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From: Dave Chinner on 18 Jun 2010 02:30
On Fri, Jun 18, 2010 at 10:27:49AM +0800, Tao Ma wrote:
> >>This patch add a new parameter BMV_IF_NO_HOLES for bvm_iflags.
> >>So with this flags, we don't use our 'out' in xfs_getbmap for
> >>a hole. The solution is a bit ugly by just don't increasing
> >>index of 'out' vector. I felt that it is not easy to skip it
> >>at the very beginning since we have the complicated check and
> >>some function like xfs_getbmapx_fix_eof_hole to adjust 'out'.
> >
> >... because I think we can safely skip xfs_getbmapx_fix_eof_hole()
> >it only modifies the hole. Hence just adding a check after the
> >attribute fork end check (which needs to detect a hole to terminate)
> >should be fine: e.g something like:
> >
> > if (map[i].br_startblock == HOLESTARTBLOCK&&
> > whichfork == XFS_ATTR_FORK) {
> > /* came to the end of attribute fork */
> > out[cur_ext].bmv_oflags |= BMV_OF_LAST;
> > goto out_free_map;
> > }
> >+ if (map[i].br_startblock == HOLESTARTBLOCK&&
> >+ (iflags& BMV_IF_NO_HOLES)) {
> >+ memset(&out[cur_ext], 0, sizeof(out[cur_ext]));
> >+ continue;
> >+ }
> >
> >Should work and avoid the worst of the ugliness.
> I am afraid it doesn't work, at least from my test. It enters a dead loop.
> I think the root cause is that your change doesn't update bmv_offset
> and bmv_length for a hole. So in the large loop,

Yes, you are right - I didn't consider the outer loop termination
properly. My bad.

I'll add your patch to my qa list and move it onwards. Thanks.

Cheers,

Dave.
--
Dave Chinner
david(a)fromorbit.com
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