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userfaultfd: hugetlbfs: gup: support VM_FAULT_RETRY

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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>
This commit is contained in:
Andrea Arcangeli 2017-02-22 15:43:13 -08:00 committed by Linus Torvalds
parent 369cd2121b
commit 87ffc118b5
3 changed files with 44 additions and 11 deletions
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5
include/linux/hugetlb.h
View File

@ -65,7 +65,8 @@ int hugetlb_mempolicy_sysctl_handler(struct ctl_table *, int,
int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *);
long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
struct page **, struct vm_area_struct **,
unsigned long *, unsigned long *, long, unsigned int);
unsigned long *, unsigned long *, long, unsigned int,
int *);
void unmap_hugepage_range(struct vm_area_struct *,
unsigned long, unsigned long, struct page *);
void __unmap_hugepage_range_final(struct mmu_gather *tlb,
@ -136,7 +137,7 @@ static inline unsigned long hugetlb_total_pages(void)
return 0;
}
#define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; })
#define follow_hugetlb_page(m,v,p,vs,a,b,i,w,n) ({ BUG(); 0; })
#define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL)
#define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; })
static inline void hugetlb_report_meminfo(struct seq_file *m)

2
mm/gup.c
View File

@ -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;
}
}

48
mm/hugetlb.c
View File

@ -4065,7 +4065,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
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 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
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;