Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[linux-2.6-block.git] / fs / namei.c

diff --git a/fs/namei.c b/fs/namei.c
index 1d9ca2d5dff68ee184bf5dbe6d0d417f1b63f245..42f8ca038254078f4cb37d1827f9c3b2da8c85ba 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1794,30 +1794,49 @@ static inline unsigned int fold_hash(unsigned long hash)
        return hash_64(hash, 32);
 }
 
+/*
+ * This is George Marsaglia's XORSHIFT generator.
+ * It implements a maximum-period LFSR in only a few
+ * instructions.  It also has the property (required
+ * by hash_name()) that mix_hash(0) = 0.
+ */
+static inline unsigned long mix_hash(unsigned long hash)
+{
+       hash ^= hash << 13;
+       hash ^= hash >> 7;
+       hash ^= hash << 17;
+       return hash;
+}
+
 #else  /* 32-bit case */
 
 #define fold_hash(x) (x)
 
+static inline unsigned long mix_hash(unsigned long hash)
+{
+       hash ^= hash << 13;
+       hash ^= hash >> 17;
+       hash ^= hash << 5;
+       return hash;
+}
+
 #endif
 
 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
 {
-       unsigned long a, mask;
-       unsigned long hash = 0;
+       unsigned long a, hash = 0;
 
        for (;;) {
                a = load_unaligned_zeropad(name);
                if (len < sizeof(unsigned long))
                        break;
-               hash += a;
-               hash *= 9;
+               hash = mix_hash(hash + a);
                name += sizeof(unsigned long);
                len -= sizeof(unsigned long);
                if (!len)
                        goto done;
        }
-       mask = bytemask_from_count(len);
-       hash += mask & a;
+       hash += a & bytemask_from_count(len);
 done:
        return fold_hash(hash);
 }
@@ -1835,7 +1854,7 @@ static inline u64 hash_name(const char *name)
        hash = a = 0;
        len = -sizeof(unsigned long);
        do {
-               hash = (hash + a) * 9;
+               hash = mix_hash(hash + a);
                len += sizeof(unsigned long);
                a = load_unaligned_zeropad(name+len);
                b = a ^ REPEAT_BYTE('/');
@@ -2266,6 +2285,33 @@ 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
@@ -2337,7 +2383,6 @@ 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 +2414,7 @@ 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);
 
@@ -2942,22 +2984,10 @@ no_open:
                dentry = lookup_real(dir, dentry, nd->flags);
                if (IS_ERR(dentry))
                        return PTR_ERR(dentry);
-
-               if (create_error) {
-                       int open_flag = op->open_flag;
-
-                       error = create_error;
-                       if ((open_flag & O_EXCL)) {
-                               if (!dentry->d_inode)
-                                       goto out;
-                       } else if (!dentry->d_inode) {
-                               goto out;
-                       } else if ((open_flag & O_TRUNC) &&
-                                  d_is_reg(dentry)) {
-                               goto out;
-                       }
-                       /* will fail later, go on to get the right error */
-               }
+       }
+       if (create_error && !dentry->d_inode) {
+               error = create_error;
+               goto out;
        }
 looked_up:
        path->dentry = dentry;
@@ -4213,7 +4243,11 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
        bool new_is_dir = false;
        unsigned max_links = new_dir->i_sb->s_max_links;
 
-       if (source == target)
+       /*
+        * Check source == target.
+        * On overlayfs need to look at underlying inodes.
+        */
+       if (vfs_select_inode(old_dentry, 0) == vfs_select_inode(new_dentry, 0))
                return 0;
 
        error = may_delete(old_dir, old_dentry, is_dir);