On Fri, Oct 15, 2021 at 12:42:37PM +0300, Nikolay Borisov wrote:

On 1.09.21 г. 20:01, Omar Sandoval wrote:

quoted

From: Omar Sandoval <redacted>

In order to allow sending and receiving compressed data without
decompressing it, we need an interface to write pre-compressed data
directly to the filesystem and the matching interface to read compressed
data without decompressing it. This adds the definitions for ioctls to
do that and detailed explanations of how to use them.

Signed-off-by: Omar Sandoval <redacted>

One minor nit below but otherwise LGTM:

Reviewed-by: Nikolay Borisov <redacted>

<snip>

quoted

+struct btrfs_ioctl_encoded_io_args {
+	/* Input parameters for both reads and writes. */
+
+	/*
+	 * iovecs containing encoded data.
+	 *
+	 * For reads, if the size of the encoded data is larger than the sum of
+	 * iov[n].iov_len for 0 <= n < iovcnt, then the ioctl fails with
+	 * ENOBUFS.
+	 *
+	 * For writes, the size of the encoded data is the sum of iov[n].iov_len
+	 * for 0 <= n < iovcnt. This must be less than 128 KiB (this limit may
+	 * increase in the future). This must also be less than or equal to
+	 * unencoded_len.
+	 */
+	const struct iovec __user *iov;
+	/* Number of iovecs. */
+	unsigned long iovcnt;
+	/*
+	 * Offset in file.
+	 *
+	 * For writes, must be aligned to the sector size of the filesystem.
+	 */
+	__s64 offset;
+	/* Currently must be zero. */
+	__u64 flags;
+

nit: A comment stating that the output params begin here could be added.

There is a comment in this spot:

	/*   
	 * For reads, the following members are filled in with the metadata for
	 * the encoded data.
	 * For writes, the following members must be set to the metadata for the
	 * encoded data.
	 */

I'll clarify it to:

        /*
	 * For reads, the following members are output parameters that will
	 * contain the returned metadata for the encoded data.
         * For writes, the following members must be set to the metadata for the
         * encoded data.
         */