Hi, This patch adds a 'du' subcommand to btrfs. 'btrfs fi du' will calculate disk usage of the target files using fiemap. For individual files, it will report a count of total bytes, and exclusive (not shared) bytes. We also calculate a 'set shared' value which is described below. Each argument to 'btrfs fi du' will have a 'set shared' value calculated for it. We define each 'set' as those files found by a recursive search of an argument to btrfs fi du. The 'set shared' value then is a sum of all shared space referenced by the set. 'set shared' takes into account overlapping shared extents, hence it isn't as simple as adding up shared extents. To efficiently find overlapping regions, we store them in an interval tree. When the scan of a file set is complete, we can walk the tree and calculate our actual shared bytes while also taking into account any duplicate or overlapping extents. The interval tree implementation is taken from Linux v4.0. I went ahead and made some small comment updates to rbtree.h and rbtree_augmented.h while I was importing this code as both are used by the interval tree and I needed to check for any code changes in those headers. Following this paragraph is a very simple example. I started with a clean btrfs fs in which i copied vmlinuz from /boot. I then made a snapshot of the fs root in 'snap1'. After the snapshot, I made a 2nd copy of vmlinuz into the main fs to give us some not-shared data. The output below shows a sum of all the space, and a 'set shared' with len exactly equal to that of the single shared file. # btrfs fi du . total exclusive set shared filename 76386304 0 ./vmlinuz 76386304 0 ./snap1/vmlinuz 76386304 0 ./snap1 0 0 ./vmlinuz.copy 152772608 0 76386304 . A git tree of the patches can be found here: https://github.com/markfasheh/btrfs-progs-patches/tree/du or if you prefer to pull: git pull https://github.com/markfasheh/btrfs-progs-patches du Comments/feedback appreciated. --Mark -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
