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    Subject[PATCH 3.18 02/92] pstore: Make spinlock per zone instead of global
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Joel Fernandes <joelaf@google.com>

    commit 109704492ef637956265ec2eb72ae7b3b39eb6f4 upstream.

    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, when ramoops's ftrace use-case has a FTRACE_PER_CPU flag
    introduced later, which splits the ftrace memory area into a single zone
    per CPU, it will eliminate the need for locking. In preparation for this,
    make the locking optional.

    Signed-off-by: Joel Fernandes <joelaf@google.com>
    [kees: updated commit message]
    Signed-off-by: Kees Cook <keescook@chromium.org>
    Cc: Leo Yan <leo.yan@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/pstore/ram_core.c | 11 +++++------
    include/linux/pstore_ram.h | 1 +
    2 files changed, 6 insertions(+), 6 deletions(-)

    --- a/fs/pstore/ram_core.c
    +++ b/fs/pstore/ram_core.c
    @@ -80,8 +80,6 @@ static void buffer_size_add_atomic(struc
    } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);
    }

    -static DEFINE_RAW_SPINLOCK(buffer_lock);
    -
    /* increase and wrap the start pointer, returning the old value */
    static size_t buffer_start_add_locked(struct persistent_ram_zone *prz, size_t a)
    {
    @@ -89,7 +87,7 @@ static size_t buffer_start_add_locked(st
    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;
    @@ -97,7 +95,7 @@ static size_t buffer_start_add_locked(st
    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;
    }
    @@ -109,7 +107,7 @@ static void buffer_size_add_locked(struc
    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)
    @@ -121,7 +119,7 @@ static void buffer_size_add_locked(struc
    atomic_set(&prz->buffer->size, new);

    exit:
    - raw_spin_unlock_irqrestore(&buffer_lock, flags);
    + raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
    }

    static size_t (*buffer_start_add)(struct persistent_ram_zone *, size_t) = buffer_start_add_atomic;
    @@ -489,6 +487,7 @@ static int persistent_ram_post_init(stru

    prz->buffer->sig = sig;
    persistent_ram_zap(prz);
    + prz->buffer_lock = __RAW_SPIN_LOCK_UNLOCKED(buffer_lock);

    return 0;
    }
    --- a/include/linux/pstore_ram.h
    +++ b/include/linux/pstore_ram.h
    @@ -39,6 +39,7 @@ 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;

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