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b=04vsPTMiopiMU58KgFzxKVTaW9vDj2J71Kw+jaUes6u1TjIKfVas2MIL6UE/KSPT3 /s9FCutL/tkdmUddBSm2DYc3nRBuyEHqKD2NDZ6J6ANwW/5j4C8i0HYk5+i3mm/oVh PqbhknJO4s9j6ZRyAK1RQ4KhowkvulMLNbfJPv1A= Date: Wed, 8 Nov 2023 13:07:51 -0800 From: Andrew Morton To: "Matthew Wilcox (Oracle)" Cc: Naoya Horiguchi , linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH 2/6] mm: Convert __do_fault() to use a folio Message-Id: <20231108130751.f515f0f3c5ce5fb5b1d70fb0@linux-foundation.org> In-Reply-To: <20231108182809.602073-3-willy@infradead.org> References: <20231108182809.602073-1-willy@infradead.org> <20231108182809.602073-3-willy@infradead.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 915C3140026 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: mph7t4gdqeytzuxgdgcf9y6y6z846mhz X-HE-Tag: 1699477677-453656 X-HE-Meta: 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 XSO9y/bp yT7c0aHY+MA0ftTtlUa1GoP3H1MUV92UDPuUKapKGn6TxxSgW/5ZqgB4k/yqjA/VrIXaYTPtuDygAgCWwW6+0dbahGDjAvH7mjZ1Oas3iWgiaH1rpl5eNAj9ZWG8V6ibLy+Wc+d5d/UArvQzbzJZqv36CmhLy1QhsmcW795hLZ3XpCHgNTQlNEPNnZtP1pQYWmGojN5QX6iJji+de25amTXktyeTLXBhOkpZKlFLJ4ORG3N5XZD1zo/TuZDvGDWKKMfzL2u8oVznYxpvQBrp6XvDqFyY2uHKLiM1neciLIn9u04uWsUXEzS0Z4APpUxIs9S8tU5segVqx/lYjHF/V3UXGlwNgRCAjh4WnQhZhsbIL4ZuhHLWJ+DmRQ/Cz3WDHdfKidvPZiexHfCk= 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, 8 Nov 2023 18:28:05 +0000 "Matthew Wilcox (Oracle)" wrote: > Convert vmf->page to a folio as soon as we're going to use it. This fixes > a bug if the fault handler returns a tail page with hardware poison; > tail pages have an invalid page->index, so we would fail to unmap the > page from the page tables. We actually have to unmap the entire folio (or > mapping_evict_folio() will Would we merely fail to unmap or is there a possibility of unmapping some random innocent other page? How might this bug manifest in userspace, worst case? > fail), so use unmap_mapping_folio() instead. > > This also saves various calls to compound_head() hidden in lock_page(), > put_page(), etc. > > Signed-off-by: Matthew Wilcox (Oracle) > Fixes: 793917d997df ("mm/readahead: Add large folio readahead") > Cc: stable@vger.kernel.org As it's cc:stable I'll pluck this patch out of the rest of the series and shall stage it for 6.7-rcX, via mm-hotfixes-unstable -> mm-hotfixes-stable -> Linus. Unless this bug is a very minor thing?