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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <CAJfpeguGksS3sCigmRi9hJdUec8qtM9f+_9jC1rJhsXT+dV01w@mail.gmail.com>
References: <CAJfpeguGksS3sCigmRi9hJdUec8qtM9f+_9jC1rJhsXT+dV01w@mail.gmail.com> <20230308143754.1976726-1-dhowells@redhat.com> <20230308143754.1976726-4-dhowells@redhat.com>
To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     dhowells@redhat.com, Jens Axboe <axboe@kernel.dk>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        Jeff Layton <jlayton@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Hillf Danton <hdanton@sina.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Christoph Hellwig <hch@lst.de>,
        John Hubbard <jhubbard@nvidia.com>,
        linux-unionfs@vger.kernel.org
Subject: Re: [PATCH v16 03/13] overlayfs: Implement splice-read
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Date:   Wed, 08 Mar 2023 15:54:36 +0000
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Miklos Szeredi <miklos@szeredi.hu> wrote:

> > +       ret =3D -EINVAL;
> > +       if (!real.file->f_op->splice_read)
> > +               goto out_fdput;
> > +
> > +       ret =3D rw_verify_area(READ, real.file, ppos, len);
> > +       if (unlikely(ret < 0))
> > +               goto out_fdput;
> > +
> > +       old_cred =3D ovl_override_creds(file_inode(in)->i_sb);
> > +       ret =3D real.file->f_op->splice_read(real.file, ppos, pipe, le=
n, flags);
> =

> I don't think you replied to my suggestion of using a helper here.
> E.g. it could be as simple as exporting do_splice_to(), or renaming it
> to vfs_splice_read() to be more readable.  It would remove the
> boilerplate and be more robust if any changes are done to the splice
> reading code.

Using do_splice_to() as a helper is probably a good idea, though both Will=
y
and Christoph seem to dislike it.

The pipe occupancy check has already been done, so I'm not sure if it shou=
ld
be repeated - though it probably wouldn't hurt.

David