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    SubjectRe: Re: Re: EXT4 regression caused 4eec7
    On Mon 13-05-13 21:56:43, Zheng Liu wrote:
    > On Mon, May 13, 2013 at 03:18:09PM +0200, Jan Kara wrote:
    > > On Sun 12-05-13 13:04:59, EUNBONG SONG wrote:
    > > >
    > > >
    > > > >> Since at this point it's safer to rollback the change and we can
    > > > >> investigate more deeply how to fix it correctly for the next
    > > > >> development cycle, this is the patch which I'm testing.
    > > >
    > > > >> - Ted
    > > >
    > > > > Hello, I've tested with your patch. But the same problem was reproduced.
    > > > > Currently, I'm trying to git bisect. If i done git bisect, i will let you know.
    > > >
    > > > Hi, I've done git bisect. and panic at jbd2_journal_put_journal_head() is caused by
    > > > ae4647fb7654676fc44a97e86eb35f9f06b99f66: "jbd2: reduce journal_head size."
    > > > I write just code patch which revert ae4647fb7654676fc44a97e86eb35f9f06b99f66 because
    > > > I don't know the root cause.
    > > This is really strange. I've verified the code and all the places
    > > modifying b_jlist or b_modified are holding bh_state lock so we should be
    > > safe...
    >
    > Hi Jan,
    >
    > Could you please take a look at this mail [1]. I don't think we hold
    > bh_state lock there.
    >
    > 1. http://www.spinics.net/lists/linux-ext4/msg38205.html
    I'll also reply to that thread but: Yes, we don't hold bh_state lock when
    reading b_jlist in that one case (that's why I wrote 'modify' and not just
    'access' in my previous email). But that's really harmless since we don't
    do any complex operations with b_jlist (only get & set) so we either see an
    old value or a new one. And that particular use is going away anyway later
    in my series.

    Honza
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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