Commit 4df8dc90 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
parent 1ada4838

kernel/cgroup.c

+76 −67
Original line number Diff line number Diff line
@@ -221,7 +221,8 @@ 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);



/**
@@ -1313,53 +1314,57 @@ 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;



	for_each_subsys(ss, i) {

	struct cgroup *cgrp = cgrp_override ?: css->cgroup;

	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)

	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;

}
@@ -1388,10 +1393,13 @@ 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
@@ -1399,20 +1407,27 @@ 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 (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;
@@ -1421,6 +1436,8 @@ 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;
@@ -1791,7 +1808,6 @@ 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;
@@ -1830,12 +1846,7 @@ 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;
@@ -2985,7 +2996,8 @@ 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;

		}
@@ -3018,7 +3030,7 @@ 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);

			}
@@ -3066,7 +3078,7 @@ err_undo_css: 
			if (css_enable & (1 << ssid))

				kill_css(css);

			else

				cgroup_clear_dir(child, 1 << ssid);

				css_clear_dir(css, NULL);

		}

	}

	goto out_unlock;
@@ -3218,7 +3230,8 @@ 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;
@@ -3249,14 +3262,16 @@ 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;
@@ -3277,7 +3292,7 @@ restart: 
			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);
@@ -3309,7 +3324,7 @@ 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;

	}
@@ -4685,7 +4700,7 @@ 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;

	}
@@ -4711,7 +4726,7 @@ 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:
@@ -4728,7 +4743,6 @@ 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.
@@ -4804,12 +4818,7 @@ 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;
@@ -4896,7 +4905,7 @@ 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

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