Re: [PATCH 02/31] fs: add new vfs_poll and file_can_poll helpers

[Christoph Hellwig <hch@lst.de>]

On Sat, Jan 06, 2018 at 07:08:53PM +0000, Al Viro wrote:
> On Thu, Jan 04, 2018 at 09:00:14AM +0100, Christoph Hellwig wrote:
> > These abstract out calls to the poll method in preparation for changes to
> > those methods.
> 
> FWIW, I would make vfs_poll()
> 
> static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
> {
> 	if (unlikely(!file->f_op->poll))
> 		return DEFAULT_POLLMASK;
> 	return file->f_op->poll(file, pt);
> }
> 
> That's safe for any struct file, some of the callers already do just that,
> the ones that have vfs_poll() under the check for file_can_poll() will
> simply optimize that piece away and the few that rely upon the knowledge
> of file_operations they are dealing with (vhost, etc.) can bloody well
> cope with the cost of the check.

Sure, works for me.