Re: [Qemu-devel] [PATCH] Fix block migration when the device size is not a multiple of 1 MB

[Pierre Riteau]

On 21 janv. 2011, at 10:16, Kevin Wolf wrote:

> Am 19.01.2011 15:59, schrieb Pierre Riteau:
>> b02bea3a85cc939f09aa674a3f1e4f36d418c007 added a check on the return
>> value of bdrv_write and aborts migration when it fails. However, if the
>> size of the block device to migrate is not a multiple of BLOCK_SIZE
>> (currently 1 MB), the last bdrv_write will fail with -EIO.
>> 
>> Fixed by calling bdrv_write with the correct size of the last block.
>> ---
>> block-migration.c |   16 +++++++++++++++-
>> 1 files changed, 15 insertions(+), 1 deletions(-)
>> 
>> diff --git a/block-migration.c b/block-migration.c
>> index 1475325..eeb9c62 100644
>> --- a/block-migration.c
>> +++ b/block-migration.c
>> @@ -635,6 +635,8 @@ static int block_load(QEMUFile *f, void *opaque, int 
>> version_id)
>>     int64_t addr;
>>     BlockDriverState *bs;
>>     uint8_t *buf;
>> +    int64_t total_sectors;
>> +    int nr_sectors;
>> 
>>     do {
>>         addr = qemu_get_be64(f);
>> @@ -656,10 +658,22 @@ static int block_load(QEMUFile *f, void *opaque, int 
>> version_id)
>>                 return -EINVAL;
>>             }
>> 
>> +            total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
>> +            if (total_sectors <= 0) {
>> +                fprintf(stderr, "Error getting length of block device 
>> %s\n", device_name);
>> +                return -EINVAL;
>> +            }
> 
> Can you resend the patch with error_report(), as Yoshi mentioned?
> 
> Also, I would move the total_sectors calculation outside the loop -
> though I have no idea how many iterations it typically has, so it might
> not improve things a lot.

Actually, it is not possible to move the total_sectors calculation outside the 
loop, since the loop can receive blocks from any device (this is why each block 
is prefixed by the device name).
I'm sending a new patch with a small optimization to avoid recalculating 
total_sectors when the device doesn't change in the next iteration.

-- 
Pierre Riteau -- PhD student, Myriads team, IRISA, Rennes, France
http://perso.univ-rennes1.fr/pierre.riteau/