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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id be18-20020a05690c009200b0054fcbf35b94sm2601627ywb.87.2023.04.16.17.45.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 16 Apr 2023 17:45:28 -0700 (PDT) Date: Sun, 16 Apr 2023 17:45:18 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Zach O'Keefe , Yang Shi , Ivan Orlov , himadrispandya@gmail.com, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, linux-mm@kvack.org, skhan@linuxfoundation.org, syzbot+9578faa5475acb35fa50@syzkaller.appspotmail.com, Mike Kravetz , "Kirill A. Shutemov" , Matthew Wilcox Subject: Re: [PATCH v2] mm: khugepaged: Fix kernel BUG in hpage_collapse_scan_file In-Reply-To: <20230416113335.caeafda1328fdd4bfe2406e8@linux-foundation.org> Message-ID: References: <20230330155305.423051-1-ivan.orlov0322@gmail.com> <20230331013301.ecgkjymaf3ws6rfb@google.com> <20230416113335.caeafda1328fdd4bfe2406e8@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Queue-Id: 359174000B X-Rspamd-Server: rspam01 X-Stat-Signature: jzet5rsxnxsdkgnq1g4itatbxnnf3mbg X-HE-Tag: 1681692329-287157 X-HE-Meta: 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 eo6rjwTr 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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: On Sun, 16 Apr 2023, Andrew Morton wrote: > > Circling back to this fix... > > The BUG() is obviously real. It's worth remembering that syzbot's reproducer involves artificially injecting page allocation failures. So although the bug may be "real", it is rather in the theoretical category, way down on my own list to look at, and I'd say not at all urgent to fix. Hugh > 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.