The patch titled
Subject: mm: userfaultfd: combine 'mode' and 'wp_copy' arguments
has been added to the -mm mm-unstable branch. Its filename is
mm-userfaultfd-combine-mode-and-wp_copy-arguments.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-userfaultfd-combine-mode-and-wp_copy-arguments.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Subject: mm: userfaultfd: combine 'mode' and 'wp_copy' arguments
Date: Tue, 14 Mar 2023 15:12:49 -0700
Many userfaultfd ioctl functions take both a 'mode' and a 'wp_copy'
argument. In future commits we plan to plumb the flags through to more
places, so we'd be proliferating the very long argument list even further.
Let's take the time to simplify the argument list. Combine the two
arguments into one - and generalize, so when we add more flags in the
future, it doesn't imply more function arguments.
Since the modes (copy, zeropage, continue) are mutually exclusive, store
them as an integer value (0, 1, 2) in the low bits. Place combine-able
flag bits in the high bits.
This is quite similar to an earlier patch proposed by Nadav Amit
("userfaultfd: introduce uffd_flags" [1]). The main difference is that
patch only handled flags, whereas this patch *also* combines the "mode"
argument into the same type to shorten the argument list.
[1]: https://lore.kernel.org/all/20220619233449.181323-2-namit@xxxxxxxxxx/
Link: https://lkml.kernel.org/r/20230314221250.682452-4-axelrasmussen@xxxxxxxxxx
Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Acked-by: James Houghton <jthoughton@xxxxxxxxxx>
Acked-by: Peter Xu <peterx@xxxxxxxxxx>
Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/userfaultfd.c | 5 +-
include/linux/hugetlb.h | 10 +---
include/linux/shmem_fs.h | 5 +-
include/linux/userfaultfd_k.h | 46 ++++++++++++-------
mm/hugetlb.c | 12 ++---
mm/shmem.c | 7 +-
mm/userfaultfd.c | 76 ++++++++++++++------------------
7 files changed, 84 insertions(+), 77 deletions(-)
--- a/fs/userfaultfd.c~mm-userfaultfd-combine-mode-and-wp_copy-arguments
+++ a/fs/userfaultfd.c
@@ -1729,6 +1729,7 @@ static int userfaultfd_copy(struct userf
struct uffdio_copy uffdio_copy;
struct uffdio_copy __user *user_uffdio_copy;
struct userfaultfd_wake_range range;
+ uffd_flags_t flags = 0;
user_uffdio_copy = (struct uffdio_copy __user *) arg;
@@ -1755,10 +1756,12 @@ static int userfaultfd_copy(struct userf
goto out;
if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP))
goto out;
+ if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP)
+ flags |= MFILL_ATOMIC_WP;
if (mmget_not_zero(ctx->mm)) {
ret = mfill_atomic_copy(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
uffdio_copy.len, &ctx->mmap_changing,
- uffdio_copy.mode);
+ flags);
mmput(ctx->mm);
} else {
return -ESRCH;
--- a/include/linux/hugetlb.h~mm-userfaultfd-combine-mode-and-wp_copy-arguments
+++ a/include/linux/hugetlb.h
@@ -162,9 +162,8 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- enum mcopy_atomic_mode mode,
- struct page **pagep,
- bool wp_copy);
+ uffd_flags_t flags,
+ struct page **pagep);
#endif /* CONFIG_USERFAULTFD */
bool hugetlb_reserve_pages(struct inode *inode, long from, long to,
struct vm_area_struct *vma,
@@ -397,9 +396,8 @@ static inline int hugetlb_mfill_atomic_p
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- enum mcopy_atomic_mode mode,
- struct page **pagep,
- bool wp_copy)
+ uffd_flags_t flags,
+ struct page **pagep)
{
BUG();
return 0;
--- a/include/linux/shmem_fs.h~mm-userfaultfd-combine-mode-and-wp_copy-arguments
+++ a/include/linux/shmem_fs.h
@@ -9,6 +9,7 @@
#include <linux/percpu_counter.h>
#include <linux/xattr.h>
#include <linux/fs_parser.h>
+#include <linux/userfaultfd_k.h>
/* inode in-kernel data */
@@ -157,11 +158,11 @@ extern int shmem_mfill_atomic_pte(pmd_t
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- bool zeropage, bool wp_copy,
+ uffd_flags_t flags,
struct page **pagep);
#else /* !CONFIG_SHMEM */
#define shmem_mfill_atomic_pte(dst_pmd, dst_vma, dst_addr, \
- src_addr, zeropage, wp_copy, pagep) ({ BUG(); 0; })
+ src_addr, flags, pagep) ({ BUG(); 0; })
#endif /* CONFIG_SHMEM */
#endif /* CONFIG_USERFAULTFD */
--- a/include/linux/userfaultfd_k.h~mm-userfaultfd-combine-mode-and-wp_copy-arguments
+++ a/include/linux/userfaultfd_k.h
@@ -40,30 +40,44 @@ extern int sysctl_unprivileged_userfault
extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
-/*
- * The mode of operation for __mcopy_atomic and its helpers.
- *
- * This is almost an implementation detail (mcopy_atomic below doesn't take this
- * as a parameter), but it's exposed here because memory-kind-specific
- * implementations (e.g. hugetlbfs) need to know the mode of operation.
- */
-enum mcopy_atomic_mode {
- /* A normal copy_from_user into the destination range. */
- MCOPY_ATOMIC_NORMAL,
- /* Don't copy; map the destination range to the zero page. */
- MCOPY_ATOMIC_ZEROPAGE,
- /* Just install pte(s) with the existing page(s) in the page cache. */
- MCOPY_ATOMIC_CONTINUE,
+/* A combined operation mode + behavior flags. */
+typedef unsigned int __bitwise uffd_flags_t;
+
+/* Mutually exclusive modes of operation. */
+enum mfill_atomic_mode {
+ MFILL_ATOMIC_COPY,
+ MFILL_ATOMIC_ZEROPAGE,
+ MFILL_ATOMIC_CONTINUE,
+ NR_MFILL_ATOMIC_MODES,
};
+#define MFILL_ATOMIC_MODE_BITS (const_ilog2(NR_MFILL_ATOMIC_MODES - 1) + 1)
+#define MFILL_ATOMIC_BIT(nr) BIT(MFILL_ATOMIC_MODE_BITS + (nr))
+#define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr))
+#define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1))
+
+static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
+{
+ return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected);
+}
+
+static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode)
+{
+ flags &= ~MFILL_ATOMIC_MODE_MASK;
+ return flags | ((__force uffd_flags_t) mode);
+}
+
+/* Flags controlling behavior. These behavior changes are mode-independent. */
+#define MFILL_ATOMIC_WP MFILL_ATOMIC_FLAG(0)
+
extern int mfill_atomic_install_pte(pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr, struct page *page,
- bool newly_allocated, bool wp_copy);
+ bool newly_allocated, uffd_flags_t flags);
extern ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start,
unsigned long src_start, unsigned long len,
- atomic_t *mmap_changing, __u64 mode);
+ atomic_t *mmap_changing, uffd_flags_t flags);
extern ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm,
unsigned long dst_start,
unsigned long len,
--- a/mm/hugetlb.c~mm-userfaultfd-combine-mode-and-wp_copy-arguments
+++ a/mm/hugetlb.c
@@ -6163,12 +6163,12 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- enum mcopy_atomic_mode mode,
- struct page **pagep,
- bool wp_copy)
+ uffd_flags_t flags,
+ struct page **pagep)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
- bool is_continue = (mode == MCOPY_ATOMIC_CONTINUE);
+ bool is_continue = uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE);
+ bool wp_enabled = (flags & MFILL_ATOMIC_WP);
struct hstate *h = hstate_vma(dst_vma);
struct address_space *mapping = dst_vma->vm_file->f_mapping;
pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
@@ -6303,7 +6303,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_
* For either: (1) CONTINUE on a non-shared VMA, or (2) UFFDIO_COPY
* with wp flag set, don't set pte write bit.
*/
- if (wp_copy || (is_continue && !vm_shared))
+ if (wp_enabled || (is_continue && !vm_shared))
writable = 0;
else
writable = dst_vma->vm_flags & VM_WRITE;
@@ -6318,7 +6318,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_
_dst_pte = huge_pte_mkdirty(_dst_pte);
_dst_pte = pte_mkyoung(_dst_pte);
- if (wp_copy)
+ if (wp_enabled)
_dst_pte = huge_pte_mkuffd_wp(_dst_pte);
set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
--- a/mm/shmem.c~mm-userfaultfd-combine-mode-and-wp_copy-arguments
+++ a/mm/shmem.c
@@ -79,7 +79,6 @@ static struct vfsmount *shm_mnt;
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <uapi/linux/memfd.h>
-#include <linux/userfaultfd_k.h>
#include <linux/rmap.h>
#include <linux/uuid.h>
@@ -2523,7 +2522,7 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pm
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- bool zeropage, bool wp_copy,
+ uffd_flags_t flags,
struct page **pagep)
{
struct inode *inode = file_inode(dst_vma->vm_file);
@@ -2555,7 +2554,7 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pm
if (!folio)
goto out_unacct_blocks;
- if (!zeropage) { /* COPY */
+ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) {
page_kaddr = kmap_local_folio(folio, 0);
/*
* The read mmap_lock is held here. Despite the
@@ -2614,7 +2613,7 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pm
goto out_release;
ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
- &folio->page, true, wp_copy);
+ &folio->page, true, flags);
if (ret)
goto out_delete_from_cache;
--- a/mm/userfaultfd.c~mm-userfaultfd-combine-mode-and-wp_copy-arguments
+++ a/mm/userfaultfd.c
@@ -58,7 +58,7 @@ struct vm_area_struct *find_dst_vma(stru
int mfill_atomic_install_pte(pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr, struct page *page,
- bool newly_allocated, bool wp_copy)
+ bool newly_allocated, uffd_flags_t flags)
{
int ret;
struct mm_struct *dst_mm = dst_vma->vm_mm;
@@ -77,7 +77,7 @@ int mfill_atomic_install_pte(pmd_t *dst_
writable = false;
if (writable)
_dst_pte = pte_mkwrite(_dst_pte);
- if (wp_copy)
+ if (flags & MFILL_ATOMIC_WP)
_dst_pte = pte_mkuffd_wp(_dst_pte);
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
@@ -132,8 +132,8 @@ static int mfill_atomic_pte_copy(pmd_t *
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- struct page **pagep,
- bool wp_copy)
+ uffd_flags_t flags,
+ struct page **pagep)
{
void *page_kaddr;
int ret;
@@ -194,7 +194,7 @@ static int mfill_atomic_pte_copy(pmd_t *
goto out_release;
ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
- page, true, wp_copy);
+ page, true, flags);
if (ret)
goto out_release;
out:
@@ -242,7 +242,7 @@ out_unlock:
static int mfill_atomic_pte_continue(pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
- bool wp_copy)
+ uffd_flags_t flags)
{
struct inode *inode = file_inode(dst_vma->vm_file);
pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
@@ -268,7 +268,7 @@ static int mfill_atomic_pte_continue(pmd
}
ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
- page, false, wp_copy);
+ page, false, flags);
if (ret)
goto out_release;
@@ -313,8 +313,7 @@ static __always_inline ssize_t mfill_ato
unsigned long dst_start,
unsigned long src_start,
unsigned long len,
- enum mcopy_atomic_mode mode,
- bool wp_copy)
+ uffd_flags_t flags)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
int vm_shared = dst_vma->vm_flags & VM_SHARED;
@@ -334,7 +333,7 @@ static __always_inline ssize_t mfill_ato
* by THP. Since we can not reliably insert a zero page, this
* feature is not supported.
*/
- if (mode == MCOPY_ATOMIC_ZEROPAGE) {
+ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
mmap_read_unlock(dst_mm);
return -EINVAL;
}
@@ -402,7 +401,7 @@ retry:
goto out_unlock;
}
- if (mode != MCOPY_ATOMIC_CONTINUE &&
+ if (!uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE) &&
!huge_pte_none_mostly(huge_ptep_get(dst_pte))) {
err = -EEXIST;
hugetlb_vma_unlock_read(dst_vma);
@@ -410,9 +409,8 @@ retry:
goto out_unlock;
}
- err = hugetlb_mfill_atomic_pte(dst_pte, dst_vma,
- dst_addr, src_addr, mode, &page,
- wp_copy);
+ err = hugetlb_mfill_atomic_pte(dst_pte, dst_vma, dst_addr,
+ src_addr, flags, &page);
hugetlb_vma_unlock_read(dst_vma);
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
@@ -466,23 +464,21 @@ extern ssize_t mfill_atomic_hugetlb(stru
unsigned long dst_start,
unsigned long src_start,
unsigned long len,
- enum mcopy_atomic_mode mode,
- bool wp_copy);
+ uffd_flags_t flags);
#endif /* CONFIG_HUGETLB_PAGE */
static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
- struct page **page,
- enum mcopy_atomic_mode mode,
- bool wp_copy)
+ uffd_flags_t flags,
+ struct page **pagep)
{
ssize_t err;
- if (mode == MCOPY_ATOMIC_CONTINUE) {
+ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) {
return mfill_atomic_pte_continue(dst_pmd, dst_vma,
- dst_addr, wp_copy);
+ dst_addr, flags);
}
/*
@@ -496,18 +492,17 @@ static __always_inline ssize_t mfill_ato
* and not in the radix tree.
*/
if (!(dst_vma->vm_flags & VM_SHARED)) {
- if (mode == MCOPY_ATOMIC_NORMAL)
+ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY))
err = mfill_atomic_pte_copy(dst_pmd, dst_vma,
- dst_addr, src_addr, page,
- wp_copy);
+ dst_addr, src_addr,
+ flags, pagep);
else
err = mfill_atomic_pte_zeropage(dst_pmd,
dst_vma, dst_addr);
} else {
err = shmem_mfill_atomic_pte(dst_pmd, dst_vma,
dst_addr, src_addr,
- mode != MCOPY_ATOMIC_NORMAL,
- wp_copy, page);
+ flags, pagep);
}
return err;
@@ -517,9 +512,8 @@ static __always_inline ssize_t mfill_ato
unsigned long dst_start,
unsigned long src_start,
unsigned long len,
- enum mcopy_atomic_mode mcopy_mode,
atomic_t *mmap_changing,
- __u64 mode)
+ uffd_flags_t flags)
{
struct vm_area_struct *dst_vma;
ssize_t err;
@@ -527,7 +521,6 @@ static __always_inline ssize_t mfill_ato
unsigned long src_addr, dst_addr;
long copied;
struct page *page;
- bool wp_copy;
/*
* Sanitize the command parameters:
@@ -577,8 +570,7 @@ retry:
* validate 'mode' now that we know the dst_vma: don't allow
* a wrprotect copy if the userfaultfd didn't register as WP.
*/
- wp_copy = mode & UFFDIO_COPY_MODE_WP;
- if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP))
+ if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP))
goto out_unlock;
/*
@@ -586,12 +578,12 @@ retry:
*/
if (is_vm_hugetlb_page(dst_vma))
return mfill_atomic_hugetlb(dst_vma, dst_start,
- src_start, len, mcopy_mode,
- wp_copy);
+ src_start, len, flags);
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
goto out_unlock;
- if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE)
+ if (!vma_is_shmem(dst_vma) &&
+ uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE))
goto out_unlock;
/*
@@ -639,7 +631,7 @@ retry:
BUG_ON(pmd_trans_huge(*dst_pmd));
err = mfill_atomic_pte(dst_pmd, dst_vma, dst_addr,
- src_addr, &page, mcopy_mode, wp_copy);
+ src_addr, flags, &page);
cond_resched();
if (unlikely(err == -ENOENT)) {
@@ -687,24 +679,24 @@ out:
ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start,
unsigned long src_start, unsigned long len,
- atomic_t *mmap_changing, __u64 mode)
+ atomic_t *mmap_changing, uffd_flags_t flags)
{
- return mfill_atomic(dst_mm, dst_start, src_start, len,
- MCOPY_ATOMIC_NORMAL, mmap_changing, mode);
+ return mfill_atomic(dst_mm, dst_start, src_start, len, mmap_changing,
+ uffd_flags_set_mode(flags, MFILL_ATOMIC_COPY));
}
ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm, unsigned long start,
unsigned long len, atomic_t *mmap_changing)
{
- return mfill_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE,
- mmap_changing, 0);
+ return mfill_atomic(dst_mm, start, 0, len, mmap_changing,
+ uffd_flags_set_mode(0, MFILL_ATOMIC_ZEROPAGE));
}
ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long start,
unsigned long len, atomic_t *mmap_changing)
{
- return mfill_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE,
- mmap_changing, 0);
+ return mfill_atomic(dst_mm, start, 0, len, mmap_changing,
+ uffd_flags_set_mode(0, MFILL_ATOMIC_CONTINUE));
}
long uffd_wp_range(struct vm_area_struct *dst_vma,
_
Patches currently in -mm which might be from axelrasmussen@xxxxxxxxxx are
mm-userfaultfd-rename-functions-for-clarity-consistency.patch
mm-userfaultfd-dont-pass-around-both-mm-and-vma.patch
mm-userfaultfd-combine-mode-and-wp_copy-arguments.patch
mm-userfaultfd-add-uffdio_continue_mode_wp-to-install-wp-ptes.patch
