1 Commits

Author	SHA1	Message	Date
Bryn M. Reeves	8b78982297	daemons: add dmfilemapd ... Add a daemon that can be launched to monitor a group of regions corresponding to the extents of a file, and to update the regions as the file's allocation changes. The daemon is intended to be started from a library interface, but can also be run from the command line: dmfilemapd <fd> <group_id> <path> <mode> [<foreground>[<log_level>]] Where fd is a file descriptor open on the mapped file, group_id is the group identifier of the mapped group and mode is either "inode" or "path". E.g.: # dmfilemapd 3 0 vm.img inode 1 3 3<vm.img ... If foreground is non-zero, the daemon will not fork to run in the background. If verbose is non-zero, libdm and daemon log messages will be printed. It is possible for the group identifier to change when regions are re-mapped: this occurs when the group leader is deleted (regroup=1 in dm_stats_update_regions_from_fd()), and another region is created before the daemon has a chance to recreate the leader region. The operation is inherently racey since there is currently no way to atomically move or resize a dm_stats region while retaining its region_id. Detect this condition and update the group_id value stored in the filemap monitor. A function is also provided in the the stats API to launch the filemap monitoring daemon: int dm_stats_start_filemapd(int fd, uint64_t group_id, const char *path, dm_filemapd_mode_t mode, unsigned foreground, unsigned verbose); This carries out the first fork and execs dmfilemapd with the arguments specified. A dm_filemapd_mode_t value is specified by the mode argument: either DM_FILEMAPD_FOLLOW_INODE, or DM_FILEMAPD_FOLLOW_PATH. A helper function, dm_filemapd_mode_from_string(), is provided to parse a string containing a valid mode name into the appropriate dm_filemapd_mode_t value.	2017-03-09 18:50:15 +00:00