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    Subject[PATCH 3.18 34/50] pstore: Allow prz to control need for locking
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

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

    From: Joel Fernandes <joelaf@google.com>

    commit 663deb47880f2283809669563c5a52ac7c6aef1a upstream.

    In preparation of not locking at all for certain buffers depending on if
    there's contention, make locking optional depending on the initialization
    of the prz.

    Signed-off-by: Joel Fernandes <joelaf@google.com>
    [kees: moved locking flag into prz instead of via caller arguments]
    Signed-off-by: Kees Cook <keescook@chromium.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/pstore/ram.c | 5 +++--
    fs/pstore/ram_core.c | 24 +++++++++++++++---------
    include/linux/pstore_ram.h | 10 +++++++++-
    3 files changed, 27 insertions(+), 12 deletions(-)

    --- a/fs/pstore/ram.c
    +++ b/fs/pstore/ram.c
    @@ -365,7 +365,7 @@ static int ramoops_init_przs(struct devi

    cxt->przs[i] = persistent_ram_new(*paddr, sz, 0,
    &cxt->ecc_info,
    - cxt->memtype);
    + cxt->memtype, 0);
    if (IS_ERR(cxt->przs[i])) {
    err = PTR_ERR(cxt->przs[i]);
    dev_err(dev, "failed to request mem region (0x%zx@0x%llx): %d\n",
    @@ -395,7 +395,8 @@ static int ramoops_init_prz(struct devic
    return -ENOMEM;
    }

    - *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info, cxt->memtype);
    + *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info,
    + cxt->memtype, 0);
    if (IS_ERR(*prz)) {
    int err = PTR_ERR(*prz);

    --- a/fs/pstore/ram_core.c
    +++ b/fs/pstore/ram_core.c
    @@ -85,9 +85,10 @@ static size_t buffer_start_add_locked(st
    {
    int old;
    int new;
    - unsigned long flags;
    + unsigned long flags = 0;

    - raw_spin_lock_irqsave(&prz->buffer_lock, flags);
    + if (!(prz->flags & PRZ_FLAG_NO_LOCK))
    + raw_spin_lock_irqsave(&prz->buffer_lock, flags);

    old = atomic_read(&prz->buffer->start);
    new = old + a;
    @@ -95,7 +96,8 @@ static size_t buffer_start_add_locked(st
    new -= prz->buffer_size;
    atomic_set(&prz->buffer->start, new);

    - raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
    + if (!(prz->flags & PRZ_FLAG_NO_LOCK))
    + raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);

    return old;
    }
    @@ -105,9 +107,10 @@ static void buffer_size_add_locked(struc
    {
    size_t old;
    size_t new;
    - unsigned long flags;
    + unsigned long flags = 0;

    - raw_spin_lock_irqsave(&prz->buffer_lock, flags);
    + if (!(prz->flags & PRZ_FLAG_NO_LOCK))
    + raw_spin_lock_irqsave(&prz->buffer_lock, flags);

    old = atomic_read(&prz->buffer->size);
    if (old == prz->buffer_size)
    @@ -119,7 +122,8 @@ static void buffer_size_add_locked(struc
    atomic_set(&prz->buffer->size, new);

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

    static size_t (*buffer_start_add)(struct persistent_ram_zone *, size_t) = buffer_start_add_atomic;
    @@ -459,7 +463,8 @@ static int persistent_ram_buffer_map(phy
    }

    static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
    - struct persistent_ram_ecc_info *ecc_info)
    + struct persistent_ram_ecc_info *ecc_info,
    + unsigned long flags)
    {
    int ret;

    @@ -488,6 +493,7 @@ static int persistent_ram_post_init(stru
    prz->buffer->sig = sig;
    persistent_ram_zap(prz);
    prz->buffer_lock = __RAW_SPIN_LOCK_UNLOCKED(buffer_lock);
    + prz->flags = flags;

    return 0;
    }
    @@ -512,7 +518,7 @@ void persistent_ram_free(struct persiste

    struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
    u32 sig, struct persistent_ram_ecc_info *ecc_info,
    - unsigned int memtype)
    + unsigned int memtype, u32 flags)
    {
    struct persistent_ram_zone *prz;
    int ret = -ENOMEM;
    @@ -527,7 +533,7 @@ struct persistent_ram_zone *persistent_r
    if (ret)
    goto err;

    - ret = persistent_ram_post_init(prz, sig, ecc_info);
    + ret = persistent_ram_post_init(prz, sig, ecc_info, flags);
    if (ret)
    goto err;

    --- a/include/linux/pstore_ram.h
    +++ b/include/linux/pstore_ram.h
    @@ -23,6 +23,13 @@
    #include <linux/types.h>
    #include <linux/init.h>

    +/*
    + * Choose whether access to the RAM zone requires locking or not. If a zone
    + * can be written to from different CPUs like with ftrace for example, then
    + * PRZ_FLAG_NO_LOCK is used. For all other cases, locking is required.
    + */
    +#define PRZ_FLAG_NO_LOCK BIT(0)
    +
    struct persistent_ram_buffer;
    struct rs_control;

    @@ -39,6 +46,7 @@ struct persistent_ram_zone {
    void *vaddr;
    struct persistent_ram_buffer *buffer;
    size_t buffer_size;
    + u32 flags;
    raw_spinlock_t buffer_lock;

    /* ECC correction */
    @@ -55,7 +63,7 @@ struct persistent_ram_zone {

    struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
    u32 sig, struct persistent_ram_ecc_info *ecc_info,
    - unsigned int memtype);
    + unsigned int memtype, u32 flags);
    void persistent_ram_free(struct persistent_ram_zone *prz);
    void persistent_ram_zap(struct persistent_ram_zone *prz);


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