[PATCH daxctl v2 3/5] libdaxctl: add daxctl_dev_set_mapping()

[Joao Martins <joao.m.martins@oracle.com>]

This API adds the ability to manually pick a range within the region
device.  Such routine allows for a admin to restore the mappings of a
device after kexec. This is specially useful for hmem dynamic devdax
which do not persistent ranges allocation through say a e.g. namespace
label storage area. It also allows an userspace application to pick
it's own ranges, should it want to avoid relying on kernel's policy.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 daxctl/lib/libdaxctl.c   | 27 +++++++++++++++++++++++++++
 daxctl/lib/libdaxctl.sym |  1 +
 daxctl/libdaxctl.h       |  2 ++
 3 files changed, 30 insertions(+)

diff --git a/daxctl/lib/libdaxctl.c b/daxctl/lib/libdaxctl.c
index 3781e9ed27d5..59fe84fee409 100644
--- a/daxctl/lib/libdaxctl.c
+++ b/daxctl/lib/libdaxctl.c
@@ -1123,6 +1123,33 @@ DAXCTL_EXPORT int daxctl_dev_set_align(struct daxctl_dev *dev, unsigned long ali
 	return 0;
 }
 
+DAXCTL_EXPORT int daxctl_dev_set_mapping(struct daxctl_dev *dev,
+					unsigned long long start,
+					unsigned long long end)
+{
+	struct daxctl_ctx *ctx = daxctl_dev_get_ctx(dev);
+	unsigned long long size = end - start + 1;
+	char buf[SYSFS_ATTR_SIZE];
+	char *path = dev->dev_buf;
+	int len = dev->buf_len;
+
+	if (snprintf(path, len, "%s/mapping", dev->dev_path) >= len) {
+		err(ctx, "%s: buffer too small!\n",
+				daxctl_dev_get_devname(dev));
+		return -ENXIO;
+	}
+
+	sprintf(buf, "%#llx-%#llx\n", start, end);
+	if (sysfs_write_attr(ctx, path, buf) < 0) {
+		err(ctx, "%s: failed to set mapping\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 08362b683678..a4e16848494b 100644
--- a/daxctl/lib/libdaxctl.sym
+++ b/daxctl/lib/libdaxctl.sym
@@ -89,4 +89,5 @@ global:
 	daxctl_mapping_get_end;
 	daxctl_mapping_get_offset;
 	daxctl_mapping_get_size;
+	daxctl_dev_set_mapping;
 } LIBDAXCTL_7;
diff --git a/daxctl/libdaxctl.h b/daxctl/libdaxctl.h
index f94a72fed85b..09439c16d6df 100644
--- a/daxctl/libdaxctl.h
+++ b/daxctl/libdaxctl.h
@@ -73,6 +73,8 @@ unsigned long long daxctl_dev_get_size(struct daxctl_dev *dev);
 int daxctl_dev_set_size(struct daxctl_dev *dev, unsigned long long size);
 unsigned long daxctl_dev_get_align(struct daxctl_dev *dev);
 int daxctl_dev_set_align(struct daxctl_dev *dev, unsigned long align);
+int daxctl_dev_set_mapping(struct daxctl_dev *dev, unsigned long long start,
+			unsigned long long end);
 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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