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authorTrond Myklebust <Trond.Myklebust@netapp.com>2009-06-22 15:09:13 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-22 21:28:25 -0700
commitcf8d2c11cb77f129675478792122f50827e5b0ae (patch)
tree85bebdff4cffbca238952e839b0cb801e6a9bfe7
parent616511d039af402670de8500d0e24495113a9cab (diff)
downloadop-kernel-dev-cf8d2c11cb77f129675478792122f50827e5b0ae.zip
op-kernel-dev-cf8d2c11cb77f129675478792122f50827e5b0ae.tar.gz
VFS: Add VFS helper functions for setting up private namespaces
The purpose of this patch is to improve the remote mount path lookup support for distributed filesystems such as the NFSv4 client. When given a mount command of the form "mount server:/foo/bar /mnt", the NFSv4 client is required to look up the filehandle for "server:/", and then look up each component of the remote mount path "foo/bar" in order to find the directory that is actually going to be mounted on /mnt. Following that remote mount path may involve following symlinks, crossing server-side mount points and even following referrals to filesystem volumes on other servers. Since the standard VFS path lookup code already supports walking paths that contain all these features (using in-kernel automounts for following referrals) we would like to be able to reuse that rather than duplicate the full path traversal functionality in the NFSv4 client code. This patch therefore defines a VFS helper function create_mnt_ns(), that sets up a temporary filesystem namespace and attaches a root filesystem to it. It exports the create_mnt_ns() and put_mnt_ns() function for use by filesystem modules. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/namespace.c45
-rw-r--r--include/linux/mnt_namespace.h1
2 files changed, 38 insertions, 8 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 6645846..a7bea8c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1937,6 +1937,21 @@ dput_out:
return retval;
}
+static struct mnt_namespace *alloc_mnt_ns(void)
+{
+ struct mnt_namespace *new_ns;
+
+ new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+ if (!new_ns)
+ return ERR_PTR(-ENOMEM);
+ atomic_set(&new_ns->count, 1);
+ new_ns->root = NULL;
+ INIT_LIST_HEAD(&new_ns->list);
+ init_waitqueue_head(&new_ns->poll);
+ new_ns->event = 0;
+ return new_ns;
+}
+
/*
* Allocate a new namespace structure and populate it with contents
* copied from the namespace of the passed in task structure.
@@ -1948,14 +1963,9 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
struct vfsmount *p, *q;
- new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
- if (!new_ns)
- return ERR_PTR(-ENOMEM);
-
- atomic_set(&new_ns->count, 1);
- INIT_LIST_HEAD(&new_ns->list);
- init_waitqueue_head(&new_ns->poll);
- new_ns->event = 0;
+ new_ns = alloc_mnt_ns();
+ if (IS_ERR(new_ns))
+ return new_ns;
down_write(&namespace_sem);
/* First pass: copy the tree topology */
@@ -2019,6 +2029,24 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
return new_ns;
}
+/**
+ * create_mnt_ns - creates a private namespace and adds a root filesystem
+ * @mnt: pointer to the new root filesystem mountpoint
+ */
+struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
+{
+ struct mnt_namespace *new_ns;
+
+ new_ns = alloc_mnt_ns();
+ if (!IS_ERR(new_ns)) {
+ mnt->mnt_ns = new_ns;
+ new_ns->root = mnt;
+ list_add(&new_ns->list, &new_ns->root->mnt_list);
+ }
+ return new_ns;
+}
+EXPORT_SYMBOL(create_mnt_ns);
+
SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
char __user *, type, unsigned long, flags, void __user *, data)
{
@@ -2264,3 +2292,4 @@ void put_mnt_ns(struct mnt_namespace *ns)
release_mounts(&umount_list);
kfree(ns);
}
+EXPORT_SYMBOL(put_mnt_ns);
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 299d11a..3beb259 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -24,6 +24,7 @@ struct proc_mounts {
struct fs_struct;
+extern struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt);
extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
struct fs_struct *);
extern void put_mnt_ns(struct mnt_namespace *ns);
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