The patch titled
Subject: mm/gup: make locked never NULL in the internal GUP functions
has been added to the -mm mm-unstable branch. Its filename is
mm-gup-make-locked-never-null-in-the-internal-gup-functions.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-make-locked-never-null-in-the-internal-gup-functions.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: Jason Gunthorpe <jgg@xxxxxxxxxx>
Subject: mm/gup: make locked never NULL in the internal GUP functions
Date: Tue, 24 Jan 2023 16:34:30 -0400
Now that NULL locked doesn't have a special meaning we can just make it
non-NULL in all cases and remove the special tests.
get_user_pages() and pin_user_pages() can safely pass in a locked = 1
get_user_pages_remote) and pin_user_pages_remote() can swap in a local
variable for locked if NULL is passed.
Remove all the NULL checks.
Link: https://lkml.kernel.org/r/9-v2-987e91b59705+36b-gup_tidy_jgg@xxxxxxxxxx
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/gup.c~mm-gup-make-locked-never-null-in-the-internal-gup-functions
+++ a/mm/gup.c
@@ -879,9 +879,9 @@ unmap:
}
/*
- * mmap_lock must be held on entry. If @locked != NULL and *@flags
- * does not include FOLL_NOWAIT, the mmap_lock may be released. If it
- * is, *@locked will be set to 0 and -EBUSY returned.
+ * mmap_lock must be held on entry. If @flags has FOLL_UNLOCKABLE but not
+ * FOLL_NOWAIT, the mmap_lock may be released. If it is, *@locked will be set
+ * to 0 and -EBUSY returned.
*/
static int faultin_page(struct vm_area_struct *vma,
unsigned long address, unsigned int *flags, bool unshare,
@@ -930,8 +930,8 @@ static int faultin_page(struct vm_area_s
* mmap lock in the page fault handler. Sanity check this.
*/
WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT);
- if (locked)
- *locked = 0;
+ *locked = 0;
+
/*
* We should do the same as VM_FAULT_RETRY, but let's not
* return -EBUSY since that's not reflecting the reality of
@@ -951,7 +951,7 @@ static int faultin_page(struct vm_area_s
}
if (ret & VM_FAULT_RETRY) {
- if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
+ if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
*locked = 0;
return -EBUSY;
}
@@ -1062,14 +1062,12 @@ static int check_vma_flags(struct vm_are
* appropriate) must be called after the page is finished with, and
* before put_page is called.
*
- * If @locked != NULL, *@locked will be set to 0 when mmap_lock is
- * released by an up_read(). That can happen if @gup_flags does not
- * have FOLL_NOWAIT.
- *
- * A caller using such a combination of @locked and @gup_flags
- * must therefore hold the mmap_lock for reading only, and recognize
- * when it's been released. Otherwise, it must be held for either
- * reading or writing and will not be released.
+ * If FOLL_UNLOCKABLE is set without FOLL_NOWAIT then the mmap_lock may
+ * be released. If this happens *@locked will be set to 0 on return.
+ *
+ * A caller using such a combination of @gup_flags must therefore hold the
+ * mmap_lock for reading only, and recognize when it's been released. Otherwise,
+ * it must be held for either reading or writing and will not be released.
*
* In most cases, get_user_pages or get_user_pages_fast should be used
* instead of __get_user_pages. __get_user_pages should be used only if
@@ -1121,7 +1119,7 @@ static long __get_user_pages(struct mm_s
i = follow_hugetlb_page(mm, vma, pages, vmas,
&start, &nr_pages, i,
gup_flags, locked);
- if (locked && *locked == 0) {
+ if (!*locked) {
/*
* We've got a VM_FAULT_RETRY
* and we've lost mmap_lock.
@@ -1354,7 +1352,7 @@ static __always_inline long __get_user_p
* The internal caller expects GUP to manage the lock internally and the
* lock must be released when this returns.
*/
- if (locked && !*locked) {
+ if (!*locked) {
if (mmap_read_lock_killable(mm))
return -EAGAIN;
must_unlock = true;
@@ -1502,6 +1500,7 @@ long populate_vma_page_range(struct vm_a
{
struct mm_struct *mm = vma->vm_mm;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
+ int local_locked = 1;
int gup_flags;
long ret;
@@ -1542,7 +1541,7 @@ long populate_vma_page_range(struct vm_a
* not result in a stack expansion that recurses back here.
*/
ret = __get_user_pages(mm, start, nr_pages, gup_flags,
- NULL, NULL, locked);
+ NULL, NULL, locked ? locked : &local_locked);
lru_add_drain();
return ret;
}
@@ -1683,7 +1682,7 @@ static long __get_user_pages_locked(stru
* The internal caller expects GUP to manage the lock internally and the
* lock must be released when this returns.
*/
- if (locked && !*locked) {
+ if (!*locked) {
if (mmap_read_lock_killable(mm))
return -EAGAIN;
must_unlock = true;
@@ -2222,11 +2221,14 @@ long get_user_pages_remote(struct mm_str
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
+ int local_locked = 1;
+
if (!is_valid_gup_args(pages, vmas, locked, &gup_flags,
FOLL_TOUCH | FOLL_REMOTE))
return -EINVAL;
- return __get_user_pages_locked(mm, start, nr_pages, pages, vmas, locked,
+ return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
+ locked ? locked : &local_locked,
gup_flags);
}
EXPORT_SYMBOL(get_user_pages_remote);
@@ -2261,11 +2263,13 @@ long get_user_pages(unsigned long start,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas)
{
+ int locked = 1;
+
if (!is_valid_gup_args(pages, vmas, NULL, &gup_flags, FOLL_TOUCH))
return -EINVAL;
return __get_user_pages_locked(current->mm, start, nr_pages, pages,
- vmas, NULL, gup_flags);
+ vmas, &locked, gup_flags);
}
EXPORT_SYMBOL(get_user_pages);
@@ -3158,10 +3162,13 @@ long pin_user_pages_remote(struct mm_str
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas, int *locked)
{
+ int local_locked = 1;
+
if (!is_valid_gup_args(pages, vmas, locked, &gup_flags,
FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE))
return 0;
- return __gup_longterm_locked(mm, start, nr_pages, pages, vmas, locked,
+ return __gup_longterm_locked(mm, start, nr_pages, pages, vmas,
+ locked ? locked : &local_locked,
gup_flags);
}
EXPORT_SYMBOL(pin_user_pages_remote);
@@ -3187,10 +3194,12 @@ long pin_user_pages(unsigned long start,
unsigned int gup_flags, struct page **pages,
struct vm_area_struct **vmas)
{
+ int locked = 1;
+
if (!is_valid_gup_args(pages, vmas, NULL, &gup_flags, FOLL_PIN))
return 0;
return __gup_longterm_locked(current->mm, start, nr_pages,
- pages, vmas, NULL, gup_flags);
+ pages, vmas, &locked, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages);
_
Patches currently in -mm which might be from jgg@xxxxxxxxxx are
mm-gup-have-internal-functions-get-the-mmap_read_lock.patch
mm-gup-remove-obsolete-foll_longterm-comment.patch
mm-gup-dont-call-__gup_longterm_locked-if-foll_longterm-cannot-be-set.patch
mm-gup-move-try_grab_page-to-mm-internalh.patch
mm-gup-simplify-the-external-interface-functions-and-consolidate-invariants.patch
mm-gup-add-an-assertion-that-the-mmap-lock-is-locked.patch
mm-gup-remove-locked-being-null-from-faultin_vma_page_range.patch
mm-gup-add-foll_unlockable.patch
mm-gup-make-locked-never-null-in-the-internal-gup-functions.patch
mm-gup-remove-pin_user_pages_fast_only.patch
mm-gup-make-get_user_pages_fast_only-return-the-common-return-value.patch
mm-gup-move-gup_must_unshare-to-mm-internalh.patch
mm-gup-move-private-gup-foll_-flags-to-internalh.patch
