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author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2018-03-23 02:17:28 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-03-28 19:24:38 +0300 |
commit | 8b8b5c4f7f3af41e9e79fd04b49a0dcfb5020d5e (patch) | |
tree | 4e610f1eb2bfada0784e7791c625f30b04e38aa1 /mm/khugepaged.c | |
parent | 5bbd932ff58f518ab2de7893940ca98f4f6c43e8 (diff) | |
download | linux-8b8b5c4f7f3af41e9e79fd04b49a0dcfb5020d5e.tar.xz |
mm/khugepaged.c: convert VM_BUG_ON() to collapse fail
commit fece2029a9e65b9a990831afe2a2b83290cbbe26 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm/khugepaged.c')
-rw-r--r-- | mm/khugepaged.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 43cb3043311b..2fe26634e1a2 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); /* |