Re: [PATCH v5] fuse: O_DIRECT support for files

[Jeff Moyer <jmoyer@redhat.com>]

Anand Avati <avati@redhat.com> writes:

> Implement ->direct_IO() method in aops. The ->direct_IO() method combines
> the existing fuse_direct_read/fuse_direct_write methods to implement
> O_DIRECT functionality.
>
> Reaching ->direct_IO() in the read path via generic_file_aio_read ensures
> proper synchronization with page cache with its existing framework.
>
> Reaching ->direct_IO() in the write path via fuse_file_aio_write is made
> to come via generic_file_direct_write() which makes it play nice with
> the page cache w.r.t other mmap pages etc.
>
> On files marked 'direct_io' by the filesystem server, IO always follows
> the fuse_direct_read/write path. There is no effect of fcntl(O_DIRECT)
> and it always succeeds.
>
> On files not marked with 'direct_io' by the filesystem server, the IO
> path depends on O_DIRECT flag by the application. This can be passed
> at the time of open() as well as via fcntl().
>
> Note that asynchronous O_DIRECT iocb jobs are completed synchronously
> always (this has been the case with FUSE even before this patch)
>
> Signed-off-by: Anand Avati <avati@redhat.com>

Looks good to me.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>