diff options
| author | Vishal Moola (Oracle) <vishal.moola@gmail.com> | 2025-03-31 19:10:24 -0700 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-04-11 17:32:36 -0700 |
| commit | a84edd52f0a0fa193f0f685769939cf84510755b (patch) | |
| tree | e2fb77bd9a6dedd531416f81ab64fc84df12719f /mm/compaction.c | |
| parent | 770c8d55c42868239c748a3ebc57c9e37755f842 (diff) | |
mm/compaction: fix bug in hugetlb handling pathway
The compaction code doesn't take references on pages until we're certain
we should attempt to handle it.
In the hugetlb case, isolate_or_dissolve_huge_page() may return -EBUSY
without taking a reference to the folio associated with our pfn. If our
folio's refcount drops to 0, compound_nr() becomes unpredictable, making
low_pfn and nr_scanned unreliable. The user-visible effect is minimal -
this should rarely happen (if ever).
Fix this by storing the folio statistics earlier on the stack (just like
the THP and Buddy cases).
Also revert commit 66fe1cf7f581 ("mm: compaction: use helper compound_nr
in isolate_migratepages_block") to make backporting easier.
Link: https://lkml.kernel.org/r/20250401021025.637333-1-vishal.moola@gmail.com
Fixes: 369fa227c219 ("mm: make alloc_contig_range handle free hugetlb pages")
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/compaction.c')
| -rw-r--r-- | mm/compaction.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 139f00c0308a..ca71fd3c3181 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -981,13 +981,13 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, } if (PageHuge(page)) { + const unsigned int order = compound_order(page); /* * skip hugetlbfs if we are not compacting for pages * bigger than its order. THPs and other compound pages * are handled below. */ if (!cc->alloc_contig) { - const unsigned int order = compound_order(page); if (order <= MAX_PAGE_ORDER) { low_pfn += (1UL << order) - 1; @@ -1011,8 +1011,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, /* Do not report -EBUSY down the chain */ if (ret == -EBUSY) ret = 0; - low_pfn += compound_nr(page) - 1; - nr_scanned += compound_nr(page) - 1; + low_pfn += (1UL << order) - 1; + nr_scanned += (1UL << order) - 1; goto isolate_fail; } |