cmd/runtimetest/main.go: Unify validateMountsExist and validateMountsOrder

[wking]

Also increase the error message detail and continue through the remaining mounts instead of breaking on the first missing/misordered mount. Based on previous discussion here and here. With this commit, a configuration like:

  "mounts": [
    {
      "destination": "/tmp",
      "type": "tmpfs",
      "source": "none"
    },
    {
      "destination": "/tmp",
      "type": "tmpfs",
      "source": "none"
    },
    {
      "destination": "/dev",
      "type": "devtmpfs",
      "source": "devtmpfs"
    }
  ]

and mountinfo like:

$ grep -n '/dev \|/tmp ' /proc/self/mountinfo
2:19 17 0:6 / /dev rw,nosuid,relatime - devtmpfs devtmpfs rw,size=10240k,nr_inodes=2043951,mode=755
25:41 17 0:38 / /tmp rw,relatime - tmpfs none rw

will generate errors like:

* mounts[1] {/tmp tmpfs none []} does not exist
* mounts[2] {/dev devtmpfs devtmpfs []} is system mount 1, while mounts[0] {/tmp tmpfs none []} is system mount 24

Grep reports 2 and 25 because it's counting from one, and runtimetest reports 1 and 24 because it's counting from zero.

Before this commit, the error was just:

* Mounts[1] /tmp is not mounted in order

[wking]

@Mashimiao had expected this unified approach to be long and complicated, but it ended up dropping over 20 lines even with the extra bookkeeping for configSys and highestMatchedConfig (which are used in the improved error messages).

[Mashimiao]

The changes are good, but I don't think something like system mount 1 really make sense. we don't need to care about what it really mounted number, we just need to care about if it is mounted in order.
And system mount is not easy understand.
I think mounts[2] {/dev devtmpfs devtmpfs []} MUST be mounted in order after mounts[0] {/tmp tmpfs none []}, but not may be better.

[wking]

On Thu, Aug 31, 2017 at 06:50:20AM +0000, Ma Shimiao wrote: The changes are good, but I don't think something like `system mount 1` really make sense. we don't need to care about what it really mounted number, we just need to care about if it is mounted in order. And `system mount` is not easy understand. I think `mounts[2] {/dev devtmpfs devtmpfs []} MUST be mounted in order after mounts[0] {/tmp tmpfs none []}, but not` may be better.

I like the system mount order information (or I wouldn't have put it in ;), but I don't feel that strongly about it. Removed in 60ab7ad → bcb5379, so now the errors look like: * mounts[1] {/tmp tmpfs none []} does not exist * mounts[2] {/dev devtmpfs devtmpfs []} mounted before mounts[0] {/tmp tmpfs none []}

[Mashimiao]

LGTM

[liangchenye]

LGTM