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Date: Tue, 14 Aug 2012 14:24:52 +0530
From: Supriya Kannery <supriyak@linux.vnet.ibm.com>
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Subject: Re: [Qemu-devel] [v2 Patch 1/9]block: Framework for reopening image
 files safely
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To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Shrinidhi Joshi <spjoshi31@gmail.com>, Stefan Hajnoczi <stefanha@gmail.com>, Jeff Cody <jcody@redhat.com>, qemu-devel@nongnu.org, Christoph Hellwig <hch@lst.de>

On 08/03/2012 01:49 AM, Luiz Capitulino wrote:
> On Tue, 31 Jul 2012 03:04:22 +0530
> Supriya Kannery<supriyak@linux.vnet.ibm.com>  wrote:
> 

>> +
>> +void bdrv_reopen_commit(BlockDriverState *bs, BDRVReopenState *rs)
>> +{
>> +    BlockDriver *drv = bs->drv;
>> +
>> +    drv->bdrv_reopen_commit(bs, rs);
>> +}
>> +
>> +void bdrv_reopen_abort(BlockDriverState *bs, BDRVReopenState *rs)
>> +{
>> +    BlockDriver *drv = bs->drv;
>> +
>> +    drv->bdrv_reopen_abort(bs, rs);
>> +}
>> +
>> +void bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp)
>> +{
>> +    BlockDriver *drv = bs->drv;
>> +    int ret = 0;
>> +    BDRVReopenState *reopen_state = NULL;
>> +
>> +    /* Quiesce IO for the given block device */
>> +    bdrv_drain_all();
>> +    ret = bdrv_flush(bs);
>> +    if (ret != 0) {
>> +        error_set(errp, QERR_IO_ERROR);
>> +        return;
>> +    }
>> +
>> +    /* Use driver specific reopen() if available */
>> +    if (drv->bdrv_reopen_prepare) {
>> +        ret = bdrv_reopen_prepare(bs,&reopen_state, bdrv_flags);
>> +         if (ret<  0) {
>> +            bdrv_reopen_abort(bs, reopen_state);
> 
> Why do you have to call bdrv_reopen_abort()? I'd expect bdrv_reopen_prepare()
> (to be able) to undo anything it has done.
> 
    Having separate abort function avoids cluttering of reopen-
prepare(). We wanted to logically separate out preparation, commit and 
abort. Same format is followed in implementations at block driver level
as well.
 -thanks, Supriya