From: Ira Weiny ira.weiny@intel.com
DAX pages were previously unprotected from longterm pins when users called get_user_pages_fast().
Use the new FOLL_LONGTERM flag to check for DEVMAP pages and fall back to regular GUP processing if a DEVMAP page is encountered.
Signed-off-by: Ira Weiny ira.weiny@intel.com --- mm/gup.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 6f32d36b3c5b..f7e759c523bb 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1439,6 +1439,9 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, goto pte_unmap;
if (pte_devmap(pte)) { + if (unlikely(flags & FOLL_LONGTERM)) + goto pte_unmap; + pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); if (unlikely(!pgmap)) { undo_dev_pagemap(nr, nr_start, pages); @@ -1578,8 +1581,11 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, if (!pmd_access_permitted(orig, flags & FOLL_WRITE)) return 0;
- if (pmd_devmap(orig)) + if (pmd_devmap(orig)) { + if (unlikely(flags & FOLL_LONGTERM)) + return 0; return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr); + }
refs = 0; page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); @@ -1904,8 +1910,20 @@ int get_user_pages_fast(unsigned long start, int nr_pages, start += nr << PAGE_SHIFT; pages += nr;
- ret = get_user_pages_unlocked(start, nr_pages - nr, pages, - gup_flags); + if (gup_flags & FOLL_LONGTERM) { + down_read(¤t->mm->mmap_sem); + ret = __gup_longterm_locked(current, current->mm, + start, nr_pages - nr, + pages, NULL, gup_flags); + up_read(¤t->mm->mmap_sem); + } else { + /* + * retain FAULT_FOLL_ALLOW_RETRY optimization if + * possible + */ + ret = get_user_pages_unlocked(start, nr_pages - nr, + pages, gup_flags); + }
/* Have to be a bit careful with return values */ if (nr > 0) {