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29 July 2024, 15:18:00 UTC
Revision fece2029a9e65b9a990831afe2a2b83290cbbe26 authored by Kirill A. Shutemov on 22 March 2018, 23:17:28 UTC, committed by Linus Torvalds on 23 March 2018, 00:07:01 UTC 
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>
1 parent 28ee90f
History
Tip revision: fece2029a9e65b9a990831afe2a2b83290cbbe26 authored by Kirill A. Shutemov on 22 March 2018, 23:17:28 UTC
mm/khugepaged.c: convert VM_BUG_ON() to collapse fail
Tip revision: fece202
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