linux-kernel - Re: [RFC PATCH 03/11] vfs: Use init

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Message-ID: <dc2e8d58-7400-63d6-b76c-7f4f6d29fcb7@kernel.dk>
Date:   Fri, 30 Jun 2023 10:05:42 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     David Howells <dhowells@...hat.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Hillf Danton <hdanton@...a.com>,
        Christian Brauner <brauner@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Christoph Hellwig <hch@....de>,
        Christian Brauner <christian@...uner.io>
Subject: Re: [RFC PATCH 03/11] vfs: Use init_kiocb() to initialise new IOCBs

On 6/30/23 10:00?AM, David Howells wrote:
> Jens Axboe <axboe@...nel.dk> wrote:
> 
>> One concern here is that we're using IOCB_WRITE here to tell if
>> sb_start_write() has been done or not, and hence whether
>> kiocb_end_write() needs to be called. You know set it earlier, which
>> means if we get a failure if we need to setup async data, then we know
>> have IOCB_WRITE set at that point even though we did not call
>> sb_start_write().
> 
> Hmmm...  It's set earlier in a number of places anyway -
> __cachefiles_write() for example.

Not sure how that's relevant, that's a private kiocb and not related to
the private one that io_uring uses?

> Btw, can you please put some comments on the IOCB_* constants?  I have
> to guess at what they mean and how they're meant to be used.  Or
> better still, get Christoph to write Documentation/core-api/iocb.rst
> describing the API? ;-)

The ones I have added do have comments, mostly, though it's not a lot of
commentary for sure... Which ones are confusing and need better
comments? Would be happy to do that. I do think the comments belong in
there rather than have a separate doc for the kiocb. Though one thing
that's confusing is the ki_private ownership. You'd think it belongs to
the owner of the kiocb, but nope, it has random uses in iomap and ocfs2
at least.

-- 
Jens Axboe