Messages in this thread | | | From | Joel Fernandes <> | Date | Tue, 30 Oct 2018 21:19:17 -0700 | Subject | Re: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap() |
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On Tue, Oct 30, 2018 at 8:57 PM, Peng15 Wang 王鹏 <wangpeng15@xiaomi.com> wrote: > >>From: Joel Fernandes <joel@joelfernandes.org> >>Sent: Wednesday, October 31, 2018 6:16 >>To: Kees Cook >>Cc: Peng15 Wang 王鹏; Anton Vorontsov; Colin Cross; Tony Luck; LKML; vipwangerxiao@gmail.com >>Subject: Re: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap() >> >>On Tue, Oct 30, 2018 at 02:52:43PM -0700, Kees Cook wrote: >>> On Tue, Oct 30, 2018 at 2:38 PM, Joel Fernandes <joel@joelfernandes.org> wrote: >>> > 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. >>> >>> I actually rearranged things a little to avoid additional round-trips >>> on the mailing list. :) >>> >>> > Since Kees already took this patch, I can just patch this in my series if >>> > Kees and you are Ok with this suggestion. >>> >>> I've put it up here: >>> https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=pstore/devel&id=ac564e023248e3f4d87917b91d12376ddfca5000 >> >>Cool, it LGTM :) >> >>- Joel >> > > Thank you all for these warm help. > > This is my first time to submit a patch to community. Feel great!
Congrats and welcome to the mother ship ;-)
- Joel
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