On Fri, 30 Jul 2010 12:29:30 +0200 Tejun Heo <tj@xxxxxxxxxx> wrote: > Hello, > > On 07/28/2010 08:16 PM, Vladislav Bolkhovitin wrote: > > In recent kernels we are experiencing a problem that in our setup > > using SCST BLOCKIO backend some BIOs are finished, i.e. the finish > > callback called for them, with error -EIO. It happens quite often, > > much more often than one would expect to have an actual IO > > error. (BLOCKIO backend just converts all incoming SCSI commands to > > the corresponding block requests.) > > > > After some investigation, we figured out, that, most likely, > > raid5.c::make_request() for some reason sometimes calls bio_endio() > > with not BIO_UPTODATE bios. > > > > We bisected it to commit: > > > > commit a82afdfcb8c0df09776b6458af6b68fc58b2e87b > > Author: Tejun Heo <tj@xxxxxxxxxx> > > Date: Fri Jul 3 17:48:16 2009 +0900 > > > > block: use the same failfast bits for bio and request > > That commit doesn't (or at least isn't supposed to) make any behavior > difference. It's just repositioning flag bits. If the commit is > actually causing the problem, I think one possibility is that whatever > code could be using hard coded constants which now are mapped to > different flags. The mixed merge changes have been in mainline for > quite some time and shipping in all major distros too and this is the > first time this is reported, so I don't think it could be a widespread > problem. > > Thanks. > The problem is that md/raid5 tests bio->bi_rw against RWA_MASK, which used to align with BIO_RW_AHEAD, and now doesn't. However the definition of bio_rw() in fs.h seems to justify that RWA_MASK should align with BIO_RW_AHEAD, as does the definition of READA. Given the current definitions, any WRITE request with BIO_RW_FAILFAST_DEV set is going to confused a number of drives which test bio_rw(bio) == WRITE I guess RWA_MASK needs to be changed to (1<<BIO_RW_AHEAD), and READA need to be change to that value too. Can I leave that to you Tejun? Thanks, NeilBrown -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel