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| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2018-03-22 16:17:28 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-03-22 17:07:01 -0700 |
| commit | fece2029a9e65b9a990831afe2a2b83290cbbe26 (patch) | |
| tree | 8c7e6a04d9cc018a4b71c5e068aa8d48b44fbb38 /mm/khugepaged.c | |
| parent | 28ee90fe6048fa7b7ceaeb8831c0e4e454a4cf89 (diff) | |
| download | lwn-fece2029a9e65b9a990831afe2a2b83290cbbe26.tar.gz lwn-fece2029a9e65b9a990831afe2a2b83290cbbe26.zip | |
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>
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 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); /* |