On Fri, Jan 16, 2009 at 07:13:41AM +0100, Nick Piggin wrote: > On Fri, Jan 16, 2009 at 03:08:30PM +0900, MinChan Kim wrote: > > On Thu, Jan 15, 2009 at 10:57:30PM -0700, Matthew Wilcox wrote: > > > Most I/O devices will do DMA to the page in question and thus the kernel > > > hasn't written to it and the CPU won't have the data in cache. For the > > > few devices which can't do DMA, it's the responsibility of the device > > > driver to call flush_dcache_page() (or some other flushing primitive). > > > > Hmm.. Now I am confusing. > > If devicer driver or with DMA makes sure cache consistency, > > Why filesystem code have to handle it ? > > Because the filesystem is accessing the page directly rathe rthan going to > IO. > > Basically, whoever reads or writes the page is responsible to avoid user > aliases. You see these calls in the VM for anonymous pages, in bounce > buffer layers, in filesystems that read or write from pages that are > exposed to userspace (ie. metadata generally need not be flushed because > it will not be mmapped by userspace). Totally, understand. Thanks for kind answering to my poor question in patience. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
