linux-kernel - Re: [PATCH 11/12] fuse: Convert from readpages to readahead

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Date:   Wed, 29 Jan 2020 23:26:05 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/12] fuse: Convert from readpages to readahead

On Wed, Jan 29, 2020 at 11:50:37AM +0100, Miklos Szeredi wrote:
> On Sat, Jan 25, 2020 at 2:36 AM Matthew Wilcox <willy@...radead.org> wrote:
> >
> > From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> >
> > Use the new readahead operation in fuse.  Switching away from the
> > read_cache_pages() helper gets rid of an implicit call to put_page(),
> > so we can get rid of the get_page() call in fuse_readpages_fill().
> > We can also get rid of the call to fuse_wait_on_page_writeback() as
> > this page is newly allocated and so cannot be under writeback.
> 
> Not sure.  fuse_wait_on_page_writeback() waits not on the page but the
> byte range indicated by the index.
> 
> Fuse writeback goes through some hoops to prevent reclaim related
> deadlocks, which means that the byte range could still be under
> writeback, yet the page belonging to that range be already reclaimed.
>  This fuse_wait_on_page_writeback() is trying to serialize reads
> against such writes.

Thanks.  I'll put that back in.