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Subject: Re: [PATCH v2] scsi: libsas: Fix disk not being scanned in after
 being removed
To: John Garry <john.g.garry@oracle.com>, Xingui Yang <yangxingui@huawei.com>,
	<jejb@linux.ibm.com>, <martin.petersen@oracle.com>,
	<damien.lemoal@opensource.wdc.com>
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	<linuxarm@huawei.com>, <prime.zeng@hisilicon.com>,
	<chenxiang66@hisilicon.com>, <kangfenglong@huawei.com>
References: <20240227090149.29039-1-yangxingui@huawei.com>
 <f8de67cb-8d0c-475d-b3f3-bc38ff097823@oracle.com>
From: Jason Yan <yanaijie@huawei.com>
Message-ID: <4067aa2d-838d-5cd8-5e93-c9c4ade995fc@huawei.com>
Date: Thu, 7 Mar 2024 10:13:33 +0800
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On 2024/3/7 2:43, John Garry wrote:
> As an aside, could libsas - and your changes here - be simpler if we 
> changed smp_execute_task() like this:
> 
> static int smp_execute_task(struct domain_device *dev, void *req /* can 
> be on the stack */, int req_size,
>                  void *resp /* can be on the stack */, int resp_size)
> {
>      struct scatterlist req_sg;
>      struct scatterlist resp_sg;
>      int ret;
>      void *_req = kmemdup(req, req_size, GFP_KERNEL);
>      void *_resp = alloc_smp_resp(resp_size);
>      if (!_req || !resp)
>          return -ENOMEM;
> 
>      sg_init_one(&req_sg, _req, req_size);
>      sg_init_one(&resp_sg, _resp, resp_size);
>      ret = smp_execute_task_sg(dev, &req_sg, &resp_sg);
>      memcpy(resp, _resp, resp_size);
>      kfree(_req);
>      kfree(_resp);
>      return ret;
> }
> 
> We need to use alloc_smp_resp() and alloc_smp_req() as we can't allocate 
> these memories on the stack for calling sg_init_one(). But if we changed 
> smp_execute_task() to memcpy from/to data on the stack, it might make 
> callers simpler. I'm not sure.

Maybe simpler. I have not check all the length of these buffers, but 
there is still a risk of stack overflow if the buffer on stack is too 
large.

Thanks,
Jason