brassow When adding paths to the round-robin path selector, we expect to get a FIFO behavior. Instead, we get FILO. This can be especially bad if we specify a repeat count of 0, because it will result in us never getting the path we wanted. Here is an example of the problem: [root@neo-04 ~]# echo "0 1024 error" | dmsetup create error [root@neo-04 ~]# echo "0 1024 zero" | dmsetup create zero [root@neo-04 ~]# echo "0 1024 multipath 0 0 1 1 round-robin 0 2 1 /dev/mapper/error 0 /dev/mapper/zero 0" | dmsetup create mpath [root@neo-04 ~]# dd if=/dev/mapper/mpath of=/dev/null 1024+0 records in 1024+0 records out [root@neo-04 ~]# dmsetup status mpath 0 1024 multipath 1 0 0 1 1 A 0 2 0 253:2 A 0 253:3 A 0 [root@neo-04 ~]# dmsetup remove mpath [root@neo-04 ~]# echo "0 1024 multipath 0 0 1 1 round-robin 0 2 1 /dev/mapper/zero 0 /dev/mapper/error 0" | dmsetup create mpath [root@neo-04 ~]# dd if=/dev/mapper/mpath of=/dev/null 1024+0 records in 1024+0 records out [root@neo-04 ~]# dmsetup status mpath 0 1024 multipath 1 0 0 1 1 A 0 2 0 253:3 A 0 253:2 F 1 The problem stems from using 'list_add' where 'list_add_tail' should have been used. Index: linux-2.6.18.1/drivers/md/dm-round-robin.c =================================================================== --- linux-2.6.18.1.orig/drivers/md/dm-round-robin.c 2006-10-31 14:21:33.000000000 -0600 +++ linux-2.6.18.1/drivers/md/dm-round-robin.c 2006-11-01 12:41:13.000000000 -0600 @@ -136,7 +136,7 @@ static int rr_add_path(struct path_selec path->pscontext = pi; - list_add(&pi->list, &s->valid_paths); + list_add_tail(&pi->list, &s->valid_paths); return 0; } -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
