linux-kernel - Re: [PATCH 1/1] Fixed to BUG_ON to WARN

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Date:   Mon, 12 Dec 2016 20:18:38 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Ozgur Karatas <okaratas@...ber.fsf.org>,
        Tariq Toukan <tariqt@...lanox.com>
Cc:     "yishaih@...lanox.com" <yishaih@...lanox.com>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] Fixed to BUG_ON to WARN_ON def

On Mon, Dec 12, 2016 at 03:04:28PM +0200, Ozgur Karatas wrote:
> Dear Romanovsky;

Please avoid top-posting in your replies.
Thanks

>
> I'm trying to learn english and I apologize for my mistake words and phrases. So, I think the code when call to "sg_set_buf" and next time set memory and buffer. For example, isn't to call "WARN_ON" function, get a error to implicit declaration, right?
>
> Because, you will use to "BUG_ON" get a error implicit declaration of functions.

I'm not sure that I followed you. mem->offset is set by sg_set_buf from
buf variable returned by dma_alloc_coherent(). HW needs to get very
precise size of this buf, in multiple of pages and aligned to pages
boundaries.

>
>         sg_set_buf(mem, buf, PAGE_SIZE << order);
>         WARN_ON(mem->offset);

See the patch inline which removes this BUG_ON in proper and safe way.

From 7babe807affa2b27d51d3610afb75b693929ea1a Mon Sep 17 00:00:00 2001
From: Leon Romanovsky <leonro@...lanox.com>
Date: Mon, 12 Dec 2016 20:02:45 +0200
Subject: [PATCH] net/mlx4: Remove BUG_ON from ICM allocation routine

This patch removes BUG_ON() macro from mlx4_alloc_icm_coherent()
by checking DMA address aligment in advance and performing proper
folding in case of error.

Fixes: 5b0bf5e25efe ("mlx4_core: Support ICM tables in coherent memory")
Reported-by: Ozgur Karatas <okaratas@...ber.fsf.org>
Signed-off-by: Leon Romanovsky <leonro@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx4/icm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/icm.c b/drivers/net/ethernet/mellanox/mlx4/icm.c
index 2a9dd46..e1f9e7c 100644
--- a/drivers/net/ethernet/mellanox/mlx4/icm.c
+++ b/drivers/net/ethernet/mellanox/mlx4/icm.c
@@ -118,8 +118,13 @@ static int mlx4_alloc_icm_coherent(struct device *dev, struct scatterlist *mem,
 	if (!buf)
 		return -ENOMEM;

+	if (offset_in_page(buf)) {
+		dma_free_coherent(dev, PAGE_SIZE << order,
+				  buf, sg_dma_address(mem));
+		return -ENOMEM;
+	}
+
 	sg_set_buf(mem, buf, PAGE_SIZE << order);
-	BUG_ON(mem->offset);
 	sg_dma_len(mem) = PAGE_SIZE << order;
 	return 0;
 }
--
2.10.2


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