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). -- 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
