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x86, mm: do not leak page->ptl for pmd page tables

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There are two code paths how page with pmd page table can be freed:
pmd_free() and pmd_free_tlb().

I've missed the second one and didn't add page table destructor call
there.  It leads to leak of page->ptl for pmd page tables, if
dynamically allocated page->ptl is in use.

The patch adds the missed destructor and modifies documentation
accordingly.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Andrey Vagin <avagin@openvz.org>
Tested-by: Andrey Vagin <avagin@openvz.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov
2013-11-21 14:32:09 -08:00
committed by Linus Torvalds
parent 3a72660b07
commit c283610e44
2 changed files with 6 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/vm/split_page_table_lock
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@@ -63,9 +63,9 @@ levels.
PMD split lock enabling requires pgtable_pmd_page_ctor() call on PMD table
allocation and pgtable_pmd_page_dtor() on freeing.
Allocation usually happens in pmd_alloc_one(), freeing in pmd_free(), but
make sure you cover all PMD table allocation / freeing paths: i.e X86_PAE
preallocate few PMDs on pgd_alloc().
Allocation usually happens in pmd_alloc_one(), freeing in pmd_free() and
pmd_free_tlb(), but make sure you cover all PMD table allocation / freeing
paths: i.e X86_PAE preallocate few PMDs on pgd_alloc().
With everything in place you can set CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK.