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

On Mon, Nov 24, 2014 at 10:49:31AM +0100, Pieter Smith wrote:

On Sun, Nov 23, 2014 at 03:23:02PM -0800, Josh Triplett wrote:

quoted

On Sun, Nov 23, 2014 at 11:29:08PM +0100, Richard Weinberger wrote:

quoted

On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith [off-list ref] wrote:

quoted

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 <redacted>
---
 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.

The suggestion wasn't to move the fs/fuse/dev.c bits; those should
definitely stay in this patch.  The suggestion was just to move the bit
of the patch defining __splice_p from this patch to patch 3.  (Note that
you need to define it before you use it, so it can't go in patch 6.)

- Josh Triplett