From: Angelo Ruocco <angeloruocco90@xxxxxxxxx> Many userspace tools and services use the proportional-share policy of the blkio/io cgroups controller. The CFQ I/O scheduler implemented this policy for the legacy block layer. To modify the weight of a group in case CFQ was in charge, the 'weight' parameter of the group must be modified. On the other hand, the BFQ I/O scheduler implements the same policy in blk-mq, but, with BFQ, the parameter to modify has a different name: bfq.weight (forced choice until legacy block was present, because two different policies cannot share a common parameter in cgroups). Due to CFQ legacy, most if not all userspace configurations still use the parameter 'weight', and for the moment do not seem likely to be changed. But, when CFQ went away with legacy block, such a parameter ceased to exist. So, a simple workaround has been proposed [1] to make all configurations work: add a symlink, named weight, to bfq.weight. This commit adds such a symlink. [1] https://lkml.org/lkml/2019/4/8/555 Suggested-by: Johannes Thumshirn <jthumshirn@xxxxxxx> Signed-off-by: Angelo Ruocco <angeloruocco90@xxxxxxxxx> Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx> --- block/bfq-cgroup.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index b3796a40a61a..59f46904cb11 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -1046,7 +1046,8 @@ struct blkcg_policy blkcg_policy_bfq = { struct cftype bfq_blkcg_legacy_files[] = { { .name = "bfq.weight", - .flags = CFTYPE_NOT_ON_ROOT, + .link_name = "weight", + .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_SYMLINKED, .seq_show = bfq_io_show_weight, .write_u64 = bfq_io_set_weight_legacy, }, @@ -1166,7 +1167,8 @@ struct cftype bfq_blkcg_legacy_files[] = { struct cftype bfq_blkg_files[] = { { .name = "bfq.weight", - .flags = CFTYPE_NOT_ON_ROOT, + .link_name = "weight", + .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_SYMLINKED, .seq_show = bfq_io_show_weight, .write = bfq_io_set_weight, }, -- 2.20.1
