linux-kernel - [PATCH v3 3/3] mm: Wait for writeback when grabbing pages to begin a write

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Date:	Wed, 4 May 2011 10:42:27 -0700
From:	"Darrick J. Wong" <djwong@...ibm.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Chris Mason <chris.mason@...cle.com>,
	Jeff Layton <jlayton@...hat.com>, Jan Kara <jack@...e.cz>,
	Dave Chinner <david@...morbit.com>,
	Joel Becker <jlbec@...lplan.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Jens Axboe <axboe@...nel.dk>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Mingming Cao <mcao@...ibm.com>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: [PATCH v3 3/3] mm: Wait for writeback when grabbing pages to begin
	a write

When grabbing a page for a buffered IO write, the mm should wait for writeback
on the page to complete so that the page does not become writable during the IO
operation.

Signed-off-by: Darrick J. Wong <djwong@...ibm.com>
---

 mm/filemap.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index c641edf..c22675f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2287,8 +2287,10 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
 		gfp_notmask = __GFP_FS;
 repeat:
 	page = find_lock_page(mapping, index);
-	if (page)
+	if (page) {
+		wait_on_page_writeback(page);
 		return page;
+	}
 
 	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
 	if (!page)
@@ -2301,6 +2303,7 @@ repeat:
 			goto repeat;
 		return NULL;
 	}
+	wait_on_page_writeback(page);
 	return page;
 }
 EXPORT_SYMBOL(grab_cache_page_write_begin);
--
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