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Re: [Qemu-devel] [PATCH v4 2/2] qemu-ga: sample fsfreeze hooks
From: |
Tomoki Sekiyama |
Subject: |
Re: [Qemu-devel] [PATCH v4 2/2] qemu-ga: sample fsfreeze hooks |
Date: |
Tue, 27 Nov 2012 11:35:01 +0900 |
User-agent: |
Mozilla/5.0 (Windows NT 5.1; rv:16.0) Gecko/20121005 Thunderbird/16.0 |
On 2012/11/26 21:40, Luiz Capitulino wrote:
> On Mon, 26 Nov 2012 20:49:17 +0900
> Tomoki Sekiyama <address@hidden> wrote:
>
>> On 2012/11/23 1:03, Luiz Capitulino wrote:
>>> On Thu, 22 Nov 2012 11:15:49 +0900
>>> Tomoki Sekiyama <address@hidden> wrote:
>>>
>>>> Adds sample hook scripts for --fsfreeze-hook option of qemu-ga.
>>>> - fsfreeze-hook : execute scripts in fsfreeze-hook.d/
>>>> - fsfreeze-hook.d.sample/mysql-flush.sh : quiesce MySQL before snapshot
>> <snip>
>>>> +# Iterate executables in directory "fsfreeze-hook.d" with the specified
>>>> args
>>>> +[ ! -d "$FSFREEZE_D" ] && exit 1
>>>> +for file in "$FSFREEZE_D"/* ; do
>>>> + is_ignored_file "$file" && continue
>>>> + [ -x "$file" ] || continue
>>>> + echo "$(date): execute $file $@" >>$LOGFILE
>>>> + "$file" "$@" >>$LOGFILE 2>&1
>>>> + STATUS=$?
>>>> + echo "$(date): $file finished with status=$STATUS" >>$LOGFILE
>>>> +done
>>>
>>> execute_fsfreeze_hook() will fail the freeze process if this script fails.
>>> Two
>>> comments:
>>>
>>> 1. Do we want to fail the freeze process if one of the sub-scripts fails?
>>> If yes, then we have to exit 1 in the first failure
>>
>> I originally thought the hooks are optional; even they failed,
>> filesystem-level
>> consistency are still kept in the snapshot.
>> However, if we are going to fail fsfreeze process by one of sub-scripts'
>> failure, we also need to notify scripts which already succeeded to pre-freeze
>> to thaw (or abort) freezing, before exit 1 here.
>
> Right, which makes things more complex. I vote for doing it the simpler way
> for now then, which is to ignore subscripts exit status. But then you should
> add exit 0 after the loop to avoid this:
I agree this way.
>>> 2. The exit status of the script will echo's exit status. I doubt we want
>>> that
>>
>> Do you mean $STATUS (not $status) is specialized in some shell environments?
>
> No, what I meant is that (afaik) when the script finishes, its return status
> to
> qemu-ga is actually going to be the latest call echo exit status because it's
> the last command executed in the loop. If echo fails (say no space) then
> the script will fail.
>
> We either, ignore any failures in qemu-ga itself (although we should at least
> print a warning there) and/or add exit 0 as the last line of the script.
Now I got the point. I will fix this at the next version.
Thanks,
--
Tomoki Sekiyama <address@hidden>
Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory