linux-kernel - Re: [PATCH v2] RDMA/umem: minor bug fix and cleanup in error handling paths

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Date:   Wed, 6 Mar 2019 03:02:36 +0200
From:   Artemy Kovalyov <artemyko@...lanox.com>
To:     John Hubbard <jhubbard@...dia.com>,
        Ira Weiny <ira.weiny@...el.com>,
        "john.hubbard@...il.com" <john.hubbard@...il.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Jason Gunthorpe" <jgg@...pe.ca>,
        Doug Ledford <dledford@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH v2] RDMA/umem: minor bug fix and cleanup in error handling
 paths



On 04/03/2019 00:37, John Hubbard wrote:
> On 3/3/19 1:52 AM, Artemy Kovalyov wrote:
>>
>>
>> On 02/03/2019 21:44, Ira Weiny wrote:
>>>
>>> On Sat, Mar 02, 2019 at 12:24:35PM -0800, john.hubbard@...il.com wrote:
>>>> From: John Hubbard <jhubbard@...dia.com>
>>>>
>>>> ...
> 
> OK, thanks for explaining! Artemy, while you're here, any thoughts about the
> release_pages, and the change of the starting point, from the other part of the
> patch:
> 
> @@ -684,9 +677,11 @@ int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp,
> u64 user_virt,
> 	mutex_unlock(&umem_odp->umem_mutex);
> 
>    		if (ret < 0) {
> -			/* Release left over pages when handling errors. */
> -			for (++j; j < npages; ++j)
release_pages() is an optimized batch put_page() so it's ok.
but! release starting from page next to one cause failure in 
ib_umem_odp_map_dma_single_page() is correct because failure flow of 
this functions already called put_page().
So release_pages(&local_page_list[j+1], npages - j-1) would be correct.
> -				put_page(local_page_list[j]);
> +			/*
> +			 * Release pages, starting at the the first page
> +			 * that experienced an error.
> +			 */
> +			release_pages(&local_page_list[j], npages - j);
>    			break;
>    		}
>    	}
> 
> ?
> 
> thanks,
>