[$] A mapping layer for filesystems

<p>In a plenary session on the second day of the Linux Storage, Filesystem,and Memory-Management Summit (LSFMM), Dave Chinner described his ideas fora virtual block address-space layer. It would allow "space accounting to beshared and managed at various layers in the storage stack". One of thetargets for this work is for filesystems on thin-provisioned devices, wherethe filesystem is larger than the storage devices holding it (and administrators areexpected to add storage as needed); in current systems, running out ofspace causes huge problems for filesystems and users because the filesystemcannot communicate that error in a usable fashion.