linux-kernel - Re: [PATCH 3/4] btrfs/ioctl: store btrfs_uring_encoded_data in io_btrfs

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Message-ID: <CADUfDZr6A51QxVWw2hJF6_FZW7QYoUHwH-JtNEgmkAefMiUjqQ@mail.gmail.com>
Date: Wed, 2 Jul 2025 15:51:28 -0400
From: Caleb Sander Mateos <csander@...estorage.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>, 
	Mark Harmstone <maharmstone@...com>, linux-btrfs@...r.kernel.org, io-uring@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] btrfs/ioctl: store btrfs_uring_encoded_data in io_btrfs_cmd

On Tue, Jul 1, 2025 at 3:06 PM Jens Axboe <axboe@...nel.dk> wrote:
>
> > @@ -4811,11 +4813,15 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
> >       loff_t pos;
> >       struct kiocb kiocb;
> >       struct extent_state *cached_state = NULL;
> >       u64 start, lockend;
> >       void __user *sqe_addr;
> > -     struct btrfs_uring_encoded_data *data = io_uring_cmd_get_async_data(cmd)->op_data;
> > +     struct io_btrfs_cmd *bc = io_uring_cmd_to_pdu(cmd, struct io_btrfs_cmd);
> > +     struct btrfs_uring_encoded_data *data = NULL;
> > +
> > +     if (cmd->flags & IORING_URING_CMD_REISSUE)
> > +             data = bc->data;
>
> Can this be a btrfs io_btrfs_cmd specific flag? Doesn't seem like it
> would need to be io_uring wide.

Maybe. But where are you thinking it would be stored? I don't think
io_uring_cmd's pdu field would work because it's not initialized
before the first call to ->uring_cmd(). That's the whole reason I
needed to add a flag to tell whether this was the first call to
->uring_cmd() or a subsequent one.
I also put the flag in the uring_cmd layer because that's where
op_data was defined. Even though btrfs is the only current user of
op_data, it seems like it was intended as a generic mechanism that
other ->uring_cmd() implementations might want to use. It seems like
the same argument would apply to this flag.
Thoughts?

Best,
Caleb