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?). 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. This patchset contains the following changes. block/blk-core.c | 118 +++++++++++++++++++++++++++++++++++++++++++----- block/blk-merge.c | 43 +++++++++++++++++ block/blk.h | 1 drivers/scsi/scsi_lib.c | 6 +- include/linux/bio.h | 43 +++++++++-------- include/linux/blkdev.h | 27 ++++++++-- 6 files changed, 199 insertions(+), 39 deletions(-) Thanks. -- tejun -- 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
