Re: [PATCH v11 14/14] btrfs: send: enable support for stream v2 and compressed writes

Nikolay Borisov
2021-10-18T12:44:26Z

On 1.09.21 г. 20:01, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
>
> Now that the new support is implemented, allow the ioctl to accept the
> flags and update the version in sysfs.

This seems like an appropriate place to bring up the discussion about
versioned streams. SO instead of adding a BTRFS_SEND_FLAG_STREAM_V2
flag, which implies that for the next version we have to add
BTRFS_SEND_FLAG_STREAM_V3 etc. Why not generalize the flag to
BTRFS_SEND_FLAG_STREAM_VERSIONED and carve an u32 from one of the
reserved fields so that in the future we simply increment the version field?

>
> Signed-off-by: Omar Sandoval <osandov@fb.com>
> ---
> fs/btrfs/send.c | 10 +++++++++-
> fs/btrfs/send.h | 2 +-
> include/uapi/linux/btrfs.h | 4 +++-
> 3 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index 0ba8dc3a9f56..90ca915fed78 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -671,7 +671,10 @@ static int send_header(struct send_ctx *sctx)
> struct btrfs_stream_header hdr;
>
> strcpy(hdr.magic, BTRFS_SEND_STREAM_MAGIC);
> - hdr.version = cpu_to_le32(BTRFS_SEND_STREAM_VERSION);
> + if (sctx->flags & BTRFS_SEND_FLAG_STREAM_V2)
> + hdr.version = cpu_to_le32(2);
> + else
> + hdr.version = cpu_to_le32(1);
>
> return write_buf(sctx->send_filp, &hdr, sizeof(hdr),
> &sctx->send_off);
> @@ -7466,6 +7469,11 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
> ret = -EINVAL;
> goto out;
> }
> + if ((arg->flags & BTRFS_SEND_FLAG_COMPRESSED) &&
> + !(arg->flags & BTRFS_SEND_FLAG_STREAM_V2)) {
> + ret = -EINVAL;
> + goto out;
> + }
>
> sctx = kzalloc(sizeof(struct send_ctx), GFP_KERNEL);
> if (!sctx) {
> diff --git a/fs/btrfs/send.h b/fs/btrfs/send.h
> index 9f4f7b96b1eb..9c83e14a43b2 100644
> --- a/fs/btrfs/send.h
> +++ b/fs/btrfs/send.h
> @@ -10,7 +10,7 @@
> #include "ctree.h"
>
> #define BTRFS_SEND_STREAM_MAGIC "btrfs-stream"
> -#define BTRFS_SEND_STREAM_VERSION 1
> +#define BTRFS_SEND_STREAM_VERSION 2
>
> /*
> * In send stream v1, no command is larger than 64k. In send stream v2, no limit
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> index 4f875f355e83..5c13e407982f 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -787,7 +787,9 @@ struct btrfs_ioctl_received_subvol_args {
> #define BTRFS_SEND_FLAG_MASK \
> (BTRFS_SEND_FLAG_NO_FILE_DATA | \
> BTRFS_SEND_FLAG_OMIT_STREAM_HEADER | \
> - BTRFS_SEND_FLAG_OMIT_END_CMD)
> + BTRFS_SEND_FLAG_OMIT_END_CMD | \
> + BTRFS_SEND_FLAG_STREAM_V2 | \
> + BTRFS_SEND_FLAG_COMPRESSED)
>
> struct btrfs_ioctl_send_args {
> __s64 send_fd; /* in */
>