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| author | Gerald Schaefer <gerald.schaefer@de.ibm.com> | 2016-03-17 15:00:04 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-03-17 16:42:14 +0100 |
| commit | fc897c95e91451271cd707ee0f71022b9b201ce9 (patch) | |
| tree | b0a44cffdfb8193ba708719e9d7a9bb033f64e61 /arch/s390 | |
| parent | 91d37211769510ae0b4747045d8f81d3b9dd4278 (diff) | |
s390/mm: handle PTE-mapped tail pages in fast gup
With the THP refcounting rework it is possible to see THP compound tail
pages mapped with PTEs during a THP split. This needs to be considered
when using page_cache_get_speculative(), which will always fail on tail
pages because ->_count is always zero. commit 7aef4172 "mm: handle
PTE-mapped tail pages in gerneric fast gup implementaiton" fixed it for
the generic fast gup code by using compound_head(page) instead of page,
but not for s390.
This patch is a 1:1 adaption of commit 7aef4172 for the s390 fast gup
code. Without this fix, gup will fall back to the slow path or fail
in the unlikely scenario that we hit a THP under splitting in-between
the page table split and the compound page split.
Cc: stable@vger.kernel.org # v4.5
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390')
| -rw-r--r-- | arch/s390/mm/gup.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c index 13dab0c1645c..3776aca22082 100644 --- a/arch/s390/mm/gup.c +++ b/arch/s390/mm/gup.c @@ -20,9 +20,9 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) { + struct page *head, *page; unsigned long mask; pte_t *ptep, pte; - struct page *page; mask = (write ? _PAGE_PROTECT : 0) | _PAGE_INVALID | _PAGE_SPECIAL; @@ -37,12 +37,14 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, return 0; VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); - if (!page_cache_get_speculative(page)) + head = compound_head(page); + if (!page_cache_get_speculative(head)) return 0; if (unlikely(pte_val(pte) != pte_val(*ptep))) { - put_page(page); + put_page(head); return 0; } + VM_BUG_ON_PAGE(compound_head(page) != head, page); pages[*nr] = page; (*nr)++; |