[PATCH v4] xfs: Make fiemap works with sparse file.

[Tao Ma]

On 08/28/2010 03:46 AM, Alex Elder wrote:
> On Thu, 2010-06-17 at 16:53 +0800, Tao Ma wrote:
>> >  Hi Dave,
>> >  On 06/14/2010 08:29 PM, Dave Chinner wrote:
>>> >  >  I just had a thought - if you want to avoid holes being reported to
>>> >  >  fiemap, then add a BMV_IF_NO_HOLES flag to xfs_getbmap() and skip
>>> >  >  holes in the mappin gloop when this flag is set. That will make
>>> >  >  fiemap fill in the full number of extents without hacking the
>>> >  >  extent count...
>> >  Here is the updated one. I have used BVM_IF_NO_HOLES in xfs_getbmap
>> >  to skip increasing index 'cur_ext'. It is a bit ugly, see my commit
>> >  log. I guess maybe we can add another flag in xfs_bmapi so that it
>> >  don't even give us the holes?
> Dave said he would commit this but it hasn't been done
> yet, so there's still time to comment!
yeah, it is never late. ;)
> 
> . . .
> 
>> >  diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
>> >  index 99587de..d49107d 100644
>> >  --- a/fs/xfs/xfs_bmap.c
>> >  +++ b/fs/xfs/xfs_bmap.c
>> >  @@ -5744,12 +5744,24 @@ xfs_getbmap(
>> >    					map[i].br_startblock))
>> >    				goto out_free_map;
>> >  
>> >  -			nexleft--;
>> >    			bmv->bmv_offset =
>> >    				out[cur_ext].bmv_offset +
>> >    				out[cur_ext].bmv_length;
>> >    			bmv->bmv_length =
>> >    				max_t(__int64_t, 0, bmvend - bmv->bmv_offset);
>> >  +
>> >  +			/*
>> >  +			 * In case we don't want to return the hole,
>> >  +			 * don't increase cur_ext so that we can reuse
>> >  +			 * it in the next loop.
>> >  +			 */
>> >  +			if ((iflags&  BMV_IF_NO_HOLES)&&
>> >  +			    out[cur_ext].bmv_block == -1LL) {
> I personally would prefer this to use:
> 		if ((iflags&  BMV_IF_NO_HOLES)&&
> 			map[i].br_startblock == HOLESTARTBLOCK) {
> 
> I think this is more obvious that this "extent" represents
> a hole (as opposed to bmv_block == -1, which is how
> xfs_getbmapx_fix_eof_hole() encodes this).
> 
> Otherwise looks good.
OK, I have updated the patch and attached it. So could you please send
it to Linus?

Regards,
Tao