Add an API for setting the size of a dax device.

This sysfs attribute is only writeable for a dynamic
dax device such as the one exported by hmem.

Signed-off-by: Joao Martins <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
---
 daxctl/lib/libdaxctl.c   | 24 ++++++++++++++++++++++++
 daxctl/lib/libdaxctl.sym |  5 +++++
 daxctl/libdaxctl.h       |  1 +
 3 files changed, 30 insertions(+)

diff --git a/daxctl/lib/libdaxctl.c b/daxctl/lib/libdaxctl.c
index ee4a069eb463..00d5f7fe61ad 100644
--- a/daxctl/lib/libdaxctl.c
+++ b/daxctl/lib/libdaxctl.c
@@ -1019,6 +1019,30 @@ DAXCTL_EXPORT unsigned long long 
daxctl_dev_get_size(struct daxctl_dev *dev)
        return dev->size;
 }
 
+DAXCTL_EXPORT int daxctl_dev_set_size(struct daxctl_dev *dev, unsigned long 
long size)
+{
+       struct daxctl_ctx *ctx = daxctl_dev_get_ctx(dev);
+       char buf[SYSFS_ATTR_SIZE];
+       char *path = dev->dev_buf;
+       int len = dev->buf_len;
+
+       if (snprintf(path, len, "%s/size", dev->dev_path) >= len) {
+               err(ctx, "%s: buffer too small!\n",
+                               daxctl_dev_get_devname(dev));
+               return -ENXIO;
+       }
+
+       sprintf(buf, "%#llx\n", size);
+       if (sysfs_write_attr(ctx, path, buf) < 0) {
+               err(ctx, "%s: failed to set size\n",
+                               daxctl_dev_get_devname(dev));
+               return -ENXIO;
+       }
+
+       dev->size = size;
+       return 0;
+}
+
 DAXCTL_EXPORT int daxctl_dev_get_target_node(struct daxctl_dev *dev)
 {
        return dev->target_node;
diff --git a/daxctl/lib/libdaxctl.sym b/daxctl/lib/libdaxctl.sym
index 87d02366a917..d8b4137c76b7 100644
--- a/daxctl/lib/libdaxctl.sym
+++ b/daxctl/lib/libdaxctl.sym
@@ -75,3 +75,8 @@ global:
        daxctl_memory_is_movable;
        daxctl_memory_online_no_movable;
 } LIBDAXCTL_6;
+
+LIBDAXCTL_8 {
+global:
+       daxctl_dev_set_size;
+} LIBDAXCTL_7;
diff --git a/daxctl/libdaxctl.h b/daxctl/libdaxctl.h
index 6c545e1f3055..e3d482743cc6 100644
--- a/daxctl/libdaxctl.h
+++ b/daxctl/libdaxctl.h
@@ -68,6 +68,7 @@ int daxctl_dev_get_major(struct daxctl_dev *dev);
 int daxctl_dev_get_minor(struct daxctl_dev *dev);
 unsigned long long daxctl_dev_get_resource(struct daxctl_dev *dev);
 unsigned long long daxctl_dev_get_size(struct daxctl_dev *dev);
+int daxctl_dev_set_size(struct daxctl_dev *dev, unsigned long long size);
 struct daxctl_ctx *daxctl_dev_get_ctx(struct daxctl_dev *dev);
 int daxctl_dev_is_enabled(struct daxctl_dev *dev);
 int daxctl_dev_disable(struct daxctl_dev *dev);
-- 
1.8.3.1
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