Re: Bug in error recovery in fs/buffer.c::__block_prepare_write()

[Anton Altaparmakov <aia21@cam.ac.uk>]

Here is the second patch (patch B).

On Fri, 2005-06-10 at 14:01 +0100, Anton Altaparmakov wrote:
[snip]
> B) If we cannot safely allow buffer_new buffers to "leak out" of
> __block_prepare_write(), then we simply would need to run a quick loop
> over the buffers clearing buffer_new on each of them if it is set just
> before returning "success" to the caller of __block_prepare_write().
[snip]

The patch for this is simple, too (it is below).

> Andrew/Linus, I would suggest that you apply at least A and perhaps B if
> you deem it necessary or want to be on the safe side.
> 
> Having had a look at the code it would seem perfectly safe to leave
> buffer_new() set and ignore patch B but I may be wrong which is why I
> did both.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

Best regards,

        Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/

--- linux-2.6.git/fs/buffer.c.old2	2005-06-10 13:35:03.000000000 +0100
+++ linux-2.6.git/fs/buffer.c	2005-06-10 13:38:14.000000000 +0100
@@ -1992,9 +1992,14 @@ static int __block_prepare_write(struct 
 		if (!buffer_uptodate(*wait_bh))
 			err = -EIO;
 	}
-	if (!err)
+	if (!err) {
+		bh = head;
+		do {
+			if (buffer_new(bh))
+				clear_buffer_new(bh);
+		} while ((bh = bh->b_this_page) != head);
 		return err;
-
+	}
 	/* Error case: */
 	/*
 	 * Zero out any newly allocated blocks to avoid exposing stale


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