Okay. Let's go with that. So I have to put the handling in vfs_splice_read():
long vfs_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
...
if (unlikely(!in->f_op->splice_read))
return warn_unsupported(in, "read");
/*
* O_DIRECT and DAX don't deal with the pagecache, so we
* allocate a buffer, copy into it and splice that into the pipe.
*/
if ((in->f_flags & O_DIRECT) || IS_DAX(in->f_mapping->host))
return copy_splice_read(in, ppos, pipe, len, flags);
return in->f_op->splice_read(in, ppos, pipe, len, flags);
}
which leaves very little in generic_file_splice_read:
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
return 0;
if (unlikely(!len))
return 0;
return filemap_splice_read(in, ppos, pipe, len, flags);
}
so I wonder if the tests in generic_file_splice_read() can be folded into
vfs_splice_read(), pointers to generic_file_splice_read() be replaced with
pointers to filemap_splice_read() and generic_file_splice_read() just be
removed.
I suspect we can't quite do this because of the *ppos check - but I wonder if
that's actually necessary since filemap_splice_read() checks against
i_size... or if the check can be moved there if we definitely want to do it.
Certainly, the zero-length check can be done in vfs_splice_read().
David
