From: Ross Zwisler ross.zwisler@linux.intel.com
commit 097963959594c5eccaba42510f7033f703211bda upstream.
Patch series "Write protect DAX PMDs in *sync path".
Currently dax_mapping_entry_mkclean() fails to clean and write protect the pmd_t of a DAX PMD entry during an *sync operation. This can result in data loss, as detailed in patch 2.
This series is based on Dan's "libnvdimm-pending" branch, which is the current home for Jan's "dax: Page invalidation fixes" series. You can find a working tree here:
https://git.kernel.org/cgit/linux/kernel/git/zwisler/linux.git/log/?h=dax_pm...
This patch (of 2):
Similar to follow_pte(), follow_pte_pmd() allows either a PTE leaf or a huge page PMD leaf to be found and returned.
Link: http://lkml.kernel.org/r/1482272586-21177-2-git-send-email-ross.zwisler@linu... Signed-off-by: Ross Zwisler ross.zwisler@linux.intel.com Suggested-by: Dave Hansen dave.hansen@intel.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Christoph Hellwig hch@lst.de Cc: Dan Williams dan.j.williams@intel.com Cc: Dave Chinner david@fromorbit.com Cc: Jan Kara jack@suse.cz Cc: Matthew Wilcox mawilcox@microsoft.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [bwh: Backported to 4.9: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/mm.h | 2 ++ mm/memory.c | 37 ++++++++++++++++++++++++++++++------- 2 files changed, 32 insertions(+), 7 deletions(-)
--- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1269,6 +1269,8 @@ int copy_page_range(struct mm_struct *ds struct vm_area_struct *vma); void unmap_mapping_range(struct address_space *mapping, loff_t const holebegin, loff_t const holelen, int even_cows); +int follow_pte_pmd(struct mm_struct *mm, unsigned long address, + pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp); int follow_pfn(struct vm_area_struct *vma, unsigned long address, unsigned long *pfn); int follow_phys(struct vm_area_struct *vma, unsigned long address, --- a/mm/memory.c +++ b/mm/memory.c @@ -3780,8 +3780,8 @@ int __pmd_alloc(struct mm_struct *mm, pu } #endif /* __PAGETABLE_PMD_FOLDED */
-static int __follow_pte(struct mm_struct *mm, unsigned long address, - pte_t **ptepp, spinlock_t **ptlp) +static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address, + pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp) { pgd_t *pgd; pud_t *pud; @@ -3798,11 +3798,20 @@ static int __follow_pte(struct mm_struct
pmd = pmd_offset(pud, address); VM_BUG_ON(pmd_trans_huge(*pmd)); - if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd))) - goto out;
- /* We cannot handle huge page PFN maps. Luckily they don't exist. */ - if (pmd_huge(*pmd)) + if (pmd_huge(*pmd)) { + if (!pmdpp) + goto out; + + *ptlp = pmd_lock(mm, pmd); + if (pmd_huge(*pmd)) { + *pmdpp = pmd; + return 0; + } + spin_unlock(*ptlp); + } + + if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd))) goto out;
ptep = pte_offset_map_lock(mm, pmd, address, ptlp); @@ -3825,9 +3834,23 @@ static inline int follow_pte(struct mm_s
/* (void) is needed to make gcc happy */ (void) __cond_lock(*ptlp, - !(res = __follow_pte(mm, address, ptepp, ptlp))); + !(res = __follow_pte_pmd(mm, address, ptepp, NULL, + ptlp))); + return res; +} + +int follow_pte_pmd(struct mm_struct *mm, unsigned long address, + pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp) +{ + int res; + + /* (void) is needed to make gcc happy */ + (void) __cond_lock(*ptlp, + !(res = __follow_pte_pmd(mm, address, ptepp, pmdpp, + ptlp))); return res; } +EXPORT_SYMBOL(follow_pte_pmd);
/** * follow_pfn - look up PFN at a user virtual address