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Date: Fri, 9 Dec 2022 09:19:37 +0000 From: "Akira Naribayashi (Fujitsu)" <a.naribayashi@...itsu.com> To: 'Mel Gorman' <mgorman@...hsingularity.net> CC: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "vbabka@...e.cz" <vbabka@...e.cz>, "rientjes@...gle.com" <rientjes@...gle.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "stable@...r.kernel.org" <stable@...r.kernel.org>, "Akira Naribayashi (Fujitsu)" <a.naribayashi@...itsu.com> Subject: RE: [PATCH] mm, compaction: fix fast_isolate_around() to stay within boundaries On Wed, 23 Nov 2022 10:26:05 +0000, Mei Gorman wrote: > On Wed, Nov 09, 2022 at 05:41:12AM +0000, Akira Naribayashi (Fujitsu) wrote: > > On Mon, 7 Nov 2022 15:43:56 +0000, Mei Gorman wrote: > > > On Mon, Nov 07, 2022 at 12:32:34PM +0000, Akira Naribayashi (Fujitsu) wrote: > > > > > Under what circumstances will this panic occur? I assume those > > > > > circumstnces are pretty rare, give that 6e2b7044c1992 was nearly two > > > > > years ago. > > > > > > > > > > Did you consider the desirability of backporting this fix into earlier > > > > > kernels? > > > > > > > > > > > > Panic can occur on systems with multiple zones in a single pageblock. > > > > > > > > > > Please provide an example of the panic and the zoneinfo. > > > > This issue is occurring in our customer's environment and cannot > > be shared publicly as it contains customer information. > > Also, the panic is occurring with the kernel in RHEL and may not > > panic with Upstream's community kernel. > > In other words, it is possible to panic on older kernels. > > I think this fix should be backported to stable kernel series. > > > > > > The reason it is rare is that it only happens in special configurations. > > > > > > How is this special configuration created? > > > > This is the case when the node boundary is not aligned to pageblock boundary. > > In that case, does this work to avoid rescanning an area that was already > isolated? In the case of your patch, I think I need to clamp the isolated_end as well. Because sometimes isolated_end < start_pfn(value before entering Scan after) < end_pfn. After re-reading the source, I think the problem is that min_pfn and low_pfn can be out of range in fast_isolate_freepages. How about the following patch? diff --git a/mm/compaction.c b/mm/compaction.c index 1f6da31dd9a5..b67b82bb4944 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1436,6 +1436,11 @@ fast_isolate_freepages(struct compact_control *cc) if (WARN_ON_ONCE(min_pfn > low_pfn)) low_pfn = min_pfn; + if (min_pfn < cc->migrate_pfn) + min_pfn = cc->migrate_pfn; + if (low_pfn < cc->migrate_pfn) + low_pfn = cc->migrate_pfn; + /* * Search starts from the last successful isolation order or the next * order to search after a previous failure
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