linux-kernel - Re: [PATCH v4 6/6] block: Update blkdev_dax

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Date:	Tue, 10 May 2016 12:49:18 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Toshi Kani <toshi.kani@....com>
Cc:	Jan Kara <jack@...e.cz>, david <david@...morbit.com>,
	Al Viro <viro@...iv.linux.org.uk>, Jens Axboe <axboe@...com>,
	Christoph Hellwig <hch@...radead.org>,
	Boaz Harrosh <boaz@...xistor.com>,
	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	micah.parrish@....com,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-block@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Vishal L Verma <vishal.l.verma@...el.com>
Subject: Re: [PATCH v4 6/6] block: Update blkdev_dax_capable() for consistency

On Tue, May 10, 2016 at 9:23 AM, Toshi Kani <toshi.kani@....com> wrote:
> blkdev_dax_capable() is similar to bdev_dax_supported(), but needs
> to remain as a separate interface for checking dax capability of
> a raw block device.
>
> Rename and relocate blkdev_dax_capable() to keep them maintained
> consistently, and call bdev_direct_access() for the dax capability
> check.
>
> There is no change in the behavior.
>
> Link: https://lkml.org/lkml/2016/5/9/950
> Signed-off-by: Toshi Kani <toshi.kani@....com>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Jens Axboe <axboe@...com>
> Cc: Andreas Dilger <adilger.kernel@...ger.ca>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Dave Chinner <david@...morbit.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Boaz Harrosh <boaz@...xistor.com>
> ---
>  block/ioctl.c          |   30 ------------------------------
>  fs/block_dev.c         |   39 +++++++++++++++++++++++++++++++++++++--
>  include/linux/blkdev.h |    1 +
>  include/linux/fs.h     |    8 --------
>  4 files changed, 38 insertions(+), 40 deletions(-)
>
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 4ff1f92..7eeda07 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -4,7 +4,6 @@
>  #include <linux/gfp.h>
>  #include <linux/blkpg.h>
>  #include <linux/hdreg.h>
> -#include <linux/badblocks.h>
>  #include <linux/backing-dev.h>
>  #include <linux/fs.h>
>  #include <linux/blktrace_api.h>
> @@ -407,35 +406,6 @@ static inline int is_unrecognized_ioctl(int ret)
>                 ret == -ENOIOCTLCMD;
>  }
>
> -#ifdef CONFIG_FS_DAX
> -bool blkdev_dax_capable(struct block_device *bdev)
> -{
> -       struct gendisk *disk = bdev->bd_disk;
> -
> -       if (!disk->fops->direct_access)
> -               return false;
> -
> -       /*
> -        * If the partition is not aligned on a page boundary, we can't
> -        * do dax I/O to it.
> -        */
> -       if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512))
> -                       || (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
> -               return false;
> -
> -       /*
> -        * If the device has known bad blocks, force all I/O through the
> -        * driver / page cache.
> -        *
> -        * TODO: support finer grained dax error handling
> -        */
> -       if (disk->bb && disk->bb->count)
> -               return false;
> -
> -       return true;
> -}
> -#endif

This will collide with my pending change to revert raw block device
dax support, and also with Vishal's DAX error handling changes.  For
coordination purposes I'm thining this should all go on top of the
branch that Vishal is putting together with the dax zeroing changes
from Jan and Christoph as well.