Messages in this thread | | | Date | Tue, 8 Sep 2015 17:16:10 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH] zram: don't copy invalid compression algorithms |
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On Tue, Sep 08, 2015 at 02:04:42PM +0900, Sergey Senozhatsky wrote: > On (09/08/15 13:50), Minchan Kim wrote: > [..] > > And it's straightforward/consistent to change the thing's state > > only if is successful. > > > > what for? I provided several good reasons not to do this, because
Several good reasons?
I just heard you claim to take care of scripts which don't check function's success at the moment function is called but check it later via reading the knob later. If we changes it, it breaks such scripts. So, with your claim, there are two assumption.
1. script doesn't check return val at the moment function completes 2. Instead, script checks it later via reading the knob again. So, conclusion is we should keep wrong input in kernel side for them.
It seems you insist on "we should keep wrong input from the userspace in the kernel to show it if user *might* ask for his debug later" What makes you think like above?
I think such assumption is really from your brain, not real usecases. Ok, I admit i'm not a god but if there is such thing in real practice, we should help them to *correct* it rather than keeping such weired thing. From the beginning, they should check his action's result with return value, not dmesg, not reading the knob later, again.
> it makes life easier for users. we added this check in Jun 25, 2015
No, it could make more bad scripts which not checks the result of the action but rely on current awkward zram's interface. Consider other knobs in the kernel. A few things popped from my mind at the moment.
/sys/block/sdb/queue/scheduler /sys/kernel/mm/transparent_hugepage/enabled /sys/kernel/debug/tracing/current_tracer /sys/devices/system/clocksource/clocksource/clocksource0/current_clocksource
They are not showing wrong input user have passed although it was failed. Could you say a example of kernel interface did intentionally like you said?
> while this functionality and scripts have been around for years, and > apparently now it's users' problem and they must go and do something.
I believe anyone shouldn't rely on it. But who knows? However, I want to make it sane(ie, only change compressor name if the action is successful). Please, let's discuss how we do it rather than whether it's useful or not.
> > > seriously, what improvement this change brings in the first place? > what does it make better and for whom?
As I mentioned, it makes zram's ABI consistent with others in kernel space so it makes user feel zram is straight-forward and sane like others.
> > -ss
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