fs/adfs: dir: update directory locking

Update directory locking such that it covers the validation of the
directory, which could fail if another thread is concurrently writing
to the same directory.  Since we may sleep, we need to use a rwsem
rather than a rw spinlock.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/adfs/dir.c

@@ -12,7 +12,7 @@
 /*
  * For future.  This should probably be per-directory.
  */
-static DEFINE_RWLOCK(adfs_dir_lock);
+static DECLARE_RWSEM(adfs_dir_rwsem);
 
 int adfs_dir_copyfrom(void *dst, struct adfs_dir *dir, unsigned int offset,
 		      size_t len)
@@ -232,26 +232,25 @@ adfs_readdir(struct file *file, struct dir_context *ctx)
 	if (ctx->pos >> 32)
 		return 0;
 
+	down_read(&adfs_dir_rwsem);
 	ret = adfs_dir_read_inode(sb, inode, &dir);
 	if (ret)
-		return ret;
+		goto unlock;
 
 	if (ctx->pos == 0) {
 		if (!dir_emit_dot(file, ctx))
-			goto free_out;
+			goto unlock_relse;
 		ctx->pos = 1;
 	}
 	if (ctx->pos == 1) {
 		if (!dir_emit(ctx, "..", 2, dir.parent_id, DT_DIR))
-			goto free_out;
+			goto unlock_relse;
 		ctx->pos = 2;
 	}
 
-	read_lock(&adfs_dir_lock);
-
 	ret = ops->setpos(&dir, ctx->pos - 2);
 	if (ret)
-		goto unlock_out;
+		goto unlock_relse;
 	while (ops->getnext(&dir, &obj) == 0) {
 		if (!dir_emit(ctx, obj.name, obj.name_len,
 			      obj.indaddr, DT_UNKNOWN))
@@ -259,12 +258,14 @@ adfs_readdir(struct file *file, struct dir_context *ctx)
 		ctx->pos++;
 	}
 
-unlock_out:
-	read_unlock(&adfs_dir_lock);
-
-free_out:
+unlock_relse:
+	up_read(&adfs_dir_rwsem);
 	adfs_dir_relse(&dir);
 	return ret;
+
+unlock:
+	up_read(&adfs_dir_rwsem);
+	return ret;
 }
 
 int
@@ -281,13 +282,13 @@ adfs_dir_update(struct super_block *sb, struct object_info *obj, int wait)
 	if (!ops->update)
 		return -EINVAL;
 
+	down_write(&adfs_dir_rwsem);
 	ret = adfs_dir_read(sb, obj->parent_id, 0, &dir);
 	if (ret)
-		goto out;
+		goto unlock;
 
-	write_lock(&adfs_dir_lock);
 	ret = ops->update(&dir, obj);
-	write_unlock(&adfs_dir_lock);
+	up_write(&adfs_dir_rwsem);
 
 	if (ret == 0)
 		adfs_dir_mark_dirty(&dir);
@@ -299,7 +300,10 @@ adfs_dir_update(struct super_block *sb, struct object_info *obj, int wait)
 	}
 
 	adfs_dir_relse(&dir);
-out:
+	return ret;
+
+unlock:
+	up_write(&adfs_dir_rwsem);
 #endif
 	return ret;
 }
@@ -336,17 +340,14 @@ static int adfs_dir_lookup_byname(struct inode *inode, const struct qstr *qstr,
 	u32 name_len;
 	int ret;
 
+	down_read(&adfs_dir_rwsem);
 	ret = adfs_dir_read_inode(sb, inode, &dir);
 	if (ret)
-		goto out;
-
-	obj->parent_id = inode->i_ino;
-
-	read_lock(&adfs_dir_lock);
+		goto unlock;
 
 	ret = ops->setpos(&dir, 0);
 	if (ret)
-		goto unlock_out;
+		goto unlock_relse;
 
 	ret = -ENOENT;
 	name = qstr->name;
@@ -357,13 +358,15 @@ static int adfs_dir_lookup_byname(struct inode *inode, const struct qstr *qstr,
 			break;
 		}
 	}
+	obj->parent_id = inode->i_ino;
 
-unlock_out:
-	read_unlock(&adfs_dir_lock);
-
-free_out:
+unlock_relse:
+	up_read(&adfs_dir_rwsem);
 	adfs_dir_relse(&dir);
-out:
+	return ret;
+
+unlock:
+	up_read(&adfs_dir_rwsem);
 	return ret;
 }