dm mpath: add retry pg init
This patch allows a failed path group initialisation command to be retried.
It adds a generic MP_RETRY flag and a "pg_init_retries" feature to
device-mapper multipath which limits the number of retries.
1. A hw handler sends a path initialization command to the storage and
the command completes with an error code indicating the command
should be retried.
2. The hardware handler calls dm_pg_init_complete() with MP_RETRY
set in err_flags to ask the dm multipath core to retry.
3. If the retry limit has not been exceeded, pg_init() is retried.
Otherwise fail_path() is called.
If you are using the userspace multipath-tools or device-mapper-multipath
package, you can set pg_init_retries in the 'device' section of your
/etc/multipath.conf file. For example:
features "2 pg_init_retries 7"
The number of PG retries attempted is reported in the 'dmsetup status' output.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Acked-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-hw-handler.h b/drivers/md/dm-hw-handler.h
index e0832e6..46809dc 100644
--- a/drivers/md/dm-hw-handler.h
+++ b/drivers/md/dm-hw-handler.h
@@ -58,5 +58,6 @@
#define MP_FAIL_PATH 1
#define MP_BYPASS_PG 2
#define MP_ERROR_IO 4 /* Don't retry this I/O */
+#define MP_RETRY 8
#endif