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Re: [Qemu-devel] Re: [PATCH 2/2] block: Cache total_sectors to reduce bd
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] Re: [PATCH 2/2] block: Cache total_sectors to reduce bdrv_getlength calls |
Date: |
Mon, 19 Apr 2010 16:31:42 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 |
Am 19.04.2010 16:26, schrieb Stefan Hajnoczi:
> On Mon, Apr 19, 2010 at 3:10 PM, Kevin Wolf <address@hidden> wrote:
>>> @@ -416,9 +417,7 @@ static int bdrv_open_common(BlockDriverState *bs, const
>>> char *filename,
>>> }
>>>
>>> bs->keep_read_only = bs->read_only = !(open_flags & BDRV_O_RDWR);
>>> - if (drv->bdrv_getlength) {
>>> - bs->total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
>>> - }
>>> + bs->total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
>>
>> Does this hunk make a difference? If drv->bdrv_getlength == NULL, we'll
>> just get back the current value.
>
> The if statement could be left as is. I removed it to reduce the
> number of places where if (drv->bdrv_getlength) is explicitly checked.
> If callers don't know the internals of bdrv_getlength() then it is
> easier to extend it without auditing and changing callers.
Makes sense, I'm not opposed to it.
> Having said that, I did add an if (drv->bdrv_getlength) check into
> bdrv_truncate...
Well, you probably can't do much about it there.
Kevin