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Re: [PATCH v5 13/17] dax: dax_iomap_fault() needs to call iomap_end()

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On Fri 07-10-16 15:09:00, Ross Zwisler wrote:
> Currently iomap_end() doesn't do anything for DAX page faults for both ext2
> and XFS.  ext2_iomap_end() just checks for a write underrun, and
> xfs_file_iomap_end() checks to see if it needs to finish a delayed
> allocation.  However, in the future iomap_end() calls might be needed to
> make sure we have balanced allocations, locks, etc.  So, add calls to
> iomap_end() with appropriate error handling to dax_iomap_fault().
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Suggested-by: Jan Kara <jack@suse.cz>
...
> @@ -1239,6 +1253,17 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
>  		break;
>  	}
>  
> + finish_iomap:
> +	if (ops->iomap_end) {
> +		if (error) {
> +			/* keep previous error */
> +			ops->iomap_end(inode, pos, PAGE_SIZE, PAGE_SIZE, flags,
> +					&iomap);

I think for the error case we should set number of 'written' bytes to 0 to
tell fs to cancel what it has prepared. This is mostly cosmetic since the
only case where I can imagine this would matter is shared write fault and
in that case we have currently no error path but still it could bite us in
the future.

Other than that the patch looks good so you can add:

Reviewed-by: Jan Kara <jack@suse.cz>

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

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[PATCH v5 00/17] re-enable DAX PMD support Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:10 +0200
  [PATCH v5 07/17] dax: remove the last BUG_ON() from fs/dax.c Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:10 +0200
    Re: [PATCH v5 07/17] dax: remove the last BUG_ON() from fs/dax.c Jan Kara <jack@suse.cz> - 2016-10-11 21:00 +0200
  [PATCH v5 04/17] ext2: remove support for DAX PMD faults Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
  [PATCH v5 01/17] ext4: allow DAX writeback for hole punch Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
  [PATCH v5 12/17] dax: add dax_iomap_sector() helper function Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 12/17] dax: add dax_iomap_sector() helper function Christoph Hellwig <hch@lst.de> - 2016-10-10 17:50 +0200
    Re: [PATCH v5 12/17] dax: add dax_iomap_sector() helper function Jan Kara <jack@suse.cz> - 2016-10-11 20:50 +0200
  [PATCH v5 13/17] dax: dax_iomap_fault() needs to call iomap_end() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 13/17] dax: dax_iomap_fault() needs to call         iomap_end() Christoph Hellwig <hch@lst.de> - 2016-10-10 18:00 +0200
      Re: [PATCH v5 13/17] dax: dax_iomap_fault() needs to call iomap_end() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-11 00:10 +0200
    Re: [PATCH v5 13/17] dax: dax_iomap_fault() needs to call iomap_end() Jan Kara <jack@suse.cz> - 2016-10-11 20:50 +0200
  [PATCH v5 16/17] xfs: use struct iomap based DAX PMD fault path Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 16/17] xfs: use struct iomap based DAX PMD fault path Jan Kara <jack@suse.cz> - 2016-10-11 20:50 +0200
  [PATCH v5 08/17] dax: consistent variable naming for DAX entries Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
  [PATCH v5 05/17] ext2: return -EIO on ext2_iomap_end() failure Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 05/17] ext2: return -EIO on ext2_iomap_end() failure Jan Kara <jack@suse.cz> - 2016-10-11 21:00 +0200
  [PATCH v5 03/17] dax: remove buffer_size_valid() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
  [PATCH v5 09/17] dax: coordinate locking for offsets in PMD range Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 09/17] dax: coordinate locking for offsets in PMD         range Christoph Hellwig <hch@lst.de> - 2016-10-10 17:50 +0200
    Re: [PATCH v5 09/17] dax: coordinate locking for offsets in PMD range Jan Kara <jack@suse.cz> - 2016-10-11 20:50 +0200
      Re: [PATCH v5 09/17] dax: coordinate locking for offsets in PMD range Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-11 23:20 +0200
  [PATCH v5 02/17] ext4: tell DAX the size of allocation holes Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
  [PATCH v5 11/17] dax: correct dax iomap code namespace Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 11/17] dax: correct dax iomap code namespace Christoph Hellwig <hch@lst.de> - 2016-10-09 17:30 +0200
      [PATCH] dax: correct dax iomap code namespace Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-10 21:10 +0200
        Re: [PATCH] dax: correct dax iomap code namespace Dave Chinner <david@fromorbit.com> - 2016-10-10 22:50 +0200
  [PATCH v5 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
  [PATCH v5 14/17] dax: move RADIX_DAX_* defines to dax.h Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 14/17] dax: move RADIX_DAX_* defines to dax.h Christoph Hellwig <hch@lst.de> - 2016-10-10 18:00 +0200
    Re: [PATCH v5 14/17] dax: move RADIX_DAX_* defines to dax.h Jan Kara <jack@suse.cz> - 2016-10-11 20:50 +0200
  [PATCH v5 10/17] dax: remove dax_pmd_fault() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
  [PATCH v5 15/17] dax: add struct iomap based DAX PMD support Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-07 23:20 +0200
    Re: [PATCH v5 15/17] dax: add struct iomap based DAX PMD support Christoph Hellwig <hch@lst.de> - 2016-10-10 18:00 +0200
      Re: [PATCH v5 15/17] dax: add struct iomap based DAX PMD support Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-11 00:10 +0200
      Re: [PATCH v5 15/17] dax: add struct iomap based DAX PMD support Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-11 23:50 +0200
    Re: [PATCH v5 15/17] dax: add struct iomap based DAX PMD support Jan Kara <jack@suse.cz> - 2016-10-11 21:00 +0200
      Re: [PATCH v5 15/17] dax: add struct iomap based DAX PMD support Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-12 01:00 +0200
        Re: [PATCH v5 15/17] dax: add struct iomap based DAX PMD support Jan Kara <jack@suse.cz> - 2016-10-12 09:50 +0200

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