From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] scatterlist: add a warning if sg_virt() is used on highmem pages
Date: Thu, 06 Dec 2012 09:47:52 +0100 [thread overview]
Message-ID: <50C05BB8.6090908@linutronix.de> (raw)
In-Reply-To: <20121205134604.17523790.akpm@linux-foundation.org>
On 12/05/2012 10:46 PM, Andrew Morton wrote:
>> --- a/include/linux/scatterlist.h
>> +++ b/include/linux/scatterlist.h
>> @@ -198,6 +198,9 @@ static inline dma_addr_t sg_phys(struct scatterlist *sg)
>> **/
>> static inline void *sg_virt(struct scatterlist *sg)
>> {
>> +#ifdef CONFIG_DEBUG_SG
>> + WARN_ON(PageHighMem(sg_page(sg)));
>> +#endif
>> return page_address(sg_page(sg)) + sg->offset;
>> }
>
> Why won't it work? page_address() will search the kmap table and will
> search for the page. If the caller had previously kmapped that page,
> all is well. If the caller has failed to kmap the page, sg_virt() will
> return a nearly-null pointer and presumably someone will later go oops.
I missed that it will work for previously mapped page. If you think
that an oops later is enough then okay, I drop this.
Sebastian
prev parent reply other threads:[~2012-12-06 8:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-05 11:28 [PATCH] scatterlist: add a warning if sg_virt() is used on highmem pages Sebastian Andrzej Siewior
2012-12-05 21:46 ` Andrew Morton
2012-12-06 8:47 ` Sebastian Andrzej Siewior [this message]
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