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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uh6FS-0000000CVGZ-3Fep; Wed, 30 Jul 2025 12:49:34 +0000 Date: Wed, 30 Jul 2025 13:49:34 +0100 From: Matthew Wilcox To: Zhang Qilong Cc: arnd@arndb.de, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, david@redhat.com, wangkefeng.wang@huawei.com, sunnanyong@huawei.com Subject: Re: [PATCH resend v2] /dev/zero: try to align PMD_SIZE for private mapping Message-ID: References: <20250730091905.383353-1-zhangqilong3@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250730091905.383353-1-zhangqilong3@huawei.com> X-Rspamd-Queue-Id: 06186C0003 X-Stat-Signature: aapiok9c98kw78p1ozzo7joen74wbwwp X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1753879780-978432 X-HE-Meta: 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 N7ZTT0bH aCZ851PO2M+5nOKnfKOesuq9Q3g9PfF0/w7r/0/KzBfK2O02O+FZAysqxYAJcbzB7wq6ZRtEujoCRZtSTbagyFlQfZ26fveYxpfo+7Ez9WT1q86tqOv53ZpNg6LmE3G2NAcaStW+50134l51//zk14vOhxZ9L4KSwxS4RCc+FPz8BQdZsQ0uOCa6nAcO3Ek3oYS5E3jusjIR87mgD/ZcO/N9G37sInoSKk0uqVwUHm70Xvyd/NziT3rxVbQ== 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: List-Subscribe: List-Unsubscribe: On Wed, Jul 30, 2025 at 05:19:05PM +0800, Zhang Qilong wrote: > + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > + return thp_get_unmapped_area(file, addr, len, pgoff, flags); > + > return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); I'm sure the build bots will give us a compiler error. If CONFIG_TRANSPARENT_HUGEPAGE is not enabled, we get: include/linux/huge_mm.h:#define thp_get_unmapped_area NULL and we chose that so that various filesystems can unconditionally set their .get_unmapped_area method to it. Which means the cpp will turn this into: if (0) return NULL(file, addr, len, pgoff, flags); and the compiler will say: error: implicit declaration of function ‘NULL’ [-Wimplicit-function-declaration]