linux-kernel - [PATCH] rd: Mark ramdisk buffers heads dirty

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Date:	Mon, 15 Oct 2007 16:42:06 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	"Theodore Ts'o" <tytso@....edu>
Subject: [PATCH] rd: Mark ramdisk buffers heads dirty


I have not observed this case but it is possible to get a dirty page
cache with clean buffer heads if we get a clean ramdisk page with
buffer heads generated by a filesystem calling __getblk and then write
to that page from user space through the block device.  Then we just
need to hit the proper window and try_to_free_buffers() will mark that
page clean and eventually drop it.  Ouch!

To fix this use the generic __set_page_dirty_buffers in the ramdisk
code so that when we mark a page dirty we also mark it's buffer heads
dirty.

Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
 drivers/block/rd.c |   13 +------------
 1 files changed, 1 insertions(+), 12 deletions(-)

diff --git a/drivers/block/rd.c b/drivers/block/rd.c
index 701ea77..84163da 100644
--- a/drivers/block/rd.c
+++ b/drivers/block/rd.c
@@ -178,23 +178,12 @@ static int ramdisk_writepages(struct address_space *mapping,
 	return 0;
 }
 
-/*
- * ramdisk blockdev pages have their own ->set_page_dirty() because we don't
- * want them to contribute to dirty memory accounting.
- */
-static int ramdisk_set_page_dirty(struct page *page)
-{
-	if (!TestSetPageDirty(page))
-		return 1;
-	return 0;
-}
-
 static const struct address_space_operations ramdisk_aops = {
 	.readpage	= ramdisk_readpage,
 	.prepare_write	= ramdisk_prepare_write,
 	.commit_write	= ramdisk_commit_write,
 	.writepage	= ramdisk_writepage,
-	.set_page_dirty	= ramdisk_set_page_dirty,
+	.set_page_dirty	= __set_page_dirty_buffers,
 	.writepages	= ramdisk_writepages,
 };
 
-- 
1.5.3.rc6.17.g1911

-
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