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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1q9Adr-004Ik4-2D; Tue, 13 Jun 2023 20:29:27 +0000 Date: Tue, 13 Jun 2023 21:29:27 +0100 From: Matthew Wilcox To: "Vishal Moola (Oracle)" Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/5] mm/gup.c: Reorganize try_get_folio() Message-ID: References: <20230613201827.9441-1-vishal.moola@gmail.com> <20230613201827.9441-5-vishal.moola@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230613201827.9441-5-vishal.moola@gmail.com> X-Rspamd-Queue-Id: E4C6EC0013 X-Rspam-User: X-Stat-Signature: w8mwq1mdj591f9onk3nqnxnaa5i5hq4b X-Rspamd-Server: rspam03 X-HE-Tag: 1686688170-314032 X-HE-Meta: U2FsdGVkX19g7rZXKU1fhbMOmP1Oi2Dhp53tWSg+xtWmhE5/d0f32KM2sgxG8XN/pwGwpWAXj+FG7QEO7llrmElLe1gVNBZOpKmdSV3vbCezLieZJCb7phd0Jp4Jy2OvqXydISfMZ1CyYDO/qaK4EKghfs9IfHcwPtjBFXqt/wfNssmOILTuD9iNsxHXgfTRHwCqaFuNPiqD281YfPiLL9S4KIwSpgcjYsnDYF3Gek0EGTQ6GJ5T/Y+H9fEoC7UWTGuqVcmqkHwjcgpPR8oTaZKrMChMAFyK9xrtQW6X/BVOpupybERK7S+KqYkVrcHVublZpzHf/RSMCgSQfDhZE2N6iBghJvBC6DLetcvKUR9meUVFcKaHrt2VKU3hmegX9DtWTCV5ld58y3mxYCSURLaEqPWoAeS0xGU1eas5sKFp8j/q6cY4hhXRqy75z4F1iX7fHiQZBl5W0VQEYTMQrp1bFpCz59apO/4tYNzYbr6MvO9WmXvqOTZWYzVdl2mANTZf6Hppr4+t4+rBMvQBqpvfcFillZChKOhMAn+A1ZY1YlxufCAb/b2HkNuQnMXJBOaK36FzNvfcK/fRFseNICO4IkxoAcYwHYTUanrvqukPKvS3FxlmhdOVYxlx2N6+16iybXrVmZJdiRcNahpfhxkc7tCkaWaaYdvKY6YrhRHESY+gn9uO7rYg+lNbV+KeHY45/2eJVhmg4jmCjEtcEn1ZoGDQIg0ysydjuglaWzOgu9dxRA2G8bWyfLoF4fYJmaPmNmnLmdMACW/OjEvGA6WOGqhkr/eDtA6TeD0wrfADxaLWqY8ZSp+TBcAhyzlzuysB3ATAFgEdFldq2IghyCMxR6AnLMQmKDpkYYIkBqu70buSoxugmzhfzI1Yj9aCI/f4/PiHpsV9C4q/7YGhXyG/mvXIIzLoW1IAQ7pomj5d5CB7CMUabvyr1LJyf9jCSqI62MWpi8GGtlkQ59b yepnbrM4 vjYFH8+fkJgdeF5yM9zOO8ZYi0CzDvJtbvQchS+y/wgcCZHZbfLmtXllJpz324AofpEZAZVkLV9UKTMoYye8XCjO4ZhmhvqHDLb3R0h6yEVPbuprAbBa8l3G3BwD4XyOUlHk8uD9atX+XZFK26HSShAH7wnQo8xJQ7iMd65ZeZ+Onj1CBdxEFQXLMst5uN5o4Nq33HV7i/Sdy0hYDkrMx9X8lyGu62c0InVUD52b/NG/7i1+mnrvRrpY5Ff/EunWWSe+N 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 Tue, Jun 13, 2023 at 01:18:26PM -0700, Vishal Moola (Oracle) wrote: > struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags) > { > + struct folio *folio; checkpatch will whinge about there not being a blank line here, and in this case, I think it's correct. > if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page))) > return NULL; > > + folio = try_get_folio(page, refs); > + > if (flags & FOLL_GET) > - return try_get_folio(page, refs); > - else if (flags & FOLL_PIN) { > - struct folio *folio; > + return folio; > > - /* > - * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a > - * right zone, so fail and let the caller fall back to the slow > - * path. > - */ > - if (unlikely((flags & FOLL_LONGTERM) && > - !is_longterm_pinnable_page(page))) > - return NULL; > + if (unlikely(!(flags & FOLL_PIN))) { > + WARN_ON_ONCE(1); > + return NULL; Don't we need to folio_put_refs() in this case? Or rather, I think the if (WARN_ON_ONCE(flags & (FOLL_PIN|FOLL_GET) == 0) { test should be first. > + /* > + * CAUTION: Don't use compound_head() on the page before this > + * point, the result won't be stable. > + */ I think we can lose the comment at this point? > + if (!folio) > + return NULL;