From: David Howells <dhowells@redhat.com>
To: viro@zeniv.linux.org.uk
Cc: linux-fsdevel@vger.kernel.org, dhowells@redhat.com,
torvalds@linux-foundation.org, ebiederm@xmission.com,
linux-security-module@vger.kernel.org
Subject: [PATCH 33/43] cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper
Date: Tue, 19 Feb 2019 16:32:55 +0000 [thread overview]
Message-ID: <155059397586.12449.13952181528654229603.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <155059366914.12449.4669870128936536848.stgit@warthog.procyon.org.uk>
From: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
kernel/cgroup/cgroup-v1.c | 87 ++++++++++++++++++++++++---------------------
1 file 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();
}
next prev parent reply other threads:[~2019-02-19 16:33 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-19 16:27 [PATCH 00/43] VFS: Introduce filesystem context David Howells
2019-02-19 16:28 ` [PATCH 01/43] fix cgroup_do_mount() handling of failure exits David Howells
2019-02-19 16:28 ` [PATCH 02/43] cgroup: saner refcounting for cgroup_root David Howells
2019-02-19 16:28 ` [PATCH 03/43] kill kernfs_pin_sb() David Howells
2019-02-19 16:28 ` [PATCH 04/43] separate copying and locking mount tree on cross-userns copies David Howells
2019-02-20 18:55 ` Alan Jenkins
2019-02-26 15:44 ` David Howells
2019-02-26 17:45 ` Alan Jenkins
2019-02-19 16:29 ` [PATCH 05/43] saner handling of temporary namespaces David Howells
2019-02-19 16:29 ` [PATCH 06/43] vfs: Introduce fs_context, switch vfs_kern_mount() to it David Howells
2019-02-19 16:29 ` [PATCH 07/43] new helpers: vfs_create_mount(), fc_mount() David Howells
2019-02-19 16:29 ` [PATCH 08/43] teach vfs_get_tree() to handle subtype, switch do_new_mount() to it David Howells
2019-02-19 16:29 ` [PATCH 09/43] new helper: do_new_mount_fc() David Howells
2019-02-19 16:29 ` [PATCH 10/43] vfs_get_tree(): evict the call of security_sb_kern_mount() David Howells
2019-02-19 16:29 ` [PATCH 11/43] convert do_remount_sb() to fs_context David Howells
2019-03-22 11:19 ` Andreas Schwab
2019-03-22 11:25 ` David Howells
2019-03-22 13:28 ` Andreas Schwab
2019-03-22 14:00 ` Andreas Schwab
2019-02-19 16:30 ` [PATCH 12/43] fs_context flavour for submounts David Howells
2019-02-19 16:30 ` [PATCH 13/43] introduce fs_context methods David Howells
2019-02-19 16:30 ` [PATCH 14/43] vfs: Introduce logging functions David Howells
2019-02-19 16:30 ` [PATCH 15/43] vfs: Add configuration parser helpers David Howells
2019-03-03 2:53 ` Al Viro
2019-02-19 16:30 ` [PATCH 16/43] vfs: Add LSM hooks for the new mount API David Howells
2019-02-19 16:30 ` [PATCH 17/43] selinux: Implement the new mount API LSM hooks David Howells
2019-02-19 16:30 ` [PATCH 18/43] smack: Implement filesystem context security hooks David Howells
2019-02-19 16:30 ` [PATCH 19/43] vfs: Put security flags into the fs_context struct David Howells
2019-02-19 16:31 ` [PATCH 20/43] vfs: Implement a filesystem superblock creation/configuration context David Howells
2019-02-19 16:31 ` [PATCH 21/43] convenience helpers: vfs_get_super() and sget_fc() David Howells
2019-02-19 16:31 ` [PATCH 22/43] introduce cloning of fs_context David Howells
2019-02-19 16:31 ` [PATCH 23/43] procfs: Move proc_fill_super() to fs/proc/root.c David Howells
2019-02-19 16:31 ` [PATCH 24/43] proc: Add fs_context support to procfs David Howells
2019-02-19 16:31 ` [PATCH 25/43] ipc: Convert mqueue fs to fs_context David Howells
2019-02-19 16:31 ` [PATCH 26/43] cgroup: start switching " David Howells
2019-02-19 16:32 ` [PATCH 27/43] cgroup: fold cgroup1_mount() into cgroup1_get_tree() David Howells
2019-02-19 16:32 ` [PATCH 28/43] cgroup: take options parsing into ->parse_monolithic() David Howells
2019-02-19 16:32 ` [PATCH 29/43] cgroup1: switch to option-by-option parsing David Howells
2019-02-19 16:32 ` [PATCH 30/43] cgroup2: " David Howells
2019-02-19 16:32 ` [PATCH 31/43] cgroup: stash cgroup_root reference into cgroup_fs_context David Howells
2019-02-19 16:32 ` [PATCH 32/43] cgroup_do_mount(): massage calling conventions David Howells
2019-02-19 16:32 ` David Howells [this message]
2019-02-19 16:33 ` [PATCH 34/43] cgroup: store a reference to cgroup_ns into cgroup_fs_context David Howells
2019-02-19 16:33 ` [PATCH 35/43] kernfs, sysfs, cgroup, intel_rdt: Support fs_context David Howells
2019-02-19 16:33 ` [PATCH 36/43] cpuset: Use fs_context David Howells
2019-02-19 16:33 ` [PATCH 37/43] hugetlbfs: Convert to fs_context David Howells
2019-02-19 16:33 ` [PATCH 38/43] vfs: Remove kern_mount_data() David Howells
2019-02-19 16:33 ` [PATCH 39/43] vfs: Provide documentation for new mount API David Howells
2019-02-19 16:34 ` [PATCH 40/43] vfs: Implement logging through fs_context David Howells
2019-02-19 16:34 ` [PATCH 41/43] vfs: Add some logging to the core users of the fs_context log David Howells
2019-02-19 16:34 ` [PATCH 42/43] afs: Add fs_context support David Howells
2019-02-19 16:34 ` [PATCH 43/43] afs: Use fs_context to pass parameters over automount David Howells
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