linux-kernel - Re: [PATCH] mm/cma: cma_declare_contiguous: correct err handling

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Date:   Tue, 19 Feb 2019 17:55:33 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Peng Fan <peng.fan@....com>
Cc:     "labbott@...hat.com" <labbott@...hat.com>,
        "mhocko@...e.com" <mhocko@...e.com>,
        "iamjoonsoo.kim@....com" <iamjoonsoo.kim@....com>,
        "rppt@...ux.vnet.ibm.com" <rppt@...ux.vnet.ibm.com>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "andreyknvl@...gle.com" <andreyknvl@...gle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "van.freenix@...il.com" <van.freenix@...il.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH] mm/cma: cma_declare_contiguous: correct err handling

On 2/14/19 9:38 PM, Andrew Morton wrote:
> On Thu, 14 Feb 2019 12:45:51 +0000 Peng Fan <peng.fan@....com> wrote:
> 
>> In case cma_init_reserved_mem failed, need to free the memblock allocated
>> by memblock_reserve or memblock_alloc_range.
>>
>> ...
>>
>> --- a/mm/cma.c
>> +++ b/mm/cma.c
>> @@ -353,12 +353,14 @@ int __init cma_declare_contiguous(phys_addr_t base,
>>  
>>  	ret = cma_init_reserved_mem(base, size, order_per_bit, name, res_cma);
>>  	if (ret)
>> -		goto err;
>> +		goto free_mem;
>>  
>>  	pr_info("Reserved %ld MiB at %pa\n", (unsigned long)size / SZ_1M,
>>  		&base);
>>  	return 0;
>>  
>> +free_mem:
>> +	memblock_free(base, size);
>>  err:
>>  	pr_err("Failed to reserve %ld MiB\n", (unsigned long)size / SZ_1M);
>>  	return ret;
> 
> This doesn't look right to me.  In the `fixed==true' case we didn't
> actually allocate anything and in the `fixed==false' case, the
> allocated memory is at `addr', not at `base'.

I think it's ok as the fixed==true path has "memblock_reserve()", but
better leave this to the memblock maintainer :)

There's also 'kmemleak_ignore_phys(addr)' which should probably be
undone (or not called at all) in the failure case. But it seems to be
missing from the fixed==true path?