[PATCH RFC POC 26/50] dma-buf: stop unwinding sync file descriptors by hand

[Christian Brauner]

Rely on the fd exit path machinery.

Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
---
 drivers/dma-buf/dma-buf.c   | 33 ++++++++++------------------
 drivers/dma-buf/sw_sync.c   | 40 +++++++++++-----------------------
 drivers/dma-buf/sync_file.c | 52 +++++++++++++--------------------------------
 3 files changed, 38 insertions(+), 87 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index d504c636dc29..f0d581fad7ae 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -440,7 +440,8 @@ static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
 	enum dma_resv_usage usage;
 	struct dma_fence *fence = NULL;
 	struct sync_file *sync_file;
-	int fd, ret;
+	int ret;
+	const struct fd_slot *fd;
 
 	if (copy_from_user(&arg, user_data, sizeof(arg)))
 		return -EFAULT;
@@ -451,14 +452,14 @@ static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
 	if ((arg.flags & DMA_BUF_SYNC_RW) == 0)
 		return -EINVAL;
 
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0)
-		return fd;
+	fd = fd_prepare(O_CLOEXEC);
+	if (IS_ERR(fd))
+		return PTR_ERR(fd);
 
 	usage = dma_resv_usage_rw(arg.flags & DMA_BUF_SYNC_WRITE);
 	ret = dma_resv_get_singleton(dmabuf->resv, usage, &fence);
 	if (ret)
-		goto err_put_fd;
+		return ret;
 
 	if (!fence)
 		fence = dma_fence_get_stub();
@@ -467,26 +468,14 @@ static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
 
 	dma_fence_put(fence);
 
-	if (!sync_file) {
-		ret = -ENOMEM;
-		goto err_put_fd;
-	}
-
-	arg.fd = fd;
-	if (copy_to_user(user_data, &arg, sizeof(arg))) {
-		ret = -EFAULT;
-		goto err_put_file;
-	}
+	if (!sync_file)
+		return -ENOMEM;
 
-	fd_install(fd, sync_file->file);
+	arg.fd = fd_stage(fd, sync_file->file);
+	if (copy_to_user(user_data, &arg, sizeof(arg)))
+		return -EFAULT;
 
 	return 0;
-
-err_put_file:
-	fput(sync_file->file);
-err_put_fd:
-	put_unused_fd(fd);
-	return ret;
 }
 
 static long dma_buf_import_sync_file(struct dma_buf *dmabuf,
diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
index 8df20b0218a9..90852950e4e3 100644
--- a/drivers/dma-buf/sw_sync.c
+++ b/drivers/dma-buf/sw_sync.c
@@ -344,8 +344,7 @@ static int sw_sync_debugfs_release(struct inode *inode, struct file *file)
 static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
 				       unsigned long arg)
 {
-	int fd = get_unused_fd_flags(O_CLOEXEC);
-	int err;
+	const struct fd_slot *fd = fd_prepare(O_CLOEXEC);
 	struct sync_pt *pt;
 	struct sync_file *sync_file;
 	struct sw_sync_create_fence_data data;
@@ -353,41 +352,26 @@ static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
 	/* SW sync fence are inherently unsafe and can deadlock the kernel */
 	add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 
-	if (fd < 0)
-		return fd;
+	if (IS_ERR(fd))
+		return PTR_ERR(fd);
 
-	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
-		err = -EFAULT;
-		goto err;
-	}
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data)))
+		return -EFAULT;
 
 	pt = sync_pt_create(obj, data.value);
-	if (!pt) {
-		err = -ENOMEM;
-		goto err;
-	}
+	if (!pt)
+		return -ENOMEM;
 
 	sync_file = sync_file_create(&pt->base);
 	dma_fence_put(&pt->base);
-	if (!sync_file) {
-		err = -ENOMEM;
-		goto err;
-	}
-
-	data.fence = fd;
-	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
-		fput(sync_file->file);
-		err = -EFAULT;
-		goto err;
-	}
+	if (!sync_file)
+		return -ENOMEM;
 
-	fd_install(fd, sync_file->file);
+	data.fence = fd_stage(fd, sync_file->file);
+	if (copy_to_user((void __user *)arg, &data, sizeof(data)))
+		return -EFAULT;
 
 	return 0;
-
-err:
-	put_unused_fd(fd);
-	return err;
 }
 
 static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 2166bbdf7e4a..316fffc4067e 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -213,56 +213,34 @@ static __poll_t sync_file_poll(struct file *file, poll_table *wait)
 static long sync_file_ioctl_merge(struct sync_file *sync_file,
 				  unsigned long arg)
 {
-	int fd = get_unused_fd_flags(O_CLOEXEC);
-	int err;
+	const struct fd_slot *fd = fd_prepare(O_CLOEXEC);
 	struct sync_file *fence2, *fence3;
 	struct sync_merge_data data;
 
-	if (fd < 0)
-		return fd;
+	if (IS_ERR(fd))
+		return PTR_ERR(fd);
 
-	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
-		err = -EFAULT;
-		goto err_put_fd;
-	}
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data)))
+		return -EFAULT;
 
-	if (data.flags || data.pad) {
-		err = -EINVAL;
-		goto err_put_fd;
-	}
+	if (data.flags || data.pad)
+		return -EINVAL;
 
 	fence2 = sync_file_fdget(data.fd2);
-	if (!fence2) {
-		err = -ENOENT;
-		goto err_put_fd;
-	}
+	if (!fence2)
+		return -ENOENT;
 
 	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);
+	if (!fence3)
+		return -ENOMEM;
 
-err_put_fence2:
-	fput(fence2->file);
+	data.fence = fd_stage(fd, fence3->file);
+	if (copy_to_user((void __user *)arg, &data, sizeof(data)))
+		return -EFAULT;
 
-err_put_fd:
-	put_unused_fd(fd);
-	return err;
+	return 0;
 }
 
 static int sync_fill_fence_info(struct dma_fence *fence,

-- 
2.53.0