On 06/12/2013 06:07 AM, H. Peter Anvin wrote: > On 06/11/2013 08:15 PM, NeilBrown wrote: >> If a drive reports that WRITE SAME works, but it doesn't, then I'm >> not sure that I can be happy about working with that drive. > > Seriously... we have that kind of problems all over the place with all > kinds of hardware. Falling back is sensible... the problem here is > *where* that needs to happen... the block layer already does, apparently. > >> If a drive has some quirky behaviour wrt WRITE SAME, then that >> should be handled in some place where 'quirks' are handled - >> certainly not in md. > > The problem here is that you don't find out ahead of time. > > Now, if I understand the issue at hand correctly is that the reporting > here was actually a Linux bug related to SATA drives behind a SAS > controller. Martin, am I right? Martin, please correct me if I'm wrong, but I think the code optimistically enabled WRITE_SAME for any drive, except of those on a sata (libata) controller. So not the drive reported that it can do WRITE_SAME, but scsi-midlayer did that. Martins patch should improve that (I still need to test it on our hardware), but I'm not sure if there won't be some hardware falling through. Cheers, Bernd -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
