diff options
| -rw-r--r-- | kernel/cgroup/cgroup-v1.c | 87 |
1 files changed, 46 insertions, 41 deletions
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 05f05d773adf..0d71fc98e73d 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -1135,7 +1135,15 @@ struct kernfs_syscall_ops cgroup1_kf_syscall_ops = { .show_path = cgroup_show_path, }; -int cgroup1_get_tree(struct fs_context *fc) +/* + * The guts of cgroup1 mount - find or create cgroup_root to use. + * Called with cgroup_mutex held; returns 0 on success, -E... on + * error and positive - in case when the candidate is busy dying. + * On success it stashes a reference to cgroup_root into given + * cgroup_fs_context; that reference is *NOT* counting towards the + * cgroup_root refcount. + */ +static int cgroup1_root_to_use(struct fs_context *fc) { struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; struct cgroup_fs_context *ctx = cgroup_fc2context(fc); @@ -1143,16 +1151,10 @@ int cgroup1_get_tree(struct fs_context *fc) struct cgroup_subsys *ss; int i, ret; - /* Check if the caller has permission to mount. */ - if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) - return -EPERM; - - cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp); - /* First find the desired set of subsystems */ ret = check_cgroupfs_options(fc); if (ret) - goto out_unlock; + return ret; /* * Destruction of cgroup root is asynchronous, so subsystems may @@ -1166,12 +1168,8 @@ int cgroup1_get_tree(struct fs_context *fc) ss->root == &cgrp_dfl_root) continue; - if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) { - mutex_unlock(&cgroup_mutex); - msleep(10); - ret = restart_syscall(); - goto out_free; - } + if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) + return 1; /* restart */ cgroup_put(&ss->root->cgrp); } @@ -1200,16 +1198,14 @@ int cgroup1_get_tree(struct fs_context *fc) (ctx->subsys_mask != root->subsys_mask)) { if (!name_match) continue; - ret = -EBUSY; - goto out_unlock; + return -EBUSY; } if (root->flags ^ ctx->flags) pr_warn("new mount options do not match the existing superblock, will be ignored\n"); ctx->root = root; - ret = 0; - goto out_unlock; + return 0; } /* @@ -1217,22 +1213,16 @@ int cgroup1_get_tree(struct fs_context *fc) * specification is allowed for already existing hierarchies but we * can't create new one without subsys specification. */ - if (!ctx->subsys_mask && !ctx->none) { - ret = cg_invalf(fc, "cgroup1: No subsys list or none specified"); - goto out_unlock; - } + if (!ctx->subsys_mask && !ctx->none) + return cg_invalf(fc, "cgroup1: No subsys list or none specified"); /* Hierarchies may only be created in the initial cgroup namespace. */ - if (ns != &init_cgroup_ns) { - ret = -EPERM; - goto out_unlock; - } + if (ns != &init_cgroup_ns) + return -EPERM; root = kzalloc(sizeof(*root), GFP_KERNEL); - if (!root) { - ret = -ENOMEM; - goto out_unlock; - } + if (!root) + return -ENOMEM; ctx->root = root; init_cgroup_root(ctx); @@ -1240,23 +1230,38 @@ int cgroup1_get_tree(struct fs_context *fc) ret = cgroup_setup_root(root, ctx->subsys_mask); if (ret) cgroup_free_root(root); + return ret; +} + +int cgroup1_get_tree(struct fs_context *fc) +{ + struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; + struct cgroup_fs_context *ctx = cgroup_fc2context(fc); + int ret; + + /* Check if the caller has permission to mount. */ + if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp); + + ret = cgroup1_root_to_use(fc); + if (!ret && !percpu_ref_tryget_live(&ctx->root->cgrp.self.refcnt)) + ret = 1; /* restart */ -out_unlock: - if (!ret && !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) { - mutex_unlock(&cgroup_mutex); - msleep(10); - return restart_syscall(); - } mutex_unlock(&cgroup_mutex); -out_free: - if (ret) - return ret; - ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns); - if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) { + if (!ret) + ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns); + + if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) { struct super_block *sb = fc->root->d_sb; dput(fc->root); deactivate_locked_super(sb); + ret = 1; + } + + if (unlikely(ret > 0)) { msleep(10); return restart_syscall(); } |