Re: [PATCH v7 05/14] ext4, dax: introduce ext4_dax_aops

Jan Kara
2018-03-29T15:40:39Z

On Wed 21-03-18 15:57:37, Dan Williams wrote:
> In preparation for the dax implementation to start associating dax pages
> to inodes via page->mapping, we need to provide a 'struct
> address_space_operations' instance for dax. Otherwise, direct-I/O
> triggers incorrect page cache assumptions and warnings.
>
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> Cc: linux-ext4@vger.kernel.org
> Cc: Jan Kara <jack@suse.cz>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Looks good, just one nit below.

> @@ -3946,6 +3961,13 @@ static const struct address_space_operations ext4_da_aops = {
> .error_remove_page = generic_error_remove_page,
> };
>
> +static const struct address_space_operations ext4_dax_aops = {
> + .direct_IO = ext4_direct_IO,

So ext4_direct_IO() for IS_DAX() files will just bail out. So could you
just provide ext4_dax_direct_IO() which will bail out and use it here? With
a similar comment as in xfs_vm_direct_IO() that open still needs this
method set... Thanks!

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR