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authorAl Viro <viro@zeniv.linux.org.uk>2019-01-17 09:42:30 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2019-02-28 03:29:33 -0500
commit6678889f0726910fc884c54f951d8c5646a04819 (patch)
tree6b83060b2272c0fc6e83773ff17556c1fdcf18a8 /kernel/cgroup
parent71d883c37e8d4484207708af56685abb39703b04 (diff)
cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'kernel/cgroup')
-rw-r--r--kernel/cgroup/cgroup-v1.c87
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();
}