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From: Yafang Shao <laoar.shao@gmail.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	Christoph Hellwig <hch@infradead.org>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH v7 2/2] xfs: avoid transaction reservation recursion
Date: Thu, 27 Aug 2020 10:59:17 +0800	[thread overview]
Message-ID: <CALOAHbA+hhiPeBh6LQcZ46Rni3TTWZu4Y8+vdTYcW5bBP5JHEA@mail.gmail.com> (raw)
In-Reply-To: <20200827024248.GA12131@dread.disaster.area>

On Thu, Aug 27, 2020 at 10:42 AM Dave Chinner <david@fromorbit.com> wrote:
>
> On Thu, Aug 27, 2020 at 10:13:15AM +0800, Yafang Shao wrote:
> > On Thu, Aug 27, 2020 at 9:58 AM Matthew Wilcox <willy@infradead.org> wrote:
> > >
> > > On Thu, Aug 27, 2020 at 09:34:44AM +0800, Yafang Shao wrote:
> > > > @@ -1500,9 +1500,9 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
> > > >
> > > >       /*
> > > >        * Given that we do not allow direct reclaim to call us, we should
> > > > -      * never be called in a recursive filesystem reclaim context.
> > > > +      * never be called while in a filesystem transaction.
> > > >        */
> > > > -     if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS))
> > > > +     if (WARN_ON_ONCE(wbc->fstrans_recursion))
> > > >               goto redirty;
> > >
> > > Erm, Dave said:
> > >
> > > > I think we should just remove
> > > > the check completely from iomap_writepage() and move it up into
> > > > xfs_vm_writepage() and xfs_vm_writepages().
> > >
> > > ie everywhere you set this new bit, just check current->journal_info.
> >
> >
> > I can't get you. Would you pls. be more specific ?
> >
> > I move the check of current->journal into xfs_vm_writepage() and
> > xfs_vm_writepages(), and I think that is the easiest way to implement
> > it.
> >
> >        /* we abort the update if there was an IO error */
> > @@ -564,6 +565,9 @@ xfs_vm_writepage(
> >  {
> >         struct xfs_writepage_ctx wpc = { };
> >
> > +       if (xfs_trans_context_active())
> > +               wbc->fstrans_recursion = 1;    <<< set for XFS only.
> > +
> >         return iomap_writepage(page, wbc, &wpc.ctx, &xfs_writeback_ops);
>
> Get rid of wbc->fstrans_recursion. Just do
>
>         if (WARN_ON_ONCE(current->journal_info))
>                 .....
>
> right here in the XFS code.
>

Understood.
But we have to implement the 'redirty' as well in the XFS code, that
may make the implementation more complicated.


-- 
Thanks
Yafang

      reply	other threads:[~2020-08-27  2:59 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-27  1:34 [PATCH v7 0/2] avoid xfs " Yafang Shao
2020-08-27  1:34 ` [PATCH v7 1/2] mm: Add become_kswapd and restore_kswapd Yafang Shao
2020-08-27  1:34 ` [PATCH v7 2/2] xfs: avoid transaction reservation recursion Yafang Shao
2020-08-27  1:58   ` Matthew Wilcox
2020-08-27  2:13     ` Yafang Shao
2020-08-27  2:42       ` Dave Chinner
2020-08-27  2:59         ` Yafang Shao [this message]

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