On Fri, Jul 03 2009, Tejun Heo wrote: > Hello, > > Block layer didn't consider failfast status while merging requests and > it led to premature failure of normal (non-failfast) IOs. Niel > Lambrechts could trigger the problem semi-reliably on ext4 when > resuming from STR. ext4 uses readahead when reading inodes and > combined with the deterministic extra SATA PHY exception cycle during > resume on the specific configuration, non-readahead inode read would > fail causing ext4 errors. Please read the following thread for > details. > > http://lkml.org/lkml/2009/5/23/21 > > This patchset contains the following four patches to fix the problem. > > 0001-block-don-t-merge-requests-of-different-failfast-se.patch > 0002-block-use-the-same-failfast-bits-for-bio-and-reques.patch > 0003-block-implement-mixed-merge-of-different-failfast-r.patch > 0004-scsi-block-update-SCSI-to-handle-mixed-merge-failur.patch > > 0001 disallows merge between requests with different failfast > settings. This one is the quick fix and should go into 2.6.31 and > later to -stable as the bug is pretty serious and may lead to data > loss. > > 0002 preps for later changes. > > 0003-0004 implements and applies mixed merge. Requests of different > failfast settings are merged as before but failure handling is updated > such that parts which shouldn't fail without retrial are properly > retried. > > I spent quite some time thinking about and testing it but I'd really > like more pairs of eyes on this patchset as dangerous bugs can go > unnoticed for quite a while in this area (anyone knows when the > failfast bug was introduced?). It must have been several releases ago. So while the bug is indeed very nasty, I don't think there's been much fallout from it. > Jens, I think the best way to merge this is to first push 0001 to > Linus's tree and then pull it into for-next and then apply the rest on > top of them. Yeah I'll do that, #1 for 2.6.31 and the rest for .32. Thanks for finding and fixing this bug! -- Jens Axboe -- 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
