On Tue, Jun 14 2016 at 10:30pm -0400, Martin K. Petersen <martin.petersen@xxxxxxxxxx> wrote: > >>>>> "Mike" == Mike Snitzer <snitzer@xxxxxxxxxx> 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. I've been consistently objecting to changing the blkdev_issue_discard() interface. Fixing the async __blkdev_issue_discard() to offer unfiltered return values is perfectly fine by me. But the ship has sailed on the blkdev_issue_discard() interface. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
