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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rpgHb-00000005O6U-43VH; Thu, 28 Mar 2024 03:18:28 +0000 Date: Thu, 28 Mar 2024 03:18:27 +0000 From: Matthew Wilcox To: Zhaoyang Huang Cc: =?utf-8?B?6buE5pyd6ZizIChaaGFveWFuZyBIdWFuZyk=?= , Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , =?utf-8?B?5bq357qq5ruoIChTdGV2ZSBLYW5nKQ==?= Subject: Re: summarize all information again at bottom//reply: reply: [PATCH] mm: fix a race scenario in folio_isolate_lru Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 582EE18000C X-Stat-Signature: 8xdwrzdphnqocm3axmthq3kia7y8kuz7 X-HE-Tag: 1711595915-369284 X-HE-Meta: U2FsdGVkX18W0j61WvHoWSlRtMtUKT6QuNJkdqCpO+aYRDEJjLveTt7ZtiWybiECvN04zZPwRVXAhYlYiIBf7Gf/fcfVLKdg9DvE1EOWmVfj/isj7PylDzqccfvImVNl0xUQMR9s0q2b0pdPOZXM9xiYlaGg2d4y0foYfDp/fIFlOwofRbA4Fp3bZlDqD9P4W+vnH5yQXJerGGbt9i593hSh38QxqZ5N4NrYChVLv/A5y9oED89u0LCI4UO+38Ua7+Mh6VIpTeZkp+mAo/zNwwtHuSi6ky+iXhlqGEEd4wz4ScYbE/ImFX7wuind1eTo85R7z80c6i4D7V87QfwvU4zfyczfGPE96T2qwt8hcn9RZypcaIiqe0dvPL5kertwevfI3tDMlSZgV/Yz4PDD98wb/G1yl2azjbxlCJQOEiL7p3nSPnlkLfhokm29seeqsJ6na6CvuCft9lFzyW6BUTKniEQL/FPRVdm9uns5oHuPFbOqZ1ejUm10hk3Zie/zdpPqFV7JjuCAbL+dYg5QBoyyzc3SZaXnzMyGPq7ijIZRDTzakEtJpzcKa3cDiCtZ2S5kpiNN6b9ZEkJL5E/la8e2XDPblf2YEOIu++q/dllnA+80V1k+uDxF5lJI5niHw9/49/TxeI0xfMJrxl7F2+3gvc30cc0WmwPyHIhLFAxSg7PPBOBl0PNdEyklqI23eGazDVfmsNuh5cn5pMF/WrBxEUWmLSgRUIvNZt++PXqv1oM6BRc5DWk/Vi7XoO2azWguxLBf8hqJysWZvyImms8fRp8E6nJHqv0IVxgedKH7s2Q5Z6qbY4B1/KVvr3wfCaLEKK3341iR56g2TnqKfuQNpLTqwld5dDiyxK9hSQ11rMejfgY81JRXuuoXIkwqnV3kJhhvy7DhKZpvtJTX4KexZSMC+ZNMGTUJyi8qcAQD+tl+nwcDaqQ2lGVhhq7wdrBMRWfGCx8HAh3gQ9A 6FGBxRBK gAFyG0NEoac3n7LYMJVwZSusrIzoWGzGTd+LX+HM8TmY1zzxAPyNCGBs9oVCtuckPZTOohGb5ZMSBF/Eo2FepxXzOe2AOlBapKTIg7E5TeQK7a+paxI8l7zVQ9y+W9WplQZ6nM1AdSaV4E7EezWdjPdXCN8OSP60NxubYowyAmj5yd/+iiwRCGNdxzmh/1p8lx1OAA+PTReX1/J0gd2O6T+3Scsnx0P8HPih4Ia6qcoQnTr8b+KR5CMnugA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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 Thu, Mar 28, 2024 at 09:27:31AM +0800, Zhaoyang Huang wrote: > ok, I missed the refcnt from alloc_pages. However, I still think it is > a bug to call readahead_folio in read_pages as the refcnt obtained by > alloc_pages should be its final guard which is paired to the one which > checked in shrink_folio_list->__remove_mapping->folio_ref_freeze(2)(this > 2 represent alloc_pages & page cache). If we removed this one without __remove_mapping() requires that the caller holds the folio locked. Since the readahead code unlocks the folio, __remove_mapping() cannot be run because the caller of __remove_mapping() will wait for the folio lock.