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author | Zi Yan <ziy@nvidia.com> | 2022-05-24 15:47:56 -0400 |
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committer | akpm <akpm@linux-foundation.org> | 2022-05-25 10:47:47 -0700 |
commit | 88ee134320b8311ca7a00630e5ba013cd0239350 (patch) | |
tree | c633cba5a7d7743ce20d5ecf1a6004b8d58db025 /mm/page_alloc.c | |
parent | bb5ced41a658e51bb72d3dc651b28e344e001ac9 (diff) | |
download | linux-88ee134320b8311ca7a00630e5ba013cd0239350.tar.gz |
mm: fix a potential infinite loop in start_isolate_page_range()
In isolate_single_pageblock() called by start_isolate_page_range(), there are some pageblock isolation issues causing a potential infinite loop when isolating a page range. This is reported by Qian Cai. 1. the pageblock was isolated by just changing pageblock migratetype without checking unmovable pages. Calling set_migratetype_isolate() to isolate pageblock properly. 2. an off-by-one error caused migrating pages unnecessarily, since the page is not crossing pageblock boundary. 3. migrating a compound page across pageblock boundary then splitting the free page later has a small race window that the free page might be allocated again, so that the code will try again, causing an potential infinite loop. Temporarily set the to-be-migrated page's pageblock to MIGRATE_ISOLATE to prevent that and bail out early if no free page is found after page migration. An additional fix to split_free_page() aims to avoid crashing in __free_one_page(). When the free page is split at the specified split_pfn_offset, free_page_order should check both the first bit of free_page_pfn and the last bit of split_pfn_offset and use the smaller one. For example, if free_page_pfn=0x10000, split_pfn_offset=0xc000, free_page_order should first be 0x8000 then 0x4000, instead of 0x4000 then 0x8000, which the original algorithm did. [akpm@linux-foundation.org: suppress min() warning] Link: https://lkml.kernel.org/r/20220524194756.1698351-1-zi.yan@sent.com Fixes: b2c9e2fbba3253 ("mm: make alloc_contig_range work at pageblock granularity") Signed-off-by: Zi Yan <ziy@nvidia.com> Reported-by: Qian Cai <quic_qiancai@quicinc.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: David Hildenbrand <david@redhat.com> Cc: Eric Ren <renzhengeek@gmail.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Mike Rapoport <rppt@linux.ibm.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r-- | mm/page_alloc.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 267599dd9706..bc93a82e51e6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1114,13 +1114,18 @@ void split_free_page(struct page *free_page, unsigned long flags; int free_page_order; + if (split_pfn_offset == 0) + return; + spin_lock_irqsave(&zone->lock, flags); del_page_from_free_list(free_page, zone, order); for (pfn = free_page_pfn; pfn < free_page_pfn + (1UL << order);) { int mt = get_pfnblock_migratetype(pfn_to_page(pfn), pfn); - free_page_order = ffs(split_pfn_offset) - 1; + free_page_order = min_t(int, + pfn ? __ffs(pfn) : order, + __fls(split_pfn_offset)); __free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order, mt, FPI_NONE); pfn += 1UL << free_page_order; |