Currently, the io-uring fixed buffer cmd flag is silently dismissed,
even though it does not work. This patch returns an error when the flag
is set, making it clear that operation is not supported.

Fixes: 34310c442e17 ("btrfs: add io_uring command for encoded reads (ENCODED_READ ioctl)")
Cc: stable@vger.kernel.org
Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
---
 fs/btrfs/ioctl.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 6c18bad53cd3..62bb9e11e8d6 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4823,6 +4823,12 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
 		ret = -EPERM;
 		goto out_acct;
 	}
+
+	if (cmd->flags & IORING_URING_CMD_FIXED) {
+		ret = -EOPNOTSUPP;
+		goto out_acct;
+	}
+
 	file = cmd->file;
 	inode = BTRFS_I(file->f_inode);
 	fs_info = inode->root->fs_info;
@@ -4959,6 +4965,11 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
 		goto out_acct;
 	}
 
+	if (cmd->flags & IORING_URING_CMD_FIXED) {
+		ret = -EOPNOTSUPP;
+		goto out_acct;
+	}
+
 	file = cmd->file;
 	sqe_addr = u64_to_user_ptr(READ_ONCE(cmd->sqe->addr));
 
-- 
2.43.0

On 3/26/25 15:57, Sidong Yang wrote:
> Currently, the io-uring fixed buffer cmd flag is silently dismissed,
> even though it does not work. This patch returns an error when the flag
> is set, making it clear that operation is not supported.

IIRC, the feature where you use the flag hasn't been merged
yet and is targeting 6.16. In this case you need to send this
patch for 6.15, and once merged stable will try to pick it up
from there.

> Fixes: 34310c442e17 ("btrfs: add io_uring command for encoded reads (ENCODED_READ ioctl)")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> ---
>   fs/btrfs/ioctl.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 6c18bad53cd3..62bb9e11e8d6 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4823,6 +4823,12 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
>   		ret = -EPERM;
>   		goto out_acct;
>   	}
> +
> +	if (cmd->flags & IORING_URING_CMD_FIXED) {
> +		ret = -EOPNOTSUPP;
> +		goto out_acct;
> +	}
> +
>   	file = cmd->file;
>   	inode = BTRFS_I(file->f_inode);
>   	fs_info = inode->root->fs_info;
> @@ -4959,6 +4965,11 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
>   		goto out_acct;
>   	}
>   
> +	if (cmd->flags & IORING_URING_CMD_FIXED) {
> +		ret = -EOPNOTSUPP;
> +		goto out_acct;
> +	}
> +
>   	file = cmd->file;
>   	sqe_addr = u64_to_user_ptr(READ_ONCE(cmd->sqe->addr));
>   

-- 
Pavel Begunkov

On Thu, Mar 27, 2025 at 02:58:11PM +0000, Pavel Begunkov wrote:
> On 3/26/25 15:57, Sidong Yang wrote:
> > Currently, the io-uring fixed buffer cmd flag is silently dismissed,
> > even though it does not work. This patch returns an error when the flag
> > is set, making it clear that operation is not supported.
> 
> IIRC, the feature where you use the flag hasn't been merged
> yet and is targeting 6.16. In this case you need to send this
> patch for 6.15, and once merged stable will try to pick it up
> from there.

Thanks, I mistakenly thought the feature would be merged in 6.15. If so,
I need send this for 6.15 after sending the patch for the fixed buffer feature.

> 
> > Fixes: 34310c442e17 ("btrfs: add io_uring command for encoded reads (ENCODED_READ ioctl)")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> > ---
> >   fs/btrfs/ioctl.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> > 
> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > index 6c18bad53cd3..62bb9e11e8d6 100644
> > --- a/fs/btrfs/ioctl.c
> > +++ b/fs/btrfs/ioctl.c
> > @@ -4823,6 +4823,12 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
> >   		ret = -EPERM;
> >   		goto out_acct;
> >   	}
> > +
> > +	if (cmd->flags & IORING_URING_CMD_FIXED) {
> > +		ret = -EOPNOTSUPP;
> > +		goto out_acct;
> > +	}
> > +
> >   	file = cmd->file;
> >   	inode = BTRFS_I(file->f_inode);
> >   	fs_info = inode->root->fs_info;
> > @@ -4959,6 +4965,11 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
> >   		goto out_acct;
> >   	}
> > +	if (cmd->flags & IORING_URING_CMD_FIXED) {
> > +		ret = -EOPNOTSUPP;
> > +		goto out_acct;
> > +	}
> > +
> >   	file = cmd->file;
> >   	sqe_addr = u64_to_user_ptr(READ_ONCE(cmd->sqe->addr));
> 
> -- 
> Pavel Begunkov
>