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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <3088368.1603790984@warthog.procyon.org.uk> References: <3088368.1603790984@warthog.procyon.org.uk> <20200827150030.282762-3-hch@lst.de> <20200827150030.282762-1-hch@lst.de> To: Christoph Hellwig Cc: dhowells@redhat.com, Linus Torvalds , Al Viro , Michael Ellerman , x86@kernel.org, Kees Cook , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 02/10] fs: don't allow splice read/write without explicit ops MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3155817.1603792294.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Tue, 27 Oct 2020 09:51:34 +0000 Message-ID: <3155818.1603792294@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org David Howells wrote: > > default_file_splice_write is the last piece of generic code that uses > > set_fs to make the uaccess routines operate on kernel pointers. It > > implements a "fallback loop" for splicing from files that do not actua= lly > > provide a proper splice_read method. The usual file systems and other > > high bandwith instances all provide a ->splice_read, so this just remo= ves > > support for various device drivers and procfs/debugfs files. If splic= e > > support for any of those turns out to be important it can be added bac= k > > by switching them to the iter ops and using generic_file_splice_read. > = > Hmmm... this causes the copy_file_range() syscall to fail with EINVAL i= n some > places where before it used to work. > = > For my part, it causes the generic/112 xfstest to fail with afs, but the= re may > be other places. > = > Is this a regression we need to fix in the VFS core? Or is it something= we > need to fix in xfstests and assume userspace will fallback to doing it i= tself? That said, for afs at least, the fix seems to be just this: diff --git a/fs/afs/file.c b/fs/afs/file.c index 395075d7fe02..2bc6adfe351a 100644 --- a/fs/afs/file.c +++ b/fs/afs/file.c @@ -33,6 +33,7 @@ const struct file_operations afs_file_operations =3D { .write_iter =3D afs_file_write, .mmap =3D afs_file_mmap, .splice_read =3D generic_file_splice_read, + .splice_write =3D iter_file_splice_write, .fsync =3D afs_fsync, .lock =3D afs_lock, .flock =3D afs_flock, David