On Tue, 2010-02-02 at 17:11 +0000, Alan Stern wrote: > On Tue, 2 Feb 2010, Oliver Neukum wrote: > > > Am Dienstag, 2. Februar 2010 13:39:35 schrieb Catalin Marinas: > > > > For storage that is correct. But what about other sources of pages, > > > > for example iSCSI? > > > > > > In the iSCSI case, does the HCD driver write directly to a page cache > > > page? Or it just fills in network packets that are copied to page cache > > > pages by the iSCSI code (sorry, I'm not familiar with this part of the > > > kernel). If the latter, the cache flushing in the HCD driver would not > > > help and it needs to be done in the iSCSI code. > > > > As far as I can tell iSCSI does a private copy. But I don't know how > > many methods to transfer code pages over USB exist. I'd say the > > conservative solution is to flush for everything but control transfers. > > This doesn't make any sense. Nobody would ever use isochronous > transfers to store data into a code page because isochronous is > unreliable. (Audio isn't a counterexample -- audio data may be mapped > to userspace, but only to data pages, not code pages. And the problem > here is to maintain consistency between the D and I caches.) My issues is with both I-D coherency and D-cache aliasing caused by pages mapped in both user and kernel space (with different colours). The flush_dcache_page() call should target both cases. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
