From 4df8dc903161c03cd9bff9077d8427fefe808e6d Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 18 Sep 2015 17:54:23 -0400 Subject: [PATCH] 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 Cc: Li Zefan Cc: Johannes Weiner --- kernel/cgroup.c | 143 +++++++++++++++++++++++++----------------------- 1 file changed, 76 insertions(+), 67 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index a4ff4965e53b..06c9d1aeea9d 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -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; + 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; } @@ -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 (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; @@ -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//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 -- 2.20.1