linux-kernel - Re: [PATCH 1/7] pstore: Make spinlock per zone instead of global

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Message-ID: <CAJWu+oo-tp-tomBSkDjerk2xNL5nKWG83LAGEnk6y7f0U48xKQ@mail.gmail.com>
Date:   Fri, 7 Oct 2016 22:44:24 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Kees Cook <keescook@...omium.org>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH 1/7] pstore: Make spinlock per zone instead of global

Apologies that not everyone got CC'd on the cover letter, like the
rest of the patch series:
https://lkml.org/lkml/2016/10/8/12

Also, this patch series is an RFC, I screwed up the subject line.

Thanks,
Joel

On Fri, Oct 7, 2016 at 10:28 PM, Joel Fernandes <joelaf@...gle.com> wrote:
>
> Currently pstore has a global spinlock for all zones. Since the zones are
> independent and modify different areas of memory, there's no need to have
> a global lock, make the lock per-zone to protect the respective zone.
>
> Signed-off-by: Joel Fernandes <joelaf@...gle.com>
> ---
>  fs/pstore/ram_core.c       | 11 +++++------
>  include/linux/pstore_ram.h |  1 +
>  2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
> index 3975dee..cb92055 100644
> --- a/fs/pstore/ram_core.c
> +++ b/fs/pstore/ram_core.c
> @@ -48,8 +48,6 @@ static inline size_t buffer_start(struct persistent_ram_zone *prz)
>         return atomic_read(&prz->buffer->start);
>  }
>
> -static DEFINE_RAW_SPINLOCK(buffer_lock);
> -
>  /* increase and wrap the start pointer, returning the old value */
>  static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
>  {
> @@ -57,7 +55,7 @@ static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
>         int new;
>         unsigned long flags;
>
> -       raw_spin_lock_irqsave(&buffer_lock, flags);
> +       raw_spin_lock_irqsave(&prz->buffer_lock, flags);
>
>         old = atomic_read(&prz->buffer->start);
>         new = old + a;
> @@ -65,7 +63,7 @@ static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
>                 new -= prz->buffer_size;
>         atomic_set(&prz->buffer->start, new);
>
> -       raw_spin_unlock_irqrestore(&buffer_lock, flags);
> +       raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
>
>         return old;
>  }
> @@ -77,7 +75,7 @@ static void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
>         size_t new;
>         unsigned long flags;
>
> -       raw_spin_lock_irqsave(&buffer_lock, flags);
> +       raw_spin_lock_irqsave(&prz->buffer_lock, flags);
>
>         old = atomic_read(&prz->buffer->size);
>         if (old == prz->buffer_size)
> @@ -89,7 +87,7 @@ static void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
>         atomic_set(&prz->buffer->size, new);
>
>  exit:
> -       raw_spin_unlock_irqrestore(&buffer_lock, flags);
> +       raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
>  }
>
>  static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
> @@ -493,6 +491,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
>
>         prz->buffer->sig = sig;
>         persistent_ram_zap(prz);
> +       prz->buffer_lock = __RAW_SPIN_LOCK_UNLOCKED(buffer_lock);
>
>         return 0;
>  }
> diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
> index c668c86..244d242 100644
> --- a/include/linux/pstore_ram.h
> +++ b/include/linux/pstore_ram.h
> @@ -40,6 +40,7 @@ struct persistent_ram_zone {
>         void *vaddr;
>         struct persistent_ram_buffer *buffer;
>         size_t buffer_size;
> +       raw_spinlock_t buffer_lock;
>
>         /* ECC correction */
>         char *par_buffer;
> --
> 2.7.4
>