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Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c60
1 files changed, 50 insertions, 10 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 6297f6bcc..a798293fc 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -12,7 +12,9 @@
#include <linux/sched.h>
#include <linux/rwsem.h>
#include <linux/hugetlb.h>
+
#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
#include "internal.h"
@@ -32,6 +34,30 @@ static struct page *no_page_table(struct vm_area_struct *vma,
return NULL;
}
+static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
+ pte_t *pte, unsigned int flags)
+{
+ /* No page to get reference */
+ if (flags & FOLL_GET)
+ return -EFAULT;
+
+ if (flags & FOLL_TOUCH) {
+ pte_t entry = *pte;
+
+ if (flags & FOLL_WRITE)
+ entry = pte_mkdirty(entry);
+ entry = pte_mkyoung(entry);
+
+ if (!pte_same(*pte, entry)) {
+ set_pte_at(vma->vm_mm, address, pte, entry);
+ update_mmu_cache(vma, address, pte);
+ }
+ }
+
+ /* Proper page table entry exists, but no corresponding struct page */
+ return -EEXIST;
+}
+
static struct page *follow_page_pte(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd, unsigned int flags)
{
@@ -73,10 +99,21 @@ retry:
page = vm_normal_page(vma, address, pte);
if (unlikely(!page)) {
- if ((flags & FOLL_DUMP) ||
- !is_zero_pfn(pte_pfn(pte)))
- goto bad_page;
- page = pte_page(pte);
+ if (flags & FOLL_DUMP) {
+ /* Avoid special (like zero) pages in core dumps */
+ page = ERR_PTR(-EFAULT);
+ goto out;
+ }
+
+ if (is_zero_pfn(pte_pfn(pte))) {
+ page = pte_page(pte);
+ } else {
+ int ret;
+
+ ret = follow_pfn_pte(vma, address, ptep, flags);
+ page = ERR_PTR(ret);
+ goto out;
+ }
}
if (flags & FOLL_GET)
@@ -114,12 +151,9 @@ retry:
unlock_page(page);
}
}
+out:
pte_unmap_unlock(ptep, ptl);
return page;
-bad_page:
- pte_unmap_unlock(ptep, ptl);
- return ERR_PTR(-EFAULT);
-
no_page:
pte_unmap_unlock(ptep, ptl);
if (!pte_none(pte))
@@ -489,9 +523,15 @@ retry:
goto next_page;
}
BUG();
- }
- if (IS_ERR(page))
+ } else if (PTR_ERR(page) == -EEXIST) {
+ /*
+ * Proper page table entry exists, but no corresponding
+ * struct page.
+ */
+ goto next_page;
+ } else if (IS_ERR(page)) {
return i ? i : PTR_ERR(page);
+ }
if (pages) {
pages[i] = page;
flush_anon_page(vma, page, start);