On Wed, 2016-05-11 at 10:15 +0200, Jan Kara wrote:
> On Tue 10-05-16 12:49:15, Vishal Verma wrote:
> >
> > In the truncate or hole-punch path in dax, we clear out sub-page
> > ranges.
> > If these sub-page ranges are sector aligned and sized, we can do the
> > zeroing through the driver instead so that error-clearing is handled
> > automatically.
> >
> > For sub-sector ranges, we still have to rely on clear_pmem and have
> > the
> > possibility of tripping over errors.
> >
> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> > Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> > Cc: Dave Chinner <david@xxxxxxxxxxxxx>
> > Cc: Jan Kara <jack@xxxxxxx>
> > Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> > Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> ...
>
> >
> > +static bool dax_range_is_aligned(struct block_device *bdev,
> > + Âstruct blk_dax_ctl *dax, unsigned
> > int offset,
> > + Âunsigned int length)
> > +{
> > + unsigned short sector_size = bdev_logical_block_size(bdev);
> > +
> > + if (!IS_ALIGNED(((u64)dax->addr + offset), sector_size))
> One more question: 'dax' is initialized in dax_zero_page_range() and
> dax->addr is going to be always NULL here. So either you forgot to
> call
> dax_map_atomic() to get the addr or the use of dax->addr is just bogus
> (which is what I currently believe since I see no way how the address
> could
> be unaligned with the sector_size)...
>
Good catch, and you're right. I don't think I actually even want to use
dax->addr for the alignment check here - I want to check if we're
aligned to the block device sector. I'm thinking something like:
if (!IS_ALIGNED(offset, sector_size))
Technically we want to check if sector * sector_size + offset is
aligned, but the first part of that is already a sector :)
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