Re: [PATCH v2] Btrfs: export btrfs space shared info to userspace

[Liu Bo <bo.li.liu@oracle.com>]

On Mon, Sep 16, 2013 at 10:55:17AM +0200, David Sterba wrote:
> On Mon, Sep 16, 2013 at 04:18:24PM +0800, Liu Bo wrote:
> > @@ -4122,7 +4136,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> >  		last = found_key.offset;
> >  		last_for_get_extent = last + 1;
> >  	}
> > -	btrfs_free_path(path);
> > +	btrfs_release_path(path);
> >  
> >  	/*
> >  	 * we might have some extents allocated but more delalloc past those
> > @@ -4192,7 +4206,24 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> >  			flags |= (FIEMAP_EXTENT_DELALLOC |
> >  				  FIEMAP_EXTENT_UNKNOWN);
> >  		} else {
> > +			unsigned long ref_cnt = 0;
> > +
> >  			disko = em->block_start + offset_in_extent;
> > +
> > +			/*
> > +			 * As btrfs supports shared space, this information
> > +			 * can be exported to userspace tools via
> > +			 * flag FIEMAP_EXTENT_SHARED.
> > +			 */
> > +			ret = iterate_inodes_from_logical(
> > +					em->block_start,
> > +					BTRFS_I(inode)->root->fs_info,
> > +					path, count_ext_ref, &ref_cnt);
> > +			if (ret < 0)
> > +				goto out_free;
> > +
> > +			if (ref_cnt > 1)
> > +				flags |= FIEMAP_EXTENT_SHARED;
> >  		}
> >  		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
> >  			flags |= FIEMAP_EXTENT_ENCODED;
> > @@ -4226,6 +4257,7 @@ out_free:
> >  out:
> >  	unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
> >  			     &cached_state, GFP_NOFS);
> > +	btrfs_free_path(path);
> 
> I think this free_path should go before unlock_extent_cached, it's not
> needed for unlock_extent_cached itself and will delay unlocking the
> path unnecessarily (it's set to leave_spinning = 1).

Path has been released and unlocked inside iterate_inodes_from_logical() though.

But yeah, path is unrelevant with unlock_extent_cached(), it can be done
earlier.

-liubo

> 
> >  	return ret;
> >  }