>>>>> "Mike" == Mike Snitzer <snit...@redhat.com> writes:
Mike, Mike> so long story short: making this change to remove this so-called Mike> "stupid behaviour" will require code like Mike> drivers/md/dm-thin.c:issue_discard(() to check the return from Mike> __blkdev_issue_discard() and if it is -EOPNOTSUPP then it should Mike> return 0. Yes, please. The original -EOPNOTSUPP equals success is a remnant from the days where discards were only a hint. And sadly that policy got encoded in the actual interface instead of being left up to the caller. Now the world has moved on. And reliable zeroout behavior, the SCSI target drivers and other kernel users need an interface that tells them exactly what happened at the bottom of the stack so they in turn can provide a deterministic result (including partial block zeroing) to their clients. It's imperative that this gets fixed up. And instead of perpetuating a weird interface that returns success on failure, let's fix DM and the callers that actually check the return of blkdev_issue_discard() so they do the right thing. I really don't understand why you are objecting so much to this. It's a trivial change that may not directly benefit DM but it helps everybody else. And it cleans up a library call that's confusing, error prone and goes against the very grain of how all our kernel interfaces work in general. -- Martin K. Petersen Oracle Linux Engineering
