From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: [PATCH 14/16] mm: extend prefault helpers to fault in more than PAGE_SIZE Date: Sun, 25 Mar 2012 19:47:41 +0200 Message-ID: <1332697663-31256-14-git-send-email-daniel.vetter@ffwll.ch> References: <1332697663-31256-1-git-send-email-daniel.vetter@ffwll.ch> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-we0-f177.google.com (mail-we0-f177.google.com [74.125.82.177]) by gabe.freedesktop.org (Postfix) with ESMTP id 6DEDF9EE9A for ; Sun, 25 Mar 2012 11:51:50 -0700 (PDT) Received: by mail-we0-f177.google.com with SMTP id p11so4606235wer.36 for ; Sun, 25 Mar 2012 11:51:50 -0700 (PDT) In-Reply-To: <1332697663-31256-1-git-send-email-daniel.vetter@ffwll.ch> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Intel Graphics Development Cc: Daniel Vetter List-Id: intel-gfx@lists.freedesktop.org drm/i915 wants to read/write more than one page in its fastpath and hence needs to prefault more than PAGE_SIZE bytes. Add new functions in filemap.h to make that possible. Also kill a copy&pasted spurious space in both functions while at it. v2: As suggested by Andrew Morton, add a multipage parameter to both functions to avoid the additional branch for the pagemap.c hotpath. My gcc 4.6 here seems to dtrt and indeed reap these branches where not needed. v3: Becaus I couldn't find a way around adding a uaddr += PAGE_SIZE to the filemap.c hotpaths (that the compiler couldn't remove again), let's go with separate new functions for the multipage use-case. v4: Adjust comment to CodingStlye. Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_gem.c | 6 +- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 +- include/linux/pagemap.h | 64 +++++++++++++++++++++++++++- 3 files changed, 66 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index d318a45..accb2cb 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -436,7 +436,7 @@ i915_gem_shmem_pread(struct drm_device *dev, mutex_unlock(&dev->struct_mutex); if (!prefaulted) { - ret = fault_in_pages_writeable(user_data, remain); + ret = fault_in_multipages_writeable(user_data, remain); /* Userspace is tricking us, but we've already clobbered * its pages with the prefault and promised to write the * data up to the first fault. Hence ignore any errors @@ -829,8 +829,8 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data, args->size)) return -EFAULT; - ret = fault_in_pages_readable((char __user *)(uintptr_t)args->data_ptr, - args->size); + ret = fault_in_multipages_readable((char __user *)(uintptr_t)args->data_ptr, + args->size); if (ret) return -EFAULT; diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c index 0e051ec..0505a62 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -967,7 +967,7 @@ validate_exec_list(struct drm_i915_gem_exec_object2 *exec, if (!access_ok(VERIFY_WRITE, ptr, length)) return -EFAULT; - if (fault_in_pages_readable(ptr, length)) + if (fault_in_multipages_readable(ptr, length)) return -EFAULT; } diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index cfaaa69..e7102a3 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -426,7 +426,7 @@ static inline int fault_in_pages_writeable(char __user *uaddr, int size) */ if (((unsigned long)uaddr & PAGE_MASK) != ((unsigned long)end & PAGE_MASK)) - ret = __put_user(0, end); + ret = __put_user(0, end); } return ret; } @@ -445,13 +445,73 @@ static inline int fault_in_pages_readable(const char __user *uaddr, int size) if (((unsigned long)uaddr & PAGE_MASK) != ((unsigned long)end & PAGE_MASK)) { - ret = __get_user(c, end); + ret = __get_user(c, end); (void)c; } } return ret; } +/* + * Multipage variants of the above prefault helpers, useful if more than + * PAGE_SIZE of date needs to be prefaulted. These are separate from the above + * functions (which only handle up to PAGE_SIZE) to avoid clobbering the + * filemap.c hotpaths. + */ +static inline int fault_in_multipages_writeable(char __user *uaddr, int size) +{ + int ret; + const char __user *end = uaddr + size - 1; + + if (unlikely(size == 0)) + return 0; + + /* + * Writing zeroes into userspace here is OK, because we know that if + * the zero gets there, we'll be overwriting it. + */ + while (uaddr <= end) { + ret = __put_user(0, uaddr); + if (ret != 0) + return ret; + uaddr += PAGE_SIZE; + } + + /* Check whether the range spilled into the next page. */ + if (((unsigned long)uaddr & PAGE_MASK) == + ((unsigned long)end & PAGE_MASK)) + ret = __put_user(0, end); + + return ret; +} + +static inline int fault_in_multipages_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; + + while (uaddr <= end) { + ret = __get_user(c, uaddr); + if (ret != 0) + return ret; + uaddr += PAGE_SIZE; + } + + /* Check whether the range spilled into the next page. */ + if (((unsigned long)uaddr & PAGE_MASK) == + ((unsigned long)end & PAGE_MASK)) { + ret = __get_user(c, end); + (void)c; + } + + return ret; +} + int add_to_page_cache_locked(struct page *page, struct address_space *mapping, pgoff_t index, gfp_t gfp_mask); int add_to_page_cache_lru(struct page *page, struct address_space *mapping, -- 1.7.7.6