Re: [PATCH v2 1/7] pstore: Make spinlock per zone instead of global

[Joel Fernandes <joelaf@google.com>]

On Thu, Nov 10, 2016 at 4:06 PM, Kees Cook <keescook@chromium.org> wrote:
> On Thu, Oct 20, 2016 at 12:34 AM, Joel Fernandes <joelaf@google.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, so we should use a per-zone lock as introduced here. Also,
>> ramoops's ftrace usecase has a FTRACE_PER_CPU flag introduced in this patch
>> series which splits the ftrace memory area into a single zone per CPU thus
>> eliminating the need for locking. In preparation for this, make the locking
>> optional.
>>
>> Signed-off-by: Joel Fernandes <joelaf@google.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
>>
>
> This one looks good, thanks. I'll get this in for -next since it's a
> good clean-up on its own.
>
Thanks.

> Have you put these patches through scripts/checkpatch.pl? Some of
> lines wrap or have wide commit messages, but that's just cosmetic to
> fix up.

I didn't have any errors, just 1 or 2 warnings about wide commit
messages yes. I'll fix those up on the other patches you commented on
and resend them, thanks!

Regards,

Joel