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Commit | Line | Data |
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2cb7cef9 BS |
1 | From cf8d2c11cb77f129675478792122f50827e5b0ae Mon Sep 17 00:00:00 2001 |
2 | From: Trond Myklebust <Trond.Myklebust@netapp.com> | |
3 | Date: Mon, 22 Jun 2009 15:09:13 -0400 | |
4 | Subject: [PATCH 2/5] VFS: Add VFS helper functions for setting up private namespaces | |
5 | ||
6 | The purpose of this patch is to improve the remote mount path lookup | |
7 | support for distributed filesystems such as the NFSv4 client. | |
8 | ||
9 | When given a mount command of the form "mount server:/foo/bar /mnt", the | |
10 | NFSv4 client is required to look up the filehandle for "server:/", and | |
11 | then look up each component of the remote mount path "foo/bar" in order | |
12 | to find the directory that is actually going to be mounted on /mnt. | |
13 | Following that remote mount path may involve following symlinks, | |
14 | crossing server-side mount points and even following referrals to | |
15 | filesystem volumes on other servers. | |
16 | ||
17 | Since the standard VFS path lookup code already supports walking paths | |
18 | that contain all these features (using in-kernel automounts for | |
19 | following referrals) we would like to be able to reuse that rather than | |
20 | duplicate the full path traversal functionality in the NFSv4 client code. | |
21 | ||
22 | This patch therefore defines a VFS helper function create_mnt_ns(), that | |
23 | sets up a temporary filesystem namespace and attaches a root filesystem to | |
24 | it. It exports the create_mnt_ns() and put_mnt_ns() function for use by | |
25 | filesystem modules. | |
26 | ||
27 | Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> | |
28 | Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> | |
29 | Acked-by: NeilBrown <neilb@suse.de> | |
30 | --- | |
31 | fs/namespace.c | 45 ++++++++++++++++++++++++++++++++++-------- | |
32 | include/linux/mnt_namespace.h | 1 | |
33 | 2 files changed, 38 insertions(+), 8 deletions(-) | |
34 | ||
35 | --- a/fs/namespace.c | |
36 | +++ b/fs/namespace.c | |
37 | @@ -1939,6 +1939,21 @@ dput_out: | |
38 | return retval; | |
39 | } | |
40 | ||
41 | +static struct mnt_namespace *alloc_mnt_ns(void) | |
42 | +{ | |
43 | + struct mnt_namespace *new_ns; | |
44 | + | |
45 | + new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); | |
46 | + if (!new_ns) | |
47 | + return ERR_PTR(-ENOMEM); | |
48 | + atomic_set(&new_ns->count, 1); | |
49 | + new_ns->root = NULL; | |
50 | + INIT_LIST_HEAD(&new_ns->list); | |
51 | + init_waitqueue_head(&new_ns->poll); | |
52 | + new_ns->event = 0; | |
53 | + return new_ns; | |
54 | +} | |
55 | + | |
56 | /* | |
57 | * Allocate a new namespace structure and populate it with contents | |
58 | * copied from the namespace of the passed in task structure. | |
59 | @@ -1950,14 +1965,9 @@ static struct mnt_namespace *dup_mnt_ns( | |
60 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; | |
61 | struct vfsmount *p, *q; | |
62 | ||
63 | - new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); | |
64 | - if (!new_ns) | |
65 | - return ERR_PTR(-ENOMEM); | |
66 | - | |
67 | - atomic_set(&new_ns->count, 1); | |
68 | - INIT_LIST_HEAD(&new_ns->list); | |
69 | - init_waitqueue_head(&new_ns->poll); | |
70 | - new_ns->event = 0; | |
71 | + new_ns = alloc_mnt_ns(); | |
72 | + if (IS_ERR(new_ns)) | |
73 | + return new_ns; | |
74 | ||
75 | down_write(&namespace_sem); | |
76 | /* First pass: copy the tree topology */ | |
77 | @@ -2021,6 +2031,24 @@ struct mnt_namespace *copy_mnt_ns(unsign | |
78 | return new_ns; | |
79 | } | |
80 | ||
81 | +/** | |
82 | + * create_mnt_ns - creates a private namespace and adds a root filesystem | |
83 | + * @mnt: pointer to the new root filesystem mountpoint | |
84 | + */ | |
85 | +struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) | |
86 | +{ | |
87 | + struct mnt_namespace *new_ns; | |
88 | + | |
89 | + new_ns = alloc_mnt_ns(); | |
90 | + if (!IS_ERR(new_ns)) { | |
91 | + mnt->mnt_ns = new_ns; | |
92 | + new_ns->root = mnt; | |
93 | + list_add(&new_ns->list, &new_ns->root->mnt_list); | |
94 | + } | |
95 | + return new_ns; | |
96 | +} | |
97 | +EXPORT_SYMBOL(create_mnt_ns); | |
98 | + | |
99 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
100 | char __user *, type, unsigned long, flags, void __user *, data) | |
101 | { | |
102 | @@ -2328,3 +2356,4 @@ void put_mnt_ns(struct mnt_namespace *ns | |
103 | release_mounts(&umount_list); | |
104 | kfree(ns); | |
105 | } | |
106 | +EXPORT_SYMBOL(put_mnt_ns); | |
107 | --- a/include/linux/mnt_namespace.h | |
108 | +++ b/include/linux/mnt_namespace.h | |
109 | @@ -22,6 +22,7 @@ struct proc_mounts { | |
110 | int event; | |
111 | }; | |
112 | ||
113 | +extern struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt); | |
114 | extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *, | |
115 | struct fs_struct *); | |
116 | extern void put_mnt_ns(struct mnt_namespace *ns); |