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Commitfece202
mm/khugepaged.c: convert VM_BUG_ON() to collapse fail
khugepaged is not yet able to convert PTE-mapped huge pages back to PMDmapped. We do not collapse such pages. See checkkhugepaged_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 PMDback 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 forwrite.Replace the VM_BUG_ON() with graceful collapse fail.Link:http://lkml.kernel.org/r/20180315152353.27989-1-kirill.shutemov@linux.intel.comFixes:b1caa95 ("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>1 parent28ee90f commitfece202
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