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mm: do not lose dirty and accessed bits in pmdp_invalidate()

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Vlastimil noted that pmdp_invalidate() is not atomic and we can lose
dirty and access bits if CPU sets them after pmdp dereference, but
before set_pmd_at().

The patch change pmdp_invalidate() to make the entry non-present
atomically and return previous value of the entry.  This value can be
used to check if CPU set dirty/accessed bits under us.

The race window is very small and I haven't seen any reports that can be
attributed to the bug.  For this reason, I don't think backporting to
stable trees needed.

Link: http://lkml.kernel.org/r/20171213105756.69879-11-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Daney <david.daney@cavium.com>
Cc: David Miller <davem@davemloft.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nitin Gupta <nitin.m.gupta@oracle.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
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 2018-01-31 16:18:16 -08:00 committed by Linus Torvalds
parent 86fa949b05
commit d52605d7cb
2 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/asm-generic/pgtable.h
View File

@ -325,7 +325,7 @@ static inline pmd_t generic_pmdp_establish(struct vm_area_struct *vma,
#endif #endif
#ifndef __HAVE_ARCH_PMDP_INVALIDATE #ifndef __HAVE_ARCH_PMDP_INVALIDATE
extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, extern pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp); pmd_t *pmdp);
#endif #endif

6
mm/pgtable-generic.c
View File

@ -181,12 +181,12 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
#endif #endif
#ifndef __HAVE_ARCH_PMDP_INVALIDATE #ifndef __HAVE_ARCH_PMDP_INVALIDATE
void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp) pmd_t *pmdp)
{ {
pmd_t entry = *pmdp; pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mknotpresent(*pmdp));
set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(entry));
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
return old;
} }
#endif #endif