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userfaultfd: shmem: allow registration of shared memory ranges 

Expand the userfaultfd_register/unregister routines to allow shared
memory VMAs.

Currently, there is no UFFDIO_ZEROPAGE and write-protection support for
shared memory VMAs, which is reflected in ioctl methods supported by
uffdio_register.

Link: http://lkml.kernel.org/r/20161216144821.5183-34-aarcange@redhat.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.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 Kravetz <mike.kravetz@oracle.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:
Mike Rapoport 2017-02-22 15:43:40 -08:00 committed by Linus Torvalds
parent cfda05267f
commit cac673292b
3 changed files with 9 additions and 16 deletions
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21
fs/userfaultfd.c
View File

@ -1098,7 +1098,8 @@ static __always_inline int validate_range(struct mm_struct *mm,
static inline bool vma_can_userfault(struct vm_area_struct *vma)
{
return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma);
return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
vma_is_shmem(vma);
}
static int userfaultfd_register(struct userfaultfd_ctx *ctx,
@ -1111,7 +1112,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
struct uffdio_register __user *user_uffdio_register;
unsigned long vm_flags, new_flags;
bool found;
bool huge_pages;
bool non_anon_pages;
unsigned long start, end, vma_end;
user_uffdio_register = (struct uffdio_register __user *) arg;
@ -1175,13 +1176,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
/*
* Search for not compatible vmas.
*
* FIXME: this shall be relaxed later so that it doesn't fail
* on tmpfs backed vmas (in addition to the current allowance
* on anonymous vmas).
*/
found = false;
huge_pages = false;
non_anon_pages = false;
for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
cond_resched();
@ -1220,8 +1217,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
/*
* Note vmas containing huge pages
*/
if (is_vm_hugetlb_page(cur))
huge_pages = true;
if (is_vm_hugetlb_page(cur) || vma_is_shmem(cur))
non_anon_pages = true;
found = true;
}
@ -1292,7 +1289,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
* userland which ioctls methods are guaranteed to
* succeed on this range.
*/
if (put_user(huge_pages ? UFFD_API_RANGE_IOCTLS_HPAGE :
if (put_user(non_anon_pages ? UFFD_API_RANGE_IOCTLS_BASIC :
UFFD_API_RANGE_IOCTLS,
&user_uffdio_register->ioctls))
ret = -EFAULT;
@ -1352,10 +1349,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
/*
* Search for not compatible vmas.
*
* FIXME: this shall be relaxed later so that it doesn't fail
* on tmpfs backed vmas (in addition to the current allowance
* on anonymous vmas).
*/
found = false;
ret = -EINVAL;

2
include/uapi/linux/userfaultfd.h
View File

@ -30,7 +30,7 @@
((__u64)1 << _UFFDIO_WAKE | \
(__u64)1 << _UFFDIO_COPY | \
(__u64)1 << _UFFDIO_ZEROPAGE)
#define UFFD_API_RANGE_IOCTLS_HPAGE \
#define UFFD_API_RANGE_IOCTLS_BASIC \
((__u64)1 << _UFFDIO_WAKE | \
(__u64)1 << _UFFDIO_COPY)

2
tools/testing/selftests/vm/userfaultfd.c
View File

@ -129,7 +129,7 @@ static void allocate_area(void **alloc_area)
#else /* HUGETLB_TEST */
#define EXPECTED_IOCTLS UFFD_API_RANGE_IOCTLS_HPAGE
#define EXPECTED_IOCTLS UFFD_API_RANGE_IOCTLS_BASIC
static int release_pages(char *rel_area)
{