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authorAndrea Arcangeli <aarcange@redhat.com>2017-02-23 02:43:13 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-23 03:41:28 +0300
commit87ffc118b54dcd4cc642723603d944673248152f (patch)
treeef5ff9a70c12b331985148ebab7629a73984c841 /mm
parent369cd2121be440543280b91056de187f625d0dbb (diff)
downloadlinux-87ffc118b54dcd4cc642723603d944673248152f.tar.xz
userfaultfd: hugetlbfs: gup: support VM_FAULT_RETRY
Add support for VM_FAULT_RETRY to follow_hugetlb_page() so that get_user_pages_unlocked/locked and "nonblocking/FOLL_NOWAIT" features will work on hugetlbfs. This is required for fully functional userfaultfd non-present support on hugetlbfs. Link: http://lkml.kernel.org/r/20161216144821.5183-25-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Michael Rapoport <RAPOPORT@il.ibm.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/gup.c2
-rw-r--r--mm/hugetlb.c48
2 files changed, 41 insertions, 9 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 55315555489d..40abe4c90383 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -572,7 +572,7 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
if (is_vm_hugetlb_page(vma)) {
i = follow_hugetlb_page(mm, vma, pages, vmas,
&start, &nr_pages, i,
- gup_flags);
+ gup_flags, nonblocking);
continue;
}
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a4b29054cc3f..f6c7ff316daf 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4065,7 +4065,7 @@ out_release_unlock:
long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page **pages, struct vm_area_struct **vmas,
unsigned long *position, unsigned long *nr_pages,
- long i, unsigned int flags)
+ long i, unsigned int flags, int *nonblocking)
{
unsigned long pfn_offset;
unsigned long vaddr = *position;
@@ -4128,16 +4128,43 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
((flags & FOLL_WRITE) &&
!huge_pte_write(huge_ptep_get(pte)))) {
int ret;
+ unsigned int fault_flags = 0;
if (pte)
spin_unlock(ptl);
- ret = hugetlb_fault(mm, vma, vaddr,
- (flags & FOLL_WRITE) ? FAULT_FLAG_WRITE : 0);
- if (!(ret & VM_FAULT_ERROR))
- continue;
-
- remainder = 0;
- break;
+ if (flags & FOLL_WRITE)
+ fault_flags |= FAULT_FLAG_WRITE;
+ if (nonblocking)
+ fault_flags |= FAULT_FLAG_ALLOW_RETRY;
+ if (flags & FOLL_NOWAIT)
+ fault_flags |= FAULT_FLAG_ALLOW_RETRY |
+ FAULT_FLAG_RETRY_NOWAIT;
+ if (flags & FOLL_TRIED) {
+ VM_WARN_ON_ONCE(fault_flags &
+ FAULT_FLAG_ALLOW_RETRY);
+ fault_flags |= FAULT_FLAG_TRIED;
+ }
+ ret = hugetlb_fault(mm, vma, vaddr, fault_flags);
+ if (ret & VM_FAULT_ERROR) {
+ remainder = 0;
+ break;
+ }
+ if (ret & VM_FAULT_RETRY) {
+ if (nonblocking)
+ *nonblocking = 0;
+ *nr_pages = 0;
+ /*
+ * VM_FAULT_RETRY must not return an
+ * error, it will return zero
+ * instead.
+ *
+ * No need to update "position" as the
+ * caller will not check it after
+ * *nr_pages is set to 0.
+ */
+ return i;
+ }
+ continue;
}
pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT;
@@ -4166,6 +4193,11 @@ same_page:
spin_unlock(ptl);
}
*nr_pages = remainder;
+ /*
+ * setting position is actually required only if remainder is
+ * not zero but it's faster not to add a "if (remainder)"
+ * branch.
+ */
*position = vaddr;
return i ? i : -EFAULT;