Christophe,
This patch to dm_simplecmd of
multipath-tools/libmultipath/devmapper.c will
disable the use of lock_fs during I/O suspension while
changing dm-multipath
device mapper maps via the DM_DEVICE_RESUME ioctl of
libdevmapper.
Disabling lock_fs will result in not flushing I/O to the
dm-multipath block
device before changing the maps for the mapped device.
Flushing I/O at this
time appears not only unnecessary for dm-multipath devices
but causes some
troublesome delays due to SCSI HBA driver target-side
timeouts when these
maps are changed as a result of paths coming and going while
upgrading
software (a non-disruptive ucode upgrade) on a storage
system.
As is the case for any change which is dependent on similar
changes in
libdevmapper and the kernel, this patch will introduce a
dependency on
libdevmapper and kernel. Not sure which versions first had
this support but
at least libdevmapper 1.02.02 and linux kernel version
2.6.18-rc2 have the
required support.
diff --git a/libmultipath/devmapper.c
b/libmultipath/devmapper.c
index c0765ae..67c7740 100644
--- a/libmultipath/devmapper.c
+++ b/libmultipath/devmapper.c
 -105,6
+105,7 dm_simplecmd (int task, const char *name
goto out;
dm_task_no_open_count(dmt);
+ dm_task_skip_lockfs(dmt); /* for DM_DEVICE_RESUME */
r = dm_task_run (dmt);
-183,6
+184,41 out:
}
Thanks,
Ed
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