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From: "Theodore Ts'o" <tytso@mit.edu>
To: torvalds@linuxfoundation.org
Cc: Linux Kernel Developers List <linux-kernel@vger.kernel.org>,
       Ext4 Developers List <linux-ext4@vger.kernel.org>,
       "Theodore Ts'o" <tytso@mit.edu>
Subject: [PATCH 1/4] block_write_full_page: Use synchronous writes for WBC_SYNC_ALL writebacks
Date: Fri,  3 Apr 2009 03:01:04 -0400
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When doing synchronous writes because wbc->sync_mode is set to
WBC_SYNC_ALL, send the write request using WRITE_SYNC, so that we
don't unduly block system calls such as fsync().

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Jan Kara <jack@suse.cz>
---
 fs/buffer.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 891e1c7..e7ebd95 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1714,6 +1714,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
 	struct buffer_head *bh, *head;
 	const unsigned blocksize = 1 << inode->i_blkbits;
 	int nr_underway = 0;
+	int write_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
 
 	BUG_ON(!PageLocked(page));
 
@@ -1805,7 +1806,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
 	do {
 		struct buffer_head *next = bh->b_this_page;
 		if (buffer_async_write(bh)) {
-			submit_bh(WRITE, bh);
+			submit_bh(write_op, bh);
 			nr_underway++;
 		}
 		bh = next;
@@ -1859,7 +1860,7 @@ recover:
 		struct buffer_head *next = bh->b_this_page;
 		if (buffer_async_write(bh)) {
 			clear_buffer_dirty(bh);
-			submit_bh(WRITE, bh);
+			submit_bh(write_op, bh);
 			nr_underway++;
 		}
 		bh = next;
-- 
1.5.6.3