[daxctl PATCH] daxctl: Opt-in to /sys/bus/dax ABI

[Dan Williams <dan.j.williams@intel.com>]

In support of the kernel's conversion of the dax-subsystem from a
'class' to a 'bus', teach the libdaxctl subsystem-layout-specific code
to parse the new layout. The kernel changes do not effect the primary
ndctl use case of putting namespaces into 'dax' mode since that uses
libnvdimm namespace device relative paths, but it does break 'ndctl list
-X' and 'daxctl list'. For that reason the kernel provides a
dax_pmem_compat driver to support the old layout and give time for
userspace components to switch.

Installation of the latest libdaxctl package arranges for a daxctl
configuration file to be dropped in /etc/modprobe.d. The modprobe
configuration blacklists dax_pmem_compat modules and sets the proper
alias for the dax_pmem module. The modprobe configuration upgrades the
default kernel handling to the /sys/bus/dax scheme.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 daxctl/lib/Makefile.am         |    3 ++
 daxctl/lib/daxctl.conf         |    2 +
 daxctl/lib/libdaxctl-private.h |   11 ++++++
 daxctl/lib/libdaxctl.c         |   70 +++++++++++++++++++++++++++++-----------
 ndctl.spec.in                  |    1 +
 util/sysfs.c                   |    2 +
 6 files changed, 68 insertions(+), 21 deletions(-)
 create mode 100644 daxctl/lib/daxctl.conf

diff --git a/daxctl/lib/Makefile.am b/daxctl/lib/Makefile.am
index 0167e3995b00..749d54a2e397 100644
--- a/daxctl/lib/Makefile.am
+++ b/daxctl/lib/Makefile.am
@@ -18,6 +18,9 @@ libdaxctl_la_SOURCES =\
 libdaxctl_la_LIBADD =\
 	$(UUID_LIBS)
 
+daxctlconfdir=$(sysconfdir)/modprobe.d
+daxctlconf_DATA = daxctl.conf
+
 EXTRA_DIST += libdaxctl.sym
 
 libdaxctl_la_LDFLAGS = $(AM_LDFLAGS) \
diff --git a/daxctl/lib/daxctl.conf b/daxctl/lib/daxctl.conf
new file mode 100644
index 000000000000..c64a088cbc0b
--- /dev/null
+++ b/daxctl/lib/daxctl.conf
@@ -0,0 +1,2 @@
+blacklist dax_pmem_compat
+alias nd:t7* dax_pmem
diff --git a/daxctl/lib/libdaxctl-private.h b/daxctl/lib/libdaxctl-private.h
index f7667324026f..4a462e7245d2 100644
--- a/daxctl/lib/libdaxctl-private.h
+++ b/daxctl/lib/libdaxctl-private.h
@@ -15,6 +15,17 @@
 
 #define DAXCTL_EXPORT __attribute__ ((visibility("default")))
 
+enum dax_subsystem {
+	DAX_UNKNOWN,
+	DAX_CLASS,
+	DAX_BUS,
+};
+
+static const char *dax_subsystems[] = {
+	[DAX_CLASS] = "/sys/class/dax",
+	[DAX_BUS] = "/sys/bus/dax/devices",
+};
+
 /**
  * struct daxctl_region - container for dax_devices
  */
diff --git a/daxctl/lib/libdaxctl.c b/daxctl/lib/libdaxctl.c
index 22f4210a7ea0..c2e3a52d6c7c 100644
--- a/daxctl/lib/libdaxctl.c
+++ b/daxctl/lib/libdaxctl.c
@@ -444,26 +444,38 @@ static void dax_devices_init(struct daxctl_region *region)
 {
 	struct daxctl_ctx *ctx = daxctl_region_get_ctx(region);
 	char daxdev_fmt[50];
-	char *region_path;
+	size_t i;
 
 	if (region->devices_init)
 		return;
 
 	region->devices_init = 1;
 	sprintf(daxdev_fmt, "dax%d.", region->id);
-	if (asprintf(&region_path, "%s/dax", region->region_path) < 0) {
-		dbg(ctx, "region path alloc fail\n");
-		return;
+	for (i = 0; i < ARRAY_SIZE(dax_subsystems); i++) {
+		char *region_path;
+
+		if (i == DAX_BUS)
+			region_path = region->region_path;
+		else if (i == DAX_CLASS) {
+			if (asprintf(&region_path, "%s/dax",
+						region->region_path) < 0) {
+				dbg(ctx, "region path alloc fail\n");
+				continue;
+			}
+		} else
+			continue;
+		sysfs_device_parse(ctx, region_path, daxdev_fmt, region,
+				add_dax_dev);
+		if (i == DAX_CLASS)
+			free(region_path);
 	}
-	sysfs_device_parse(ctx, region_path, daxdev_fmt, region, add_dax_dev);
-	free(region_path);
 }
 
-static char *dax_region_path(const char *base, const char *device)
+static char *dax_region_path(const char *device, enum dax_subsystem subsys)
 {
 	char *path, *region_path, *c;
 
-	if (asprintf(&path, "%s/%s", base, device) < 0)
+	if (asprintf(&path, "%s/%s", dax_subsystems[subsys], device) < 0)
 		return NULL;
 
 	/* dax_region must be the instance's direct parent */
@@ -472,7 +484,11 @@ static char *dax_region_path(const char *base, const char *device)
 	if (!region_path)
 		return NULL;
 
-	/* 'region_path' is now regionX/dax/daxX.Y', trim back to regionX */
+	/*
+	 * 'region_path' is now regionX/dax/daxX.Y' (DAX_CLASS), or
+	 * regionX/daxX.Y (DAX_BUS), trim it back to the regionX
+	 * component
+	 */
 	c = strrchr(region_path, '/');
 	if (!c) {
 		free(region_path);
@@ -480,6 +496,9 @@ static char *dax_region_path(const char *base, const char *device)
 	}
 	*c = '\0';
 
+	if (subsys == DAX_BUS)
+		return region_path;
+
 	c = strrchr(region_path, '/');
 	if (!c) {
 		free(region_path);
@@ -490,20 +509,15 @@ static char *dax_region_path(const char *base, const char *device)
 	return region_path;
 }
 
-static void dax_regions_init(struct daxctl_ctx *ctx)
+static void __dax_regions_init(struct daxctl_ctx *ctx, enum dax_subsystem subsys)
 {
-	const char *base = "/sys/class/dax";
 	struct dirent *de;
-	DIR *dir;
+	DIR *dir = NULL;
 
-	if (ctx->regions_init)
-		return;
-
-	ctx->regions_init = 1;
-
-	dir = opendir(base);
+	dir = opendir(dax_subsystems[subsys]);
 	if (!dir) {
-		dbg(ctx, "no dax regions found\n");
+		dbg(ctx, "no dax regions found via: %s\n",
+				dax_subsystems[subsys]);
 		return;
 	}
 
@@ -516,7 +530,7 @@ static void dax_regions_init(struct daxctl_ctx *ctx)
 			continue;
 		if (sscanf(de->d_name, "dax%d.%d", &region_id, &id) != 2)
 			continue;
-		dev_path = dax_region_path(base, de->d_name);
+		dev_path = dax_region_path(de->d_name, subsys);
 		if (!dev_path) {
 			err(ctx, "dax region path allocation failure\n");
 			continue;
@@ -529,6 +543,22 @@ static void dax_regions_init(struct daxctl_ctx *ctx)
 	closedir(dir);
 }
 
+static void dax_regions_init(struct daxctl_ctx *ctx)
+{
+	size_t i;
+
+	if (ctx->regions_init)
+		return;
+
+	ctx->regions_init = 1;
+
+	for (i = 0; i < ARRAY_SIZE(dax_subsystems); i++) {
+		if (i == DAX_UNKNOWN)
+			continue;
+		__dax_regions_init(ctx, i);
+	}
+}
+
 DAXCTL_EXPORT struct daxctl_dev *daxctl_dev_get_first(struct daxctl_region *region)
 {
 	dax_devices_init(region);
diff --git a/ndctl.spec.in b/ndctl.spec.in
index 26396d4abad7..60d9e6fedf71 100644
--- a/ndctl.spec.in
+++ b/ndctl.spec.in
@@ -136,6 +136,7 @@ make check
 %defattr(-,root,root)
 %doc README.md
 %license COPYING licenses/BSD-MIT licenses/CC0
+%config(noreplace) %{_sysconfdir}/modprobe.d/daxctl.conf
 %{_libdir}/libdaxctl.so.*
 
 %files -n DNAME
diff --git a/util/sysfs.c b/util/sysfs.c
index 0440fd0f49a3..9f7bc1f4930f 100644
--- a/util/sysfs.c
+++ b/util/sysfs.c
@@ -91,7 +91,7 @@ int __sysfs_device_parse(struct log_ctx *ctx, const char *base_path,
 	struct dirent *de;
 	DIR *dir;
 
-	log_dbg(ctx, "base: %s dev: %s\n", base_path, dev_name);
+	log_dbg(ctx, "base: '%s' dev: '%s'\n", base_path, dev_name);
 	dir = opendir(base_path);
 	if (!dir) {
 		log_dbg(ctx, "no \"%s\" devices found\n", dev_name);

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