linux-kernel - Re: [PATCH v5 3/9] iov_iter: Use IOCB/IOMAP_WRITE if available rather than iterator direction

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Message-ID: <Y8AUTlRibL+pGDJN@infradead.org>
Date:   Thu, 12 Jan 2023 06:08:14 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/9] iov_iter: Use IOCB/IOMAP_WRITE if available
 rather than iterator direction

On Thu, Jan 12, 2023 at 10:31:01AM +0000, David Howells wrote:
> > And use the information in the request for this one (see patch below),
> > and then move this patch first in the series, add an explicit direction
> > parameter in the gup_flags to the get/pin helper and drop iov_iter_rw
> > and the whole confusing source/dest information in the iov_iter entirely,
> > which is a really nice big tree wide cleanup that remove redundant
> > information.
> 
> Fine by me, but Al might object as I think he wanted the internal checks.  Al?

I'm happy to have another discussion, but the fact the information in
the iov_iter is 98% redundant and various callers got it wrong and
away is a pretty good sign that we should drop this information.  It
also nicely simplified the API.