From: Punit Agrawal punit.agrawal@arm.com
commit d63206ee32b6e64b0e12d46e5d6004afd9913713 upstream.
When speculatively taking references to a hugepage using page_cache_add_speculative() in gup_huge_pmd(), it is assumed that the page returned by pmd_page() is the head page. Although normally true, this assumption doesn't hold when the hugepage comprises of successive page table entries such as when using contiguous bit on arm64 at PTE or PMD levels.
This can be addressed by ensuring that the page passed to page_cache_add_speculative() is the real head or by de-referencing the head page within the function.
We take the first approach to keep the usage pattern aligned with page_cache_get_speculative() where users already pass the appropriate page, i.e., the de-referenced head.
Apply the same logic to fix gup_huge_[pud|pgd]() as well.
[punit.agrawal@arm.com: fix arm64 ltp failure] Link: http://lkml.kernel.org/r/20170619170145.25577-5-punit.agrawal@arm.com Link: http://lkml.kernel.org/r/20170522133604.11392-3-punit.agrawal@arm.com Signed-off-by: Punit Agrawal punit.agrawal@arm.com Acked-by: Steve Capper steve.capper@arm.com Cc: Michal Hocko mhocko@suse.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.vnet.ibm.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: Mark Rutland mark.rutland@arm.com Cc: Hillf Danton hillf.zj@alibaba-inc.com Cc: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ajay Kaher akaher@vmware.com Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/gup.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
--- a/mm/gup.c +++ b/mm/gup.c @@ -1130,8 +1130,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_ return 0;
refs = 0; - head = pmd_page(orig); - page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); tail = page; do { pages[*nr] = page; @@ -1140,6 +1139,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_ refs++; } while (addr += PAGE_SIZE, addr != end);
+ head = compound_head(pmd_page(orig)); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1176,8 +1176,7 @@ static int gup_huge_pud(pud_t orig, pud_ return 0;
refs = 0; - head = pud_page(orig); - page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); tail = page; do { pages[*nr] = page; @@ -1186,6 +1185,7 @@ static int gup_huge_pud(pud_t orig, pud_ refs++; } while (addr += PAGE_SIZE, addr != end);
+ head = compound_head(pud_page(orig)); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1218,8 +1218,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_ return 0;
refs = 0; - head = pgd_page(orig); - page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); + page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); tail = page; do { pages[*nr] = page; @@ -1228,6 +1227,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_ refs++; } while (addr += PAGE_SIZE, addr != end);
+ head = compound_head(pgd_page(orig)); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0;