linux-kernel - Re: ext3 on latest -git: BUG: unable to handle kernel NULL pointer dereference at 0000000c

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Date:	Thu, 17 Jul 2008 09:57:46 -0400
From:	Josef Bacik <jbacik@...hat.com>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	Josef Bacik <josef@...icpanda.com>, linux-ext4@...r.kernel.org,
	sct@...hat.com, akpm@...ux-foundation.org, adilger@....com,
	Johannes Weiner <hannes@...urebad.de>,
	linux-kernel@...r.kernel.org
Subject: Re: ext3 on latest -git: BUG: unable to handle kernel NULL pointer
	dereference at 0000000c

On Thu, Jul 17, 2008 at 03:39:24PM +0200, Vegard Nossum wrote:
> On Thu, Jul 17, 2008 at 3:34 PM, Josef Bacik <josef@...icpanda.com> wrote:
> >> Yeah, the full log exists at
> >>
> >>    http://folk.uio.no/vegardno/linux/log-1216293934.txt
> >>
> >> I think this is the interesting part:
> >
> > Hmm well the journal should have aborted, but it looks like it didn't,
> > are you mounting with errors=continue by any chance?  Thanks much,
> 
> No, this is the command I used:
> 
>         mount -o loop disk mnt
> 
> I think this looks interesting:
> 
> EXT3-fs error (device loop0) in ext3_reserve_inode_write: IO failure
> 
> The code in ext3_reserve_inode_write() is here:
> 
>         err = ext3_journal_get_write_access(handle, iloc->bh);
>         if (err) {
>                 brelse(iloc->bh);
>                 iloc->bh = NULL;
>         }
> 
> Maybe it should do something different here?
> 
> But I don't know :-)
> 
> Thanks for helping out!
> 
>

Can you try this patch out and see if it fixes the problem?  I didn't compile
test it, so you may need to tweak somethings, but it should work.  Thanks,

Signed-off-by: Josef Bacik <jbacik@...hat.com>

 
Index: linux-2.6/fs/ext3/inode.c
===================================================================
--- linux-2.6.orig/fs/ext3/inode.c
+++ linux-2.6/fs/ext3/inode.c
@@ -2023,13 +2023,27 @@ static void ext3_clear_blocks(handle_t *
 		unsigned long count, __le32 *first, __le32 *last)
 {
 	__le32 *p;
+	int ret;
+
 	if (try_to_extend_transaction(handle, inode)) {
 		if (bh) {
 			BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
-			ext3_journal_dirty_metadata(handle, bh);
+			ret = ext3_journal_dirty_metadata(handle, bh);
+			if (ret) {
+				ext3_std_error(inode->i_sb, ret);
+				return;
+			}
 		}
-		ext3_mark_inode_dirty(handle, inode);
-		ext3_journal_test_restart(handle, inode);
+		ret = ext3_mark_inode_dirty(handle, inode);
+		if (ret)
+			return;
+
+		ret = ext3_journal_test_restart(handle, inode);
+		if (ret) {
+			ext3_std_error(inode->i_sb, ret);
+			return;
+		}
+
 		if (bh) {
 			BUFFER_TRACE(bh, "retaking write access");
 			ext3_journal_get_write_access(handle, bh);
--
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