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Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c66
1 files changed, 21 insertions, 45 deletions
diff --git a/mm/gup.c b/mm/gup.c
index ae096ea7583f..e869c634cc9a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -381,22 +381,13 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
}
/*
- * FOLL_FORCE or a forced COW break can write even to unwritable pte's,
- * but only after we've gone through a COW cycle and they are dirty.
+ * FOLL_FORCE can write to even unwritable pte's, but only
+ * after we've gone through a COW cycle and they are dirty.
*/
static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
{
- return pte_write(pte) || ((flags & FOLL_COW) && pte_dirty(pte));
-}
-
-/*
- * A (separate) COW fault might break the page the other way and
- * get_user_pages() would return the page from what is now the wrong
- * VM. So we need to force a COW break at GUP time even for reads.
- */
-static inline bool should_force_cow_break(struct vm_area_struct *vma, unsigned int flags)
-{
- return is_cow_mapping(vma->vm_flags) && (flags & (FOLL_GET | FOLL_PIN));
+ return pte_write(pte) ||
+ ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
}
static struct page *follow_page_pte(struct vm_area_struct *vma,
@@ -843,7 +834,7 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
goto unmap;
*page = pte_page(*pte);
}
- if (unlikely(!try_get_page(*page))) {
+ if (unlikely(!try_grab_page(*page, gup_flags))) {
ret = -ENOMEM;
goto unmap;
}
@@ -1067,11 +1058,9 @@ static long __get_user_pages(struct mm_struct *mm,
goto out;
}
if (is_vm_hugetlb_page(vma)) {
- if (should_force_cow_break(vma, foll_flags))
- foll_flags |= FOLL_WRITE;
i = follow_hugetlb_page(mm, vma, pages, vmas,
&start, &nr_pages, i,
- foll_flags, locked);
+ gup_flags, locked);
if (locked && *locked == 0) {
/*
* We've got a VM_FAULT_RETRY
@@ -1085,10 +1074,6 @@ static long __get_user_pages(struct mm_struct *mm,
continue;
}
}
-
- if (should_force_cow_break(vma, foll_flags))
- foll_flags |= FOLL_WRITE;
-
retry:
/*
* If we have a pending SIGKILL, don't keep faulting pages and
@@ -1270,6 +1255,9 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
BUG_ON(*locked != 1);
}
+ if (flags & FOLL_PIN)
+ atomic_set(&mm->has_pinned, 1);
+
/*
* FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
* is to set FOLL_GET if the caller wants pages[] filled in (but has
@@ -2500,13 +2488,13 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
return 1;
}
-static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
+static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pmd_t *pmdp;
- pmdp = pmd_offset(&pud, addr);
+ pmdp = pmd_offset_lockless(pudp, pud, addr);
do {
pmd_t pmd = READ_ONCE(*pmdp);
@@ -2543,13 +2531,13 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
return 1;
}
-static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
+static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pud_t *pudp;
- pudp = pud_offset(&p4d, addr);
+ pudp = pud_offset_lockless(p4dp, p4d, addr);
do {
pud_t pud = READ_ONCE(*pudp);
@@ -2564,20 +2552,20 @@ static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
PUD_SHIFT, next, flags, pages, nr))
return 0;
- } else if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
+ } else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr))
return 0;
} while (pudp++, addr = next, addr != end);
return 1;
}
-static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
+static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
p4d_t *p4dp;
- p4dp = p4d_offset(&pgd, addr);
+ p4dp = p4d_offset_lockless(pgdp, pgd, addr);
do {
p4d_t p4d = READ_ONCE(*p4dp);
@@ -2589,7 +2577,7 @@ static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
P4D_SHIFT, next, flags, pages, nr))
return 0;
- } else if (!gup_pud_range(p4d, addr, next, flags, pages, nr))
+ } else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr))
return 0;
} while (p4dp++, addr = next, addr != end);
@@ -2617,7 +2605,7 @@ static void gup_pgd_range(unsigned long addr, unsigned long end,
if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
PGDIR_SHIFT, next, flags, pages, nr))
return;
- } else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr))
+ } else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr))
return;
} while (pgdp++, addr = next, addr != end);
}
@@ -2675,6 +2663,9 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
FOLL_FAST_ONLY)))
return -EINVAL;
+ if (gup_flags & FOLL_PIN)
+ atomic_set(&current->mm->has_pinned, 1);
+
if (!(gup_flags & FOLL_FAST_ONLY))
might_lock_read(&current->mm->mmap_lock);
@@ -2689,19 +2680,6 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
return -EFAULT;
/*
- * The FAST_GUP case requires FOLL_WRITE even for pure reads,
- * because get_user_pages() may need to cause an early COW in
- * order to avoid confusing the normal COW routines. So only
- * targets that are already writable are safe to do by just
- * looking at the page tables.
- *
- * NOTE! With FOLL_FAST_ONLY we allow read-only gup_fast() here,
- * because there is no slow path to fall back on. But you'd
- * better be careful about possible COW pages - you'll get _a_
- * COW page, but not necessarily the one you intended to get
- * depending on what COW event happens after this. COW may break
- * the page copy in a random direction.
- *
* Disable interrupts. The nested form is used, in order to allow
* full, general purpose use of this routine.
*
@@ -2714,8 +2692,6 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
*/
if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) {
unsigned long fast_flags = gup_flags;
- if (!(gup_flags & FOLL_FAST_ONLY))
- fast_flags |= FOLL_WRITE;
local_irq_save(flags);
gup_pgd_range(addr, end, fast_flags, pages, &nr_pinned);
generated by cgit v1.2.3 (git 2.39.0) at 2025-02-02 04:56:09 +0300