linux-ext4 - Re: [PATCH] ext4: More buffer head reference leaks

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Message-ID: <6601abe90907150800m4924e35fi13dd4eea6fe7f327@mail.gmail.com>
Date:	Wed, 15 Jul 2009 08:00:43 -0700
From:	Curt Wohlgemuth <curtw@...gle.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: More buffer head reference leaks

On Tue, Jul 14, 2009 at 10:52 PM, Aneesh Kumar
K.V<aneesh.kumar@...ux.vnet.ibm.com> wrote:
> On Tue, Jul 14, 2009 at 01:58:29PM -0700, Curt Wohlgemuth wrote:
>> After the patch I posted last week regarding buffer head ref leaks in
>> no-journal mode, I looked at all the code that uses buffer heads and
>> searched for more potential leaks.
>>
>> The patch below fixes the issues I found; these can occur even when a
>> journal is present.
>>
>> The change to inode.c fixes a double release if
>> ext4_journal_get_create_access() fails.
>>
>> The changes to namei.c are more complicated.  add_dirent_to_buf() will
>> release the input buffer head EXCEPT when it returns -ENOSPC.  There are
>> some callers of this routine that don't always do the brelse() in the event
>> that -ENOSPC is returned.  Unfortunately, to put this fix into ext4_add_entry()
>> required capturing the return value of make_indexed_dir() and
>> add_dirent_to_buf().
>>
>> I'd appreciate comments on these changes, in particular if I'm just missing
>> something obvious here.
>>
>>        Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>
>>
>> ---
>> diff -Naur orig/fs/ext4/inode.c new/fs/ext4/inode.c
>> --- orig/fs/ext4/inode.c      2009-07-14 11:19:01.000000000 -0700
>> +++ new/fs/ext4/inode.c       2009-07-14 11:51:42.000000000 -0700
>> @@ -758,8 +758,9 @@
>>               BUFFER_TRACE(bh, "call get_create_access");
>>               err = ext4_journal_get_create_access(handle, bh);
>>               if (err) {
>> +                     /* Don't brelse(bh) here; it's done in journal_forget()
>> +                      * below */
>>                       unlock_buffer(bh);
>> -                     brelse(bh);
>>                       goto failed;
>>               }
>>
>
> I am not able to find the journal_foget call in the path. brelse is
> dropping the buffer_head reference got from sb_getblk right ? Can you
> tell me what is that i am missing ?

Look at the code at the "failed" label.  For each of the allocated BHs
thus far, there's a call to ext4_journal_forget().

Oops, I should have put "ext4_journal_forget()" in the comment; my apologies.

I'll resend this out, along with a change to ext4_add_entry() to
remove the gotos.

Thanks,
Curt

>
>
>> diff -Naur orig/fs/ext4/namei.c new/fs/ext4/namei.c
>> --- orig/fs/ext4/namei.c      2009-07-14 11:19:46.000000000 -0700
>> +++ new/fs/ext4/namei.c       2009-07-14 11:19:28.000000000 -0700
>> @@ -1498,12 +1498,14 @@
>
> .. snip..
>
> -aneesh
>
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