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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> From: Baokun Li X-Mozilla-Draft-Info: internal/draft; vcard=0; receipt=0; DSN=0; uuencode=0; attachmentreminder=0; deliveryformat=1 X-Identity-Key: id2 Fcc: imap://libaokun%40huaweicloud.com@cnp3.mail02.huawei.com/Sent In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:Syh0CgBnvUUWb_xojropBg--.48200S3 X-Coremail-Antispam: 1UD129KBjvJXoW7Kw4ktw47Kw13CF47Zr43Wrg_yoW8Jw4xpF WvkF1IqFykJr1kZF1kZw13JFyak3y8JF4UCay7t3sxuFn8Ja4agrsFk3WFkFySkryUAw10 qFWxtrZ7u3ZxA37anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvYb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUXVWUAwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS 14v26r1q6r43MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I 8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8 ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x 0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_ Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBIdaVFxhVjvjDU0xZFpf9x07 UG-eOUUUUU= X-CM-SenderInfo: 5olet0hnxqqx5xdzvxpfor3voofrz/1tbiAQAMBWj7UbRPggABsy X-Rspam-User: X-Rspamd-Queue-Id: 0918B20005 X-Rspamd-Server: rspam03 X-Stat-Signature: qby8r3gb3mezfqekygtqa57knfifc1cg X-HE-Tag: 1761373993-321075 X-HE-Meta: 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 Ga2Lobn8 cBG7gQTnIFAG6+F13nO9NIIoeB/OeAM9oaOnzJiyXPIt18brhgjuZF8lg7DXyx/Fv+gIr8m16B+td8tx05COsYSpTDc0P0y0rW7ht2mP4lFmiAoFfB8ngAYnc5suLM1rAKXVreQMT/dARs5GN+fr0MzISmX/CyVRcVko3oAksoi15g6Yc3//lbSQW6nFJXqucISyS 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