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nvmet: add buffered I/O support for file backed ns

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Add a new "buffered_io" attribute, which disabled direct I/O and thus
enables page cache based caching when enabled.   The attribute can only
be changed when the namespace is disabled as the file has to be reopend
for the change to take effect.

The possibly blocking read/write are deferred to a newly introduced
global workqueue.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Chaitanya Kulkarni
2018-06-20 00:01:41 -04:00
committed by Christoph Hellwig
parent 0866bf0c37
commit 55eb942eda
4 changed files with 67 additions and 5 deletions
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29
drivers/nvme/target/configfs.c
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@@ -407,11 +407,40 @@ static ssize_t nvmet_ns_enable_store(struct config_item *item,
CONFIGFS_ATTR(nvmet_ns_, enable);
static ssize_t nvmet_ns_buffered_io_show(struct config_item *item, char *page)
{
return sprintf(page, "%d\n", to_nvmet_ns(item)->buffered_io);
}
static ssize_t nvmet_ns_buffered_io_store(struct config_item *item,
const char *page, size_t count)
{
struct nvmet_ns *ns = to_nvmet_ns(item);
bool val;
if (strtobool(page, &val))
return -EINVAL;
mutex_lock(&ns->subsys->lock);
if (ns->enabled) {
pr_err("disable ns before setting buffered_io value.\n");
mutex_unlock(&ns->subsys->lock);
return -EINVAL;
}
ns->buffered_io = val;
mutex_unlock(&ns->subsys->lock);
return count;
}
CONFIGFS_ATTR(nvmet_ns_, buffered_io);
static struct configfs_attribute *nvmet_ns_attrs[] = {
&nvmet_ns_attr_device_path,
&nvmet_ns_attr_device_nguid,
&nvmet_ns_attr_device_uuid,
&nvmet_ns_attr_enable,
&nvmet_ns_attr_buffered_io,
NULL,
};