drm/i915 wants to read/write more than one page in its fastpath and hence needs to prefault more than PAGE_SIZE bytes.
I've checked the callsites and they all already clamp size when calling fault_in_pages_* to the same as for the subsequent __copy_to|from_user and hence don't rely on the implicit clamping to PAGE_SIZE.
Also kill a copy&pasted spurious space in both functions while at it.
Cc: linux-mm@kvack.org Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch --- include/linux/pagemap.h | 28 ++++++++++++++++++---------- 1 files changed, 18 insertions(+), 10 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index cfaaa69..689527d 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -408,6 +408,7 @@ extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter); static inline int fault_in_pages_writeable(char __user *uaddr, int size) { int ret; + char __user *end = uaddr + size - 1;
if (unlikely(size == 0)) return 0; @@ -416,17 +417,20 @@ static inline int fault_in_pages_writeable(char __user *uaddr, int size) * Writing zeroes into userspace here is OK, because we know that if * the zero gets there, we'll be overwriting it. */ - ret = __put_user(0, uaddr); + while (uaddr <= end) { + ret = __put_user(0, uaddr); + if (ret != 0) + return ret; + uaddr += PAGE_SIZE; + } if (ret == 0) { - char __user *end = uaddr + size - 1; - /* * If the page was already mapped, this will get a cache miss * for sure, so try to avoid doing it. */ - if (((unsigned long)uaddr & PAGE_MASK) != + if (((unsigned long)uaddr & PAGE_MASK) == ((unsigned long)end & PAGE_MASK)) - ret = __put_user(0, end); + ret = __put_user(0, end); } return ret; } @@ -435,17 +439,21 @@ static inline int fault_in_pages_readable(const char __user *uaddr, int size) { volatile char c; int ret; + const char __user *end = uaddr + size - 1;
if (unlikely(size == 0)) return 0;
- ret = __get_user(c, uaddr); + while (uaddr <= end) { + ret = __get_user(c, uaddr); + if (ret != 0) + return ret; + uaddr += PAGE_SIZE; + } if (ret == 0) { - const char __user *end = uaddr + size - 1; - - if (((unsigned long)uaddr & PAGE_MASK) != + if (((unsigned long)uaddr & PAGE_MASK) == ((unsigned long)end & PAGE_MASK)) { - ret = __get_user(c, end); + ret = __get_user(c, end); (void)c; } }