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Re: [Qemu-devel] [PATCH] Avoid divide by zero when there is no block dev
From: |
Pierre Riteau |
Subject: |
Re: [Qemu-devel] [PATCH] Avoid divide by zero when there is no block device to migrate |
Date: |
Wed, 12 Jan 2011 12:01:21 +0100 |
On 11 janv. 2011, at 12:54, Kevin Wolf wrote:
> Am 25.12.2010 21:52, schrieb Pierre Riteau:
>> When block migration is requested and no read-write block device is
>> present, a divide by zero exception is triggered because
>> total_sector_sum equals zero.
>>
>> Signed-off-by: Pierre Riteau <address@hidden>
>
> Maybe in this case we should generate an error before actually starting
> with block migration. If you bothered to request block migration you
> certainly didn't have in mind to do nothing.
I had in mind a scenario where a management system would use block migration
all the time, regardless of what kind of devices were plugged in the VM.
If we throw an error, should it be a fatal error? Or just a migration failed
result given to the monitor?
>> ---
>> block-migration.c | 6 +++++-
>> 1 files changed, 5 insertions(+), 1 deletions(-)
>>
>> diff --git a/block-migration.c b/block-migration.c
>> index 1475325..d62d63e 100644
>> --- a/block-migration.c
>> +++ b/block-migration.c
>> @@ -350,7 +350,11 @@ static int blk_mig_save_bulked_block(Monitor *mon,
>> QEMUFile *f)
>> }
>> }
>>
>> - progress = completed_sector_sum * 100 /
>> block_mig_state.total_sector_sum;
>> + if (block_mig_state.total_sector_sum != 0) {
>> + progress = completed_sector_sum * 100 /
>> block_mig_state.total_sector_sum;
>
> This exceeds 80 characters per line.
>
>> + } else {
>> + progress = 100;
>> + }
>> if (progress != block_mig_state.prev_progress) {
>> block_mig_state.prev_progress = progress;
>> qemu_put_be64(f, (progress << BDRV_SECTOR_BITS)
>
> Kevin
--
Pierre Riteau -- PhD student, Myriads team, IRISA, Rennes, France
http://perso.univ-rennes1.fr/pierre.riteau/