On Tue, Jun 01, 2010 at 03:35:28PM -0400, Chris Mason wrote: > On Wed, Jun 02, 2010 at 04:46:49AM +1000, Nick Piggin wrote: > > On Tue, Jun 01, 2010 at 02:09:05PM -0400, Chris Mason wrote: > > > On Tue, Jun 01, 2010 at 04:54:53PM +0000, James Bottomley wrote: > > > > > > > For self > > > > induced errors (as long as we can detect them) I think we can just > > > > forget about it ... if the changed page is important, the I/O request > > > > gets repeated (modulo the problem of too great a frequency of changes > > > > leading to us never successfully writing it) or it gets dropped because > > > > the file was truncated or the data deleted for some other reason. > > > > > > Sorry, how can we tell the errors that are self induced from the evil > > > bit flipping cable induced errors? > > > > Block layer should retry it with bounce pages. That would be a lot nicer > > than forcing all upper layers to avoid the problem. > > > > So the idea is that we have sent down a buffer and it changed in flight. > The block layer is going to say: oh look, the crcs don't match, I'll > bounce it, recrc it and send again. But, there are at least 3 reasons the crc > will change: > > 1) filesystem changed it > 2) corruption on the wire or in the raid controller > 3) the page was corrupted while the IO layer was doing the IO. > > 1 and 2 are easy, we bounce, retry and everyone continues on with > their lives. With #3, we'll recrc and send the IO down again thinking > the data is correct when really we're writing garbage. > > How can we tell these three cases apart? Do we really need to handle #3? It could have happened before the checksum was calculated. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
