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authorMiklos Szeredi <mszeredi@redhat.com>2016-05-11 01:16:37 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2016-05-10 23:56:28 -0400
commit3c9fe8cdff1b889a059a30d22f130372f2b3885f (patch)
tree29f9b50b15ebbea097686abd2b0a71dedfcc128d
parent9409e22acdfc9153f88d9b1ed2bd2a5b34d2d3ca (diff)
downloadlinux-3c9fe8cdff1b889a059a30d22f130372f2b3885f.tar.gz
vfs: add lookup_hash() helper
Overlayfs needs lookup without inode_permission() and already has the name hash (in form of dentry->d_name on overlayfs dentry). It also doesn't support filesystems with d_op->d_hash() so basically it only needs the actual hashed lookup from lookup_one_len_unlocked() So add a new helper that does unlocked lookup of a hashed name. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
-rw-r--r--fs/namei.c33
-rw-r--r--include/linux/namei.h2
2 files changed, 30 insertions, 5 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 3ef87d673bbe..1a1ea79a7ba0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2267,6 +2267,33 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
EXPORT_SYMBOL(vfs_path_lookup);
/**
+ * lookup_hash - lookup single pathname component on already hashed name
+ * @name: name and hash to lookup
+ * @base: base directory to lookup from
+ *
+ * The name must have been verified and hashed (see lookup_one_len()). Using
+ * this after just full_name_hash() is unsafe.
+ *
+ * This function also doesn't check for search permission on base directory.
+ *
+ * Use lookup_one_len_unlocked() instead, unless you really know what you are
+ * doing.
+ *
+ * Do not hold i_mutex; this helper takes i_mutex if necessary.
+ */
+struct dentry *lookup_hash(const struct qstr *name, struct dentry *base)
+{
+ struct dentry *ret;
+
+ ret = lookup_dcache(name, base, 0);
+ if (!ret)
+ ret = lookup_slow(name, base, 0);
+
+ return ret;
+}
+EXPORT_SYMBOL(lookup_hash);
+
+/**
* lookup_one_len - filesystem helper to lookup single pathname component
* @name: pathname component to lookup
* @base: base directory to lookup from
@@ -2337,7 +2364,6 @@ struct dentry *lookup_one_len_unlocked(const char *name,
struct qstr this;
unsigned int c;
int err;
- struct dentry *ret;
this.name = name;
this.len = len;
@@ -2369,10 +2395,7 @@ struct dentry *lookup_one_len_unlocked(const char *name,
if (err)
return ERR_PTR(err);
- ret = lookup_dcache(&this, base, 0);
- if (!ret)
- ret = lookup_slow(&this, base, 0);
- return ret;
+ return lookup_hash(&this, base);
}
EXPORT_SYMBOL(lookup_one_len_unlocked);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 77d01700daf7..ec5ec2818a28 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -79,6 +79,8 @@ extern int kern_path_mountpoint(int, const char *, struct path *, unsigned int);
extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
+struct qstr;
+extern struct dentry *lookup_hash(const struct qstr *, struct dentry *);
extern int follow_down_one(struct path *);
extern int follow_down(struct path *);