Re: [PATCH RESEND net-next 07/15] smc: remote memory buffers (RMBs) (fwd)

[Ursula Braun <ubraun@linux.vnet.ibm.com>]

Hi Julia,

I am afraid I do not understand your question. This is how the code is 
supposed to work:

An SMC-R connection is allowed to run with one of 16 discrete possible 
buffer sizes and requires contiguous memory for this buffer. If there is 
no buffer available that can be reused (from a previous SMC-R 
connection), a new one is allocated. If allocation fails, the code 
"continues" and reduces the desired buffer size to the next smaller 
buffer size, and tries to reuse or allocate memory of this size. 
"continue" stops, if the lowest possible value has been tried without 
success. In this case tmp_bufsize_short is negative and -ENOMEM is returned.

On 08/09/2016 02:09 PM, Julia Lawall wrote:
> Is there a guarantee that the contrinues can't fall off the end of the
> loop?
>
> julia
>
> ---------- Forwarded message ----------
> Date: Tue, 9 Aug 2016 20:06:24 +0800
> From: kbuild test robot <fengguang.wu@intel.com>
> To: kbuild@01.org
> Cc: Julia Lawall <julia.lawall@lip6.fr>
> Subject: Re: [PATCH RESEND net-next 07/15] smc: remote memory buffers (RMBs)
>
> CC: kbuild-all@01.org
> In-Reply-To: <1470737580-43012-8-git-send-email-ubraun@linux.vnet.ibm.com>
> TO: Ursula Braun <ubraun@linux.vnet.ibm.com>
> CC: davem@davemloft.net
> CC: netdev@vger.kernel.org, linux-s390@vger.kernel.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, utz.bacher@de.ibm.com, ubraun@linux.vnet.ibm.com
>
> Hi Ursula,
>
> [auto build test WARNING on net-next/master]
>
> url:    https://github.com/0day-ci/linux/commits/Ursula-Braun/net-smc-Shared-Memory-Communications-RDMA/20160809-182526
> :::::: branch date: 2 hours ago
> :::::: commit date: 2 hours ago
>
>>> net/smc/smc_core.c:570:17-25: ERROR: reference preceded by free on line 549
>    net/smc/smc_core.c:570:17-25: ERROR: reference preceded by free on line 560
>    net/smc/smc_core.c:507:20-31: ERROR: reference preceded by free on line 486
>    net/smc/smc_core.c:507:20-31: ERROR: reference preceded by free on line 497
>
> git remote add linux-review https://github.com/0day-ci/linux
> git remote update linux-review
> git checkout 2e8eda2734f14a860721121549f05e5ecd13d81d
> vim +570 net/smc/smc_core.c
>
> 2e8eda27 Ursula Braun 2016-08-09  543  			break; /* give up with -ENOMEM */
> 2e8eda27 Ursula Braun 2016-08-09  544  		rmb_desc->cpu_addr = kzalloc(tmp_bufsize,
> 2e8eda27 Ursula Braun 2016-08-09  545  					     GFP_KERNEL | __GFP_NOWARN |
> 2e8eda27 Ursula Braun 2016-08-09  546  					     __GFP_NOMEMALLOC |
> 2e8eda27 Ursula Braun 2016-08-09  547  					     __GFP_NORETRY);
> 2e8eda27 Ursula Braun 2016-08-09  548  		if (!rmb_desc->cpu_addr) {
> 2e8eda27 Ursula Braun 2016-08-09 @549  			kfree(rmb_desc);
> 2e8eda27 Ursula Braun 2016-08-09  550  			/* if RMB allocation has failed,
> 2e8eda27 Ursula Braun 2016-08-09  551  			 * try a smaller one
> 2e8eda27 Ursula Braun 2016-08-09  552  			 */
> 2e8eda27 Ursula Braun 2016-08-09  553  			continue;
> 2e8eda27 Ursula Braun 2016-08-09  554  		}
> 2e8eda27 Ursula Braun 2016-08-09  555  		rc = smc_ib_buf_map(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
> 2e8eda27 Ursula Braun 2016-08-09  556  				    tmp_bufsize, rmb_desc,
> 2e8eda27 Ursula Braun 2016-08-09  557  				    DMA_FROM_DEVICE);
> 2e8eda27 Ursula Braun 2016-08-09  558  		if (rc) {
> 2e8eda27 Ursula Braun 2016-08-09  559  			kfree(rmb_desc->cpu_addr);
> 2e8eda27 Ursula Braun 2016-08-09  560  			kfree(rmb_desc);
> 2e8eda27 Ursula Braun 2016-08-09  561  			continue; /* if mapping failed, try smaller one */
> 2e8eda27 Ursula Braun 2016-08-09  562  		}
> 2e8eda27 Ursula Braun 2016-08-09  563  		rmb_desc->used = 1;
> 2e8eda27 Ursula Braun 2016-08-09  564  		write_lock_bh(&lgr->rmbs_lock);
> 2e8eda27 Ursula Braun 2016-08-09  565  		list_add(&rmb_desc->list,
> 2e8eda27 Ursula Braun 2016-08-09  566  			 &lgr->rmbs[tmp_bufsize_short]);
> 2e8eda27 Ursula Braun 2016-08-09  567  		write_unlock_bh(&lgr->rmbs_lock);
> 2e8eda27 Ursula Braun 2016-08-09  568  		break;
> 2e8eda27 Ursula Braun 2016-08-09  569  	}
> 2e8eda27 Ursula Braun 2016-08-09 @570  	if (rmb_desc && rmb_desc->cpu_addr) {
> 2e8eda27 Ursula Braun 2016-08-09  571  		conn->rmb_desc = rmb_desc;
> 2e8eda27 Ursula Braun 2016-08-09  572  		conn->rmbe_size = tmp_bufsize;
> 2e8eda27 Ursula Braun 2016-08-09  573  		conn->rmbe_size_short = tmp_bufsize_short;
>
> ---
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>