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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 Subject: Re: [PATCH -next 1/2] mm: compaction: convert to use a folio in isolate_migratepages_block() Content-Language: en-US From: Kefeng Wang To: Matthew Wilcox CC: , , , , References: <20230612143414.186389-1-wangkefeng.wang@huawei.com> <99dabd49-16c7-2858-e502-1bb390e13859@huawei.com> In-Reply-To: <99dabd49-16c7-2858-e502-1bb390e13859@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: C5CFA120006 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: gou4jczs3n5orx36whpqng8st7kuhzzw X-HE-Tag: 1686741667-48584 X-HE-Meta: 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 2s9+Ckxt 8csakqh+K4iG9y4zza0sp9t2x8SbdsX/JyIlS787KtFqW13WsFNbHbf3O++pE4muGEE/9yvwBQz2+zUA3ERa9zvSYhM5zZuppnhIS7T3cIsSeBfA/G+M1ZFntIwtSN3KiIZ231ayNRUxGGaDDWbgFLDIGfUN8AnnM1bZl71FnAiJihSOtnOBni6o/Jg== 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 2023/6/13 9:53, Kefeng Wang wrote: > > > On 2023/6/12 22:41, Matthew Wilcox wrote: >> On Mon, Jun 12, 2023 at 10:34:13PM +0800, Kefeng Wang wrote: >>> @@ -959,7 +960,8 @@ isolate_migratepages_block(struct compact_control >>> *cc, unsigned long low_pfn, >>>                    * Hugepage was successfully isolated and placed >>>                    * on the cc->migratepages list. >>>                    */ >>> -                low_pfn += compound_nr(page) - 1; >>> +                folio = page_folio(page); >>> +                low_pfn += folio_nr_pages(folio) - 1; >>>                   goto isolate_success_no_list; >> >> Why is this safe?  That is, how do we know that the folio can't be >> dissolved under us at this point, then reallocated and hit the >> VM_BUG_ON_PGFLAGS(PageTail(page), page) in folio_flags() when we >> test folio_test_large()? > > This is successfully isolated path, after isolate_hugetlb(),  the folio > reference is incremented, so I think the folio can't be dissolved here, > correct me if I am wrong. Hi Matthew，is it enough for the above conversion from page to folio with reference?