dm log: userspace add luid to distinguish between concurrent log instances
Device-mapper userspace logs (like the clustered log) are
identified by a universally unique identifier (UUID). This
identifier is used to associate requests from the kernel to
a specific log in userspace. The UUID must be unique everywhere,
since multiple machines may use this identifier when communicating
about a particular log, as is the case for cluster logs.
Sometimes, device-mapper/LVM may re-use a UUID. This is the
case during pvmoves, when moving from one segment of an LV
to another, or when resizing a mirror, etc. In these cases,
a new log is created with the same UUID and loaded in the
"inactive" slot. When a device-mapper "resume" is issued,
the "live" table is deactivated and the new "inactive" table
becomes "live". (The "inactive" table can also be removed
via a device-mapper 'clear' command.)
The above two issues were colliding. More than one log was being
created with the same UUID, and there was no way to distinguish
between them. So, sometimes the wrong log would be swapped
out during the exchange.
The solution is to create a locally unique identifier,
'luid', to go along with the UUID. This new identifier is used
to determine exactly which log is being referenced by the kernel
when the log exchange is made. The identifier is not
universally safe, but it does not need to be, since
create/destroy/suspend/resume operations are bound to a specific
machine; and these are the operations that make up the exchange.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-log-userspace-base.c b/drivers/md/dm-log-userspace-base.c
index c49da0a..6e186b1 100644
--- a/drivers/md/dm-log-userspace-base.c
+++ b/drivers/md/dm-log-userspace-base.c
@@ -21,6 +21,7 @@
struct dm_target *ti;
uint32_t region_size;
region_t region_count;
+ uint64_t luid;
char uuid[DM_UUID_LEN];
char *usr_argv_str;
@@ -63,7 +64,7 @@
* restored.
*/
retry:
- r = dm_consult_userspace(uuid, request_type, data,
+ r = dm_consult_userspace(uuid, lc->luid, request_type, data,
data_size, rdata, rdata_size);
if (r != -ESRCH)
@@ -74,14 +75,15 @@
set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout(2*HZ);
DMWARN("Attempting to contact userspace log server...");
- r = dm_consult_userspace(uuid, DM_ULOG_CTR, lc->usr_argv_str,
+ r = dm_consult_userspace(uuid, lc->luid, DM_ULOG_CTR,
+ lc->usr_argv_str,
strlen(lc->usr_argv_str) + 1,
NULL, NULL);
if (!r)
break;
}
DMINFO("Reconnected to userspace log server... DM_ULOG_CTR complete");
- r = dm_consult_userspace(uuid, DM_ULOG_RESUME, NULL,
+ r = dm_consult_userspace(uuid, lc->luid, DM_ULOG_RESUME, NULL,
0, NULL, NULL);
if (!r)
goto retry;
@@ -153,6 +155,9 @@
return -ENOMEM;
}
+ /* The ptr value is sufficient for local unique id */
+ lc->luid = (uint64_t)lc;
+
lc->ti = ti;
if (strlen(argv[0]) > (DM_UUID_LEN - 1)) {
@@ -172,7 +177,7 @@
}
/* Send table string */
- r = dm_consult_userspace(lc->uuid, DM_ULOG_CTR,
+ r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_CTR,
ctr_str, str_size, NULL, NULL);
if (r == -ESRCH) {
@@ -182,7 +187,7 @@
/* Since the region size does not change, get it now */
rdata_size = sizeof(rdata);
- r = dm_consult_userspace(lc->uuid, DM_ULOG_GET_REGION_SIZE,
+ r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_GET_REGION_SIZE,
NULL, 0, (char *)&rdata, &rdata_size);
if (r) {
@@ -211,7 +216,7 @@
int r;
struct log_c *lc = log->context;
- r = dm_consult_userspace(lc->uuid, DM_ULOG_DTR,
+ r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_DTR,
NULL, 0,
NULL, NULL);
@@ -226,7 +231,7 @@
int r;
struct log_c *lc = log->context;
- r = dm_consult_userspace(lc->uuid, DM_ULOG_PRESUSPEND,
+ r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_PRESUSPEND,
NULL, 0,
NULL, NULL);
@@ -238,7 +243,7 @@
int r;
struct log_c *lc = log->context;
- r = dm_consult_userspace(lc->uuid, DM_ULOG_POSTSUSPEND,
+ r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_POSTSUSPEND,
NULL, 0,
NULL, NULL);
@@ -251,7 +256,7 @@
struct log_c *lc = log->context;
lc->in_sync_hint = 0;
- r = dm_consult_userspace(lc->uuid, DM_ULOG_RESUME,
+ r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_RESUME,
NULL, 0,
NULL, NULL);