Jan Kara <jack@xxxxxxx> writes: > On Tue 02-01-18 13:51:49, Dan Williams wrote: >> On Tue, Jan 2, 2018 at 1:44 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: >> > On Sat, Dec 23, 2017 at 04:56:43PM -0800, Dan Williams wrote: >> >> In support of testing truncate colliding with dma add a mechanism that >> >> delays the completion of block I/O requests by a programmable number of >> >> seconds. This allows a truncate operation to be issued while page >> >> references are held for direct-I/O. >> >> >> >> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> >> > >> > Why not put this in the generic bio layer code and then write a >> > generic fstest to exercise this truncate vs direct IO completion >> > race condition on all types of storage and filesystems? >> > >> > i.e. if it sits in a nvdimm test suite, it's never going to be run >> > by filesystem developers.... >> >> I do want to get it into xfstests eventually. I picked the nvdimm >> infrastructure for expediency of getting the fix developed. Also, I >> consider the collision in the non-dax case a solved problem since the >> core mm will keep the page out of circulation indefinitely. > > Yes, but there are different races that could happen even for regular page > cache pages. So I also think it would be worthwhile to have this inside the > block layer possibly as part of the generic fault-injection framework which > is already there for fail_make_request. That already supports various > filtering, frequency, and other options that could be useful. Or consider extending the dm-delay target (which delays the queuing of bios) to support delaying the completions. I'm not sure I'm a fan of sticking all sorts of debug code into the generic I/O submission path. Cheers, Jeff
