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author | Tejun Heo <tj@kernel.org> | 2014-04-23 11:13:16 -0400 |
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committer | Tejun Heo <tj@kernel.org> | 2014-04-23 11:13:16 -0400 |
commit | f817de98513d060023be4fa1d061b29a6515273e (patch) | |
tree | 5777f99dc477cd8e332358e9d284a9b2bc064610 /kernel | |
parent | 7fd8c565d8a501486d63d7ee07fd6582e97db437 (diff) | |
download | linux-stable-f817de98513d060023be4fa1d061b29a6515273e.tar.gz linux-stable-f817de98513d060023be4fa1d061b29a6515273e.tar.bz2 linux-stable-f817de98513d060023be4fa1d061b29a6515273e.zip |
cgroup: prepare migration path for unified hierarchy
Unified hierarchy implementation would require re-migrating tasks onto
the same cgroup on the default hierarchy to reflect updated effective
csses. Update cgroup_migrate_prepare_dst() so that it accepts NULL as
the destination cgrp. When NULL is specified, the destination is
considered to be the cgroup on the default hierarchy associated with
each css_set.
After this change, the identity check in cgroup_migrate_add_src()
isn't sufficient for noop detection as the associated csses may change
without any cgroup association changing. The only way to tell whether
a migration is noop or not is testing whether the source and
destination csets are identical. The noop check in
cgroup_migrate_add_src() is removed and cset identity test is added to
cgroup_migreate_prepare_dst(). If it's detected that source and
destination csets are identical, the cset is removed removed from
@preloaded_csets and all the migration nodes are cleared which makes
cgroup_migrate() ignore the cset.
Also, make the function append the destination css_sets to
@preloaded_list so that destination css_sets always come after source
css_sets.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/cgroup.c | 34 |
1 files changed, 23 insertions, 11 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 15eb2273d80b..8c2835a9e192 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1902,10 +1902,6 @@ static void cgroup_migrate_add_src(struct css_set *src_cset, src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root); - /* nothing to do if this cset already belongs to the cgroup */ - if (src_cgrp == dst_cgrp) - return; - if (!list_empty(&src_cset->mg_preload_node)) return; @@ -1920,13 +1916,14 @@ static void cgroup_migrate_add_src(struct css_set *src_cset, /** * cgroup_migrate_prepare_dst - prepare destination css_sets for migration - * @dst_cgrp: the destination cgroup + * @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 put them on - * @preloaded_csets. + * 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. * * This function must be called after cgroup_migrate_add_src() has been * called on each migration source css_set. After migration is performed @@ -1937,19 +1934,34 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, struct list_head *preloaded_csets) { LIST_HEAD(csets); - struct css_set *src_cset; + struct css_set *src_cset, *tmp_cset; lockdep_assert_held(&cgroup_mutex); /* look up the dst cset for each src cset and link it to src */ - list_for_each_entry(src_cset, preloaded_csets, mg_preload_node) { + 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); + dst_cset = find_css_set(src_cset, + dst_cgrp ?: src_cset->dfl_cgrp); if (!dst_cset) goto err; WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset); + + /* + * If src cset equals dst, it's noop. Drop the src. + * cgroup_migrate() will skip the cset too. Note that we + * can't handle src == dst as some nodes are used by both. + */ + if (src_cset == dst_cset) { + src_cset->mg_src_cgrp = NULL; + list_del_init(&src_cset->mg_preload_node); + put_css_set(src_cset, false); + put_css_set(dst_cset, false); + continue; + } + src_cset->mg_dst_cset = dst_cset; if (list_empty(&dst_cset->mg_preload_node)) @@ -1958,7 +1970,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, put_css_set(dst_cset, false); } - list_splice(&csets, preloaded_csets); + list_splice_tail(&csets, preloaded_csets); return 0; err: cgroup_migrate_finish(&csets); |