linux-kernel - [PATCH 2/2] writeback: elevate queue_io() into wb

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Date:	Tue, 26 Apr 2011 22:44:02 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mel@...ux.vnet.ibm.com>,
	Dave Chinner <david@...morbit.com>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Itaru Kitayama <kitayama@...bb4u.ne.jp>,
	Minchan Kim <minchan.kim@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: [PATCH 2/2] writeback: elevate queue_io() into wb_writeback()

Code refactor for more logical code layout.
No behavior change.

- remove the mis-named __writeback_inodes_sb()

- wb_writeback()/writeback_inodes_wb() will decide when to queue_io()
  before calling __writeback_inodes_wb()

Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
---
 fs/fs-writeback.c |   27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

--- linux-next.orig/fs/fs-writeback.c	2011-04-26 13:20:17.000000000 +0800
+++ linux-next/fs/fs-writeback.c	2011-04-26 13:30:19.000000000 +0800
@@ -570,17 +570,13 @@ static int writeback_sb_inodes(struct su
 	return 1;
 }
 
-void writeback_inodes_wb(struct bdi_writeback *wb,
-		struct writeback_control *wbc)
+static void __writeback_inodes_wb(struct bdi_writeback *wb,
+				  struct writeback_control *wbc)
 {
 	int ret = 0;
 
 	if (!wbc->wb_start)
 		wbc->wb_start = jiffies; /* livelock avoidance */
-	spin_lock(&wb->list_lock);
-
-	if (list_empty(&wb->b_io))
-		queue_io(wb, wbc);
 
 	while (!list_empty(&wb->b_io)) {
 		struct inode *inode = wb_inode(wb->b_io.prev);
@@ -596,19 +592,16 @@ void writeback_inodes_wb(struct bdi_writ
 		if (ret)
 			break;
 	}
-	spin_unlock(&wb->list_lock);
 	/* Leave any unwritten inodes on b_io */
 }
 
-static void __writeback_inodes_sb(struct super_block *sb,
-		struct bdi_writeback *wb, struct writeback_control *wbc)
+void writeback_inodes_wb(struct bdi_writeback *wb,
+		struct writeback_control *wbc)
 {
-	WARN_ON(!rwsem_is_locked(&sb->s_umount));
-
 	spin_lock(&wb->list_lock);
 	if (list_empty(&wb->b_io))
 		queue_io(wb, wbc);
-	writeback_sb_inodes(sb, wb, wbc, true);
+	__writeback_inodes_wb(wb, wbc);
 	spin_unlock(&wb->list_lock);
 }
 
@@ -674,7 +667,7 @@ static long wb_writeback(struct bdi_writ
 	 * The intended call sequence for WB_SYNC_ALL writeback is:
 	 *
 	 *      wb_writeback()
-	 *          __writeback_inodes_sb()     <== called only once
+	 *          writeback_sb_inodes()       <== called only once
 	 *              write_cache_pages()     <== called once for each inode
 	 *                   (quickly) tag currently dirty pages
 	 *                   (maybe slowly) sync all tagged pages
@@ -722,10 +715,14 @@ static long wb_writeback(struct bdi_writ
 
 retry:
 		trace_wbc_writeback_start(&wbc, wb->bdi);
+		spin_lock(&wb->list_lock);
+		if (list_empty(&wb->b_io))
+			queue_io(wb, &wbc);
 		if (work->sb)
-			__writeback_inodes_sb(work->sb, wb, &wbc);
+			writeback_sb_inodes(work->sb, wb, &wbc, true);
 		else
-			writeback_inodes_wb(wb, &wbc);
+			__writeback_inodes_wb(wb, &wbc);
+		spin_unlock(&wb->list_lock);
 		trace_wbc_writeback_written(&wbc, wb->bdi);
 
 		work->nr_pages -= write_chunk - wbc.nr_to_write;
--
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