[PATCH v1 19/23] cachefiles: implement .demand_read() for demand read

[Matthew Wilcox]

On Wed, Jan 12, 2022 at 05:02:13PM +0800, JeffleXu wrote:
> I'm afraid IDR can't be replaced by xarray here. Because we need an 'ID'
> for each pending read request, so that after fetching data from remote,
> user daemon could notify kernel which read request has finished by this
> 'ID'.
> 
> Currently this 'ID' is get from idr_alloc(), and actually identifies the
> position of corresponding read request inside the IDR tree. I can't find
> similar API of xarray implementing similar function, i.e., returning an
> 'ID'.

xa_alloc().