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Wong" , linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 05/14] iomap: Support THPs in invalidatepage Message-ID: <20201014200019.GA1119840@bfoster> References: <20201014030357.21898-1-willy@infradead.org> <20201014030357.21898-6-willy@infradead.org> <20201014163347.GI9832@magnolia> <20201014172634.GP20115@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201014172634.GP20115@casper.infradead.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 14, 2020 at 06:26:34PM +0100, Matthew Wilcox wrote: > On Wed, Oct 14, 2020 at 09:33:47AM -0700, Darrick J. Wong wrote: > > > @@ -1415,7 +1420,6 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc, > > > */ > > > if (wpc->ops->discard_page) > > > wpc->ops->discard_page(page); > > > - ClearPageUptodate(page); > > > > Er, I don't get it -- why do we now leave the page up to date after > > writeback fails? > > The page is still uptodate -- every byte in this page is at least as new > as the corresponding bytes on disk. > That seems rather odd if the preceding ->discard_page() turned an underlying delalloc block into a hole. Technically the original written data is still in the page, but it's no longer allocated/mapped or dirty so really no longer in sync with on-disk state. Hm? Brian