linux-kernel - Re: [PATCH] Fuse: Add backing file support for uring

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Message-ID: <db432e5b-fc90-487e-b261-7771766c56cb@bsbernd.com>
Date: Fri, 21 Feb 2025 16:24:59 +0100
From: Bernd Schubert <bernd@...ernd.com>
To: Moinak Bhattacharyya <moinakb001@...il.com>,
 Miklos Szeredi <miklos@...redi.hu>, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
 Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH] Fuse: Add backing file support for uring_cmd



On 2/21/25 16:19, Moinak Bhattacharyya wrote:
> Add support for opening and closing backing files in the
> fuse_uring_cmd callback. Store backing_map (for open) and backing_id
> (for close) in the uring_cmd data.
> ---
>  fs/fuse/dev_uring.c       | 50 +++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/fuse.h |  6 +++++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> index ebd2931b4f2a..df73d9d7e686 100644
> --- a/fs/fuse/dev_uring.c
> +++ b/fs/fuse/dev_uring.c
> @@ -1033,6 +1033,40 @@ fuse_uring_create_ring_ent(struct io_uring_cmd *cmd,
>   return ent;
>  }
> 
> +/*
> + * Register new backing file for passthrough, getting backing map
> from URING_CMD data
> + */
> +static int fuse_uring_backing_open(struct io_uring_cmd *cmd,
> + unsigned int issue_flags, struct fuse_conn *fc)
> +{
> + const struct fuse_backing_map *map = io_uring_sqe_cmd(cmd->sqe);
> + int ret = fuse_backing_open(fc, map);
> +
> + if (ret < 0) {
> + return ret;
> + }
> +
> + io_uring_cmd_done(cmd, ret, 0, issue_flags);
> + return 0;
> +}
> +
> +/*
> + * Remove file from passthrough tracking, getting backing_id from
> URING_CMD data
> + */
> +static int fuse_uring_backing_close(struct io_uring_cmd *cmd,
> + unsigned int issue_flags, struct fuse_conn *fc)
> +{
> + const int *backing_id = io_uring_sqe_cmd(cmd->sqe);
> + int ret = fuse_backing_close(fc, *backing_id);
> +
> + if (ret < 0) {
> + return ret;
> + }
> +
> + io_uring_cmd_done(cmd, ret, 0, issue_flags);
> + return 0;
> +}
> +
>  /*
>   * Register header and payload buffer with the kernel and puts the
>   * entry as "ready to get fuse requests" on the queue
> @@ -1144,6 +1178,22 @@ int fuse_uring_cmd(struct io_uring_cmd *cmd,
> unsigned int issue_flags)
>   return err;
>   }
>   break;
> + case FUSE_IO_URING_CMD_BACKING_OPEN:
> + err = fuse_uring_backing_open(cmd, issue_flags, fc);
> + if (err) {
> + pr_info_once("FUSE_IO_URING_CMD_BACKING_OPEN failed err=%d\n",
> +     err);
> + return err;
> + }
> + break;
> + case FUSE_IO_URING_CMD_BACKING_CLOSE:
> + err = fuse_uring_backing_close(cmd, issue_flags, fc);
> + if (err) {
> + pr_info_once("FUSE_IO_URING_CMD_BACKING_CLOSE failed err=%d\n",
> +     err);
> + return err;
> + }
> + break;
>   default:
>   return -EINVAL;
>   }
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index 5e0eb41d967e..634265da1328 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
> @@ -1264,6 +1264,12 @@ enum fuse_uring_cmd {
> 
>   /* commit fuse request result and fetch next request */
>   FUSE_IO_URING_CMD_COMMIT_AND_FETCH = 2,
> +
> + /* add new backing file for passthrough */
> + FUSE_IO_URING_CMD_BACKING_OPEN = 3,
> +
> + /* remove passthrough file by backing_id */
> + FUSE_IO_URING_CMD_BACKING_CLOSE = 4,
>  };
> 
>  /**
> --
> 2.39.5 (Apple Git-154)
> 

This is hard to read - all formatting got lost? Other than that looks
reasonable.


Thanks,
Bernd