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Commit Graph

8 Commits

Author SHA1 Message Date
Bryn M. Reeves
b5252a51a5 dmfilemapd: pass correct dirp to closedir() 2017-03-29 16:54:44 +01:00
Bryn M. Reeves
481a522dd7 dmfilemapd: do not closdir(pid_d) unless it is open 2017-03-29 16:48:32 +01:00
Bryn M. Reeves
d71071a1af dmfilemapd: log closedir errors with log_sys_error() 2017-03-29 16:04:15 +01:00
Bryn M. Reeves
77a7ed065f dmfilemapd: ensure path argument is absolute
Require that the path argument to dmfilemapd be an absolute path
and document this in tool output, libdevmapper.h and dmfilemapd.8.

The check is also enforced by dm_stats_start_filemapd() to avoid
forking a new process with an invalid path argument.
2017-03-13 11:44:05 +00:00
Bryn M. Reeves
9b0aba5fe9 dmfilemapd: return error for wrong number of args
The initial check on argc incorrectly returns 1 when the wrong
number of arguments are present, causing a segfault in main()
when no arguments are given:

  # dmfilemapd
  Wrong number of arguments.
  usage: dmfilemapd <fd> <group_id> <path> <mode> [<foreground>[<log_level>]]
  Segmentation fault (core dumped)
2017-03-13 11:09:11 +00:00
Bryn M. Reeves
a9341b18ef daemons: use DEFAULT_PROC_DIR in dmfilemapd
Include defaults.h and use it to obtain the default procfs mount
point in dmfilemapd.
2017-03-10 17:26:47 +00:00
Bryn M. Reeves
1ba11aa7ee dmfilemapd: always set the program_id after listing regions
The filemap daemon takes its program_id from the regions it is
managing: use DM_STATS_ALL_PROGRAMS when retrieving an initial
listing and then obtain the correct program_id from the group
leader.
2017-03-09 21:20:27 +00:00
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