linux-kernel - Re: [PATCH] pstore: reset ftrace_read_cnt at ramoops_pstore

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Date:	Fri, 7 Mar 2014 10:58:43 +0800
From:	Liu ShuoX <shuox.liu@...el.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Tony Luck <tony.luck@...el.com>,
	Colin Cross <ccross@...roid.com>,
	Anton Vorontsov <anton@...msg.org>,
	yanmin_zhang@...ux.intel.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] pstore: reset ftrace_read_cnt at ramoops_pstore_open

On Tue  4.Mar'14 at 11:11:11 -0800, Kees Cook wrote:
>On Mon, Mar 3, 2014 at 5:40 PM, Liu ShuoX <shuox.liu@...el.com> wrote:
>> On Mon  3.Mar'14 at 11:45:59 -0800, Kees Cook wrote:
>>>
>>> On Thu, Feb 27, 2014 at 10:37 PM,  <shuox.liu@...el.com> wrote:
>>>>
>>>> From: Liu ShuoX <shuox.liu@...el.com>
>>>>
>>>> ftrace_read_cnt need to be reset in open to support mutli times
>>>> getting the records.
>>>>
>>>> Signed-off-by: Liu ShuoX <shuox.liu@...el.com>
>>>> ---
>>>>  fs/pstore/ram.c | 1 +
>>>>  1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
>>>> index fa8cef2..a5d0cab 100644
>>>> --- a/fs/pstore/ram.c
>>>> +++ b/fs/pstore/ram.c
>>>> @@ -101,6 +101,7 @@ static int ramoops_pstore_open(struct pstore_info
>>>> *psi)
>>>>
>>>>         cxt->dump_read_cnt = 0;
>>>>         cxt->console_read_cnt = 0;
>>>> +       cxt->ftrace_read_cnt = 0;
>>>>         return 0;
>>>>  }
>>>
>>>
>>> I think we need a separate function for "clear" for the
>>> ramoops_context struct. IIUC, we're missing a similar initialization
>>> in ramoops_probe, which lacks both console_read_cnt=0 and
>>> ftrace_read_cnt=0. Then both places could call this?
>>
>> Hi Kees,
>> Currently, we have only one static ramoops_context named oops_cxt.
>> *_read_cnt should be initialized to 0 as default. Need we still add
>> such function for 'clear'?
>
>We have the pstore-global "oops_cxt" context. It is "initialized" only
>once in ramoops_probe (and seems to needlessly set dump_read_cnt to
>0). Otherwise, the context is initialized via ramoops_register_dummy
>from module parameters (and initialized to zero with kzalloc).
>
>So, I think my initial comment about "clear" is probably not right,
>but that ramoops_pstore_open should be doing that (i.e. your original
>patch is close). However, I think I'd like to see the needless zeroing
>in ramoops_probe removed, and the "variables that need clearing on
>open" documented in comments in "struct ramoops_context". That should
>make this code more clear to read next time. :)
Sorry for delay reply. How about below patch?

From: Liu ShuoX <shuox.liu@...el.com>

ftrace_read_cnt need to be reset in open to support mutli times
getting the records.

Signed-off-by: Liu ShuoX <shuox.liu@...el.com>
---
  fs/pstore/ram.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index fa8cef2..9fe5b13 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -86,6 +86,7 @@ struct ramoops_context {
  	struct persistent_ram_ecc_info ecc_info;
  	unsigned int max_dump_cnt;
  	unsigned int dump_write_cnt;
+	/* _read_cnt need clear on ramoops_pstore_open */
  	unsigned int dump_read_cnt;
  	unsigned int console_read_cnt;
  	unsigned int ftrace_read_cnt;
@@ -101,6 +102,7 @@ static int ramoops_pstore_open(struct pstore_info *psi)
  
  	cxt->dump_read_cnt = 0;
  	cxt->console_read_cnt = 0;
+	cxt->ftrace_read_cnt = 0;
  	return 0;
  }
  
@@ -428,7 +430,6 @@ static int ramoops_probe(struct platform_device *pdev)
  	if (pdata->ftrace_size && !is_power_of_2(pdata->ftrace_size))
  		pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
  
-	cxt->dump_read_cnt = 0;
  	cxt->size = pdata->mem_size;
  	cxt->phys_addr = pdata->mem_address;
  	cxt->record_size = pdata->record_size;
-- 
1.8.3.2

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