Re: [PATCH v11 07/14] btrfs: add definitions + documentation for encoded I/O ioctls

[Nikolay Borisov <nborisov@suse.com>]

On 1.09.21 г. 20:01, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> 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 <osandov@fb.com>

One minor nit below but otherwise LGTM:

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

<snip>

> +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.

>