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Wong" Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, linux-kernel@vger.kernel.org, kernel@pankajraghav.com, mcgrof@kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, yi.zhang@huawei.com, yangerkun@huawei.com, chengzhihao1@huawei.com, libaokun1@huawei.com References: <20251025032221.2905818-1-libaokun@huaweicloud.com> <20251025032221.2905818-23-libaokun@huaweicloud.com> Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:Syh0CgBXrUVdb_xoutIpBg--.48673S3 X-Coremail-Antispam: 1UD129KBjvJXoW7Kw4ktw47Kw13CF47Zr43Wrg_yoW8Jw4xpF WvkF1IqFykJr1kZF1kZw13JFyak3y8JF4UCay7t3sxuFn8Ja4agrsFk3WFkFySkryUAw10 qFWxtrZ7u3ZxA37anT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvYb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUXVWUAwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS 14v26r4a6rW5MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I 8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8 ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x 0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_ Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBIdaVFxhVjvjDU0xZFpf9x07 j4eHgUUUUU= X-CM-SenderInfo: 5olet0hnxqqx5xdzvxpfor3voofrz/1tbiAgAMBWj7Ua9PfQABsV X-Rspamd-Server: rspam05 X-Stat-Signature: qby8r3gb3mezfqekygtqa57knfifc1cg X-Rspam-User: X-Rspamd-Queue-Id: 4DB89A0006 X-HE-Tag: 1761374057-511186 X-HE-Meta: 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 1R1WqBAU FKvIiCHJlvegBKM5TTeDVISvJCWTIVHNmUU1v+ee0N6Gte3dn0ObhZgdzILKCEeEtUbjbLkgI57ixMuUI96mowyTn+Om+NHtSkoQumYExXIa+qLqDCNYF28kwlZFak30wOcaL3X8aeJGagbnkESHRViRzrf9t4ktbxkDClTHJBJqybynREnQirI1mAuIIQYF0/aPS 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 2025-10-25 12:45, Matthew Wilcox wrote: > On Sat, Oct 25, 2025 at 11:22:18AM +0800, libaokun@huaweicloud.com wrote: >> + while (1) { >> + folio = __filemap_get_folio(mapping, index, fgp_flags, >> + gfp & ~__GFP_NOFAIL); >> + if (!IS_ERR(folio) || !(gfp & __GFP_NOFAIL)) >> + return folio; >> + >> + if (PTR_ERR(folio) != -ENOMEM && PTR_ERR(folio) != -EAGAIN) >> + return folio; >> + >> + memalloc_retry_wait(gfp); >> + } > No, absolutely not. We're not having open-coded GFP_NOFAIL semantics. > The right way forward is for ext4 to use iomap, not for buffer heads > to support large block sizes. ext4 only calls getblk_unmovable or __getblk when reading critical metadata. Both of these functions set __GFP_NOFAIL to ensure that metadata reads do not fail due to memory pressure. Both functions eventually call grow_dev_folio(), which is why we handle the __GFP_NOFAIL logic there. xfs_buf_alloc_backing_mem() has similar logic, but XFS manages its own metadata, allowing it to use vmalloc for memory allocation. ext4 Direct I/O has already switched to iomap, and patches to support iomap for Buffered I/O are currently under iteration. But as far as I know, iomap does not support metadata, and XFS does not use iomap to read metadata either. Am I missing something here? -- With Best Regards, Baokun Li