linux-kernel - Re: [PATCH v6 01/34] vfs: Unconditionally set IOCB_WRITE in call_write

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Message-ID: <2731230.1674128066@warthog.procyon.org.uk>
Date:   Thu, 19 Jan 2023 11:34:26 +0000
From:   David Howells <dhowells@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 01/34] vfs: Unconditionally set IOCB_WRITE in call_write_iter()

Christoph Hellwig <hch@...radead.org> wrote:

> We want to be consistent for sync vs async submission.  So I think yes,
> we want to do the get_current_ioprio for most of them, exceptions
> beeing aio and io_uring - those could use a __init_iocb or
> init_iocb_ioprio variant that passs in the explicit priority if we want
> to avoid the call if it would be overriden later.

io_uring is a bit problematic in this regard.  io_prep_rw() starts the
initialisation of the kiocb, so io_read() and io_write() can't just
reinitialise it.  OTOH, I'm not sure io_prep_rw() has sufficient information
to hand.

I wonder if I should add a flag to struct io_op_def to indicate that this is
going to be a write operation and maybe add a REQ_F_WRITE flag that gets set
by that.

David