[1/2] libndctl: add ndctl_pfn_has_align() api

Commit Message

Dan Williams Nov. 10, 2016, 1:28 a.m. UTC

In support of preventing create-namespace attempts to write the 'align'
attribute on kernels that do not have the capability, add this detection
api.

We would not have needed this if ndctl_pfn_get_align() returned -ENOENT
instead of zero, live and learn.

Signed-off-by: Dan Williams <[e-mail]>
---
 ndctl/lib/libndctl.c   |   16 ++++++++++++++++
 ndctl/lib/libndctl.sym |    1 +
 ndctl/libndctl.h.in    |    1 +
 3 files changed, 18 insertions(+)

Patch

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index 82b11a0d3ac9..eed418936a38 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -4231,6 +4231,22 @@  NDCTL_EXPORT unsigned long ndctl_pfn_get_align(struct ndctl_pfn *pfn)
 	return pfn->align;
 }
 
+NDCTL_EXPORT int ndctl_pfn_has_align(struct ndctl_pfn *pfn)
+{
+	struct ndctl_ctx *ctx = ndctl_pfn_get_ctx(pfn);
+	char *path = pfn->pfn_buf;
+	int len = pfn->buf_len;
+	struct stat st;
+
+	if (snprintf(path, len, "%s/align", pfn->pfn_path) >= len) {
+		err(ctx, "%s: buffer too small!\n",
+				ndctl_pfn_get_devname(pfn));
+		return 0;
+	}
+
+	return stat(path, &st) == 0;
+}
+
 NDCTL_EXPORT int ndctl_pfn_set_align(struct ndctl_pfn *pfn, unsigned long align)
 {
 	struct ndctl_ctx *ctx = ndctl_pfn_get_ctx(pfn);
diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
index 6bd032ea7526..603c386cc2a1 100644
--- a/ndctl/lib/libndctl.sym
+++ b/ndctl/lib/libndctl.sym
@@ -231,6 +231,7 @@  global:
 	ndctl_pfn_get_align;
 	ndctl_pfn_get_size;
 	ndctl_pfn_get_resource;
+	ndctl_pfn_has_align;
 	ndctl_pfn_set_align;
 	ndctl_pfn_set_namespace;
 	ndctl_pfn_get_bus;
diff --git a/ndctl/libndctl.h.in b/ndctl/libndctl.h.in
index d3379f76e1f9..9d7219894ed7 100644
--- a/ndctl/libndctl.h.in
+++ b/ndctl/libndctl.h.in
@@ -566,6 +566,7 @@  int ndctl_pfn_set_location(struct ndctl_pfn *pfn, enum ndctl_pfn_loc loc);
 enum ndctl_pfn_loc ndctl_pfn_get_location(struct ndctl_pfn *pfn);
 int ndctl_pfn_set_uuid(struct ndctl_pfn *pfn, uuid_t uu);
 void ndctl_pfn_get_uuid(struct ndctl_pfn *pfn, uuid_t uu);
+int ndctl_pfn_has_align(struct ndctl_pfn *pfn);
 int ndctl_pfn_set_align(struct ndctl_pfn *pfn, unsigned long align);
 unsigned long ndctl_pfn_get_align(struct ndctl_pfn *pfn);
 unsigned long long ndctl_pfn_get_resource(struct ndctl_pfn *pfn);