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authorJosef 'Jeff' Sipek <jsipek@cs.sunysb.edu>2007-07-19 01:48:18 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 10:04:45 -0700
commit16f1820028d660d9da9c03b2ae7e98253c11795b (patch)
tree08939a5d7fcc02c76739a9dce38052da598d74d5 /include/linux
parentb6a2fea39318e43fee84fa7b0b90d68bed92d2ba (diff)
fs: introduce vfs_path_lookup
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@cs.sunysb.edu> Cc: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Christoph Hellwig <hch@lst.de> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Neil Brown <neilb@suse.de> Cc: Michael Halcrow <mhalcrow@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/namei.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/namei.h b/include/linux/namei.h
index b7dd24917f0d..2e21af0989d9 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -69,6 +69,8 @@ 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 *);