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. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
