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Re: [PATCH 5/7] zram: use crypto api to check alg availability

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Hello,

On (05/27/16 18:04), Minchan Kim wrote:
> > It is fundamentally impossible to get a list of all *potential*
> > algorithms if you allow loadable modules.  By definition someone
> > could load a new module and thus introduce a new algorithm.
> 
> Thanks for the quick response. I understand now.
> 
> Sergey,
> 
> Then, shouldn't we add functionality to load new algorithm although
> there is no entry in zcomp backend array?

can do, sure: make find_backend() depend on crypto_has_comp() only,
*may be* printk a message when we have a mismatch in backends array
and crypto_has_comp(). but not really sure about the latter one.

> The main reason we changed to crypto is to support various compression
> algorithm for zram so we should be able to support anyone who want to
> use custom crypto compression module.

yes.

> A idea is that let's not adding new compression string into backend
> array from now on and deprecates /zram/comp_algorithm to show name.

I'd really prefer not to deprecate /zram/comp_algorithm now.

> So, from now on, users should be aware of the compression naming and
> load module by oneself. It's not kind but I hope admins already knows
> what cryto compressor they have.

um, I'm not in love with this approach.

what admins? zram users may be completely unaware of the existence of
the crypto API and the kernel rebuild process. for some people switching
to new zram will be a matter of "apt-get upgrade/pacman -Syu", not
"git am ...; make menuconfig; make -j...". this looks like a major step
back. keeping this dummy list of compressing backends around does not take
a lot of effort, especially if we will make it unimportant for find_backend()
and only use it for that nice user-friendly `cat /zram/comp_algorithm`
output.

	-ss

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[PATCH 0/7] zram: switch to crypto api Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-05-25 15:40 +0200
  [PATCH 6/7] zram: delete custom lzo/lz4 Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-05-25 15:40 +0200
  [PATCH 5/7] zram: use crypto api to check alg availability Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-05-25 15:40 +0200
    Re: [PATCH 5/7] zram: use crypto api to check alg availability Minchan Kim <minchan@kernel.org> - 2016-05-27 07:00 +0200
      Re: [PATCH 5/7] zram: use crypto api to check alg availability Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-05-27 10:00 +0200
        Re: [PATCH 5/7] zram: use crypto api to check alg availability Minchan Kim <minchan@kernel.org> - 2016-05-27 10:30 +0200
          Re: [PATCH 5/7] zram: use crypto api to check alg availability Herbert Xu <herbert@gondor.apana.org.au> - 2016-05-27 10:50 +0200
            Re: [PATCH 5/7] zram: use crypto api to check alg availability Minchan Kim <minchan@kernel.org> - 2016-05-27 11:10 +0200
              Re: [PATCH 5/7] zram: use crypto api to check alg availability Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-05-29 04:30 +0200
                Re: [PATCH 5/7] zram: use crypto api to check alg availability Minchan Kim <minchan@kernel.org> - 2016-05-30 06:50 +0200
                Re: [PATCH 5/7] zram: use crypto api to check alg availability Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-05-30 07:00 +0200
  [PATCH 1/7] zram: rename zstrm find-release functions Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-05-25 15:40 +0200
    Re: [PATCH 1/7] zram: rename zstrm find-release functions Minchan Kim <minchan@kernel.org> - 2016-05-26 02:50 +0200
      Re: [PATCH 1/7] zram: rename zstrm find-release functions Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-05-26 03:10 +0200
  Re: [PATCH 0/7] zram: switch to crypto api Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-26 02:50 +0200
    Re: [PATCH 0/7] zram: switch to crypto api Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-05-26 03:20 +0200
      Re: [PATCH 0/7] zram: switch to crypto api Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-26 04:00 +0200
  Re: [PATCH 0/7] zram: switch to crypto api Minchan Kim <minchan@kernel.org> - 2016-05-26 03:00 +0200
    Re: [PATCH 0/7] zram: switch to crypto api Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-05-26 03:10 +0200

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