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Re: [Qemu-devel] [RFC PATCH 5/5] qemu_aio_get used to clear all allocate
From: |
Frediano Ziglio |
Subject: |
Re: [Qemu-devel] [RFC PATCH 5/5] qemu_aio_get used to clear all allocated buffer |
Date: |
Wed, 20 Jul 2011 15:45:34 +0200 |
2011/7/20 Kevin Wolf <address@hidden>:
> Am 20.07.2011 09:57, schrieb Frediano Ziglio:
>> Signed-off-by: Frediano Ziglio <address@hidden>
>> ---
>> block/qcow.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/block/qcow.c b/block/qcow.c
>> index 007fb57..8fd1ee5 100644
>> --- a/block/qcow.c
>> +++ b/block/qcow.c
>> @@ -499,7 +499,6 @@ static QCowAIOCB *qcow_aio_setup(BlockDriverState *bs,
>> int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
>> int is_write, QCowAIOCB *acb)
>> {
>> - memset(acb, 0, sizeof(*acb));
>> acb->bs = bs;
>> acb->sector_num = sector_num;
>> acb->qiov = qiov;
>> @@ -509,6 +508,7 @@ static QCowAIOCB *qcow_aio_setup(BlockDriverState *bs,
>> if (is_write)
>> qemu_iovec_to_buffer(qiov, acb->buf);
>> } else {
>> + acb->orig_buf = NULL;
>> acb->buf = (uint8_t *)qiov->iov->iov_base;
>> }
>> acb->nb_sectors = nb_sectors;
>
> What does this fix? Removing the memset looks like changing code for no
> obvious reason. Is there any state in acb that must survive qcow_aio_setup?
>
> Kevin
>
No, this is not a fix, just an optimization, memset was used to clear
entire structure but all fields are set by qcow_aio_setup, only
orig_buf left.
The comment, I must admit is terrible! And it's mine! I'll rewrite all
comments, perhaps merge some commits and send all patches again.
Frediano
- [Qemu-devel] [RFC PATCH 0/5] Coroutines cleanup, Frediano Ziglio, 2011/07/20
- [Qemu-devel] [RFC PATCH 1/5] allocate AIO on stack, Frediano Ziglio, 2011/07/20
- [Qemu-devel] [RFC PATCH 2/5] use more stack, Frediano Ziglio, 2011/07/20
- [Qemu-devel] [RFC PATCH 3/5] more stack work, Frediano Ziglio, 2011/07/20
- [Qemu-devel] [RFC PATCH 4/5] avoid dandling pointers, Frediano Ziglio, 2011/07/20
- [Qemu-devel] [RFC PATCH 5/5] qemu_aio_get used to clear all allocated buffer, Frediano Ziglio, 2011/07/20
- Re: [Qemu-devel] [RFC PATCH 0/5] Coroutines cleanup, Kevin Wolf, 2011/07/20