This is a note to let you know that I've just added the patch titled
mm, compaction: make fast_isolate_freepages() stay within zone
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-compaction-make-fast_isolate_freepages-stay-within-zone.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6e2b7044c199229a3d20cefbd3184968238c4184 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@xxxxxxx>
Date: Wed, 24 Feb 2021 12:09:39 -0800
Subject: mm, compaction: make fast_isolate_freepages() stay within zone
From: Vlastimil Babka <vbabka@xxxxxxx>
commit 6e2b7044c199229a3d20cefbd3184968238c4184 upstream.
Compaction always operates on pages from a single given zone when
isolating both pages to migrate and freepages. Pageblock boundaries are
intersected with zone boundaries to be safe in case zone starts or ends in
the middle of pageblock. The use of pageblock_pfn_to_page() protects
against non-contiguous pageblocks.
The functions fast_isolate_freepages() and fast_isolate_around() don't
currently protect the fast freepage isolation thoroughly enough against
these corner cases, and can result in freepage isolation operate outside
of zone boundaries:
- in fast_isolate_freepages() if we get a pfn from the first pageblock
of a zone that starts in the middle of that pageblock, 'highest' can
be a pfn outside of the zone.
If we fail to isolate anything in this function, we may then call
fast_isolate_around() on a pfn outside of the zone and there
effectively do a set_pageblock_skip(page_to_pfn(highest)) which may
currently hit a VM_BUG_ON() in some configurations
- fast_isolate_around() checks only the zone end boundary and not
beginning, nor that the pageblock is contiguous (with
pageblock_pfn_to_page()) so it's possible that we end up calling
isolate_freepages_block() on a range of pfn's from two different
zones and end up e.g. isolating freepages under the wrong zone's
lock.
This patch should fix the above issues.
Link: https://lkml.kernel.org/r/20210217173300.6394-1-vbabka@xxxxxxx
Fixes: 5a811889de10 ("mm, compaction: use free lists to quickly locate a migration target")
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1248,7 +1248,7 @@ static void
fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated)
{
unsigned long start_pfn, end_pfn;
- struct page *page = pfn_to_page(pfn);
+ struct page *page;
/* Do not search around if there are enough pages already */
if (cc->nr_freepages >= cc->nr_migratepages)
@@ -1259,8 +1259,12 @@ fast_isolate_around(struct compact_contr
return;
/* Pageblock boundaries */
- start_pfn = pageblock_start_pfn(pfn);
- end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone)) - 1;
+ start_pfn = max(pageblock_start_pfn(pfn), cc->zone->zone_start_pfn);
+ end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone));
+
+ page = pageblock_pfn_to_page(start_pfn, end_pfn, cc->zone);
+ if (!page)
+ return;
/* Scan before */
if (start_pfn != pfn) {
@@ -1362,7 +1366,8 @@ fast_isolate_freepages(struct compact_co
pfn = page_to_pfn(freepage);
if (pfn >= highest)
- highest = pageblock_start_pfn(pfn);
+ highest = max(pageblock_start_pfn(pfn),
+ cc->zone->zone_start_pfn);
if (pfn >= low_pfn) {
cc->fast_search_fail = 0;
@@ -1432,7 +1437,8 @@ fast_isolate_freepages(struct compact_co
} else {
if (cc->direct_compaction && pfn_valid(min_pfn)) {
page = pageblock_pfn_to_page(min_pfn,
- pageblock_end_pfn(min_pfn),
+ min(pageblock_end_pfn(min_pfn),
+ zone_end_pfn(cc->zone)),
cc->zone);
cc->free_pfn = min_pfn;
}
Patches currently in stable-queue which might be from vbabka@xxxxxxx are
queue-5.10/mm-compaction-make-fast_isolate_freepages-stay-within-zone.patch
queue-5.10/mm-thp-shmem-make-khugepaged-obey-tmpfs-mount-flags.patch
queue-5.10/mm-compaction-fix-misbehaviors-of-fast_find_migrateb.patch
queue-5.10/proc-use-kvzalloc-for-our-kernel-buffer.patch
queue-5.10/mm-rmap-fix-potential-pte_unmap-on-an-not-mapped-pte.patch
