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Commit 6678889

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Al Viro
committed
cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1 parent 71d883c commit 6678889

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+46
-41
lines changed

1 file changed

+46
-41
lines changed

‎kernel/cgroup/cgroup-v1.c

Lines changed: 46 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -1135,24 +1135,26 @@ struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
11351135
.show_path = cgroup_show_path,
11361136
};
11371137

1138-
int cgroup1_get_tree(struct fs_context *fc)
1138+
/*
1139+
* The guts of cgroup1 mount - find or create cgroup_root to use.
1140+
* Called with cgroup_mutex held; returns 0 on success, -E... on
1141+
* error and positive - in case when the candidate is busy dying.
1142+
* On success it stashes a reference to cgroup_root into given
1143+
* cgroup_fs_context; that reference is *NOT* counting towards the
1144+
* cgroup_root refcount.
1145+
*/
1146+
static int cgroup1_root_to_use(struct fs_context *fc)
11391147
{
11401148
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
11411149
struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
11421150
struct cgroup_root *root;
11431151
struct cgroup_subsys *ss;
11441152
int i, ret;
11451153

1146-
/* Check if the caller has permission to mount. */
1147-
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
1148-
return -EPERM;
1149-
1150-
cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1151-
11521154
/* First find the desired set of subsystems */
11531155
ret = check_cgroupfs_options(fc);
11541156
if (ret)
1155-
goto out_unlock;
1157+
return ret;
11561158

11571159
/*
11581160
* Destruction of cgroup root is asynchronous, so subsystems may
@@ -1166,12 +1168,8 @@ int cgroup1_get_tree(struct fs_context *fc)
11661168
ss->root == &cgrp_dfl_root)
11671169
continue;
11681170

1169-
if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
1170-
mutex_unlock(&cgroup_mutex);
1171-
msleep(10);
1172-
ret = restart_syscall();
1173-
goto out_free;
1174-
}
1171+
if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt))
1172+
return 1; /* restart */
11751173
cgroup_put(&ss->root->cgrp);
11761174
}
11771175

@@ -1200,63 +1198,70 @@ int cgroup1_get_tree(struct fs_context *fc)
12001198
(ctx->subsys_mask != root->subsys_mask)) {
12011199
if (!name_match)
12021200
continue;
1203-
ret = -EBUSY;
1204-
goto out_unlock;
1201+
return -EBUSY;
12051202
}
12061203

12071204
if (root->flags ^ ctx->flags)
12081205
pr_warn("new mount options do not match the existing superblock, will be ignored\n");
12091206

12101207
ctx->root = root;
1211-
ret = 0;
1212-
goto out_unlock;
1208+
return 0;
12131209
}
12141210

12151211
/*
12161212
* No such thing, create a new one. name= matching without subsys
12171213
* specification is allowed for already existing hierarchies but we
12181214
* can't create new one without subsys specification.
12191215
*/
1220-
if (!ctx->subsys_mask && !ctx->none) {
1221-
ret = cg_invalf(fc, "cgroup1: No subsys list or none specified");
1222-
goto out_unlock;
1223-
}
1216+
if (!ctx->subsys_mask && !ctx->none)
1217+
return cg_invalf(fc, "cgroup1: No subsys list or none specified");
12241218

12251219
/* Hierarchies may only be created in the initial cgroup namespace. */
1226-
if (ns != &init_cgroup_ns) {
1227-
ret = -EPERM;
1228-
goto out_unlock;
1229-
}
1220+
if (ns != &init_cgroup_ns)
1221+
return -EPERM;
12301222

12311223
root = kzalloc(sizeof(*root), GFP_KERNEL);
1232-
if (!root) {
1233-
ret = -ENOMEM;
1234-
goto out_unlock;
1235-
}
1224+
if (!root)
1225+
return -ENOMEM;
12361226

12371227
ctx->root = root;
12381228
init_cgroup_root(ctx);
12391229

12401230
ret = cgroup_setup_root(root, ctx->subsys_mask);
12411231
if (ret)
12421232
cgroup_free_root(root);
1233+
return ret;
1234+
}
1235+
1236+
int cgroup1_get_tree(struct fs_context *fc)
1237+
{
1238+
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
1239+
struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1240+
int ret;
1241+
1242+
/* Check if the caller has permission to mount. */
1243+
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
1244+
return -EPERM;
1245+
1246+
cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1247+
1248+
ret = cgroup1_root_to_use(fc);
1249+
if (!ret && !percpu_ref_tryget_live(&ctx->root->cgrp.self.refcnt))
1250+
ret = 1; /* restart */
12431251

1244-
out_unlock:
1245-
if (!ret && !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
1246-
mutex_unlock(&cgroup_mutex);
1247-
msleep(10);
1248-
return restart_syscall();
1249-
}
12501252
mutex_unlock(&cgroup_mutex);
1251-
out_free:
1252-
if (ret)
1253-
return ret;
12541253

1255-
ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns);
1256-
if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
1254+
if (!ret)
1255+
ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns);
1256+
1257+
if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) {
12571258
struct super_block *sb = fc->root->d_sb;
12581259
dput(fc->root);
12591260
deactivate_locked_super(sb);
1261+
ret = 1;
1262+
}
1263+
1264+
if (unlikely(ret > 0)) {
12601265
msleep(10);
12611266
return restart_syscall();
12621267
}

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