|
 |
981c2a |
From: Martin Wilck <mwilck@suse.com>
|
|
|
981c2a |
Date: Mon, 20 Apr 2020 22:29:09 +0200
|
|
|
981c2a |
Subject: dm mpath: switch paths in dm_blk_ioctl() code path
|
|
|
981c2a |
Patch-mainline: v5.8-rc1
|
|
|
981c2a |
Git-commit: 2361ae595352dec015d14292f1b539242d8446d6
|
|
|
981c2a |
References: bsc#1167574, bsc#1175995, bsc#1184485
|
|
|
981c2a |
|
|
|
981c2a |
SCSI LUN passthrough code such as qemu's "scsi-block" device model
|
|
|
981c2a |
pass every IO to the host via SG_IO ioctls. Currently, dm-multipath
|
|
|
981c2a |
calls choose_pgpath() only in the block IO code path, not in the ioctl
|
|
|
981c2a |
code path (unless current_pgpath is NULL). This has the effect that no
|
|
|
981c2a |
path switching and thus no load balancing is done for SCSI-passthrough
|
|
|
981c2a |
IO, unless the active path fails.
|
|
|
981c2a |
|
|
|
981c2a |
Fix this by using the same logic in multipath_prepare_ioctl() as in
|
|
|
981c2a |
multipath_clone_and_map().
|
|
|
981c2a |
|
|
|
981c2a |
Note: The allegedly best path selection algorithm, service-time,
|
|
|
981c2a |
still wouldn't work perfectly, because the io size of the current
|
|
|
981c2a |
request is always set to 0. Changing that for the IO passthrough
|
|
|
981c2a |
case would require the ioctl cmd and arg to be passed to dm's
|
|
|
981c2a |
prepare_ioctl() method.
|
|
|
981c2a |
|
|
|
981c2a |
Signed-off-by: Martin Wilck <mwilck@suse.com>
|
|
|
981c2a |
Reviewed-by: Hannes Reinecke <hare@suse.de>
|
|
|
981c2a |
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
|
|
|
981c2a |
---
|
|
|
981c2a |
drivers/md/dm-mpath.c | 2 +-
|
|
|
981c2a |
1 file changed, 1 insertion(+), 1 deletion(-)
|
|
|
981c2a |
|
|
|
981c2a |
--- a/drivers/md/dm-mpath.c
|
|
|
981c2a |
+++ b/drivers/md/dm-mpath.c
|
|
|
981c2a |
@@ -1862,7 +1862,7 @@ static int multipath_prepare_ioctl(struc
|
|
|
981c2a |
int r;
|
|
|
981c2a |
|
|
|
981c2a |
current_pgpath = READ_ONCE(m->current_pgpath);
|
|
|
981c2a |
- if (!current_pgpath)
|
|
|
981c2a |
+ if (!current_pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
|
|
|
981c2a |
current_pgpath = choose_pgpath(m, 0);
|
|
|
981c2a |
|
|
|
981c2a |
if (current_pgpath) {
|