The patch titled
fs: introduce vfs_path_lookup
has been added to the -mm tree. Its filename is
fs-introduce-vfs_path_lookup.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
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------------------------------------------------------
Subject: fs: introduce vfs_path_lookup
From: "Josef 'Jeff' Sipek" <jsipek@xxxxxxxxxxxxx>
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.
Signed-off-by: Josef 'Jeff' Sipek <jsipek@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Michael Halcrow <mhalcrow@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/namei.c | 32 ++++++++++++++++++++++++++++++++
include/linux/namei.h | 2 ++
2 files changed, 34 insertions(+)
diff -puN fs/namei.c~fs-introduce-vfs_path_lookup fs/namei.c
--- a/fs/namei.c~fs-introduce-vfs_path_lookup
+++ a/fs/namei.c
@@ -1172,6 +1172,37 @@ int fastcall path_lookup(const char *nam
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 -puN include/linux/namei.h~fs-introduce-vfs_path_lookup include/linux/namei.h
--- a/include/linux/namei.h~fs-introduce-vfs_path_lookup
+++ a/include/linux/namei.h
@@ -70,6 +70,8 @@ extern int FASTCALL(__user_walk_fd(int d
#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 *);
_
Patches currently in -mm which might be from jsipek@xxxxxxxxxxxxx are
git-unionfs.patch
ecryptfs-move-ecryptfs-docs-into-documentation-filesystems.patch
fs-introduce-vfs_path_lookup.patch
sunrpc-use-vfs_path_lookup.patch
nfsctl-use-vfs_path_lookup.patch
fs-mark-link_path_walk-static.patch
fs-remove-path_walk-export.patch
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