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metadata: add comments describing lock_args for lvmlockd

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This commit is contained in:
David Teigland 2015-07-09 15:14:19 -05:00
parent 841c3478fd
commit cb14bbdbc9
1 changed files with 40 additions and 0 deletions
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40
lib/format_text/import_vsn1.c
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@ -600,6 +600,25 @@ static int _read_lvnames(struct format_instance *fid __attribute__((unused)),
return 0;
}
/*
* The LV lock_args string is generated in lvmlockd, and the content
* depends on the lock_type.
*
* lock_type dlm does not use LV lock_args, so the LV lock_args field
* is just set to "dlm".
*
* lock_type sanlock uses the LV lock_args field to save the
* location on disk of that LV's sanlock lock. The disk name is
* specified in the VG lock_args. The lock_args string begins
* with a version number, e.g. 1.0.0, followed by a colon, followed
* by a number. The number is the offset on disk where sanlock is
* told to find the LV's lock.
* e.g. lock_args = 1.0.0:70254592
* means that the lock is located at offset 70254592.
*
* The lvmlockd code for each specific lock manager also validates
* the lock_args before using it to access the lock manager.
*/
if (dm_config_get_str(lvn, "lock_args", &str)) {
if (!(lv->lock_args = dm_pool_strdup(mem, str)))
return_0;
@ -828,6 +847,27 @@ static struct volume_group *_read_vg(struct format_instance *fid,
goto bad;
}
/*
* The VG lock_args string is generated in lvmlockd, and the content
* depends on the lock_type. lvmlockd begins the lock_args string
* with a version number, e.g. 1.0.0, followed by a colon, followed
* by a string that depends on the lock manager. The string after
* the colon is information needed to use the lock manager for the VG.
*
* For sanlock, the string is the name of the internal LV used to store
* sanlock locks. lvmlockd needs to know where the locks are located
* so it can pass that location to sanlock which needs to access the locks.
* e.g. lock_args = 1.0.0:lvmlock
* means that the locks are located on the the LV "lvmlock".
*
* For dlm, the string is the dlm cluster name. lvmlockd needs to use
* a dlm lockspace in this cluster to use the VG.
* e.g. lock_args = 1.0.0:foo
* means that the host needs to be a member of the cluster "foo".
*
* The lvmlockd code for each specific lock manager also validates
* the lock_args before using it to access the lock manager.
*/
if (dm_config_get_str(vgn, "lock_args", &str)) {
if (!(vg->lock_args = dm_pool_strdup(vg->vgmem, str)))
goto bad;