On 4/8/19 9:04 AM, Johannes Thumshirn wrote: > [+Cc Michal ] > On Mon, Apr 08, 2019 at 04:54:39PM +0200, Paolo Valente wrote: >> >> >>> Il giorno 8 apr 2019, alle ore 16:49, Johannes Thumshirn <jthumshirn@xxxxxxx> ha scritto: >>> >>> On Mon, Apr 08, 2019 at 04:39:35PM +0200, Paolo Valente wrote: >>>> From: Angelo Ruocco <angeloruocco90@xxxxxxxxx> >>>> >>>> When bfq was merged into mainline, there were two I/O schedulers that >>>> implemented the proportional-share policy: bfq for blk-mq and cfq for >>>> legacy blk. bfq's interface files in the blkio/io controller have the >>>> same names as cfq. But the cgroups interface doesn't allow two >>>> entities to use the same name for their files, so for bfq we had to >>>> prepend the "bfq" prefix to each of its files. However no legacy code >>>> uses these modified file names. This naming also causes confusion, as, >>>> e.g., in [1]. >>>> >>>> Now cfq has gone with legacy blk, so there is no need any longer for >>>> these prefixes in (the never used) bfq names. In view of this fact, this >>>> commit removes these prefixes, thereby enabling legacy code to truly >>>> use the proportional share policy in blk-mq. >>>> >>>> [1] https://github.com/systemd/systemd/issues/7057 >>> >>> Hmm, but isn't this a user-space facing interface and thus some sort of ABI? >>> Do you know what's using it and what breaks due to this conversion? >>> >> >> Yep, but AFAIK, the problem is exactly the opposite: nobody uses these >> names for the proportional-share policy, or wants to use these names. I'm >> CCing Lennart too, in case he has some improbable news on this. >> >> So the idea is to align names to what people expect, possibly before >> more confusion arises. > > OK, crazy idea, not sure if Jens and Tejun will beat me for this, but > symlinks? > > This way we can a) keep the old files and b) have them point to the new (a.k.a > cfq style) files. I did consider that, and that would be doable. But honestly, I'm having a hard time seeing what issue we are attempting to fix by doing this. -- Jens Axboe
