linux-kernel - Re: [PATCH v13 03/12] splice: Do splice read from a buffered file without using ITER

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Message-ID: <Y+pMx2HhY0dOiRl3@infradead.org>
Date:   Mon, 13 Feb 2023 06:44:23 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>,
        Al Viro <viro@...iv.linux.org.uk>,
        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>, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Christoph Hellwig <hch@....de>,
        John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH v13 03/12] splice: Do splice read from a buffered file
 without using ITER_PIPE

On Mon, Feb 13, 2023 at 11:15:37AM +0000, David Howells wrote:
> I'm not sure I want ki_flags setting from f_iocb_flags I should've said.  I'm
> not sure how the IOCB_* flags that I import from there will affect the
> operation of the synchronous read splice.

The same way as they did in the old ITER_PIPE based
generic_file_splice_read that uses init_sync_kiocb?  And if there's any
questions about them we need to do a deep audit.

> IOCB_NOWAIT, for example, or, for

I'd expect a set IOCB_NOWAIT to make the function return -EAGAIN
when it has to block.

> that matter, IOCB_APPEND.

IOCB_APPEND has no effect on reads of any kind.