The only change since V3, is the fix for a vfsmount reference leak in the
nfsctl patch (pointed out by hch).
Stackable file systems, among others, frequently need to lookup paths or
path components starting from an arbitrary point in the namespace
(identified by a dentry and a vfsmount). Currently, such file systems use
lookup_one_len, which is frowned upon [1] as it does not pass the lookup
intent along; not passing a lookup intent, for example, can trigger BUG_ON's
when stacking on top of NFSv4.
The first patch introduces a new lookup function to allow lookup starting
from an arbitrary point in the namespace. This approach has been suggested
by Christoph Hellwig [2].
The second patch changes sunrpc to use vfs_path_lookup.
The third patch changes nfsctl.c to use vfs_path_lookup.
The fourth patch marks link_path_walk static.
The fifth, and last patch, unexports path_walk because it is no longer
unnecessary to call it directly, and using the new vfs_path_lookup is
cleaner.
For example, the following snippet of code, looks up "some/path/component"
in a directory pointed to by parent_{dentry,vfsmnt}:
err = vfs_path_lookup(parent_dentry, parent_vfsmnt,
"some/path/component", 0, &nd);
if (!err) {
/* exits */
...
/* once done, release the references */
path_release(&nd);
} else if (err == -ENOENT) {
/* doesn't exist */
} else {
/* other error */
}
VFS functions such as lookup_create can be used on the nameidata structure
to pass the create intent to the file system.
Josef 'Jeff' Sipek.
[1] http://lkml.org/lkml/2007/3/9/95
[2] http://lkml.org/lkml/2007/5/4/51
use vfs_path_lookup instead of open-coding the necessary functionality.
Signed-off-by: Josef 'Jeff' Sipek <[email protected]>
Acked-by: Trond Myklebust <[email protected]>
---
net/sunrpc/rpc_pipe.c | 16 +++++++---------
1 files changed, 7 insertions(+), 9 deletions(-)
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index 5887457..db6f231 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -451,21 +451,19 @@ void rpc_put_mount(void)
static int
rpc_lookup_parent(char *path, struct nameidata *nd)
{
+ struct vfsmount *mnt;
+
if (path[0] == '\0')
return -ENOENT;
- nd->mnt = rpc_get_mount();
- if (IS_ERR(nd->mnt)) {
+
+ mnt = rpc_get_mount();
+ if (IS_ERR(mnt)) {
printk(KERN_WARNING "%s: %s failed to mount "
"pseudofilesystem \n", __FILE__, __FUNCTION__);
- return PTR_ERR(nd->mnt);
+ return PTR_ERR(mnt);
}
- mntget(nd->mnt);
- nd->dentry = dget(rpc_mount->mnt_root);
- nd->last_type = LAST_ROOT;
- nd->flags = LOOKUP_PARENT;
- nd->depth = 0;
- if (path_walk(path, nd)) {
+ if (vfs_path_lookup(mnt->mnt_root, mnt, path, LOOKUP_PARENT, nd)) {
printk(KERN_WARNING "%s: %s failed to find path %s\n",
__FILE__, __FUNCTION__, path);
rpc_put_mount();
--
1.5.2.rc1.165.gaf9b
Signed-off-by: Josef 'Jeff' Sipek <[email protected]>
---
fs/namei.c | 4 +++-
include/linux/namei.h | 1 -
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index a30efbc..50285a1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -107,6 +107,8 @@
* any extra contention...
*/
+static int fastcall link_path_walk(const char *name, struct nameidata *nd);
+
/* In order to reduce some races, while at the same time doing additional
* checking and hopefully speeding things up, we copy filenames to the
* kernel data space before using them..
@@ -998,7 +1000,7 @@ return_err:
* Retry the whole path once, forcing real lookup requests
* instead of relying on the dcache.
*/
-int fastcall link_path_walk(const char *name, struct nameidata *nd)
+static int fastcall link_path_walk(const char *name, struct nameidata *nd)
{
struct nameidata save = *nd;
int result;
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 4718788..d60a5eb 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -73,7 +73,6 @@ extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *));
extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
const char *, unsigned int, struct nameidata *);
extern int FASTCALL(path_walk(const char *, struct nameidata *));
-extern int FASTCALL(link_path_walk(const char *, struct nameidata *));
extern void path_release(struct nameidata *);
extern void path_release_on_umount(struct nameidata *);
--
1.5.2.rc1.165.gaf9b
Signed-off-by: Josef 'Jeff' Sipek <[email protected]>
---
fs/namei.c | 3 +--
include/linux/namei.h | 1 -
2 files changed, 1 insertions(+), 3 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 50285a1..15f45ac 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1024,7 +1024,7 @@ static int fastcall link_path_walk(const char *name, struct nameidata *nd)
return result;
}
-int fastcall path_walk(const char * name, struct nameidata *nd)
+static int fastcall path_walk(const char * name, struct nameidata *nd)
{
current->total_link_count = 0;
return link_path_walk(name, nd);
@@ -2810,7 +2810,6 @@ EXPORT_SYMBOL(page_symlink_inode_operations);
EXPORT_SYMBOL(path_lookup);
EXPORT_SYMBOL(vfs_path_lookup);
EXPORT_SYMBOL(path_release);
-EXPORT_SYMBOL(path_walk);
EXPORT_SYMBOL(permission);
EXPORT_SYMBOL(vfs_permission);
EXPORT_SYMBOL(file_permission);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index d60a5eb..e378e1f 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -72,7 +72,6 @@ extern int FASTCALL(__user_walk_fd(int dfd, const char __user *, unsigned, struc
extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *));
extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
const char *, unsigned int, struct nameidata *);
-extern int FASTCALL(path_walk(const char *, struct nameidata *));
extern void path_release(struct nameidata *);
extern void path_release_on_umount(struct nameidata *);
--
1.5.2.rc1.165.gaf9b
use vfs_path_lookup instead of open-coding the necessary functionality.
Signed-off-by: Josef 'Jeff' Sipek <[email protected]>
Acked-by: NeilBrown <[email protected]>
---
fs/nfsctl.c | 16 ++++++----------
1 files changed, 6 insertions(+), 10 deletions(-)
diff --git a/fs/nfsctl.c b/fs/nfsctl.c
index c043136..51f1b31 100644
--- a/fs/nfsctl.c
+++ b/fs/nfsctl.c
@@ -23,19 +23,15 @@
static struct file *do_open(char *name, int flags)
{
struct nameidata nd;
+ struct vfsmount *mnt;
int error;
- nd.mnt = do_kern_mount("nfsd", 0, "nfsd", NULL);
+ mnt = do_kern_mount("nfsd", 0, "nfsd", NULL);
+ if (IS_ERR(mnt))
+ return (struct file *)mnt;
- if (IS_ERR(nd.mnt))
- return (struct file *)nd.mnt;
-
- nd.dentry = dget(nd.mnt->mnt_root);
- nd.last_type = LAST_ROOT;
- nd.flags = 0;
- nd.depth = 0;
-
- error = path_walk(name, &nd);
+ error = vfs_path_lookup(mnt->mnt_root, mnt, name, 0, &nd);
+ mntput(mnt); /* drop do_kern_mount reference */
if (error)
return ERR_PTR(error);
--
1.5.2.rc1.165.gaf9b
Signed-off-by: Josef 'Jeff' Sipek <[email protected]>
---
fs/namei.c | 32 ++++++++++++++++++++++++++++++++
include/linux/namei.h | 2 ++
2 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 580162b..a30efbc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1172,6 +1172,37 @@ int fastcall path_lookup(const char *name, unsigned int flags,
return do_path_lookup(AT_FDCWD, name, flags, nd);
}
+/**
+ * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
+ * @dentry: pointer to dentry of the base directory
+ * @mnt: pointer to vfs mount of the base directory
+ * @name: pointer to file name
+ * @flags: lookup flags
+ * @nd: pointer to nameidata
+ */
+int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
+ const char *name, unsigned int flags,
+ struct nameidata *nd)
+{
+ int retval;
+
+ /* same as do_path_lookup */
+ nd->last_type = LAST_ROOT;
+ nd->flags = flags;
+ nd->depth = 0;
+
+ nd->mnt = mntget(mnt);
+ nd->dentry = dget(dentry);
+
+ retval = path_walk(name, nd);
+ if (unlikely(!retval && !audit_dummy_context() && nd->dentry &&
+ nd->dentry->d_inode))
+ audit_inode(name, nd->dentry->d_inode);
+
+ return retval;
+
+}
+
static int __path_lookup_intent_open(int dfd, const char *name,
unsigned int lookup_flags, struct nameidata *nd,
int open_flags, int create_mode)
@@ -2775,6 +2806,7 @@ EXPORT_SYMBOL(__page_symlink);
EXPORT_SYMBOL(page_symlink);
EXPORT_SYMBOL(page_symlink_inode_operations);
EXPORT_SYMBOL(path_lookup);
+EXPORT_SYMBOL(vfs_path_lookup);
EXPORT_SYMBOL(path_release);
EXPORT_SYMBOL(path_walk);
EXPORT_SYMBOL(permission);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 0ab27ba..4718788 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -70,6 +70,8 @@ extern int FASTCALL(__user_walk_fd(int dfd, const char __user *, unsigned, struc
#define user_path_walk_link(name,nd) \
__user_walk_fd(AT_FDCWD, name, 0, nd)
extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *));
+extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
+ const char *, unsigned int, struct nameidata *);
extern int FASTCALL(path_walk(const char *, struct nameidata *));
extern int FASTCALL(link_path_walk(const char *, struct nameidata *));
extern void path_release(struct nameidata *);
--
1.5.2.rc1.165.gaf9b