Does ZFS or UFS classify FS Metatada I/O requests with specific BIO_META like flag?

[Leo Prasath Arulraj]

Linux file systems pass down a metadata flag with block i/o requests so
that the device driver below the file system have this information.
This flag could be set on those block I/O requests that the file system
issues to file system metadata information like FS inodes, journal , block
allocation bitmaps etc. on the disk.

Examples:
1) Ext3: This thread here :
http://lists.linuxfoundation.org/pipermail/containers/2009-April/017126.html
 says ext3 file system sets this flag on metadata i/o requests so that it
is prioritized over data i/o requests in the I/O controller for the disk.

2) Ext4: This thread tells how ext4 tags all journal i/o with the metadata
flag : http://www.spinics.net/lists/linux-ext4/msg18213.html
3) XFS: This thread says XFS file system tags metadata I/O requests for
better merging: http://oss.sgi.com/pipermail/xfs/2009-November/004631.html



I want to know if the FreeBSD filesystem UFS and ZFS set any such flag.
>From a skim through the source code, it does not seem so because the bio
structure itself does not have any such flag in the first place :
http://fxr.watson.org/fxr/source/sys/bio.h?v=FREEBSD10#L143,144

I approciate any help regarding this.

Thanks,
Leo