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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qH8s7-00AOCy-Ko; Wed, 05 Jul 2023 20:13:07 +0000 Date: Wed, 5 Jul 2023 21:13:07 +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: <20230705194335.273790-3-sidhartha.kumar@oracle.com> X-Rspamd-Queue-Id: DC2E31C001B X-Rspam-User: X-Stat-Signature: kh4gqexrrg5ntqyho3mjdg8kwchbq3rw X-Rspamd-Server: rspam01 X-HE-Tag: 1688587992-950929 X-HE-Meta: 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 9yCT0Bqk LUma2SMnrHU2klqY4doam9nEir5NUWkoD5LotUBTgqRKHUMiLp0FrHY525nD1g8oLksbCeCRxxYidHZ7I3E++CbrbixpdrDIWci3fr8WYEPlzmK4au4IWqOpJBWCjxIiexQ9RNiKYpUciQjbxhvvQebnXn2v70Qs/D/GqN6nd3CBomMfDro0afRX+jrLeN9odPT8zjpymi5+oCJYasGIwLVmQW47tPn1qGyyGFHkdYqHotEI= 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 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? Signed-off-by: Matthew Wilcox (Oracle)