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

[Kevin Wolf <kwolf@redhat.com>]

Am 21.01.2011 12:38, schrieb 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.

Right, I should have read a bit more context... I won't insist on an
optimization in this case, but if you like to do it, go ahead.

Kevin