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Date: Fri, 15 Jan 2021 12:09:06 -0500
From: Peter Xu <peterx@...hat.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>,
Mike Kravetz <mike.kravetz@...cle.com>, peterx@...hat.com,
Jerome Glisse <jglisse@...hat.com>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Hugh Dickins <hughd@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Matthew Wilcox <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Nadav Amit <nadav.amit@...il.com>
Subject: [PATCH RFC 29/30] userfaultfd: Enable write protection for shmem & hugetlbfs
We've had all the necessary changes ready for both shmem and hugetlbfs. Turn
on all the shmem/hugetlbfs switches for userfaultfd-wp.
Now we can remove the flags parameter for vma_can_userfault() since not used
any more. Meanwhile, we can expand UFFD_API_RANGE_IOCTLS_BASIC with
_UFFDIO_WRITEPROTECT too because all existing types now support write
protection mode.
Since vma_can_userfault() will be used elsewhere, move into userfaultfd_k.h.
Signed-off-by: Peter Xu <peterx@...hat.com>
---
fs/userfaultfd.c | 17 ++++-------------
include/linux/userfaultfd_k.h | 7 +++++++
include/uapi/linux/userfaultfd.h | 3 ++-
mm/userfaultfd.c | 10 +++-------
4 files changed, 16 insertions(+), 21 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 3264ec46242b..88ad90fc8539 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1307,15 +1307,6 @@ static __always_inline int validate_range(struct mm_struct *mm,
return 0;
}
-static inline bool vma_can_userfault(struct vm_area_struct *vma,
- unsigned long vm_flags)
-{
- /* FIXME: add WP support to hugetlbfs and shmem */
- return vma_is_anonymous(vma) ||
- ((is_vm_hugetlb_page(vma) || vma_is_shmem(vma)) &&
- !(vm_flags & VM_UFFD_WP));
-}
-
static int userfaultfd_register(struct userfaultfd_ctx *ctx,
unsigned long arg)
{
@@ -1394,7 +1385,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
/* check not compatible vmas */
ret = -EINVAL;
- if (!vma_can_userfault(cur, vm_flags))
+ if (!vma_can_userfault(cur))
goto out_unlock;
/*
@@ -1453,7 +1444,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
do {
cond_resched();
- BUG_ON(!vma_can_userfault(vma, vm_flags));
+ BUG_ON(!vma_can_userfault(vma));
BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
vma->vm_userfaultfd_ctx.ctx != ctx);
WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
@@ -1602,7 +1593,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
* provides for more strict behavior to notice
* unregistration errors.
*/
- if (!vma_can_userfault(cur, cur->vm_flags))
+ if (!vma_can_userfault(cur))
goto out_unlock;
found = true;
@@ -1616,7 +1607,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
do {
cond_resched();
- BUG_ON(!vma_can_userfault(vma, vma->vm_flags));
+ BUG_ON(!vma_can_userfault(vma));
/*
* Nothing to do: this vma is already registered into this
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 7d14444862d4..fd7031173949 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -16,6 +16,7 @@
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <asm-generic/pgtable_uffd.h>
+#include <linux/hugetlb_inline.h>
/*
* CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
@@ -88,6 +89,12 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
return vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP);
}
+static inline bool vma_can_userfault(struct vm_area_struct *vma)
+{
+ return vma_is_anonymous(vma) || vma_is_shmem(vma) ||
+ is_vm_hugetlb_page(vma);
+}
+
extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
extern void dup_userfaultfd_complete(struct list_head *);
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index e7e98bde221f..83bcd739de50 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -39,7 +39,8 @@
(__u64)1 << _UFFDIO_WRITEPROTECT)
#define UFFD_API_RANGE_IOCTLS_BASIC \
((__u64)1 << _UFFDIO_WAKE | \
- (__u64)1 << _UFFDIO_COPY)
+ (__u64)1 << _UFFDIO_COPY | \
+ (__u64)1 << _UFFDIO_WRITEPROTECT)
/*
* Valid ioctl command number range with this API is from 0x00 to
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 1dff5b9a2c26..3ad52f01553b 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -445,7 +445,6 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
err = mfill_zeropage_pte(dst_mm, dst_pmd,
dst_vma, dst_addr);
} else {
- VM_WARN_ON_ONCE(wp_copy);
if (!zeropage)
err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
dst_vma, dst_addr,
@@ -671,15 +670,12 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
err = -ENOENT;
dst_vma = find_dst_vma(dst_mm, start, len);
- /*
- * Make sure the vma is not shared, that the dst range is
- * both valid and fully within a single existing vma.
- */
- if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
+
+ if (!dst_vma)
goto out_unlock;
if (!userfaultfd_wp(dst_vma))
goto out_unlock;
- if (!vma_is_anonymous(dst_vma))
+ if (!vma_can_userfault(dst_vma))
goto out_unlock;
if (is_vm_hugetlb_page(dst_vma)) {
--
2.26.2
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