dma-buf/sync_file: de-stage sync_file

sync_file is useful to connect one or more fences to the file. The file is
used by userspace to track fences between drivers that share DMA bufs.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/dma-buf/sync_file.c

@@ -0,0 +1,395 @@
+/*
+ * drivers/dma-buf/sync_file.c
+ *
+ * Copyright (C) 2012 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/export.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/anon_inodes.h>
+#include <linux/sync_file.h>
+#include <uapi/linux/sync_file.h>
+
+static const struct file_operations sync_file_fops;
+
+static struct sync_file *sync_file_alloc(int size)
+{
+	struct sync_file *sync_file;
+
+	sync_file = kzalloc(size, GFP_KERNEL);
+	if (!sync_file)
+		return NULL;
+
+	sync_file->file = anon_inode_getfile("sync_file", &sync_file_fops,
+					     sync_file, 0);
+	if (IS_ERR(sync_file->file))
+		goto err;
+
+	kref_init(&sync_file->kref);
+
+	init_waitqueue_head(&sync_file->wq);
+
+	return sync_file;
+
+err:
+	kfree(sync_file);
+	return NULL;
+}
+
+static void fence_check_cb_func(struct fence *f, struct fence_cb *cb)
+{
+	struct sync_file_cb *check;
+	struct sync_file *sync_file;
+
+	check = container_of(cb, struct sync_file_cb, cb);
+	sync_file = check->sync_file;
+
+	if (atomic_dec_and_test(&sync_file->status))
+		wake_up_all(&sync_file->wq);
+}
+
+/**
+ * sync_file_create() - creates a sync file
+ * @fence:	fence to add to the sync_fence
+ *
+ * Creates a sync_file containg @fence. Once this is called, the sync_file
+ * takes ownership of @fence. The sync_file can be released with
+ * fput(sync_file->file). Returns the sync_file or NULL in case of error.
+ */
+struct sync_file *sync_file_create(struct fence *fence)
+{
+	struct sync_file *sync_file;
+
+	sync_file = sync_file_alloc(offsetof(struct sync_file, cbs[1]));
+	if (!sync_file)
+		return NULL;
+
+	sync_file->num_fences = 1;
+	atomic_set(&sync_file->status, 1);
+	snprintf(sync_file->name, sizeof(sync_file->name), "%s-%s%d-%d",
+		 fence->ops->get_driver_name(fence),
+		 fence->ops->get_timeline_name(fence), fence->context,
+		 fence->seqno);
+
+	sync_file->cbs[0].fence = fence;
+	sync_file->cbs[0].sync_file = sync_file;
+	if (fence_add_callback(fence, &sync_file->cbs[0].cb,
+			       fence_check_cb_func))
+		atomic_dec(&sync_file->status);
+
+	return sync_file;
+}
+EXPORT_SYMBOL(sync_file_create);
+
+/**
+ * sync_file_fdget() - get a sync_file from an fd
+ * @fd:		fd referencing a fence
+ *
+ * Ensures @fd references a valid sync_file, increments the refcount of the
+ * backing file. Returns the sync_file or NULL in case of error.
+ */
+static struct sync_file *sync_file_fdget(int fd)
+{
+	struct file *file = fget(fd);
+
+	if (!file)
+		return NULL;
+
+	if (file->f_op != &sync_file_fops)
+		goto err;
+
+	return file->private_data;
+
+err:
+	fput(file);
+	return NULL;
+}
+
+static void sync_file_add_pt(struct sync_file *sync_file, int *i,
+			     struct fence *fence)
+{
+	sync_file->cbs[*i].fence = fence;
+	sync_file->cbs[*i].sync_file = sync_file;
+
+	if (!fence_add_callback(fence, &sync_file->cbs[*i].cb,
+				fence_check_cb_func)) {
+		fence_get(fence);
+		(*i)++;
+	}
+}
+
+/**
+ * sync_file_merge() - merge two sync_files
+ * @name:	name of new fence
+ * @a:		sync_file a
+ * @b:		sync_file b
+ *
+ * Creates a new sync_file which contains copies of all the fences in both
+ * @a and @b.  @a and @b remain valid, independent sync_file. Returns the
+ * new merged sync_file or NULL in case of error.
+ */
+static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
+					 struct sync_file *b)
+{
+	int num_fences = a->num_fences + b->num_fences;
+	struct sync_file *sync_file;
+	int i, i_a, i_b;
+	unsigned long size = offsetof(struct sync_file, cbs[num_fences]);
+
+	sync_file = sync_file_alloc(size);
+	if (!sync_file)
+		return NULL;
+
+	atomic_set(&sync_file->status, num_fences);
+
+	/*
+	 * Assume sync_file a and b are both ordered and have no
+	 * duplicates with the same context.
+	 *
+	 * If a sync_file can only be created with sync_file_merge
+	 * and sync_file_create, this is a reasonable assumption.
+	 */
+	for (i = i_a = i_b = 0; i_a < a->num_fences && i_b < b->num_fences; ) {
+		struct fence *pt_a = a->cbs[i_a].fence;
+		struct fence *pt_b = b->cbs[i_b].fence;
+
+		if (pt_a->context < pt_b->context) {
+			sync_file_add_pt(sync_file, &i, pt_a);
+
+			i_a++;
+		} else if (pt_a->context > pt_b->context) {
+			sync_file_add_pt(sync_file, &i, pt_b);
+
+			i_b++;
+		} else {
+			if (pt_a->seqno - pt_b->seqno <= INT_MAX)
+				sync_file_add_pt(sync_file, &i, pt_a);
+			else
+				sync_file_add_pt(sync_file, &i, pt_b);
+
+			i_a++;
+			i_b++;
+		}
+	}
+
+	for (; i_a < a->num_fences; i_a++)
+		sync_file_add_pt(sync_file, &i, a->cbs[i_a].fence);
+
+	for (; i_b < b->num_fences; i_b++)
+		sync_file_add_pt(sync_file, &i, b->cbs[i_b].fence);
+
+	if (num_fences > i)
+		atomic_sub(num_fences - i, &sync_file->status);
+	sync_file->num_fences = i;
+
+	strlcpy(sync_file->name, name, sizeof(sync_file->name));
+	return sync_file;
+}
+
+static void sync_file_free(struct kref *kref)
+{
+	struct sync_file *sync_file = container_of(kref, struct sync_file,
+						     kref);
+	int i;
+
+	for (i = 0; i < sync_file->num_fences; ++i) {
+		fence_remove_callback(sync_file->cbs[i].fence,
+				      &sync_file->cbs[i].cb);
+		fence_put(sync_file->cbs[i].fence);
+	}
+
+	kfree(sync_file);
+}
+
+static int sync_file_release(struct inode *inode, struct file *file)
+{
+	struct sync_file *sync_file = file->private_data;
+
+	kref_put(&sync_file->kref, sync_file_free);
+	return 0;
+}
+
+static unsigned int sync_file_poll(struct file *file, poll_table *wait)
+{
+	struct sync_file *sync_file = file->private_data;
+	int status;
+
+	poll_wait(file, &sync_file->wq, wait);
+
+	status = atomic_read(&sync_file->status);
+
+	if (!status)
+		return POLLIN;
+	if (status < 0)
+		return POLLERR;
+	return 0;
+}
+
+static long sync_file_ioctl_merge(struct sync_file *sync_file,
+				  unsigned long arg)
+{
+	int fd = get_unused_fd_flags(O_CLOEXEC);
+	int err;
+	struct sync_file *fence2, *fence3;
+	struct sync_merge_data data;
+
+	if (fd < 0)
+		return fd;
+
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
+		err = -EFAULT;
+		goto err_put_fd;
+	}
+
+	if (data.flags || data.pad) {
+		err = -EINVAL;
+		goto err_put_fd;
+	}
+
+	fence2 = sync_file_fdget(data.fd2);
+	if (!fence2) {
+		err = -ENOENT;
+		goto err_put_fd;
+	}
+
+	data.name[sizeof(data.name) - 1] = '\0';
+	fence3 = sync_file_merge(data.name, sync_file, fence2);
+	if (!fence3) {
+		err = -ENOMEM;
+		goto err_put_fence2;
+	}
+
+	data.fence = fd;
+	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
+		err = -EFAULT;
+		goto err_put_fence3;
+	}
+
+	fd_install(fd, fence3->file);
+	fput(fence2->file);
+	return 0;
+
+err_put_fence3:
+	fput(fence3->file);
+
+err_put_fence2:
+	fput(fence2->file);
+
+err_put_fd:
+	put_unused_fd(fd);
+	return err;
+}
+
+static void sync_fill_fence_info(struct fence *fence,
+				 struct sync_fence_info *info)
+{
+	strlcpy(info->obj_name, fence->ops->get_timeline_name(fence),
+		sizeof(info->obj_name));
+	strlcpy(info->driver_name, fence->ops->get_driver_name(fence),
+		sizeof(info->driver_name));
+	if (fence_is_signaled(fence))
+		info->status = fence->status >= 0 ? 1 : fence->status;
+	else
+		info->status = 0;
+	info->timestamp_ns = ktime_to_ns(fence->timestamp);
+}
+
+static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
+				       unsigned long arg)
+{
+	struct sync_file_info info;
+	struct sync_fence_info *fence_info = NULL;
+	__u32 size;
+	int ret, i;
+
+	if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
+		return -EFAULT;
+
+	if (info.flags || info.pad)
+		return -EINVAL;
+
+	/*
+	 * Passing num_fences = 0 means that userspace doesn't want to
+	 * retrieve any sync_fence_info. If num_fences = 0 we skip filling
+	 * sync_fence_info and return the actual number of fences on
+	 * info->num_fences.
+	 */
+	if (!info.num_fences)
+		goto no_fences;
+
+	if (info.num_fences < sync_file->num_fences)
+		return -EINVAL;
+
+	size = sync_file->num_fences * sizeof(*fence_info);
+	fence_info = kzalloc(size, GFP_KERNEL);
+	if (!fence_info)
+		return -ENOMEM;
+
+	for (i = 0; i < sync_file->num_fences; ++i)
+		sync_fill_fence_info(sync_file->cbs[i].fence, &fence_info[i]);
+
+	if (copy_to_user(u64_to_user_ptr(info.sync_fence_info), fence_info,
+			 size)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+no_fences:
+	strlcpy(info.name, sync_file->name, sizeof(info.name));
+	info.status = atomic_read(&sync_file->status);
+	if (info.status >= 0)
+		info.status = !info.status;
+
+	info.num_fences = sync_file->num_fences;
+
+	if (copy_to_user((void __user *)arg, &info, sizeof(info)))
+		ret = -EFAULT;
+	else
+		ret = 0;
+
+out:
+	kfree(fence_info);
+
+	return ret;
+}
+
+static long sync_file_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg)
+{
+	struct sync_file *sync_file = file->private_data;
+
+	switch (cmd) {
+	case SYNC_IOC_MERGE:
+		return sync_file_ioctl_merge(sync_file, arg);
+
+	case SYNC_IOC_FILE_INFO:
+		return sync_file_ioctl_fence_info(sync_file, arg);
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+static const struct file_operations sync_file_fops = {
+	.release = sync_file_release,
+	.poll = sync_file_poll,
+	.unlocked_ioctl = sync_file_ioctl,
+	.compat_ioctl = sync_file_ioctl,
+};
+