From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx135.postini.com [74.125.245.135]) by kanga.kvack.org (Postfix) with SMTP id EB6296B002C for ; Thu, 1 Mar 2012 14:26:35 -0500 (EST) Received: by wgbdt12 with SMTP id dt12so91504wgb.26 for ; Thu, 01 Mar 2012 11:26:34 -0800 (PST) MIME-Version: 1.0 From: Daniel Vetter Subject: [PATCH] mm: extend prefault helpers to fault in more than PAGE_SIZE Date: Thu, 1 Mar 2012 20:22:59 +0100 Message-Id: <1330629779-1449-1-git-send-email-daniel.vetter@ffwll.ch> In-Reply-To: <20120229153216.8c3ae31d.akpm@linux-foundation.org> References: <20120229153216.8c3ae31d.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Intel Graphics Development , DRI Development , LKML , Linux MM , Daniel Vetter 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. Cc: linux-mm@kvack.org 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 | 62 +++++++++++++++++++++++++++- 3 files changed, 64 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 544e528..3e631fc 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 @@ -822,8 +822,8 @@ 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 81687af..ef87f52 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -955,7 +955,7 @@ 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..0a91375 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 +445,71 @@ 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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