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author | 2014-02-12 09:29:49 -0500 | |
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committer | 2014-02-12 09:29:49 -0500 | |
commit | 21a2d3430ba8c188af405a5c2eb9c06bdcb6add6 (patch) | |
tree | 7fc1d9be2e3297a53c64c7599bf2760cacbf6187 /kernel | |
parent | cgroup: remove cftype_set (diff) | |
download | linux-21a2d3430ba8c188af405a5c2eb9c06bdcb6add6.tar.gz linux-21a2d3430ba8c188af405a5c2eb9c06bdcb6add6.tar.bz2 linux-21a2d3430ba8c188af405a5c2eb9c06bdcb6add6.zip |
cgroup: simplify dynamic cftype addition and removal
Dynamic cftype addition and removal using cgroup_add/rm_cftypes()
respectively has been quite hairy due to vfs i_mutex. As i_mutex
nests outside cgroup_mutex, cgroup_mutex has to be released and
regrabbed on each iteration through the hierarchy complicating the
process. Now that i_mutex is no longer in play, it can be simplified.
* Just holding cgroup_tree_mutex is enough. No need to meddle with
cgroup_mutex.
* No reason to play the unlock - relock - check serial_nr dancing.
Everything can be atomically while holding cgroup_tree_mutex.
* cgroup_cfts_prepare() is replaced with direct locking of
cgroup_tree_mutex.
* cgroup_cfts_commit() no longer fiddles with locking. It just
applies the cftypes change to the existing cgroups in the hierarchy.
Renamed to cgroup_cfts_apply().
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 | 87 |
1 files changed, 32 insertions, 55 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 506ebd61d1c2..f4409715a2f5 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2305,46 +2305,19 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], return 0; } -static void cgroup_cfts_prepare(void) - __acquires(&cgroup_mutex) -{ - /* - * Thanks to the entanglement with vfs inode locking, we can't walk - * the existing cgroups under cgroup_mutex and create files. - * Instead, we use css_for_each_descendant_pre() and drop RCU read - * lock before calling cgroup_addrm_files(). - */ - mutex_lock(&cgroup_tree_mutex); - mutex_lock(&cgroup_mutex); -} - -static int cgroup_cfts_commit(struct cftype *cfts, bool is_add) - __releases(&cgroup_mutex) +static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add) { LIST_HEAD(pending); struct cgroup_subsys *ss = cfts[0].ss; struct cgroup *root = &ss->root->top_cgroup; - struct cgroup *prev = NULL; struct cgroup_subsys_state *css; - u64 update_before; int ret = 0; - mutex_unlock(&cgroup_mutex); + lockdep_assert_held(&cgroup_tree_mutex); - /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */ - if (!cfts || ss->root == &cgroup_dummy_root) { - mutex_unlock(&cgroup_tree_mutex); + /* don't bother if @ss isn't attached */ + if (ss->root == &cgroup_dummy_root) return 0; - } - - cgroup_get_root(ss->root); - - /* - * All cgroups which are created after we drop cgroup_mutex will - * have the updated set of files, so we only need to update the - * cgroups created before the current @cgroup_serial_nr_next. - */ - update_before = cgroup_serial_nr_next; /* add/rm files for all cgroups created before */ css_for_each_descendant_pre(css, cgroup_css(root, ss)) { @@ -2353,22 +2326,13 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add) if (cgroup_is_dead(cgrp)) continue; - cgroup_get(cgrp); - if (prev) - cgroup_put(prev); - prev = cgrp; - - if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp)) { - ret = cgroup_addrm_files(cgrp, cfts, is_add); - if (is_add) - kernfs_activate(cgrp->kn); - } + ret = cgroup_addrm_files(cgrp, cfts, is_add); if (ret) break; } - mutex_unlock(&cgroup_tree_mutex); - cgroup_put(prev); - cgroup_put_root(ss->root); + + if (is_add && !ret) + kernfs_activate(root->kn); return ret; } @@ -2419,6 +2383,19 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) return 0; } +static int cgroup_rm_cftypes_locked(struct cftype *cfts) +{ + lockdep_assert_held(&cgroup_tree_mutex); + + if (!cfts || !cfts[0].ss) + return -ENOENT; + + list_del(&cfts->node); + cgroup_apply_cftypes(cfts, false); + cgroup_exit_cftypes(cfts); + return 0; +} + /** * cgroup_rm_cftypes - remove an array of cftypes from a subsystem * @cfts: zero-length name terminated array of cftypes @@ -2432,15 +2409,12 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) */ int cgroup_rm_cftypes(struct cftype *cfts) { - if (!cfts || !cfts[0].ss) - return -ENOENT; - - cgroup_cfts_prepare(); - list_del(&cfts->node); - cgroup_cfts_commit(cfts, false); + int ret; - cgroup_exit_cftypes(cfts); - return 0; + mutex_lock(&cgroup_tree_mutex); + ret = cgroup_rm_cftypes_locked(cfts); + mutex_unlock(&cgroup_tree_mutex); + return ret; } /** @@ -2465,11 +2439,14 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) if (ret) return ret; - cgroup_cfts_prepare(); + mutex_lock(&cgroup_tree_mutex); + list_add_tail(&cfts->node, &ss->cfts); - ret = cgroup_cfts_commit(cfts, true); + ret = cgroup_apply_cftypes(cfts, true); if (ret) - cgroup_rm_cftypes(cfts); + cgroup_rm_cftypes_locked(cfts); + + mutex_unlock(&cgroup_tree_mutex); return ret; } EXPORT_SYMBOL_GPL(cgroup_add_cftypes); |