[ndctl PATCH 2/2] ndctl/namespace: introduce ndctl_namespace_is_configurable()

[Vishal Verma <vishal.l.verma@intel.com>]

The motivation for this change is that we want to refrain from
(re)configuring what appear to be partially configured namespaces.
Namespaces may end up in a state that looks partially configured when
the kernel isn't able to enable a namespace due to mismatched
PAGE_SIZE expectations. In such cases, ndctl should not treat those
as unconfigured 'seed' namespaces, and reuse them.

Add a new ndctl_namespace_is_configurable API, whish tests whether a
namespaces is active, and whether it is partially configured. If neither
are true, then it can be used for (re)configuration. Additionally, deal
with the corner case of ND_DEVICE_NAMESPACE_IO (legacy PMEM) namespaces
by testing whether the size attribute is read-only (which indicates such
a namespace). Legacy namespaces always appear as configured, since their
size cannot be changed, but they are also always re-configurable.

Use this API in namespace_reconfig() and namespace_create() to enable
this partial configuration detection.

Cc: Dan Williams <dan.j.williams@intel.com>
Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---

Hi Aneesh - could you please test these patches and see if they work for
the pfn_sb PAGE_SIZE mismatch scenario?

 ndctl/lib/libndctl.c   | 37 +++++++++++++++++++++++++++++++++++++
 ndctl/lib/libndctl.sym |  4 ++++
 ndctl/libndctl.h       |  1 +
 ndctl/namespace.c      |  6 +++---
 util/sysfs.c           | 18 ++++++++++++++++++
 util/sysfs.h           |  3 +++
 6 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index 6596f94..1674cf9 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -3985,6 +3985,21 @@ static void region_refresh_children(struct ndctl_region *region)
 	daxs_init(region);
 }
 
+static bool namespace_size_is_writeable(struct ndctl_namespace *ndns)
+{
+	struct ndctl_ctx *ctx = ndctl_namespace_get_ctx(ndns);
+	char *path = ndns->ndns_buf;
+	int len = ndns->buf_len;
+
+	if (snprintf(path, len, "%s/size", ndns->ndns_path) >= len) {
+		err(ctx, "%s: buffer too small!\n",
+				ndctl_namespace_get_devname(ndns));
+		return false;
+	}
+
+	return sysfs_attr_writable(ctx, path);
+}
+
 NDCTL_EXPORT bool ndctl_namespace_is_active(struct ndctl_namespace *ndns)
 {
 	struct ndctl_btt *btt = ndctl_namespace_get_btt(ndns);
@@ -4182,6 +4197,28 @@ NDCTL_EXPORT int ndctl_namespace_is_configured(struct ndctl_namespace *ndns)
 	}
 }
 
+/*
+ * Check if a given 'seed' namespace is ok to configure.
+ * If a size or uuid is present, it is considered not configurable, except
+ * in the case of legacy (ND_DEVICE_NAMESPACE_IO) namespaces. In that case,
+ * the size is never zero, but the namespace can still be reconfigured.
+ * Detect this by testing whether the size is writable. If it is not writable,
+ * then it is ok to (re)configure. In other words, legacy namespaces are always
+ * 'configured', but they are also always 'configurable'.
+ */
+NDCTL_EXPORT int ndctl_namespace_is_configurable(struct ndctl_namespace *ndns)
+{
+	if (ndctl_namespace_is_active(ndns))
+		return 0;
+	if (ndctl_namespace_is_configured(ndns)) {
+		if (!namespace_size_is_writeable(ndns))
+			return 1;
+		return 0;
+	}
+	/* !active and !configured is configurable */
+	return 1;
+}
+
 NDCTL_EXPORT void ndctl_namespace_get_uuid(struct ndctl_namespace *ndns, uuid_t uu)
 {
 	memcpy(uu, ndns->uuid, sizeof(uuid_t));
diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
index c93c1ee..835d36b 100644
--- a/ndctl/lib/libndctl.sym
+++ b/ndctl/lib/libndctl.sym
@@ -423,3 +423,7 @@ LIBNDCTL_21 {
 LIBNDCTL_22 {
 	ndctl_dimm_security_is_frozen;
 } LIBNDCTL_21;
+
+LIBNDCTL_23 {
+	ndctl_namespace_is_configurable;
+} LIBNDCTL_22;
diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
index db398b3..e4dd22f 100644
--- a/ndctl/libndctl.h
+++ b/ndctl/libndctl.h
@@ -491,6 +491,7 @@ int ndctl_namespace_disable_safe(struct ndctl_namespace *ndns);
 bool ndctl_namespace_is_active(struct ndctl_namespace *ndns);
 int ndctl_namespace_is_valid(struct ndctl_namespace *ndns);
 int ndctl_namespace_is_configured(struct ndctl_namespace *ndns);
+int ndctl_namespace_is_configurable(struct ndctl_namespace *ndns);
 int ndctl_namespace_delete(struct ndctl_namespace *ndns);
 int ndctl_namespace_set_uuid(struct ndctl_namespace *ndns, uuid_t uu);
 void ndctl_namespace_get_uuid(struct ndctl_namespace *ndns, uuid_t uu);
diff --git a/ndctl/namespace.c b/ndctl/namespace.c
index ccd46d0..2979e78 100644
--- a/ndctl/namespace.c
+++ b/ndctl/namespace.c
@@ -779,7 +779,7 @@ static struct ndctl_namespace *region_get_namespace(struct ndctl_region *region)
 	/* prefer the 0th namespace if it is idle */
 	ndctl_namespace_foreach(region, ndns)
 		if (ndctl_namespace_get_id(ndns) == 0
-				&& !ndctl_namespace_is_active(ndns))
+				&& ndctl_namespace_is_configurable(ndns))
 			return ndns;
 	return ndctl_region_get_namespace_seed(region);
 }
@@ -819,7 +819,7 @@ static int namespace_create(struct ndctl_region *region)
 		p.size = available;
 
 	ndns = region_get_namespace(region);
-	if (!ndns || ndctl_namespace_is_active(ndns)) {
+	if (!ndns || !ndctl_namespace_is_configurable(ndns)) {
 		debug("%s: no %s namespace seed\n", devname,
 				ndns ? "idle" : "available");
 		return -EAGAIN;
@@ -1066,7 +1066,7 @@ static int namespace_reconfig(struct ndctl_region *region,
 	}
 
 	ndns = region_get_namespace(region);
-	if (!ndns || !ndctl_namespace_is_active(ndns)) {
+	if (!ndns || !ndctl_namespace_is_configurable(ndns)) {
 		debug("%s: no %s namespace seed\n",
 				ndctl_region_get_devname(region),
 				ndns ? "idle" : "available");
diff --git a/util/sysfs.c b/util/sysfs.c
index 9f7bc1f..773eeff 100644
--- a/util/sysfs.c
+++ b/util/sysfs.c
@@ -20,6 +20,7 @@
 #include <ctype.h>
 #include <fcntl.h>
 #include <dirent.h>
+#include <stdbool.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/ioctl.h>
@@ -84,6 +85,23 @@ int __sysfs_write_attr_quiet(struct log_ctx *ctx, const char *path,
 	return write_attr(ctx, path, buf, 1);
 }
 
+bool __sysfs_attr_writable(struct log_ctx *ctx, const char *path)
+{
+	int fd = open(path, O_WRONLY|O_CLOEXEC);
+	bool rc = false;
+
+	if (fd < 0) {
+		if (errno != EACCES)
+			log_dbg(ctx, "failed to open %s: %s\n",
+				path, strerror(errno));
+	} else {
+		rc = true;
+	}
+
+	close(fd);
+	return rc;
+}
+
 int __sysfs_device_parse(struct log_ctx *ctx, const char *base_path,
 		const char *dev_name, void *parent, add_dev_fn add_dev)
 {
diff --git a/util/sysfs.h b/util/sysfs.h
index fb169c6..e487ed4 100644
--- a/util/sysfs.h
+++ b/util/sysfs.h
@@ -14,6 +14,7 @@
 #define __UTIL_SYSFS_H__
 
 #include <string.h>
+#include <stdbool.h>
 
 typedef void *(*add_dev_fn)(void *parent, int id, const char *dev_path);
 
@@ -24,12 +25,14 @@ int __sysfs_read_attr(struct log_ctx *ctx, const char *path, char *buf);
 int __sysfs_write_attr(struct log_ctx *ctx, const char *path, const char *buf);
 int __sysfs_write_attr_quiet(struct log_ctx *ctx, const char *path,
 		const char *buf);
+bool __sysfs_attr_writable(struct log_ctx *ctx, const char *path);
 int __sysfs_device_parse(struct log_ctx *ctx, const char *base_path,
 		const char *dev_name, void *parent, add_dev_fn add_dev);
 
 #define sysfs_read_attr(c, p, b) __sysfs_read_attr(&(c)->ctx, (p), (b))
 #define sysfs_write_attr(c, p, b) __sysfs_write_attr(&(c)->ctx, (p), (b))
 #define sysfs_write_attr_quiet(c, p, b) __sysfs_write_attr_quiet(&(c)->ctx, (p), (b))
+#define sysfs_attr_writable(c, p) __sysfs_attr_writable(&(c)->ctx, (p))
 #define sysfs_device_parse(c, b, d, p, fn) __sysfs_device_parse(&(c)->ctx, \
 		(b), (d), (p), (fn))
 
-- 
2.20.1
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org