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Message-Id: <1238017510-26784-5-git-send-email-eric@anholt.net>
Date: Wed, 25 Mar 2009 14:45:08 -0700
From: Eric Anholt <eric@...olt.net>
To: linux-kernel@...r.kernel.org
Cc: dri-devel@...ts.sourceforge.net, Eric Anholt <eric@...olt.net>
Subject: [PATCH 4/6] drm/i915: Fix lock order reversal in shmem pread path.
Signed-off-by: Eric Anholt <eric@...olt.net>
---
drivers/gpu/drm/i915/i915_gem.c | 221 ++++++++++++++++++++++++++++++++++-----
1 files changed, 195 insertions(+), 26 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index bdc7326..010af90 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -137,6 +137,24 @@ i915_gem_create_ioctl(struct drm_device *dev, void *data,
}
static inline int
+fast_shmem_read(struct page **pages,
+ loff_t page_base, int page_offset,
+ char __user *data,
+ int length)
+{
+ char __iomem *vaddr;
+ int ret;
+
+ vaddr = kmap_atomic(pages[page_base >> PAGE_SHIFT], KM_USER0);
+ if (vaddr == NULL)
+ return -ENOMEM;
+ ret = __copy_to_user_inatomic(data, vaddr + page_offset, length);
+ kunmap_atomic(vaddr, KM_USER0);
+
+ return ret;
+}
+
+static inline int
slow_shmem_copy(struct page *dst_page,
int dst_offset,
struct page *src_page,
@@ -164,6 +182,179 @@ slow_shmem_copy(struct page *dst_page,
}
/**
+ * This is the fast shmem pread path, which attempts to copy_from_user directly
+ * from the backing pages of the object to the user's address space. On a
+ * fault, it fails so we can fall back to i915_gem_shmem_pwrite_slow().
+ */
+static int
+i915_gem_shmem_pread_fast(struct drm_device *dev, struct drm_gem_object *obj,
+ struct drm_i915_gem_pread *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;
+
+ 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_cpu_read_domain_range(obj, args->offset,
+ args->size);
+ if (ret != 0)
+ goto fail_put_pages;
+
+ obj_priv = obj->driver_private;
+ offset = args->offset;
+
+ 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_read(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 pread path, which allocates temporary storage
+ * in kernel space to copy_to_user into outside of the struct_mutex, so we
+ * can copy out of the object's backing pages while holding the struct mutex
+ * and not take page faults.
+ */
+static int
+i915_gem_shmem_pread_slow(struct drm_device *dev, struct drm_gem_object *obj,
+ struct drm_i915_gem_pread *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, yet we 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_cpu_read_domain_range(obj, args->offset,
+ args->size);
+ if (ret != 0)
+ goto fail_put_pages;
+
+ obj_priv = obj->driver_private;
+ offset = args->offset;
+
+ 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(user_pages[data_page_index],
+ data_page_offset,
+ obj_priv->pages[shmem_page_index],
+ shmem_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++) {
+ SetPageDirty(user_pages[i]);
+ page_cache_release(user_pages[i]);
+ }
+ kfree(user_pages);
+
+ return ret;
+}
+
+/**
* Reads data from the object referenced by handle.
*
* On error, the contents of *data are undefined.
@@ -175,8 +366,6 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
struct drm_i915_gem_pread *args = data;
struct drm_gem_object *obj;
struct drm_i915_gem_object *obj_priv;
- ssize_t read;
- loff_t offset;
int ret;
obj = drm_gem_object_lookup(dev, file_priv, args->handle);
@@ -194,33 +383,13 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
return -EINVAL;
}
- mutex_lock(&dev->struct_mutex);
-
- ret = i915_gem_object_set_cpu_read_domain_range(obj, args->offset,
- args->size);
- if (ret != 0) {
- drm_gem_object_unreference(obj);
- mutex_unlock(&dev->struct_mutex);
- return ret;
- }
-
- offset = args->offset;
-
- read = vfs_read(obj->filp, (char __user *)(uintptr_t)args->data_ptr,
- args->size, &offset);
- if (read != args->size) {
- drm_gem_object_unreference(obj);
- mutex_unlock(&dev->struct_mutex);
- if (read < 0)
- return read;
- else
- return -EINVAL;
- }
+ ret = i915_gem_shmem_pread_fast(dev, obj, args, file_priv);
+ if (ret != 0)
+ ret = i915_gem_shmem_pread_slow(dev, obj, args, file_priv);
drm_gem_object_unreference(obj);
- mutex_unlock(&dev->struct_mutex);
- return 0;
+ return ret;
}
/* This is the fast write path which cannot handle
--
1.6.2.1
--
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