linux-ext4 - Re: [PATCH v10 24/25] fuse: Convert from readpages to readahead

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Date:   Wed, 25 Mar 2020 15:43:02 +0100
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-erofs@...ts.ozlabs.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        ocfs2-devel@....oracle.com, linux-xfs <linux-xfs@...r.kernel.org>,
        Dave Chinner <dchinner@...hat.com>,
        William Kucharski <william.kucharski@...cle.com>
Subject: Re: [PATCH v10 24/25] fuse: Convert from readpages to readahead

On Wed, Mar 25, 2020 at 1:02 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Wed, Mar 25, 2020 at 10:42:56AM +0100, Miklos Szeredi wrote:
> > > +       while ((page = readahead_page(rac))) {
> > > +               if (fuse_readpages_fill(&data, page) != 0)
> >
> > Shouldn't this unlock + put page on error?
>
> We're certainly inconsistent between the two error exits from
> fuse_readpages_fill().  But I think we can simplify the whole thing
> ... how does this look to you?

Nice, overall.

>
> -       while ((page = readahead_page(rac))) {
> -               if (fuse_readpages_fill(&data, page) != 0)
> +               nr_pages = min(readahead_count(rac), fc->max_pages);

Missing fc->max_read clamp.

> +               ia = fuse_io_alloc(NULL, nr_pages);
> +               if (!ia)
>                         return;
> +               ap = &ia->ap;
> +               __readahead_batch(rac, ap->pages, nr_pages);

nr_pages = __readahead_batch(...)?

This will give consecutive pages, right?

Thanks,
Miklos