linux-kernel - Re: [BUG] lib: zram lz4 compression/decompression still broken on big endian

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Date:	Thu, 7 Apr 2016 23:07:02 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Rui Salvaterra <rsalvaterra@...il.com>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, eunb.song@...sung.com,
	minchan@...nel.org, linux-mm@...ck.org,
	Chanho Min <chanho.min@....com>,
	Kyungsik Lee <kyungsik.lee@....com>
Subject: Re: [BUG] lib: zram lz4 compression/decompression still broken on
 big endian

On (04/07/16 13:33), Rui Salvaterra wrote:
[..]
> Hi again, Sergey

Hello,

> Thanks for the patch, I'll test it as soon as possible. I agree with
> your second option, usually one selects lz4 when (especially
> decompression) speed is paramount, so it needs all the help it can
> get.

thanks!

> Speaking of fishy, the 64-bit detection code also looks suspiciously
> bogus. Some of the identifiers don't even exist anywhere in the kernel
> (__ppc64__, por example, after grepping all .c and .h files).
> Shouldn't we instead check for CONFIG_64BIT or BITS_PER_LONG == 64?

definitely a good question. personally, I'd prefer to test for
CONFIG_64BIT only, looking at this hairy

  /* Detects 64 bits mode */
  #if (defined(__x86_64__) || defined(__x86_64) || defined(__amd64__) \
         || defined(__ppc64__) || defined(__LP64__))

and remove/rewrite a bunch of other stuff. but the thing with cleanups
is that they don't fix anything, while potentially can introduce bugs.
it's more risky to touch the stable code. /* well, removing those 'ghost'
identifiers is sort of OK to me */. but that's just my opinion, I'll
leave it to you and Greg.

	-ss