linux-kernel - [patch 2/3] fs: buffer don't PageUptodate without page locked

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Message-Id: <20070206054947.21042.32493.sendpatchset@linux.site>
Date:	Tue,  6 Feb 2007 09:02:23 +0100 (CET)
From:	Nick Piggin <npiggin@...e.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Hugh Dickins <hugh@...itas.com>, Andrew Morton <akpm@...l.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Memory Management <linux-mm@...ck.org>,
	Linux Filesystems <linux-fsdevel@...r.kernel.org>
Subject: [patch 2/3] fs: buffer don't PageUptodate without page locked

__block_write_full_page is calling SetPageUptodate without the page locked.
This is unusual, but not incorrect, as PG_writeback is still set.

However with the previous patch, this is now a problem: so don't bother
setting the page uptodate in this case (it is weird that the write path
does such a thing anyway). Instead just leave it to the read side to bring
the page uptodate when it notices that all buffers are uptodate.

Signed-off-by: Nick Piggin <npiggin@...e.de>

Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -1679,6 +1679,7 @@ static int __block_write_full_page(struc
 	 */
 	BUG_ON(PageWriteback(page));
 	set_page_writeback(page);
+	unlock_page(page);
 
 	do {
 		struct buffer_head *next = bh->b_this_page;
@@ -1688,7 +1689,6 @@ static int __block_write_full_page(struc
 		}
 		bh = next;
 	} while (bh != head);
-	unlock_page(page);
 
 	err = 0;
 done:
@@ -1698,17 +1698,8 @@ done:
 		 * clean.  Someone wrote them back by hand with
 		 * ll_rw_block/submit_bh.  A rare case.
 		 */
-		int uptodate = 1;
-		do {
-			if (!buffer_uptodate(bh)) {
-				uptodate = 0;
-				break;
-			}
-			bh = bh->b_this_page;
-		} while (bh != head);
-		if (uptodate)
-			SetPageUptodate(page);
 		end_page_writeback(page);
+
 		/*
 		 * The page and buffer_heads can be released at any time from
 		 * here on.
-
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