Re: [PATCH][RFC] splice support

[Jeff Garzik <jeff@garzik.org>]

Jens Axboe wrote:

> index 509ccec..23e2c7c 100644
> --- a/fs/ext2/file.c
> +++ b/fs/ext2/file.c
> @@ -53,6 +53,8 @@ const struct file_operations ext2_file_o
>  	.readv		= generic_file_readv,
>  	.writev		= generic_file_writev,
>  	.sendfile	= generic_file_sendfile,
> +	.splice_read	= generic_file_splice_read,
> +	.splice_write	= generic_file_splice_write,
>  };
>  
>  #ifdef CONFIG_EXT2_FS_XIP
> diff --git a/fs/ext3/file.c b/fs/ext3/file.c
> index 783a796..1efefb6 100644
> --- a/fs/ext3/file.c
> +++ b/fs/ext3/file.c
> @@ -119,6 +119,8 @@ const struct file_operations ext3_file_o
>  	.release	= ext3_release_file,
>  	.fsync		= ext3_sync_file,
>  	.sendfile	= generic_file_sendfile,
> +	.splice_read	= generic_file_splice_read,
> +	.splice_write	= generic_file_splice_write,

> +static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
> +			   unsigned long flags)
> +{
> +	if (out->f_op && out->f_op->splice_write)
> +		return out->f_op->splice_write(pipe, out, len, flags);

1) What are the consequences of doing

	if (f_op->splice_write)
		f_op->splice_write(...);
	else
		generic_file_splice_write(...);

to cause sys_splice() to default to supported?

2) Do you really have to test f_op itself for NULL?  Is that a stealth 
closed-file check or something?  I would be surprised if f_op was ever 
really NULL.

	Jeff