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Shutemov" , Matthew Wilcox Subject: Re: [PATCH v2] mm: khugepaged: Fix kernel BUG in hpage_collapse_scan_file Message-Id: <20230416113335.caeafda1328fdd4bfe2406e8@linux-foundation.org> In-Reply-To: References: <20230330155305.423051-1-ivan.orlov0322@gmail.com> <20230331013301.ecgkjymaf3ws6rfb@google.com> X-Mailer: Sylpheed 3.7.0 (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-Stat-Signature: qeyjtqsma3sscibkfsrzgjdrp99knqpq X-Rspam-User: X-Rspamd-Queue-Id: 2DE71C0006 X-Rspamd-Server: rspam06 X-HE-Tag: 1681670017-631071 X-HE-Meta: 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 zCVMpCFg 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 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: Circling back to this fix... The BUG() is obviously real. We're unsure that Ivan's fix is the best one. We haven't identified a Fixes:, and as this report is against the 6.2 kernel, a cc:stable will be needed. According to the sysbot bisection (https://syzkaller.appspot.com/bug?id=7d6bb3760e026ece7524500fe44fb024a0e959fc), this is present in linux-5.19, so it might predate Zach's 58ac9a8993a13ebc changes. But that bisection claim might be misleading. And Zach is offline for a few months. So can people please take a look and see if we can get this wrapped up? Matthew, the assertion failure is in the VM_BUG_ON(index != xas.xa_index); which was added in 77da9389b9d5f, so perhaps you could take a look? Thanks.