From: NARIBAYASHI Akira a.naribayashi@fujitsu.com
commit be21b32afe470c5ae98e27e49201158a47032942 upstream.
Depending on the memory configuration, isolate_freepages_block() may scan pages out of the target range and causes panic.
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 fix this problem for older kernels as well.
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@fujitsu.com Fixes: 6e2b7044c199 ("mm, compaction: make fast_isolate_freepages() stay within zone"). Signed-off-by: NARIBAYASHI Akira a.naribayashi@fujitsu.com Cc: David Rientjes rientjes@google.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/compaction.c | 18 +++++------------- 1 file changed, 5 insertions(+), 13 deletions(-)
--- a/mm/compaction.c +++ b/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; }