linux-kernel - RE: [RFC PATCH v2 04/11] pstore: Add compression support to pstore

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Date:	Wed, 4 Sep 2013 01:44:57 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Aruna Balakrishnaiah <aruna@...ux.vnet.ibm.com>,
	"Luck, Tony" <tony.luck@...el.com>
CC:	"linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"jkenisto@...ux.vnet.ibm.com" <jkenisto@...ux.vnet.ibm.com>,
	"cbouatmailru@...il.com" <cbouatmailru@...il.com>,
	"mahesh@...ux.vnet.ibm.com" <mahesh@...ux.vnet.ibm.com>,
	"ccross@...roid.com" <ccross@...roid.com>
Subject: RE: [RFC PATCH v2 04/11] pstore: Add compression support to pstore

Aruna,

Sorry for the late response.

> Seiji,
> 
> Could you let us know the efivars buffer size with which the pstore is
> registered when
> the failure occurred.

I looked into the issue today.

I added some debug message just before pstore_compress().
As you can see below, the buffer size is a fixed value(1024).
Therefore, the size doesn't seem to be related to the failure directly.

Also, in the failure case, zlib_deflate() returns Z_OK and stream.avail_out is zero.
So, I thought big_oops_buf_sz is too big in my environment.
And then, I tuned  big_oops_buf_sz to (psinfo->bufsize * 100) / 53.

At the same time, while looking into this issue, I had two concerns about current cording.

1) In pstore_decompress(), why not use zlib_inflateInit2() instead of zlib_inflateInit()?
     If you use zlib_deflateInit2()  for specifying window_bit at compressing time, 
     zlib_inflateInit2() seems to be appropriate for decompressing.
     (Please see a comment about inflateInit2() in include/linux/zlib.h and source code of crypto/deflate.c)

2) As looking at crypto/deflate.c, stream->workspace is kzalloced at the beginning of 
   compressing/decompressing time.
    So, in pstore case,  stream.workspace must be initialized to 0 with memset() in pstore_compress()/decompress().

I did three things above, tuning big_oops_buf_sz, using zlib_inflateInit2() and initializing stream.workspace , in my environment.
As a result, compressions/decmpressions of all entries succeeded with efivars driver.

<snip>
Panic#2 Part1
<4>[   75.665020]  [<ffffffff811af59c>] SyS_write+0x4c/0xa0
<4>[   75.665020]  [<ffffffff8168be82>] system_call_fastpath+0x16/0x1b
<4>[   75.665020] Code: ef e8 ff f7 ff ff eb d8 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 0f 1f 44 00 00 55 c7 05 cc f3 c9 00 01 00 00 00 48 89 e5 0f ae f8 <c6> 04 25 00 00 00 00 01 5d c3 0f 1f 44 00 00 55 31 c0 c7 05 5e 
<1>[   75.665020] RIP  [<ffffffff813d3946>] sysrq_handle_crash+0x16/0x20
<4>[   75.665020]  RSP <ffff88007852de80>
<4>[   75.665020] CR2: 0000000000000000
<4>[   75.665020] ---[ end trace 97bb4a1f8d3fe7b2 ]---
<3>[   75.665020] pstore_dump hsize=13 len=2155 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=13 len=2246 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore: compression failed for Part 2 returned -5
<3>[   75.665020] pstore: Capture uncompressed oops/panic report of Part 2
<3>[   75.665020] pstore_dump hsize=13 len=2239 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=13 len=2231 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=13 len=2185 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore: compression failed for Part 5 returned -5
<3>[   75.665020] pstore: Capture uncompressed oops/panic report of Part 5
<3>[   75.665020] pstore_dump hsize=13 len=2234 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=13 len=2208 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=13 len=2218 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=13 len=2222 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore: compression failed for Part 9 returned -5
<3>[   75.665020] pstore: Capture uncompressed oops/panic report of Part 9
<3>[   75.665020] pstore_dump hsize=14 len=2256 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=14 len=2219 big_oops_buf_sz=2275 psinfo->bufsize=1024
<3>[   75.665020] pstore_dump hsize=14 len=2226 big_oops_buf_sz=2275 psinfo->bufsize=1024
<0>[   75.665020] Kernel panic - not syncing: Fatal exception
<3>[   75.665020] drm_kms_helper: panic occurred, switching back to text console
<snip>

Seiji
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