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mm: Don't pin ZERO_PAGE in pin_user_pages()
[linux-block.git]
/
mm
/
gup.c
diff --git
a/mm/gup.c
b/mm/gup.c
index ff689c88a35781f1d9aeccd00458028a308cdb42..ad28261dcafdcb4f373dd9b715047729eb7f5035 100644
(file)
--- a/
mm/gup.c
+++ b/
mm/gup.c
@@
-51,7
+51,8
@@
static inline void sanity_check_pinned_pages(struct page **pages,
struct page *page = *pages;
struct folio *folio = page_folio(page);
struct page *page = *pages;
struct folio *folio = page_folio(page);
- if (!folio_test_anon(folio))
+ if (is_zero_page(page) ||
+ !folio_test_anon(folio))
continue;
if (!folio_test_large(folio) || folio_test_hugetlb(folio))
VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page);
continue;
if (!folio_test_large(folio) || folio_test_hugetlb(folio))
VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page);
@@
-131,6
+132,13
@@
struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
else if (flags & FOLL_PIN) {
struct folio *folio;
else if (flags & FOLL_PIN) {
struct folio *folio;
+ /*
+ * Don't take a pin on the zero page - it's not going anywhere
+ * and it is used in a *lot* of places.
+ */
+ if (is_zero_page(page))
+ return page_folio(page);
+
/*
* Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
* right zone, so fail and let the caller fall back to the slow
/*
* Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
* right zone, so fail and let the caller fall back to the slow
@@
-180,6
+188,8
@@
struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
{
if (flags & FOLL_PIN) {
static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
{
if (flags & FOLL_PIN) {
+ if (is_zero_folio(folio))
+ return;
node_stat_mod_folio(folio, NR_FOLL_PIN_RELEASED, refs);
if (folio_test_large(folio))
atomic_sub(refs, &folio->_pincount);
node_stat_mod_folio(folio, NR_FOLL_PIN_RELEASED, refs);
if (folio_test_large(folio))
atomic_sub(refs, &folio->_pincount);
@@
-224,6
+234,13
@@
int __must_check try_grab_page(struct page *page, unsigned int flags)
if (flags & FOLL_GET)
folio_ref_inc(folio);
else if (flags & FOLL_PIN) {
if (flags & FOLL_GET)
folio_ref_inc(folio);
else if (flags & FOLL_PIN) {
+ /*
+ * Don't take a pin on the zero page - it's not going anywhere
+ * and it is used in a *lot* of places.
+ */
+ if (is_zero_page(page))
+ return 0;
+
/*
* Similar to try_grab_folio(): be sure to *also*
* increment the normal page refcount field at least once,
/*
* Similar to try_grab_folio(): be sure to *also*
* increment the normal page refcount field at least once,
@@
-2970,6
+2987,8
@@
static int internal_get_user_pages_fast(unsigned long start,
len = nr_pages << PAGE_SHIFT;
if (check_add_overflow(start, len, &end))
return 0;
len = nr_pages << PAGE_SHIFT;
if (check_add_overflow(start, len, &end))
return 0;
+ if (end > TASK_SIZE_MAX)
+ return -EFAULT;
if (unlikely(!access_ok((void __user *)start, len)))
return -EFAULT;
if (unlikely(!access_ok((void __user *)start, len)))
return -EFAULT;
@@
-3077,6
+3096,9
@@
EXPORT_SYMBOL_GPL(get_user_pages_fast);
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for further details.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for further details.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page() will not remove pins from it.
*/
int pin_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
*/
int pin_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
@@
-3108,6
+3130,9
@@
EXPORT_SYMBOL_GPL(pin_user_pages_fast);
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page*() will not remove pins from it.
*/
long pin_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
*/
long pin_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
@@
-3141,6
+3166,9
@@
EXPORT_SYMBOL(pin_user_pages_remote);
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page*() will not remove pins from it.
*/
long pin_user_pages(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
*/
long pin_user_pages(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
@@
-3159,6
+3187,9
@@
EXPORT_SYMBOL(pin_user_pages);
* pin_user_pages_unlocked() is the FOLL_PIN variant of
* get_user_pages_unlocked(). Behavior is the same, except that this one sets
* FOLL_PIN and rejects FOLL_GET.
* pin_user_pages_unlocked() is the FOLL_PIN variant of
* get_user_pages_unlocked(). Behavior is the same, except that this one sets
* FOLL_PIN and rejects FOLL_GET.
+ *
+ * Note that if a zero_page is amongst the returned pages, it will not have
+ * pins in it and unpin_user_page*() will not remove pins from it.
*/
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags)
*/
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags)