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author | Tejun Heo <tj@kernel.org> | 2016-03-08 11:51:26 -0500 |
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committer | Tejun Heo <tj@kernel.org> | 2016-03-08 11:51:26 -0500 |
commit | e4857982f49d21c05a84351b56724bf353022355 (patch) | |
tree | dc2e6039b714635e36ab148ed1ef20a9cbb01f4a /kernel/cgroup.c | |
parent | 37ff9f8f474216d0cfca7565a4e0caa521ee6e7e (diff) | |
download | linux-stable-e4857982f49d21c05a84351b56724bf353022355.tar.gz linux-stable-e4857982f49d21c05a84351b56724bf353022355.tar.bz2 linux-stable-e4857982f49d21c05a84351b56724bf353022355.zip |
cgroup: use css_set->mg_dst_cgrp for the migration target cgroup
Migration can be multi-target on the default hierarchy when a
controller is enabled - processes belonging to each child cgroup have
to be moved to the child cgroup itself to refresh css association.
This isn't a problem for cgroup_migrate_add_src() as each source
css_set still maps to single source and target cgroups; however,
cgroup_migrate_prepare_dst() is called once after all source css_sets
are added and thus might not have a single destination cgroup. This
is currently worked around by specifying NULL for @dst_cgrp and using
the source's default cgroup as destination as the only multi-target
migration in use is self-targetting. While this works, it's subtle
and clunky.
As all taget cgroups are already specified while preparing the source
css_sets, this clunkiness can easily be removed by recording the
target cgroup in each source css_set. This patch adds
css_set->mg_dst_cgrp which is recorded on cgroup_migrate_src() and
used by cgroup_migrate_prepare_dst(). This also makes migration code
ready for arbitrary multi-target migration.
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r-- | kernel/cgroup.c | 26 |
1 files changed, 13 insertions, 13 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 5dd761355033..fbd3e99a4e98 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2473,6 +2473,7 @@ static void cgroup_migrate_finish(struct list_head *preloaded_csets) spin_lock_bh(&css_set_lock); list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) { cset->mg_src_cgrp = NULL; + cset->mg_dst_cgrp = NULL; cset->mg_dst_cset = NULL; list_del_init(&cset->mg_preload_node); put_css_set_locked(cset); @@ -2511,32 +2512,31 @@ static void cgroup_migrate_add_src(struct css_set *src_cset, return; WARN_ON(src_cset->mg_src_cgrp); + WARN_ON(src_cset->mg_dst_cgrp); WARN_ON(!list_empty(&src_cset->mg_tasks)); WARN_ON(!list_empty(&src_cset->mg_node)); src_cset->mg_src_cgrp = src_cgrp; + src_cset->mg_dst_cgrp = dst_cgrp; get_css_set(src_cset); list_add(&src_cset->mg_preload_node, preloaded_csets); } /** * cgroup_migrate_prepare_dst - prepare destination css_sets for migration - * @dst_cgrp: the destination cgroup (may be %NULL) * @preloaded_csets: list of preloaded source css_sets * - * Tasks are about to be moved to @dst_cgrp and all the source css_sets - * have been preloaded to @preloaded_csets. This function looks up and - * pins all destination css_sets, links each to its source, and append them - * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each - * source css_set is assumed to be its cgroup on the default hierarchy. + * Tasks are about to be moved and all the source css_sets have been + * preloaded to @preloaded_csets. This function looks up and pins all + * destination css_sets, links each to its source, and append them to + * @preloaded_csets. * * This function must be called after cgroup_migrate_add_src() has been * called on each migration source css_set. After migration is performed * using cgroup_migrate(), cgroup_migrate_finish() must be called on * @preloaded_csets. */ -static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, - struct list_head *preloaded_csets) +static int cgroup_migrate_prepare_dst(struct list_head *preloaded_csets) { LIST_HEAD(csets); struct css_set *src_cset, *tmp_cset; @@ -2547,8 +2547,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, list_for_each_entry_safe(src_cset, tmp_cset, preloaded_csets, mg_preload_node) { struct css_set *dst_cset; - dst_cset = find_css_set(src_cset, - dst_cgrp ?: src_cset->dfl_cgrp); + dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp); if (!dst_cset) goto err; @@ -2561,6 +2560,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, */ if (src_cset == dst_cset) { src_cset->mg_src_cgrp = NULL; + src_cset->mg_dst_cgrp = NULL; list_del_init(&src_cset->mg_preload_node); put_css_set(src_cset); put_css_set(dst_cset); @@ -2657,7 +2657,7 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp, spin_unlock_bh(&css_set_lock); /* prepare dst csets and commit */ - ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets); + ret = cgroup_migrate_prepare_dst(&preloaded_csets); if (!ret) ret = cgroup_migrate(leader, threadgroup, dst_cgrp->root); @@ -2916,7 +2916,7 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp) spin_unlock_bh(&css_set_lock); /* NULL dst indicates self on default hierarchy */ - ret = cgroup_migrate_prepare_dst(NULL, &preloaded_csets); + ret = cgroup_migrate_prepare_dst(&preloaded_csets); if (ret) goto out_finish; @@ -4156,7 +4156,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from) cgroup_migrate_add_src(link->cset, to, &preloaded_csets); spin_unlock_bh(&css_set_lock); - ret = cgroup_migrate_prepare_dst(to, &preloaded_csets); + ret = cgroup_migrate_prepare_dst(&preloaded_csets); if (ret) goto out_err; |