On Fri, Sep 24, 2021 at 06:18:14PM +0100, David Howells wrote: > Rather than depending on .direct_IO to point to something to indicate that > direct I/O is supported, add a 'supports' bitmask that we can test, since > we only need one bit. Why would you add mapping->aops->supports instead of using one of the free bits in mapping->flags? enum mapping_flags in pagemap.h. It could also be a per-fs flag, or per-sb flag, but it's fewer dereferences at check time if it's in mapping->flags.