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Date: Tue, 11 Aug 2015 13:58:07 -0400
From: Tejun Heo <tj@...nel.org>
To: hannes@...xchg.org, lizefan@...wei.com
Cc: mhocko@...nel.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>
Subject: [PATCH 6/8] cgroup: restructure file creation / removal handling
The file creation / removal path has always been a bit icky and the
planned notification update requires css during file creation.
Restructure as follows.
* cgroup_addrm_files() now takes both @css and @cgrp and is only
called directly by other file handling functions.
* cgroup_populate/clear_dir() are replaced with
css_populate/clear_dir() taking @css and @cgrp_override.
@cgrp_override is used only when files needs to be created on /
removed from a cgroup which isn't attached to @css which happens
during subsystem rebinds. Subsystem loops are moved to the callers.
* cgroup_add_file() now takes both @css and @cgrp. @css isn't used
yet but will be used by the planned notification update.
This patch doens't cause any behavior changes.
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Li Zefan <lizefan@...wei.com>
Cc: Johannes Weiner <hannes@...xchg.org>
---
kernel/cgroup.c | 143 ++++++++++++++++++++++++++++++--------------------------
1 file changed, 76 insertions(+), 67 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 67d2ba3..b287522 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -200,7 +200,8 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
bool visible);
static void css_release(struct percpu_ref *ref);
static void kill_css(struct cgroup_subsys_state *css);
-static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
+static int cgroup_addrm_files(struct cgroup_subsys_state *css,
+ struct cgroup *cgrp, struct cftype cfts[],
bool is_add);
/* IDR wrappers which synchronize using cgroup_idr_lock */
@@ -1218,53 +1219,57 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
}
/**
- * cgroup_clear_dir - remove subsys files in a cgroup directory
- * @cgrp: target cgroup
- * @subsys_mask: mask of the subsystem ids whose files should be removed
+ * css_clear_dir - remove subsys files in a cgroup directory
+ * @css: taget css
+ * @cgrp_override: specify if target cgroup is different from css->cgroup
*/
-static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
+static void css_clear_dir(struct cgroup_subsys_state *css,
+ struct cgroup *cgrp_override)
{
- struct cgroup_subsys *ss;
- int i;
+ struct cgroup *cgrp = cgrp_override ?: css->cgroup;
+ struct cftype *cfts;
- for_each_subsys(ss, i) {
- struct cftype *cfts;
-
- if (!(subsys_mask & (1 << i)))
- continue;
- list_for_each_entry(cfts, &ss->cfts, node)
- cgroup_addrm_files(cgrp, cfts, false);
- }
+ list_for_each_entry(cfts, &css->ss->cfts, node)
+ cgroup_addrm_files(css, cgrp, cfts, false);
}
/**
- * cgroup_populate_dir - create subsys files in a cgroup directory
- * @cgrp: target cgroup
- * @subsys_mask: mask of the subsystem ids whose files should be added
+ * css_populate_dir - create subsys files in a cgroup directory
+ * @css: target css
+ * @cgrp_overried: specify if target cgroup is different from css->cgroup
*
* On failure, no file is added.
*/
-static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
+static int css_populate_dir(struct cgroup_subsys_state *css,
+ struct cgroup *cgrp_override)
{
- struct cgroup_subsys *ss;
- int i, ret = 0;
+ struct cgroup *cgrp = cgrp_override ?: css->cgroup;
+ struct cftype *cfts, *failed_cfts;
+ int ret;
- /* process cftsets of each subsystem */
- for_each_subsys(ss, i) {
- struct cftype *cfts;
+ if (!css->ss) {
+ if (cgroup_on_dfl(cgrp))
+ cfts = cgroup_dfl_base_files;
+ else
+ cfts = cgroup_legacy_base_files;
- if (!(subsys_mask & (1 << i)))
- continue;
+ return cgroup_addrm_files(&cgrp->self, cgrp, cfts, true);
+ }
- list_for_each_entry(cfts, &ss->cfts, node) {
- ret = cgroup_addrm_files(cgrp, cfts, true);
- if (ret < 0)
- goto err;
+ list_for_each_entry(cfts, &css->ss->cfts, node) {
+ ret = cgroup_addrm_files(css, cgrp, cfts, true);
+ if (ret < 0) {
+ failed_cfts = cfts;
+ goto err;
}
}
return 0;
err:
- cgroup_clear_dir(cgrp, subsys_mask);
+ list_for_each_entry(cfts, &css->ss->cfts, node) {
+ if (cfts == failed_cfts)
+ break;
+ cgroup_addrm_files(css, cgrp, cfts, false);
+ }
return ret;
}
@@ -1293,10 +1298,13 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
if (dst_root == &cgrp_dfl_root)
tmp_ss_mask &= ~cgrp_dfl_root_inhibit_ss_mask;
- ret = cgroup_populate_dir(dcgrp, tmp_ss_mask);
- if (ret) {
- if (dst_root != &cgrp_dfl_root)
- return ret;
+ for_each_subsys_which(ss, ssid, &tmp_ss_mask) {
+ struct cgroup *scgrp = &ss->root->cgrp;
+ int tssid;
+
+ ret = css_populate_dir(cgroup_css(scgrp, ss), dcgrp);
+ if (!ret)
+ continue;
/*
* Rebinding back to the default root is not allowed to
@@ -1304,20 +1312,27 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
* be rare. Moving subsystems back and forth even more so.
* Just warn about it and continue.
*/
- if (cgrp_dfl_root_visible) {
- pr_warn("failed to create files (%d) while rebinding 0x%lx to default root\n",
- ret, ss_mask);
- pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
+ if (dst_root == &cgrp_dfl_root) {
+ if (cgrp_dfl_root_visible) {
+ pr_warn("failed to create files (%d) while rebinding 0x%lx to default root\n",
+ ret, ss_mask);
+ pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
+ }
+ continue;
}
+
+ for_each_subsys_which(ss, tssid, &tmp_ss_mask) {
+ if (tssid == ssid)
+ break;
+ css_clear_dir(cgroup_css(scgrp, ss), dcgrp);
+ }
+ return ret;
}
/*
* Nothing can fail from this point on. Remove files for the
* removed subsystems and rebind each subsystem.
*/
- for_each_subsys_which(ss, ssid, &ss_mask)
- cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
-
for_each_subsys_which(ss, ssid, &ss_mask) {
struct cgroup_root *src_root = ss->root;
struct cgroup *scgrp = &src_root->cgrp;
@@ -1326,6 +1341,8 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
WARN_ON(!css || cgroup_css(dcgrp, ss));
+ css_clear_dir(css, NULL);
+
RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
rcu_assign_pointer(dcgrp->subsys[ssid], css);
ss->root = dst_root;
@@ -1691,7 +1708,6 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask)
{
LIST_HEAD(tmp_links);
struct cgroup *root_cgrp = &root->cgrp;
- struct cftype *base_files;
struct css_set *cset;
int i, ret;
@@ -1730,12 +1746,7 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask)
}
root_cgrp->kn = root->kf_root->kn;
- if (root == &cgrp_dfl_root)
- base_files = cgroup_dfl_base_files;
- else
- base_files = cgroup_legacy_base_files;
-
- ret = cgroup_addrm_files(root_cgrp, base_files, true);
+ ret = css_populate_dir(&root_cgrp->self, NULL);
if (ret)
goto destroy_root;
@@ -2884,7 +2895,8 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
ret = create_css(child, ss,
cgrp->subtree_control & (1 << ssid));
else
- ret = cgroup_populate_dir(child, 1 << ssid);
+ ret = css_populate_dir(cgroup_css(child, ss),
+ NULL);
if (ret)
goto err_undo_css;
}
@@ -2917,7 +2929,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
if (css_disable & (1 << ssid)) {
kill_css(css);
} else {
- cgroup_clear_dir(child, 1 << ssid);
+ css_clear_dir(css, NULL);
if (ss->css_reset)
ss->css_reset(css);
}
@@ -2965,7 +2977,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
if (css_enable & (1 << ssid))
kill_css(css);
else
- cgroup_clear_dir(child, 1 << ssid);
+ css_clear_dir(css, NULL);
}
}
goto out_unlock;
@@ -3117,7 +3129,8 @@ static int cgroup_kn_set_ugid(struct kernfs_node *kn)
return kernfs_setattr(kn, &iattr);
}
-static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
+static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
+ struct cftype *cft)
{
char name[CGROUP_FILE_NAME_MAX];
struct kernfs_node *kn;
@@ -3148,14 +3161,16 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
/**
* cgroup_addrm_files - add or remove files to a cgroup directory
- * @cgrp: the target cgroup
+ * @css: the target css
+ * @cgrp: the target cgroup (usually css->cgroup)
* @cfts: array of cftypes to be added
* @is_add: whether to add or remove
*
* Depending on @is_add, add or remove files defined by @cfts on @cgrp.
* For removals, this function never fails.
*/
-static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
+static int cgroup_addrm_files(struct cgroup_subsys_state *css,
+ struct cgroup *cgrp, struct cftype cfts[],
bool is_add)
{
struct cftype *cft, *cft_end = NULL;
@@ -3176,7 +3191,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
continue;
if (is_add) {
- ret = cgroup_add_file(cgrp, cft);
+ ret = cgroup_add_file(css, cgrp, cft);
if (ret) {
pr_warn("%s: failed to add %s, err=%d\n",
__func__, cft->name, ret);
@@ -3208,7 +3223,7 @@ static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
if (cgroup_is_dead(cgrp))
continue;
- ret = cgroup_addrm_files(cgrp, cfts, is_add);
+ ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
if (ret)
break;
}
@@ -4584,7 +4599,7 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
css->id = err;
if (visible) {
- err = cgroup_populate_dir(cgrp, 1 << ss->id);
+ err = css_populate_dir(css, NULL);
if (err)
goto err_free_id;
}
@@ -4610,7 +4625,7 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
err_list_del:
list_del_rcu(&css->sibling);
- cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
+ css_clear_dir(css, NULL);
err_free_id:
cgroup_idr_remove(&ss->css_idr, css->id);
err_free_percpu_ref:
@@ -4627,7 +4642,6 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
struct cgroup_root *root;
struct cgroup_subsys *ss;
struct kernfs_node *kn;
- struct cftype *base_files;
int ssid, ret;
/* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
@@ -4703,12 +4717,7 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
if (ret)
goto out_destroy;
- if (cgroup_on_dfl(cgrp))
- base_files = cgroup_dfl_base_files;
- else
- base_files = cgroup_legacy_base_files;
-
- ret = cgroup_addrm_files(cgrp, base_files, true);
+ ret = css_populate_dir(&cgrp->self, NULL);
if (ret)
goto out_destroy;
@@ -4795,7 +4804,7 @@ static void kill_css(struct cgroup_subsys_state *css)
* This must happen before css is disassociated with its cgroup.
* See seq_css() for details.
*/
- cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
+ css_clear_dir(css, NULL);
/*
* Killing would put the base ref, but we need to keep it alive
--
2.4.3
--
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