linux-kernel - Re: [PATCH v5 4/7] fs/fuse: support compiling out splice

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Date:	Tue, 25 Nov 2014 12:49:16 -0800
From:	josh@...htriplett.org
To:	Pieter Smith <pieter@...sman.nl>
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	fuse-devel@...ts.sourceforge.net, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 4/7] fs/fuse: support compiling out splice

On Tue, Nov 25, 2014 at 08:42:42PM +0100, Pieter Smith wrote:
> On Tue, Nov 25, 2014 at 03:17:13PM +0100, Miklos Szeredi wrote:
> > [Trimming CC.  Please do the same for other patches.  I for one am not
> > interested in the general tinification discussion]
> > 
> > On Tue, Nov 25, 2014 at 08:19:39AM +0100, Pieter Smith wrote:
> > > To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
> > > struct is exported by fs/splice. The goal of the larger patch set is to
> > > completely compile out fs/splice, so uses of the exported struct need to be
> > > compiled out along with fs/splice.
> > > 
> > > This patch therefore compiles out splice support in fs/fuse when
> > > CONFIG_SYSCALL_SPLICE is undefined.
> > > 
> > > Signed-off-by: Pieter Smith <pieter@...sman.nl>
> > > ---
> > >  fs/fuse/dev.c | 9 +++++++--
> > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > > index ca88731..e984302 100644
> > > --- a/fs/fuse/dev.c
> > > +++ b/fs/fuse/dev.c
> > > @@ -1191,8 +1191,9 @@ __releases(fc->lock)
> > >   * request_end().  Otherwise add it to the processing list, and set
> > >   * the 'sent' flag.
> > >   */
> > > -static ssize_t fuse_dev_do_read(struct fuse_conn *fc, struct file *file,
> > > -				struct fuse_copy_state *cs, size_t nbytes)
> > > +static ssize_t __maybe_unused
> > > +fuse_dev_do_read(struct fuse_conn *fc, struct file *file,
> > > +		 struct fuse_copy_state *cs, size_t nbytes)
> > 
> > fuse_dev_do_read() is definitely going to remain used.  So no point in adding
> > __maybe_unused.
> 
> Off course, but at least gcc now also is aware that this is intentional and
> nicely refrains from nagging you with a warning.

GCC shouldn't be warning about an unused fuse_dev_do_read; please
recheck.  It will always get used by fuse_dev_read, which
unconditionally gets used in the .aio_read field of fuse_dev_operations.

- Josh Triplett
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