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| author | Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> | 2020-05-05 12:47:10 +0530 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-05-05 21:20:14 +1000 |
| commit | ec4abf1e70cf6a3fe6e571d640260005c997c6e1 (patch) | |
| tree | 462eec65473b6412610769f1c37e4efbf0f21b7d /arch/powerpc/mm/book3s64 | |
| parent | c46241a370a61f0f264791abb9fc869016e749ce (diff) | |
| download | linux-ec4abf1e70cf6a3fe6e571d640260005c997c6e1.tar.bz2 | |
powerpc/mm/hash64: use _PAGE_PTE when checking for pte_present
This makes the pte_present check stricter by checking for additional _PAGE_PTE
bit. A level 1 pte pointer (THP pte) can be switched to a pointer to level 0 pte
page table page by following two operations.
1) THP split.
2) madvise(MADV_DONTNEED) in parallel to page fault.
A lockless page table walk need to make sure we can handle such changes
gracefully.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200505071729.54912-4-aneesh.kumar@linux.ibm.com
Diffstat (limited to 'arch/powerpc/mm/book3s64')
| -rw-r--r-- | arch/powerpc/mm/book3s64/hash_utils.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index e951e87a974d..525eac4ee2c2 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -1350,8 +1350,15 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea, goto bail; } - /* Add _PAGE_PRESENT to the required access perm */ - access |= _PAGE_PRESENT; + /* + * Add _PAGE_PRESENT to the required access perm. If there are parallel + * updates to the pte that can possibly clear _PAGE_PTE, catch that too. + * + * We can safely use the return pte address in rest of the function + * because we do set H_PAGE_BUSY which prevents further updates to pte + * from generic code. + */ + access |= _PAGE_PRESENT | _PAGE_PTE; /* * Pre-check access permissions (will be re-checked atomically |