drm/i915: Fix lock order reversal in shmem pwrite path.

Like the GTT pwrite path fix, this uses an optimistic path and a
fallback to get_user_pages.  Note that this means we have to stop using
vfs_write and roll it ourselves.

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 205 insertions, 20 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b998d659fd98..bdc7326052df 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -136,6 +136,33 @@ i915_gem_create_ioctl(struct drm_device *dev, void *data,
         return 0;
 }
 
+static inline int
+slow_shmem_copy(struct page *dst_page,
+                int dst_offset,
+                struct page *src_page,
+                int src_offset,
+                int length)
+{
+        char *dst_vaddr, *src_vaddr;
+
+        dst_vaddr = kmap_atomic(dst_page, KM_USER0);
+        if (dst_vaddr == NULL)
+                return -ENOMEM;
+
+        src_vaddr = kmap_atomic(src_page, KM_USER1);
+        if (src_vaddr == NULL) {
+                kunmap_atomic(dst_vaddr, KM_USER0);
+                return -ENOMEM;
+        }
+
+        memcpy(dst_vaddr + dst_offset, src_vaddr + src_offset, length);
+
+        kunmap_atomic(src_vaddr, KM_USER1);
+        kunmap_atomic(dst_vaddr, KM_USER0);
+
+        return 0;
+}
+
 /**
  * Reads data from the object referenced by handle.
  *
@@ -243,6 +270,23 @@ slow_kernel_write(struct io_mapping *mapping,
         return 0;
 }
 
+static inline int
+fast_shmem_write(struct page **pages,
+                 loff_t page_base, int page_offset,
+                 char __user *data,
+                 int length)
+{
+        char __iomem *vaddr;
+
+        vaddr = kmap_atomic(pages[page_base >> PAGE_SHIFT], KM_USER0);
+        if (vaddr == NULL)
+                return -ENOMEM;
+        __copy_from_user_inatomic(vaddr + page_offset, data, length);
+        kunmap_atomic(vaddr, KM_USER0);
+
+        return 0;
+}
+
 /**
  * This is the fast pwrite path, where we copy the data directly from the
  * user into the GTT, uncached.
@@ -423,39 +467,175 @@ out_unpin_pages:
         return ret;
 }
 
+/**
+ * This is the fast shmem pwrite path, which attempts to directly
+ * copy_from_user into the kmapped pages backing the object.
+ */
 static int
-i915_gem_shmem_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
-                      struct drm_i915_gem_pwrite *args,
-                      struct drm_file *file_priv)
+i915_gem_shmem_pwrite_fast(struct drm_device *dev, struct drm_gem_object *obj,
+                           struct drm_i915_gem_pwrite *args,
+                           struct drm_file *file_priv)
 {
+        struct drm_i915_gem_object *obj_priv = obj->driver_private;
+        ssize_t remain;
+        loff_t offset, page_base;
+        char __user *user_data;
+        int page_offset, page_length;
         int ret;
-        loff_t offset;
-        ssize_t written;
+
+        user_data = (char __user *) (uintptr_t) args->data_ptr;
+        remain = args->size;
 
         mutex_lock(&dev->struct_mutex);
 
+        ret = i915_gem_object_get_pages(obj);
+        if (ret != 0)
+                goto fail_unlock;
+
         ret = i915_gem_object_set_to_cpu_domain(obj, 1);
-        if (ret) {
-                mutex_unlock(&dev->struct_mutex);
-                return ret;
+        if (ret != 0)
+                goto fail_put_pages;
+
+        obj_priv = obj->driver_private;
+        offset = args->offset;
+        obj_priv->dirty = 1;
+
+        while (remain > 0) {
+                /* Operation in this page
+                 *
+                 * page_base = page offset within aperture
+                 * page_offset = offset within page
+                 * page_length = bytes to copy for this page
+                 */
+                page_base = (offset & ~(PAGE_SIZE-1));
+                page_offset = offset & (PAGE_SIZE-1);
+                page_length = remain;
+                if ((page_offset + remain) > PAGE_SIZE)
+                        page_length = PAGE_SIZE - page_offset;
+
+                ret = fast_shmem_write(obj_priv->pages,
+                                       page_base, page_offset,
+                                       user_data, page_length);
+                if (ret)
+                        goto fail_put_pages;
+
+                remain -= page_length;
+                user_data += page_length;
+                offset += page_length;
         }
 
+fail_put_pages:
+        i915_gem_object_put_pages(obj);
+fail_unlock:
+        mutex_unlock(&dev->struct_mutex);
+
+        return ret;
+}
+
+/**
+ * This is the fallback shmem pwrite path, which uses get_user_pages to pin
+ * the memory and maps it using kmap_atomic for copying.
+ *
+ * This avoids taking mmap_sem for faulting on the user's address while the
+ * struct_mutex is held.
+ */
+static int
+i915_gem_shmem_pwrite_slow(struct drm_device *dev, struct drm_gem_object *obj,
+                           struct drm_i915_gem_pwrite *args,
+                           struct drm_file *file_priv)
+{
+        struct drm_i915_gem_object *obj_priv = obj->driver_private;
+        struct mm_struct *mm = current->mm;
+        struct page **user_pages;
+        ssize_t remain;
+        loff_t offset, pinned_pages, i;
+        loff_t first_data_page, last_data_page, num_pages;
+        int shmem_page_index, shmem_page_offset;
+        int data_page_index,  data_page_offset;
+        int page_length;
+        int ret;
+        uint64_t data_ptr = args->data_ptr;
+
+        remain = args->size;
+
+        /* Pin the user pages containing the data.  We can't fault while
+         * holding the struct mutex, and all of the pwrite implementations
+         * want to hold it while dereferencing the user data.
+         */
+        first_data_page = data_ptr / PAGE_SIZE;
+        last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
+        num_pages = last_data_page - first_data_page + 1;
+
+        user_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
+        if (user_pages == NULL)
+                return -ENOMEM;
+
+        down_read(&mm->mmap_sem);
+        pinned_pages = get_user_pages(current, mm, (uintptr_t)args->data_ptr,
+                                      num_pages, 0, 0, user_pages, NULL);
+        up_read(&mm->mmap_sem);
+        if (pinned_pages < num_pages) {
+                ret = -EFAULT;
+                goto fail_put_user_pages;
+        }
+
+        mutex_lock(&dev->struct_mutex);
+
+        ret = i915_gem_object_get_pages(obj);
+        if (ret != 0)
+                goto fail_unlock;
+
+        ret = i915_gem_object_set_to_cpu_domain(obj, 1);
+        if (ret != 0)
+                goto fail_put_pages;
+
+        obj_priv = obj->driver_private;
         offset = args->offset;
+        obj_priv->dirty = 1;
 
-        written = vfs_write(obj->filp,
-                            (char __user *)(uintptr_t) args->data_ptr,
-                            args->size, &offset);
-        if (written != args->size) {
-                mutex_unlock(&dev->struct_mutex);
-                if (written < 0)
-                        return written;
-                else
-                        return -EINVAL;
+        while (remain > 0) {
+                /* Operation in this page
+                 *
+                 * shmem_page_index = page number within shmem file
+                 * shmem_page_offset = offset within page in shmem file
+                 * data_page_index = page number in get_user_pages return
+                 * data_page_offset = offset with data_page_index page.
+                 * page_length = bytes to copy for this page
+                 */
+                shmem_page_index = offset / PAGE_SIZE;
+                shmem_page_offset = offset & ~PAGE_MASK;
+                data_page_index = data_ptr / PAGE_SIZE - first_data_page;
+                data_page_offset = data_ptr & ~PAGE_MASK;
+
+                page_length = remain;
+                if ((shmem_page_offset + page_length) > PAGE_SIZE)
+                        page_length = PAGE_SIZE - shmem_page_offset;
+                if ((data_page_offset + page_length) > PAGE_SIZE)
+                        page_length = PAGE_SIZE - data_page_offset;
+
+                ret = slow_shmem_copy(obj_priv->pages[shmem_page_index],
+                                      shmem_page_offset,
+                                      user_pages[data_page_index],
+                                      data_page_offset,
+                                      page_length);
+                if (ret)
+                        goto fail_put_pages;
+
+                remain -= page_length;
+                data_ptr += page_length;
+                offset += page_length;
         }
 
+fail_put_pages:
+        i915_gem_object_put_pages(obj);
+fail_unlock:
         mutex_unlock(&dev->struct_mutex);
+fail_put_user_pages:
+        for (i = 0; i < pinned_pages; i++)
+                page_cache_release(user_pages[i]);
+        kfree(user_pages);
 
-        return 0;
+        return ret;
 }
 
 /**
@@ -502,8 +682,13 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
                         ret = i915_gem_gtt_pwrite_slow(dev, obj, args,
                                                        file_priv);
                 }
-        } else
-                ret = i915_gem_shmem_pwrite(dev, obj, args, file_priv);
+        } else {
+                ret = i915_gem_shmem_pwrite_fast(dev, obj, args, file_priv);
+                if (ret == -EFAULT) {
+                        ret = i915_gem_shmem_pwrite_slow(dev, obj, args,
+                                                         file_priv);
+                }
+        }
 
 #if WATCH_PWRITE
         if (ret)