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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2018-03-22 16:17:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-03-22 17:07:01 -0700
commitfece2029a9e65b9a990831afe2a2b83290cbbe26 (patch)
tree8c7e6a04d9cc018a4b71c5e068aa8d48b44fbb38
parent28ee90fe6048fa7b7ceaeb8831c0e4e454a4cf89 (diff)
downloadlinux-stericsson-fece2029a9e65b9a990831afe2a2b83290cbbe26.tar.gz
mm/khugepaged.c: convert VM_BUG_ON() to collapse fail
khugepaged is not yet able to convert PTE-mapped huge pages back to PMD mapped. We do not collapse such pages. See check khugepaged_scan_pmd(). But if between khugepaged_scan_pmd() and __collapse_huge_page_isolate() somebody managed to instantiate THP in the range and then split the PMD back to PTEs we would have a problem -- VM_BUG_ON_PAGE(PageCompound(page)) will get triggered. It's possible since we drop mmap_sem during collapse to re-take for write. Replace the VM_BUG_ON() with graceful collapse fail. Link: http://lkml.kernel.org/r/20180315152353.27989-1-kirill.shutemov@linux.intel.com Fixes: b1caa957ae6d ("khugepaged: ignore pmd tables with THP mapped with ptes") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Laura Abbott <labbott@redhat.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/khugepaged.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b7e2268dfc9a..c15da1ea7e63 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -530,7 +530,12 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
goto out;
}
- VM_BUG_ON_PAGE(PageCompound(page), page);
+ /* TODO: teach khugepaged to collapse THP mapped with pte */
+ if (PageCompound(page)) {
+ result = SCAN_PAGE_COMPOUND;
+ goto out;
+ }
+
VM_BUG_ON_PAGE(!PageAnon(page), page);
/*