Tejun, Paolo,

On Tue, 17 Sep 2019 at 23:32, Tejun Heo [off-list ref] wrote:

Hello,

On Tue, Sep 17, 2019 at 06:51:48PM +0200, Paolo Valente wrote:

quoted

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.

So, I wrote the iocost switching patch and don't have a strong
interest in whether bfq prefix should get dropped or not.  However, I
gotta point out that flipping interface this way is way out of the
norm.

In the previous release cycle, the right thing to do was dropping the
bfq prefix but that wasn't possible because bfq's interface wasn't
compatible at that point and didn't made to be compatible in time.

Sounds like we really should send those relevant patches for stable,
to set the correct ground. Then using a symlink, to make sure we don't
brake current ABI, right?

[...]

Kind regards
Uffe