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Message-ID: <50C05BB8.6090908@linutronix.de> Date: Thu, 06 Dec 2012 09:47:52 +0100 From: Sebastian Andrzej Siewior <bigeasy@...utronix.de> To: Andrew Morton <akpm@...ux-foundation.org> CC: linux-kernel@...r.kernel.org Subject: Re: [PATCH] scatterlist: add a warning if sg_virt() is used on highmem pages 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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