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https://github.com/torvalds/linux
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23bf1b6be9
Make kernfs support superblock creation/mount/remount with fs_context.
This requires that sysfs, cgroup and intel_rdt, which are built on kernfs,
be made to support fs_context also.
Notes:
(1) A kernfs_fs_context struct is created to wrap fs_context and the
kernfs mount parameters are moved in here (or are in fs_context).
(2) kernfs_mount{,_ns}() are made into kernfs_get_tree(). The extra
namespace tag parameter is passed in the context if desired
(3) kernfs_free_fs_context() is provided as a destructor for the
kernfs_fs_context struct, but for the moment it does nothing except
get called in the right places.
(4) sysfs doesn't wrap kernfs_fs_context since it has no parameters to
pass, but possibly this should be done anyway in case someone wants to
add a parameter in future.
(5) A cgroup_fs_context struct is created to wrap kernfs_fs_context and
the cgroup v1 and v2 mount parameters are all moved there.
(6) cgroup1 parameter parsing error messages are now handled by invalf(),
which allows userspace to collect them directly.
(7) cgroup1 parameter cleanup is now done in the context destructor rather
than in the mount/get_tree and remount functions.
Weirdies:
(*) cgroup_do_get_tree() calls cset_cgroup_from_root() with locks held,
but then uses the resulting pointer after dropping the locks. I'm
told this is okay and needs commenting.
(*) The cgroup refcount web. This really needs documenting.
(*) cgroup2 only has one root?
Add a suggestion from Thomas Gleixner in which the RDT enablement code is
placed into its own function.
[folded a leak fix from Andrey Vagin]
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc: Tejun Heo <tj@kernel.org>
cc: Li Zefan <lizefan@huawei.com>
cc: Johannes Weiner <hannes@cmpxchg.org>
cc: cgroups@vger.kernel.org
cc: fenghua.yu@intel.com
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
115 lines
2.5 KiB
C
115 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* fs/sysfs/symlink.c - operations for initializing and mounting sysfs
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#include <linux/fs.h>
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#include <linux/magic.h>
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#include <linux/mount.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/user_namespace.h>
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#include <linux/fs_context.h>
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#include <net/net_namespace.h>
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#include "sysfs.h"
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static struct kernfs_root *sysfs_root;
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struct kernfs_node *sysfs_root_kn;
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static int sysfs_get_tree(struct fs_context *fc)
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{
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struct kernfs_fs_context *kfc = fc->fs_private;
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int ret;
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ret = kernfs_get_tree(fc);
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if (ret)
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return ret;
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if (kfc->new_sb_created)
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fc->root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
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return 0;
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}
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static void sysfs_fs_context_free(struct fs_context *fc)
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{
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struct kernfs_fs_context *kfc = fc->fs_private;
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if (kfc->ns_tag)
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kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag);
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kernfs_free_fs_context(fc);
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kfree(kfc);
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}
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static const struct fs_context_operations sysfs_fs_context_ops = {
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.free = sysfs_fs_context_free,
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.get_tree = sysfs_get_tree,
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};
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static int sysfs_init_fs_context(struct fs_context *fc)
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{
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struct kernfs_fs_context *kfc;
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struct net *netns;
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if (!(fc->sb_flags & SB_KERNMOUNT)) {
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if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
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return -EPERM;
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}
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kfc = kzalloc(sizeof(struct kernfs_fs_context), GFP_KERNEL);
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if (!kfc)
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return -ENOMEM;
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kfc->ns_tag = netns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
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kfc->root = sysfs_root;
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kfc->magic = SYSFS_MAGIC;
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fc->fs_private = kfc;
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fc->ops = &sysfs_fs_context_ops;
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if (fc->user_ns)
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put_user_ns(fc->user_ns);
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fc->user_ns = get_user_ns(netns->user_ns);
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fc->global = true;
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return 0;
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}
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static void sysfs_kill_sb(struct super_block *sb)
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{
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void *ns = (void *)kernfs_super_ns(sb);
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kernfs_kill_sb(sb);
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kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
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}
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static struct file_system_type sysfs_fs_type = {
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.name = "sysfs",
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.init_fs_context = sysfs_init_fs_context,
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.kill_sb = sysfs_kill_sb,
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.fs_flags = FS_USERNS_MOUNT,
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};
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int __init sysfs_init(void)
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{
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int err;
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sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
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NULL);
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if (IS_ERR(sysfs_root))
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return PTR_ERR(sysfs_root);
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sysfs_root_kn = sysfs_root->kn;
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err = register_filesystem(&sysfs_fs_type);
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if (err) {
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kernfs_destroy_root(sysfs_root);
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return err;
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}
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return 0;
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}
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