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dkim=fail ("headers rsa verify failed") header.d=fujitsu.com header.s=fj1 header.b=DlW1kdSs; spf=pass (imf28.hostedemail.com: domain of a.naribayashi@fujitsu.com designates 68.232.159.87 as permitted sender) smtp.mailfrom=a.naribayashi@fujitsu.com; dmarc=pass (policy=none) header.from=fujitsu.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-Rspamd-Server: rspam05 X-Rspam-User: X-HE-Tag: 1667824361-137265 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000964, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Sorry, I may not have sent the email correctly.=20 I will resend it. On Thu, 27 Oct 2022 20:26:04 +0000 Andrew Morton wrote: > On Wed, 26 Oct 2022 20:24:38 +0900 NARIBAYASHI Akira wrote: >=20 > > Depending on the memory configuration, isolate_freepages_block() may > > scan pages out of the target range and causes panic. > >=20 > > The problem is that pfn as argument of fast_isolate_around() could > > be out of the target range. Therefore we should consider the case > > where pfn < start_pfn, and also the case where end_pfn < pfn. > >=20 > > This problem should have been addressd by the commit 6e2b7044c199 > > ("mm, compaction: make fast_isolate_freepages() stay within zone") > > but there was an oversight. > >=20 > > Case1: pfn < start_pfn > >=20 > > > > | node X's zone | node Y's zone > > +-----------------+------------------------------... > > pageblock ^ ^ ^ > > +-----------+-----------+-----------+-----------+... > > ^ ^ ^ > > ^ ^ end_pfn > > ^ start_pfn =3D cc->zone->zone_start_pfn > > pfn > > <---------> scanned range by "Scan After" > >=20 > > Case2: end_pfn < pfn > >=20 > > > > | node X's zone | node Y's zone > > +-----------------+------------------------------... > > pageblock ^ ^ ^ > > +-----------+-----------+-----------+-----------+... > > ^ ^ ^ > > ^ ^ pfn > > ^ end_pfn > > start_pfn > > <---------> scanned range by "Scan Before" > >=20 > > It seems that there is no good reason to skip nr_isolated pages > > just after given pfn. So let perform simple scan from start to end > > instead of dividing the scan into "Before" and "After". >=20 > Under what circumstances will this panic occur? I assume those > circumstnces are pretty rare, give that 6e2b7044c1992 was nearly two > years ago. >=20 > Did you consider the desirability of backporting this fix into earlier > kernels? Panic can occur on systems with multiple zones in a single pageblock. The reason it is rare is that it only happens in special configurations. Depending on how many similar systems there are, it may be a good idea to f= ix this problem for older kernels as well.