On Tue, Mar 13, 2012 at 11:34:46AM +0100, Florian Schmaus wrote:
> From: Andor Daam <andor.daam@xxxxxxxxxxxxxx>
>
> This patch makes dynamic enabling/disabling of zcache via a sysfsnode possible.
There should be an patch to the Documentation/ABI/testing for these parameters.
> The node is used to toggle the preexisting zcache_freeze variable to
> stop/start accepting pages by zcache.
What is the reasoning to do this in the frontend instead of the backend (Cleancache/frontswap)?
>
> Signed-off-by: Andor Daam <andor.daam@xxxxxxxxxxxxxx>
> Signed-off-by: Florian Schmaus <fschmaus@xxxxxxxxx>
> Signed-off-by: Stefan Hengelein <ilendir@xxxxxxxxxxxxxx>
> ---
> drivers/staging/zcache/zcache-main.c | 57 +++++++++++++++++++++++++++++-----
> 1 files changed, 49 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
> index 2734dac..1bece03 100644
> --- a/drivers/staging/zcache/zcache-main.c
> +++ b/drivers/staging/zcache/zcache-main.c
> @@ -469,6 +469,15 @@ out:
> }
>
> /*
> + * When zcache is disabled ("frozen"), pools can be created and destroyed,
> + * but all puts (and thus all other operations that require memory allocation)
> + * must fail. If zcache is unfrozen, accepts puts, then frozen again,
> + * data consistency requires all puts while frozen to be converted into
> + * flushes.
> + */
> +static bool zcache_freeze;
> +
> +/*
> * The following routines handle shrinking of ephemeral pages by evicting
> * pages "least valuable" first.
> */
> @@ -913,6 +922,45 @@ static struct kobj_attribute zcache_zv_page_count_policy_percent_attr = {
> .show = zv_page_count_policy_percent_show,
> .store = zv_page_count_policy_percent_store,
> };
> +
> +static ssize_t zcache_freeze_show(struct kobject *kobj,
> + struct kobj_attribute *attr,
> + char *buf)
> +{
> + if (zcache_freeze)
> + return sprintf(buf, "1\n");
> + else
> + return sprintf(buf, "0\n");
> +}
> +
> +static ssize_t zcache_freeze_store(struct kobject *kobj,
> + struct kobj_attribute *attr,
> + const char *buf, size_t count)
> +{
> + unsigned int val;
> + int err;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + err = kstrtouint(buf, 10, &val);
> + if (err)
> + return -EINVAL;
> +
> + if (val > 0)
> + zcache_freeze = true;
> + else
> + zcache_freeze = false;
> +
> + return count;
> +}
> +
> +static struct kobj_attribute zcache_freeze_attr = {
> + .attr = { .name = "zcache_freeze", .mode = 0644 },
> + .show = zcache_freeze_show,
> + .store = zcache_freeze_store,
> +};
> +
> #endif
>
> /*
> @@ -1515,6 +1563,7 @@ static struct attribute *zcache_attrs[] = {
> &zcache_zv_max_zsize_attr.attr,
> &zcache_zv_max_mean_zsize_attr.attr,
> &zcache_zv_page_count_policy_percent_attr.attr,
> + &zcache_freeze_attr.attr,
> NULL,
> };
>
> @@ -1524,14 +1573,6 @@ static struct attribute_group zcache_attr_group = {
> };
>
> #endif /* CONFIG_SYSFS */
> -/*
> - * When zcache is disabled ("frozen"), pools can be created and destroyed,
> - * but all puts (and thus all other operations that require memory allocation)
> - * must fail. If zcache is unfrozen, accepts puts, then frozen again,
> - * data consistency requires all puts while frozen to be converted into
> - * flushes.
> - */
> -static bool zcache_freeze;
>
> /*
> * zcache shrinker interface (only useful for ephemeral pages, so zbud only)
> --
> 1.7.5.4
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