aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorJosef 'Jeff' Sipek <jsipek@cs.sunysb.edu>2007-07-19 04:48:18 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 13:04:45 -0400
commit16f1820028d660d9da9c03b2ae7e98253c11795b (patch)
tree08939a5d7fcc02c76739a9dce38052da598d74d5
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>
-rw-r--r--fs/namei.c32
-rw-r--r--include/linux/namei.h2
2 files changed, 34 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c
index defaa47c11d4..3bdb29615a9d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1172,6 +1172,37 @@ int fastcall path_lookup(const char *name, unsigned int flags,
1172 return do_path_lookup(AT_FDCWD, name, flags, nd); 1172 return do_path_lookup(AT_FDCWD, name, flags, nd);
1173} 1173}
1174 1174
1175/**
1176 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1177 * @dentry: pointer to dentry of the base directory
1178 * @mnt: pointer to vfs mount of the base directory
1179 * @name: pointer to file name
1180 * @flags: lookup flags
1181 * @nd: pointer to nameidata
1182 */
1183int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1184 const char *name, unsigned int flags,
1185 struct nameidata *nd)
1186{
1187 int retval;
1188
1189 /* same as do_path_lookup */
1190 nd->last_type = LAST_ROOT;
1191 nd->flags = flags;
1192 nd->depth = 0;
1193
1194 nd->mnt = mntget(mnt);
1195 nd->dentry = dget(dentry);
1196
1197 retval = path_walk(name, nd);
1198 if (unlikely(!retval && !audit_dummy_context() && nd->dentry &&
1199 nd->dentry->d_inode))
1200 audit_inode(name, nd->dentry->d_inode);
1201
1202 return retval;
1203
1204}
1205
1175static int __path_lookup_intent_open(int dfd, const char *name, 1206static int __path_lookup_intent_open(int dfd, const char *name,
1176 unsigned int lookup_flags, struct nameidata *nd, 1207 unsigned int lookup_flags, struct nameidata *nd,
1177 int open_flags, int create_mode) 1208 int open_flags, int create_mode)
@@ -2774,6 +2805,7 @@ EXPORT_SYMBOL(__page_symlink);
2774EXPORT_SYMBOL(page_symlink); 2805EXPORT_SYMBOL(page_symlink);
2775EXPORT_SYMBOL(page_symlink_inode_operations); 2806EXPORT_SYMBOL(page_symlink_inode_operations);
2776EXPORT_SYMBOL(path_lookup); 2807EXPORT_SYMBOL(path_lookup);
2808EXPORT_SYMBOL(vfs_path_lookup);
2777EXPORT_SYMBOL(path_release); 2809EXPORT_SYMBOL(path_release);
2778EXPORT_SYMBOL(path_walk); 2810EXPORT_SYMBOL(path_walk);
2779EXPORT_SYMBOL(permission); 2811EXPORT_SYMBOL(permission);
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
69#define user_path_walk_link(name,nd) \ 69#define user_path_walk_link(name,nd) \
70 __user_walk_fd(AT_FDCWD, name, 0, nd) 70 __user_walk_fd(AT_FDCWD, name, 0, nd)
71extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *)); 71extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *));
72extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
73 const char *, unsigned int, struct nameidata *);
72extern int FASTCALL(path_walk(const char *, struct nameidata *)); 74extern int FASTCALL(path_walk(const char *, struct nameidata *));
73extern int FASTCALL(link_path_walk(const char *, struct nameidata *)); 75extern int FASTCALL(link_path_walk(const char *, struct nameidata *));
74extern void path_release(struct nameidata *); 76extern void path_release(struct nameidata *);