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Subject[PATCH 1/2] rbd: RBD_DEV_FLAG_THICK rbd_dev_flags bit
This patch adds a user interface to prevent from issuing discard
requests onto the specified rbd device. This is needed for
thick-provisioned images. To avoid discarding allocated blocks on
thick-provision image, users can specify this flag bit via sysfs
(/sys/bus/rbd/devices/<dev-id>/thick).

When users write "1" to the file, rbd doesn't issue discard
operation; meanwhile, if users write "0" to the file then rbd
issues discard operation.

Signed-off-by: Hitoshi Kamei <hitoshi.kamei.xm@hitachi.com>
Cc: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
---
drivers/block/rbd.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 8e40da093766..dba60ef43a47 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -427,6 +427,7 @@ enum rbd_dev_flags {
RBD_DEV_FLAG_EXISTS, /* mapped snapshot has not been deleted */
RBD_DEV_FLAG_REMOVING, /* this mapping is being removed */
RBD_DEV_FLAG_BLACKLISTED, /* our ceph_client is blacklisted */
+ RBD_DEV_FLAG_THICK, /* image is thick-provisioned */
};

static DEFINE_MUTEX(client_mutex); /* Serialize client creation */
@@ -4011,6 +4012,15 @@ static void rbd_queue_workfn(struct work_struct *work)
goto err;
}

+ /* Ignore/skip discard requests for thick-provision image */
+
+ if (op_type == OBJ_OP_DISCARD &&
+ test_bit(RBD_DEV_FLAG_THICK, &rbd_dev->flags)) {
+ dout("%s: Ignored a discard request\n", __func__);
+ result = 0;
+ goto err_rq;
+ }
+
/* Ignore/skip any zero-length requests */

if (!length) {
@@ -4600,6 +4610,32 @@ static ssize_t rbd_image_refresh(struct device *dev,
return size;
}

+static ssize_t rbd_thick_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf,
+ size_t size)
+{
+ struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
+
+ spin_lock_irq(&rbd_dev->lock);
+ if (!strncmp(buf, "1", size))
+ set_bit(RBD_DEV_FLAG_THICK, &rbd_dev->flags);
+ else if (!strncmp(buf, "0", size))
+ clear_bit(RBD_DEV_FLAG_THICK, &rbd_dev->flags);
+ spin_unlock_irq(&rbd_dev->lock);
+
+ return size;
+}
+
+static ssize_t rbd_thick_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
+ int is_thick = test_bit(RBD_DEV_FLAG_THICK, &rbd_dev->flags) ? 1 : 0;
+
+ return sprintf(buf, "%d\n", is_thick);
+}
+
static DEVICE_ATTR(size, S_IRUGO, rbd_size_show, NULL);
static DEVICE_ATTR(features, S_IRUGO, rbd_features_show, NULL);
static DEVICE_ATTR(major, S_IRUGO, rbd_major_show, NULL);
@@ -4616,6 +4652,7 @@ static DEVICE_ATTR(refresh, S_IWUSR, NULL, rbd_image_refresh);
static DEVICE_ATTR(current_snap, S_IRUGO, rbd_snap_show, NULL);
static DEVICE_ATTR(snap_id, S_IRUGO, rbd_snap_id_show, NULL);
static DEVICE_ATTR(parent, S_IRUGO, rbd_parent_show, NULL);
+static DEVICE_ATTR(thick, 0644, rbd_thick_show, rbd_thick_store);

static struct attribute *rbd_attrs[] = {
&dev_attr_size.attr,
@@ -4634,6 +4671,7 @@ static struct attribute *rbd_attrs[] = {
&dev_attr_snap_id.attr,
&dev_attr_parent.attr,
&dev_attr_refresh.attr,
+ &dev_attr_thick.attr,
NULL
};

--
2.15.1

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