linux-kernel - Re: [PATCH 20/56] fs/ext4: support compiling out splice

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Date:	Thu, 13 Nov 2014 16:28:50 -0800
From:	josh@...htriplett.org
To:	Pieter Smith <pieter@...sman.nl>
Cc:	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	"open list:EXT4 FILE SYSTEM" <linux-ext4@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 20/56] fs/ext4: support compiling out splice

On Thu, Nov 13, 2014 at 10:22:57PM +0100, Pieter Smith wrote:
> Compile out splice support from ext4 when the splice-family of syscalls is not
> supported by the system (i.e. CONFIG_SYSCALL_SPLICE is undefined).
> 
> Signed-off-by: Pieter Smith <pieter@...sman.nl>

See below; you shouldn't need this or similar patches for most
filesystems at all.

>  fs/ext4/file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index aca7b24..c9d2962 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -595,8 +595,8 @@ const struct file_operations ext4_file_operations = {
>  	.open		= ext4_file_open,
>  	.release	= ext4_release_file,
>  	.fsync		= ext4_sync_file,
> -	.splice_read	= generic_file_splice_read,
> -	.splice_write	= iter_file_splice_write,
> +	SPLICE_READ_INIT(generic_file_splice_read)
> +	SPLICE_WRITE_INIT(iter_file_splice_write)

You can just define iter_file_splice_write as NULL when configuring out
splice.  You could almost do the same for generic_file_splice_read, but
a couple of implementations of filesystem-specific splice functions
actually call it; you can make it a no-op static inline, though.

- Josh Triplett
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