Subject: Re: [fuse-devel] [PATCH 4/6] fs/fuse: support compiling out splice

From: Pieter Smith <[email-masked]>
Date: Mon, 24 Nov 2014 10:49:31 +0100

On Sun, Nov 23, 2014 at 03:23:02PM -0800, Josh Triplett wrote:
> On Sun, Nov 23, 2014 at 11:29:08PM +0100, Richard Weinberger wrote:
> > On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith <[email-masked]> 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 <[email-masked]>
> > > ---
> > >  fs/fuse/dev.c      | 4 ++--
> > >  include/linux/fs.h | 6 ++++++
> > >  2 files changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > > index ca88731..f8f92a4 100644
> > > --- a/fs/fuse/dev.c
> > > +++ b/fs/fuse/dev.c
> > > @@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
> > >         return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
> > >  }
> > >
> > > -static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > +static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > >                                     struct pipe_inode_info *pipe,
> > >                                     size_t len, unsigned int flags)
> > >  {
> > > @@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
> > >         .llseek         = no_llseek,
> > >         .read           = do_sync_read,
> > >         .aio_read       = fuse_dev_read,
> > > -       .splice_read    = fuse_dev_splice_read,
> > > +       .splice_read    = __splice_p(fuse_dev_splice_read),
> > >         .write          = do_sync_write,
> > >         .aio_write      = fuse_dev_write,
> > >         .splice_write   = fuse_dev_splice_write,
> > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > index a957d43..04c0975 100644
> > > --- a/include/linux/fs.h
> > > +++ b/include/linux/fs.h
> > > @@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> > >                         int datasync);
> > >  extern void block_sync_page(struct page *page);
> > >
> > > +#ifdef CONFIG_SYSCALL_SPLICE
> > > +#define __splice_p(x) x
> > > +#else
> > > +#define __splice_p(x) NULL
> > > +#endif
> > > +
> > 
> > This needs to go into a different patch.
> > One logical change per patch please. :-)
> 
> Easy enough to merge this one into the patch introducing
> CONFIG_SYSCALL_SPLICE, then.
> 
> - Josh Triplett

The patch introducing CONFIG_SYSCALL_SPLICE (PATCH 3) only compiles out the
syscalls. PATCH 6 on the other hand, compiles out fs/splice.c. This patch
allows fs/fuse to be compiled when fs/splice.c is compiled out. If I am to
squash it, it would be logical to include it in PATCH 6, not 3.

Is this agreeable?

PATCH 5 does the same as this one for net/core. Should I still keep PATCH 5
separate from a maintainership perspective?

- Pieter Smith