hlfs_rm_snapshot remove a snapshot not taken

bug总述
========
hlfs_rm_snapshot设计的目的是删除一个snapshot, 
但是如果这个snapshot根本就没有
take,我们再去删除这个snapshot，这时我们应该给出用户一个提�
��，你要删除的snapshot
不存在。存在以下场景，可能会出现问题,
用户删除snapshot时，名字给错了，但是咱们系统没给出提示，
那么他还以为自己删除了。

测试环境
=========
Distributor ID: Ubuntu
Description:    Ubuntu 10.04.3 LTS
Release:        10.04
Codename:       lucid
Linux jiawei-laptop 2.6.32-37-generic #81-Ubuntu SMP Fri Dec 2
20:35:14 UTC 2011 i686 GNU/Linux

测试用例
=========
#include <glib.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include "api/hlfs.h"
#include "hlfs_log.h"

#define REQ_SIZE 4096
#define TOTAL_SIZE 40960

typedef struct {
       struct hlfs_ctrl *ctrl;
} Fixture;

static void
do_snapshot(Fixture *fixture, int i) {
       g_message("enter func %s", __func__);
       char buffer[128];
       memset(buffer, 0, 128);
       if (0 == i) {
               sprintf(buffer, "%s%d", "snapshot", i);
               g_message("%d buffer is [%s]", i, buffer);
               int ret = hlfs_take_snapshot(fixture->ctrl, buffer);
               g_assert(ret == 0);
       } else if (1 == i) {
               sprintf(buffer, "%s", " ");
               g_message("%d buffer is [%s]", i, buffer);
               int ret = hlfs_take_snapshot(fixture->ctrl, buffer);
               g_assert(ret == 0);
       } else if (2 == i) {
               sprintf(buffer, "%s", "+");
               g_message("%d buffer is [%s]", i, buffer);
               int ret = hlfs_take_snapshot(fixture->ctrl, buffer);
               g_assert(ret == 0);
       } else if (3 == i) {
               sprintf(buffer, "%s", "##@");
               g_message("%d buffer is [%s]", i, buffer);
               int ret = hlfs_take_snapshot(fixture->ctrl, buffer);
               g_assert(ret == 0);
       } else if (4 == i) {
               sprintf(buffer, "%s", "..");
               g_message("%d buffer is [%s]", i, buffer);
               int ret = hlfs_take_snapshot(fixture->ctrl, buffer);
               g_assert(ret == 0);
       } else if (5 == i) {
               sprintf(buffer, "%s", " **");
               g_message("%d buffer is [%s]", i, buffer);
               int ret = hlfs_take_snapshot(fixture->ctrl, buffer);
               g_assert(ret == 0);
       } else if (6 == i) {
               sprintf(buffer, "%s", "1234");
               g_message("%d buffer is [%s]", i, buffer);
               int ret = hlfs_take_snapshot(fixture->ctrl, buffer);
               g_assert(ret == 0);
       }
       g_message("leave func %s", __func__);
       return ;
}

static void
take_snapshot(Fixture *fixture, const void *data) {
       g_message("enter func %s", __func__);
       char content[REQ_SIZE];
       int offset = 0;
       int i = 0;

       memset(content, 0, REQ_SIZE);
       while (offset < TOTAL_SIZE) {
               int ret1 = hlfs_write(fixture->ctrl, content, REQ_SIZE, offset);
               g_assert_cmpint(ret1, ==, REQ_SIZE);
               do_snapshot(fixture, i);
               offset += REQ_SIZE;
               i += 1;
       }
       g_message("leave func %s", __func__);
       return;
}

static void
hlfs_rm_snapshot_setup(Fixture *fixture, const void *data) {
       g_message("enter func %s", __func__);
       const char *uri = (const char *)data;
       fixture->ctrl = init_hlfs(uri);
       int ret = hlfs_open(fixture->ctrl, 1);
       g_assert_cmpint(ret, == , 0);
       g_assert(fixture->ctrl != NULL);
       take_snapshot(fixture, data);
       g_message("leave func %s", __func__);
       return ;
}

static void
test_hlfs_rm_snapshot(Fixture *fixture, const void *data) {
       g_message("enter func %s", __func__);
       const char *uri = (const char *) data;
       int ret = 0;
       ret = hlfs_rm_snapshot(uri, "snapshot0");
       g_assert(ret == 0);
       ret = hlfs_rm_snapshot(uri, "bug here");
       g_assert(ret == 0);
       g_message("leave func %s", __func__);
       return ;
}

static void
hlfs_rm_snapshot_tear_down(Fixture *fixture, const void *data) {
       g_message("enter func %s", __func__);
       hlfs_close(fixture->ctrl);
       deinit_hlfs(fixture->ctrl);
       g_message("leave func %s", __func__);
       return;
}

int main(int argc, char **argv) {
       g_message("enter func %s", __func__);
       if (log4c_init()) {
               g_message("log4c init error!");
       }
       g_test_init(&argc, &argv, NULL);
       g_test_add("/misc/hlfs_rm_snapshot",
                               Fixture,
                               "local:///tmp/testenv/testfs",
                               hlfs_rm_snapshot_setup,
                               test_hlfs_rm_snapshot,
                               hlfs_rm_snapshot_tear_down);
       g_message("leave func %s", __func__);
       return g_test_run();
}

用例分析
===========
调用hlfs_take_snapshot创建了以下snapshot
"snapshot0"
" "
"+"
"##@"
".."
" **"
"1234"

调用hlfs_rm_snapshot删除以下snapshot
"snapshot0"
"bug here"

期望输出
=========
+snapshot0#1325165574277#8240#
+ #1325165574333#16660#
++#1325165574401#25080#
+##@#1325165574445#33500#
+..#1325165574490#41920#
+ **#1325165574535#50340#
+1234#1325165574579#58760#
-snapshot0###

实际输出
========
+snapshot0#1325165574277#8240#
+ #1325165574333#16660#
++#1325165574401#25080#
+##@#1325165574445#33500#
+..#1325165574490#41920#
+ **#1325165574535#50340#
+1234#1325165574579#58760#
-snapshot0###
-bug here###

bug分析
=======
我们在删除“bug here”快照之前，根本没有take 
它，也就是说删除这个bug的记录
不应该放到snapshot.txt文件中，至少应该给用户一个提示，“��
�所删除的快照不存在”
或者其他形式。

出现bug的原因
==============
在删除某个快照之前，没有判断此刻这个快照是否存在

这个bug的目前状态
=================
目前这个bug还没解决，我会尽快进行处理。
Original issue reported on code.google.com by harryxi...@gmail.com on 29 Dec 2011 at 1:58
HarryWei / cloudxy

hlfs_rm_snapshot remove a snapshot not taken #6
