linux-kernel - Re: [PATCH v3] RDMA/umem: minor bug fix in error handling path

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Message-ID: <20190304115713.GD30058@iweiny-DESK2.sc.intel.com>
Date:   Mon, 4 Mar 2019 03:57:14 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     john.hubbard@...il.com
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        John Hubbard <jhubbard@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Doug Ledford <dledford@...hat.com>, linux-rdma@...r.kernel.org
Subject: Re: [PATCH v3] RDMA/umem: minor bug fix in error handling path

On Mon, Mar 04, 2019 at 11:46:45AM -0800, john.hubbard@...il.com wrote:
> From: John Hubbard <jhubbard@...dia.com>
> 
> 1. Bug fix: fix an off by one error in the code that
> cleans up if it fails to dma-map a page, after having
> done a get_user_pages_remote() on a range of pages.
> 
> 2. Refinement: for that same cleanup code, release_pages()
> is better than put_page() in a loop.
> 
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Doug Ledford <dledford@...hat.com>
> Cc: linux-rdma@...r.kernel.org
> Cc: linux-mm@...ck.org
> Signed-off-by: John Hubbard <jhubbard@...dia.com>

Signed-off-by: Ira Weiny <ira.weiny@...el.com>

> ---
>  drivers/infiniband/core/umem_odp.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
> index acb882f279cb..d45735b02e07 100644
> --- a/drivers/infiniband/core/umem_odp.c
> +++ b/drivers/infiniband/core/umem_odp.c
> @@ -40,6 +40,7 @@
>  #include <linux/vmalloc.h>
>  #include <linux/hugetlb.h>
>  #include <linux/interval_tree_generic.h>
> +#include <linux/pagemap.h>
>  
>  #include <rdma/ib_verbs.h>
>  #include <rdma/ib_umem.h>
> @@ -684,9 +685,11 @@ 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)
> -				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;
>  		}
>  	}
> -- 
> 2.21.0
>