On 06/04/2010 07:23 PM, Jan Kara wrote: > On Thu 03-06-10 19:09:52, Boaz Harrosh wrote: >> [Topic] >> How to not let pages change while in IO >> >> [Abstract] >> As seen in a long thread on the fsdvel scsi mailing lists. Lots of >> people have headaches and sleep less nights because individual pages >> can change while in IO and/or DMA. Though each one as slightly different >> needs, the mechanics look to be the same. > Hmm, I don't think it's really about "how to not let pages change" - that > is doable by using wait_on_page_writeback() in ->page_mkwrite and > ->write_begin. I think the discussion is more about whether we should do it > or whether we should rechecksum and resubmit IO in case of checksum failure > as Nick proposed... > > Honza I have hijacked the DIF threads but, No, my proposal is for a general toolset that could be used for all the above as well as DIF if needed. Surly even with DIF the keep-constant vs retransmit is a matter of machine+link speed multiply by faulting work loads. So there might be situations where an admin wants to choose. With other none checksum fixtures, like RAID5/MIRROR this is not always an option and it becomes keep-constant vs copy. (That is complete workload copy). So for these setups the option is clear. No? I'm glad that you think it is easy/doable to implement. And I'll surly test your above receipt. Do you think it would be acceptable as a generic per-sb tunable. So for instance an ext3 over RAID5 could turn this on and eliminate the data copy? Lets talk about this in LSF Boaz >> People that care: >> - Mirror and RAID people that need on disk consistency. >> - Network storage that wants data checksum. >> - DIF/DIX people >> - ... >> >> I for one know nothing of the subject but am a RAID person and would >> like a solution that does not force me to copy the complete data load. >> >> Please lets get all the VM VFS and drivers people in one room and see >> if we can have a Linux solution to this problem -- 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
