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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qH8yK-00AOT6-In; Wed, 05 Jul 2023 20:19:32 +0000 Date: Wed, 5 Jul 2023 21:19:32 +0100 From: Matthew Wilcox To: Sidhartha Kumar Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org Subject: Re: [PATCH v2 3/4] mm/memory: convert do_shared_fault() to folios Message-ID: References: <20230705194335.273790-1-sidhartha.kumar@oracle.com> <20230705194335.273790-3-sidhartha.kumar@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D9F6A40020 X-Stat-Signature: hhmtqm479gz8gcnzp6dfuqfnghor9dmi X-HE-Tag: 1688588376-455462 X-HE-Meta: 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 9r4p4Kka oEYOUVapKA1i+r2X3gr+DAQfcfjwlZAmx/yiQ0DEMUp5Ha4D5RRKlwCtV8yNGvH+dxfV+XWT20dN9qnBpofHBSZNoB98+eXLNPv353N/8G5F8y6+8FXj5h/u8Tqu0B56BbXuym/6/MvGzaPcO1PZsyYSEU0MLujYQrl4sTuKhkC8qFZy4Am1jEae/nlAlmkavyk1eamD4iU0Lde0tiiIcsVK8mQEpROTsSc4XFKgA3SI1shE= 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, Jul 05, 2023 at 01:16:25PM -0700, Sidhartha Kumar wrote: > On 7/5/23 1:13 PM, Matthew Wilcox wrote: > > On Wed, Jul 05, 2023 at 12:43:34PM -0700, Sidhartha Kumar wrote: > > > /* > > > * Check if the backing address space wants to know that the page is > > > * about to become writable > > > */ > > > if (vma->vm_ops->page_mkwrite) { > > > - unlock_page(vmf->page); > > > + folio_unlock(folio); > > > tmp = do_page_mkwrite(vmf); > > > if (unlikely(!tmp || > > > (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { > > > - put_page(vmf->page); > > > + folio_put(folio); > > > > This is _probably_ OK. However, do_page_mkwrite() calls > > vm_ops->page_mkwrite(), and I think it's theoretically possible for the > > driver to replace vmf->page with a different one. The chance of them > > actually doing that is pretty low (particularly if they return error or > > nopage!), but I'm going to flag it just in case it comes up. > > > > Also, should we pass a folio to do_page_mkwrite() instead of having it > > extract the folio from vmf->page? > > I can take a look at doing this in a follow-up patch. > > > > Signed-off-by: Matthew Wilcox (Oracle) > > Did you mean for this to be reviewed-by? Uh, yes. Maybe I need to get more rest ...