On Sun, 10 Nov 2019, Oliver Neukum wrote:
Am Freitag, den 08.11.2019, 10:35 -0500 schrieb Alan Stern:
On Fri, 8 Nov 2019, Greg Kroah-Hartman wrote:
On Thu, Nov 07, 2019 at 12:32:45PM +0100, Oliver Neukum wrote:
Am Dienstag, den 05.11.2019, 17:38 +0100 schrieb Greg Kroah-Hartman:
> Given this information, perhaps you will decide that the revert is > worthwhile.
Damned if I do, damned if I do not. Check for usbip and special case it?
We should be able to do that in the host controller driver for usbip, right? What is the symptom if you use a UAS device with usbip and this commit?
Yes, that patch should then also be applied. Then it will work. Without it, commands will fail, as transfers will end prematurely.
Ok, I'm confused now. I just checked, and I really have no idea what needs to be backported anymore. 3ae62a42090f ("UAS: fix alignment of scatter/gather segments") was backported to all of the stable kernels, and now we reverted it.
So what else needs to be done here?
In one sense, nothing needs to be done. 3ae62a42090f was intended to fix a long-standing problem with USBIP, but people reported a
OK, now I am a bit confused. AFAICT 3ae62a42090f actually did fix the issue. So if you simply revert it, the issue will reappear.
Correct. I think.
regression in performance. (Admittedly, the report was about the correponding change to usb-storage, not the change to uas, but it's reasonable to think the effect would be the same.) So in line with the
Yes.
no-regressions policy, we only need to revert the commit -- which you have already done.
But that breaks UAS over USBIP, doesn't it?
It was already broken to start with. The attempted fix caused a regression, so the fix must be reverted.
On the other hand, the long-standing problem in USBIP can be fixed by back-porting commit ea44d190764b. But since that commit isn't a bug-fix (and since it's rather large), you may question whether it is appropriate for the -stable kernel series.
It certainly is large. But without it UAS won't work over USBIP, will it? I think that is the central question we need to answer here.
You are right. If Greg is okay with porting ea44d190764b to the stable kernels, I won't object.
Alan Stern