linux-ext4 - Re: potential memory leak on transaction commit

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Date:	Tue, 15 Mar 2011 14:39:08 +0800
From:	Zhang Huan <zhhuan@...il.com>
To:	linux-ext4@...r.kernel.org
Subject: Re: potential memory leak on transaction commit

Hi,

I would like to know if there is more comment on this?

On Tue, Mar 8, 2011 at 19:40, Zhang Huan <zhhuan@...il.com> wrote:
> Hi all,
>
> There is potential memory leak of journal head in function
> jbd2_journal_commit_transaction. The problem is that JBD2 will not
> reclaim the journal head of commit record if error occurs or journal is
> abotred.
>
> I use the following script to reproduce this issue, on a RHEL6 system. I
> found it very easy to reproduce with async commit enabled.
>
> mount /dev/sdb /mnt -o journal_checksum,journal_async_commit
> touch /mnt/xxx
> echo offline > /sys/block/sdb/device/state
> sync
> umount /mnt
> rmmod ext4
> rmmod jbd2
>
> Removal of the jbd2 module will make slab complaining that
> "cache `jbd2_journal_head': can't free all objects".
>
>
> Here is my fix for this issue. The commit record should be reclaimed no
> matter error occurs or not.
>
> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> index f3ad159..37a973a 100644
> --- a/fs/jbd2/commit.c
> +++ b/fs/jbd2/commit.c
> @@ -105,6 +105,8 @@ static int journal_submit_commit_record(journal_t *journal,
>        int ret;
>        struct timespec now = current_kernel_time();
>
> +       *cbh = NULL;
> +
>        if (is_journal_aborted(journal))
>                return 0;
>
> @@ -808,7 +810,7 @@ wait_for_iobuf:
>                if (err)
>                        __jbd2_journal_abort_hard(journal);
>        }
> -       if (!err && !is_journal_aborted(journal))
> +       if (cbh)
>                err = journal_wait_on_commit_record(journal, cbh);
>        if (JBD2_HAS_INCOMPAT_FEATURE(journal,
>                                      JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT) &&
>
>
>
> PS: Just out of curiosity, why would journal_submit_commit_record return a
> value of 1 instead of an error number if get descriptor buffer is failed.
>
>
> Zhang Huan
>

Zhang Huan
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