The patch titled
Subject: mm, compaction: fix fast_isolate_around() to stay within boundaries
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-compaction-fix-fast_isolate_around-to-stay-within-boundaries.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-fix-fast_isolate_around-to-stay-within-boundaries.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: NARIBAYASHI Akira <a.naribayashi@xxxxxxxxxxx>
Subject: mm, compaction: fix fast_isolate_around() to stay within boundaries
Date: Wed, 26 Oct 2022 20:24:38 +0900
Depending on the memory configuration, isolate_freepages_block() may scan
pages out of the target range and causes panic.
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.
This problem should have been addressd by the commit 6e2b7044c199 ("mm,
compaction: make fast_isolate_freepages() stay within zone") but there was
an oversight.
Case1: pfn < start_pfn
<at memory compaction for node Y>
| node X's zone | node Y's zone
+-----------------+------------------------------...
pageblock ^ ^ ^
+-----------+-----------+-----------+-----------+...
^ ^ ^
^ ^ end_pfn
^ start_pfn = cc->zone->zone_start_pfn
pfn
<---------> scanned range by "Scan After"
Case2: end_pfn < pfn
<at memory compaction for node X>
| node X's zone | node Y's zone
+-----------------+------------------------------...
pageblock ^ ^ ^
+-----------+-----------+-----------+-----------+...
^ ^ ^
^ ^ pfn
^ end_pfn
start_pfn
<---------> scanned range by "Scan Before"
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".
Link: https://lkml.kernel.org/r/20221026112438.236336-1-a.naribayashi@xxxxxxxxxxx
Fixes: 6e2b7044c199 ("mm, compaction: make fast_isolate_freepages() stay within zone").
Signed-off-by: NARIBAYASHI Akira <a.naribayashi@xxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/compaction.c~mm-compaction-fix-fast_isolate_around-to-stay-within-boundaries
+++ a/mm/compaction.c
@@ -1344,7 +1344,7 @@ move_freelist_tail(struct list_head *fre
}
static void
-fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated)
+fast_isolate_around(struct compact_control *cc, unsigned long pfn)
{
unsigned long start_pfn, end_pfn;
struct page *page;
@@ -1365,21 +1365,13 @@ fast_isolate_around(struct compact_contr
if (!page)
return;
- /* Scan before */
- if (start_pfn != pfn) {
- isolate_freepages_block(cc, &start_pfn, pfn, &cc->freepages, 1, false);
- if (cc->nr_freepages >= cc->nr_migratepages)
- return;
- }
-
- /* Scan after */
- start_pfn = pfn + nr_isolated;
- if (start_pfn < end_pfn)
- isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
+ isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
/* Skip this pageblock in the future as it's full or nearly full */
if (cc->nr_freepages < cc->nr_migratepages)
set_pageblock_skip(page);
+
+ return;
}
/* Search orders in round-robin fashion */
@@ -1556,7 +1548,7 @@ fast_isolate_freepages(struct compact_co
return cc->free_pfn;
low_pfn = page_to_pfn(page);
- fast_isolate_around(cc, low_pfn, nr_isolated);
+ fast_isolate_around(cc, low_pfn);
return low_pfn;
}
_
Patches currently in -mm which might be from a.naribayashi@xxxxxxxxxxx are
mm-compaction-fix-fast_isolate_around-to-stay-within-boundaries.patch
