Re: [PATCH v4 3/3] fuse: deduplicate the oversized-request error selection

[Joanne Koong]

On Tue, Jul 14, 2026 at 4:54 PM Xiang Mei <xmei5@xxxxxxx> wrote:
>
> fuse_dev_do_read() and fuse_uring_args_to_ring() both pick the error for
> a request that does not fit the server's buffer, and both special-case
> FUSE_SETXATTR.  Move that choice into a helper so the two transports
> cannot drift apart.
>
> No functional change.
>
> Signed-off-by: Xiang Mei <xmei5@xxxxxxx>
> ---
> v4: introduce fuse_req_too_large_error as a helper
>
>  fs/fuse/dev.c        | 5 +----
>  fs/fuse/dev_uring.c  | 2 +-
>  fs/fuse/fuse_dev_i.h | 7 +++++++
>  3 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index b8e43e374b35..56c38aca7389 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1584,10 +1584,7 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
>
>         /* If request is too large, reply with an error and restart the read */
>         if (nbytes < reqsize) {
> -               req->out.h.error = -EIO;
> -               /* SETXATTR is special, since it may contain too large data */
> -               if (args->opcode == FUSE_SETXATTR)
> -                       req->out.h.error = -E2BIG;
> +               req->out.h.error = fuse_req_too_large_error(args);
>                 fuse_request_end(req);
>                 goto restart;
>         }
> diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> index 4529505b2bca..cebd8f871627 100644
> --- a/fs/fuse/dev_uring.c
> +++ b/fs/fuse/dev_uring.c
> @@ -729,7 +729,7 @@ static int fuse_uring_args_to_ring(struct fuse_ring *ring, struct fuse_req *req,
>         }
>
>         if (fuse_len_args(num_args, (struct fuse_arg *)in_args) > ent->payload_sz)
> -               return args->opcode == FUSE_SETXATTR ? -E2BIG : -EIO;
> +               return fuse_req_too_large_error(args);
>
>         /* copy the payload */
>         err = fuse_copy_args(&cs, num_args, args->in_pages,
> diff --git a/fs/fuse/fuse_dev_i.h b/fs/fuse/fuse_dev_i.h
> index b511aaab6bfc..4958158c0f02 100644
> --- a/fs/fuse/fuse_dev_i.h
> +++ b/fs/fuse/fuse_dev_i.h
> @@ -13,6 +13,8 @@
>  #include <linux/workqueue.h>
>  #include <linux/fs.h>
>
> +#include "args.h"
> +
>  /* Ordinary requests have even IDs, while interrupts IDs are odd */
>  #define FUSE_INT_REQ_BIT (1ULL << 0)
>  #define FUSE_REQ_ID_STEP (1ULL << 1)
> @@ -367,6 +369,11 @@ static inline struct fuse_dev *__fuse_get_dev(struct file *file)
>         return fud;
>  }
>
> +static inline int fuse_req_too_large_error(struct fuse_args *args)
> +{
> +       return args->opcode == FUSE_SETXATTR ? -E2BIG : -EIO;
> +}

Could you add a comment to the top of this function? Maybe something
like "A request whose payload size exceeds the transport buffer size
is rejected with -EIO. The exception is FUSE_SETXATTR whose value may
legitimately be oversized and is rejected with -E2BIG, matching the
vfs setxattr path".

Reviewed-by: Joanne Koong <joannelkoong@xxxxxxxxx>

Thanks,
Joanne