com>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 0fca820..4f8ec63 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -334,9 +334,6 @@ __writeback_single_inode(struct inode *inode, struct 
writeback_control *wbc)
 		WARN_ON(inode->i_state & I_WILL_FREE);
 
 	if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_SYNC)) {
-		struct address_space *mapping = inode->i_mapping;
-		int ret;
-
 		/*
 		 * We're skipping this inode because it's locked, and we're not
 		 * doing writeback-for-data-integrity.  Move it to s_more_io so
@@ -345,15 +342,7 @@ __writeback_single_inode(struct inode *inode, struct 
writeback_control *wbc)
 		 * completed a full scan of s_io.
 		 */
 		requeue_io(inode);
-
-		/*
-		 * Even if we don't actually write the inode itself here,
-		 * we can at least start some of the data writeout..
-		 */
-		spin_unlock(&inode_lock);
-		ret = do_writepages(mapping, wbc);
-		spin_lock(&inode_lock);
-		return ret;
+		return 0;
 	}
 
 	/*
-- 
Qi Yong
--
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