45 lines
1.5 KiB
Diff
45 lines
1.5 KiB
Diff
From 6abb0cfdc1f6a42367a20ac2baf4099fc8af08b5 Mon Sep 17 00:00:00 2001
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
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Date: Wed, 10 Aug 2016 09:54:30 -0700
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Subject: [PATCH] mm, rmap: fix false positive VM_BUG() in page_add_file_rmap()
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PageTransCompound() doesn't distinguish THP from from any other type of
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compound pages. This can lead to false-positive VM_BUG_ON() in
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page_add_file_rmap() if called on compound page from a driver[1].
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I think we can exclude such cases by checking if the page belong to a
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mapping.
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The VM_BUG_ON_PAGE() is downgraded to VM_WARN_ON_ONCE(). This path
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should not cause any harm to non-THP page, but good to know if we step
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on anything else.
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[1]
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http://lkml.kernel.org/r/c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com
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Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
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Reported-by: Laura Abbott <labbott@redhat.com>
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---
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mm/rmap.c | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/mm/rmap.c b/mm/rmap.c
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index 709bc83..d4f5606 100644
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--- a/mm/rmap.c
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+++ b/mm/rmap.c
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@@ -1284,8 +1284,9 @@ void page_add_file_rmap(struct page *page, bool compound)
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VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
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__inc_node_page_state(page, NR_SHMEM_PMDMAPPED);
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} else {
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- if (PageTransCompound(page)) {
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- VM_BUG_ON_PAGE(!PageLocked(page), page);
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+ if (PageTransCompound(page) && page_mapping(page)) {
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+ VM_WARN_ON_ONCE(!PageLocked(page));
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+
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SetPageDoubleMap(compound_head(page));
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if (PageMlocked(page))
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clear_page_mlock(compound_head(page));
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--
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2.7.4
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