LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Joel Fernandes <joel@joelfernandes.org>
To: Peng Wang <wangpeng15@xiaomi.com>
Cc: keescook@chromium.org, anton@enomsg.org, ccross@android.com,
	tony.luck@intel.com, linux-kernel@vger.kernel.org,
	vipwangerxiao@gmail.com
Subject: Re: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap()
Date: Tue, 30 Oct 2018 14:38:18 -0700	[thread overview]
Message-ID: <20181030213818.GA32621@google.com> (raw)
In-Reply-To: <20181030075234.21137-1-wangpeng15@xiaomi.com>

On Tue, Oct 30, 2018 at 03:52:34PM +0800, Peng Wang wrote:
> When initialing prz with invalid data in buffer(no PERSISTENT_RAM_SIG),
> function call path is like this:
> 
> ramoops_init_prz ->
> |
> |-> persistent_ram_new -> persistent_ram_post_init -> persistent_ram_zap
> |
> |-> persistent_ram_zap
> 
> As we can see, persistent_ram_zap() is called twice.
> We can avoid this by adding an option to persistent_ram_new(), and
> only call persistent_ram_zap() when it is needed.
> 
> Signed-off-by: Peng Wang <wangpeng15@xiaomi.com>
> ---
>  fs/pstore/ram.c            | 4 +---
>  fs/pstore/ram_core.c       | 5 +++--
>  include/linux/pstore_ram.h | 1 +
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index ffcff6516e89..b51901f97dc2 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -640,7 +640,7 @@ static int ramoops_init_prz(const char *name,
>  
>  	label = kasprintf(GFP_KERNEL, "ramoops:%s", name);
>  	*prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info,
> -				  cxt->memtype, 0, label);
> +				  cxt->memtype, PRZ_FLAG_ZAP_OLD, label);
>  	if (IS_ERR(*prz)) {
>  		int err = PTR_ERR(*prz);

Looks good to me except the minor comment below:

>  
> @@ -649,8 +649,6 @@ static int ramoops_init_prz(const char *name,
>  		return err;
>  	}
>  
> -	persistent_ram_zap(*prz);
> -
>  	*paddr += sz;
>  
>  	return 0;
> diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
> index 12e21f789194..2ededd1ea1c2 100644
> --- a/fs/pstore/ram_core.c
> +++ b/fs/pstore/ram_core.c
> @@ -505,15 +505,16 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
>  			pr_debug("found existing buffer, size %zu, start %zu\n",
>  				 buffer_size(prz), buffer_start(prz));
>  			persistent_ram_save_old(prz);
> -			return 0;
> +			if (!(prz->flags & PRZ_FLAG_ZAP_OLD))
> +				return 0;

This could be written differently.

We could just do:

if (prz->flags & PRZ_FLAG_ZAP_OLD)
	persistent_ram_zap(prz);

And remove the zap from below below.

Since Kees already took this patch, I can just patch this in my series if
Kees and you are Ok with this suggestion.

Sorry for the delay in my RFC series, I just got back from paternity leave
and I'm catching up with email.

thanks,

- Joel

>  		}
>  	} else {
>  		pr_debug("no valid data in buffer (sig = 0x%08x)\n",
>  			 prz->buffer->sig);
> +		prz->buffer->sig = sig;
>  	}
>  
>  	/* Rewind missing or invalid memory area. */
> -	prz->buffer->sig = sig;
>  	persistent_ram_zap(prz);
>  
>  	return 0;

  parent reply	other threads:[~2018-10-30 21:38 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-30  7:52 Peng Wang
2018-10-30 21:21 ` Kees Cook
2018-10-30 21:38 ` Joel Fernandes [this message]
2018-10-30 21:52   ` Kees Cook
2018-10-30 22:16     ` Joel Fernandes
2018-10-31  3:57       ` Peng15 Wang 王鹏
2018-10-31  4:19         ` Joel Fernandes

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181030213818.GA32621@google.com \
    --to=joel@joelfernandes.org \
    --cc=anton@enomsg.org \
    --cc=ccross@android.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=tony.luck@intel.com \
    --cc=vipwangerxiao@gmail.com \
    --cc=wangpeng15@xiaomi.com \
    --subject='Re: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).