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

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Message-ID: <2416073.1676328192@warthog.procyon.org.uk>
Date:   Mon, 13 Feb 2023 22:43:12 +0000
From:   David Howells <dhowells@...hat.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     dhowells@...hat.com, Jens Axboe <axboe@...nel.dk>,
        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>, 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

Guenter Roeck <linux@...ck-us.net> wrote:

> [    4.660118] PC is at 0x0
> [    4.660248] LR is at filemap_read_folio+0x17/0x4e

Do you know what the filesystem is that's being read from?

I think the problem is that there are a few filesystems/drivers that call
generic_file_splice_read() but don't have a ->read_folio().  Now most of these
can be made to call direct_splice_read() instead, leaving just coda, overlayfs
and shmem.

Coda and overlayfs can be made to pass the request down a layer.  I'm about to
look into shmem.

David