linux-kernel - [PATCH] vfs: Fix vmtruncate() regression

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Date:	Wed, 13 Jan 2010 21:14:09 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Nick Piggin <npiggin@...e.de>, Al Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] vfs: Fix vmtruncate() regression


If __block_prepare_write() was failed in block_write_begin(), the
allocated blocks can be outside of ->i_size.

But new truncate_pagecache() in vmtuncate() does nothing if new < old.
It means the above usage is not working anymore.

So, this patch fixes it by removing "new < old" check. It would need
more cleanup/change. But, now -rc and truncate working is in progress,
so, this tried to fix it minimum change.

Acked-by: Nick Piggin <npiggin@...e.de>
Signed-off-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
---

 mm/truncate.c |   28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff -puN mm/truncate.c~truncate_pagecache-fix mm/truncate.c
--- linux-2.6/mm/truncate.c~truncate_pagecache-fix	2010-01-12 05:43:06.000000000 +0900
+++ linux-2.6-hirofumi/mm/truncate.c	2010-01-12 05:43:06.000000000 +0900
@@ -522,22 +522,20 @@ EXPORT_SYMBOL_GPL(invalidate_inode_pages
  */
 void truncate_pagecache(struct inode *inode, loff_t old, loff_t new)
 {
-	if (new < old) {
-		struct address_space *mapping = inode->i_mapping;
+	struct address_space *mapping = inode->i_mapping;
 
-		/*
-		 * unmap_mapping_range is called twice, first simply for
-		 * efficiency so that truncate_inode_pages does fewer
-		 * single-page unmaps.  However after this first call, and
-		 * before truncate_inode_pages finishes, it is possible for
-		 * private pages to be COWed, which remain after
-		 * truncate_inode_pages finishes, hence the second
-		 * unmap_mapping_range call must be made for correctness.
-		 */
-		unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
-		truncate_inode_pages(mapping, new);
-		unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
-	}
+	/*
+	 * unmap_mapping_range is called twice, first simply for
+	 * efficiency so that truncate_inode_pages does fewer
+	 * single-page unmaps.  However after this first call, and
+	 * before truncate_inode_pages finishes, it is possible for
+	 * private pages to be COWed, which remain after
+	 * truncate_inode_pages finishes, hence the second
+	 * unmap_mapping_range call must be made for correctness.
+	 */
+	unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
+	truncate_inode_pages(mapping, new);
+	unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
 }
 EXPORT_SYMBOL(truncate_pagecache);
 
_
--
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