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Tue, 30 Oct 2018 14:38:19 -0700 (PDT) Date: Tue, 30 Oct 2018 14:38:18 -0700 From: Joel Fernandes To: Peng Wang 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() Message-ID: <20181030213818.GA32621@google.com> References: <20181030075234.21137-1-wangpeng15@xiaomi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181030075234.21137-1-wangpeng15@xiaomi.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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;