[$] Block-device snapshots with blksnap

As a general rule, one need not have worked in the technology industry forlong before the value of good data backups becomes clear. Creating abackup that is truly good, though, can be a challenge if the filesystem inquestion is actively being changed while the backup process runs. Over theyears, various ways of addressing this problem have been developed, rangingfrom simply shutting down the system while backups run to a variety ofsnapshotting mechanisms. The kernel may be about to get another approachto snapshots should the blksnappatch set from Sergei Shtepa find its way into the mainline.