Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 19 Jul 2021 21:45:53 +0800
From:   Gao Xiang <hsiangkao@linux.alibaba.com>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Andreas Gr?nbacher <andreas.gruenbacher@gmail.com>,
        linux-erofs@lists.ozlabs.org,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "Darrick J. Wong" <djwong@kernel.org>, Chao Yu <chao@kernel.org>,
        Liu Bo <bo.liu@linux.alibaba.com>,
        Joseph Qi <joseph.qi@linux.alibaba.com>,
        Liu Jiang <gerry@linux.alibaba.com>
Subject: Re: [PATCH 1/2] iomap: support tail packing inline read
Message-ID: <YPWCEW3wBx3nOahn@B-P7TQMD6M-0146.local>
Mail-Followup-To: Christoph Hellwig <hch@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        Andreas Gr?nbacher <andreas.gruenbacher@gmail.com>,
        linux-erofs@lists.ozlabs.org,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "Darrick J. Wong" <djwong@kernel.org>, Chao Yu <chao@kernel.org>,
        Liu Bo <bo.liu@linux.alibaba.com>,
        Joseph Qi <joseph.qi@linux.alibaba.com>,
        Liu Jiang <gerry@linux.alibaba.com>
References: <YPGDZYT9OxdgNYf2@casper.infradead.org>
 <YPGQB3zT4Wp4Q38X@B-P7TQMD6M-0146.local>
 <YPGbNCdCNXIpNdqd@casper.infradead.org>
 <YPGfqLcSiH3/z2RT@B-P7TQMD6M-0146.local>
 <CAHpGcMJzEiJUbD=7ZOdH7NF+gq9MuEi8=ym34ay7QAm5_91s7g@mail.gmail.com>
 <YPLdSja/4FBsjss/@B-P7TQMD6M-0146.local>
 <YPLw0uc1jVKI8uKo@casper.infradead.org>
 <YPL0LqHzEbUY4zY/@B-P7TQMD6M-0146.local>
 <YPMkKfegS+9KzEhK@casper.infradead.org>
 <YPVfxn6/oCPBZpKu@infradead.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <YPVfxn6/oCPBZpKu@infradead.org>
Precedence: bulk

On Mon, Jul 19, 2021 at 12:19:34PM +0100, Christoph Hellwig wrote:
> On Sat, Jul 17, 2021 at 07:40:41PM +0100, Matthew Wilcox wrote:
> > Well, either sense of a WARN_ON is wrong.
> > 
> > For a file which is PAGE_SIZE + 3 bytes in size, to_iomap_page() will
> > be NULL.  For a file which is PAGE_SIZE/2 + 3 bytes in size,
> > to_iomap_page() will not be NULL.  (assuming the block size is <=
> > PAGE_SIZE / 2).
> > 
> > I think we need a prep patch that looks something like this:
> 
> Something like this is where we should eventually end up, but it
> also affects the read from disk case so we need to be careful.

I also think it'd be better to leave this hunk as it-is (don't
touch it in this patch), I mean just

iop = iomap_page_create(inode, page);

as
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/iomap/buffered-io.c?id=229adf3c64dbeae4e2f45fb561907ada9fcc0d0c#n256

since iomap_read_inline_data() now calls iomap_set_range_uptodate() to
set blocks uptodate rather than SetPageUptodate() directly and we also
have iomap_page_release() as well.

Some follow-up optimized patch can be raised up independently since
it's somewhat out of current topic for now.

Thanks,
Gao Xiang