From: John Groves <[email protected]>

Putting a daxdev in famfs mode means binding it to fsdev_dax.ko
(drivers/dax/fsdev.c). Finding a daxdev bound to fsdev_dax means
it is in famfs mode.

The test is added to the destructive test suite since it
modifies device modes.

With devdax, famfs, and system-ram modes, the previous logic that assumed
'not in mode X means in mode Y' needed to get slightly more complicated

Add explicit mode detection functions:
- daxctl_dev_is_famfs_mode(): check if bound to fsdev_dax driver
- daxctl_dev_is_devdax_mode(): check if bound to device_dax driver

Fix mode transition logic in device.c:
- disable_devdax_device(): verify device is actually in devdax mode
- disable_famfs_device(): verify device is actually in famfs mode
- All reconfig_mode_*() functions now explicitly check each mode
- Handle unknown mode with error instead of wrong assumption

Modify json.c to show 'unknown' if device is not in a recognized mode.

Signed-off-by: John Groves <[email protected]>
---
 daxctl/device.c                | 126 ++++++++++++++++++++++++++++++---
 daxctl/json.c                  |   6 +-
 daxctl/lib/libdaxctl-private.h |   2 +
 daxctl/lib/libdaxctl.c         |  77 ++++++++++++++++++++
 daxctl/lib/libdaxctl.sym       |   7 ++
 daxctl/libdaxctl.h             |   3 +
 6 files changed, 210 insertions(+), 11 deletions(-)

diff --git a/daxctl/device.c b/daxctl/device.c
index e3993b1..14e1796 100644
--- a/daxctl/device.c
+++ b/daxctl/device.c
@@ -42,6 +42,7 @@ enum dev_mode {
        DAXCTL_DEV_MODE_UNKNOWN,
        DAXCTL_DEV_MODE_DEVDAX,
        DAXCTL_DEV_MODE_RAM,
+       DAXCTL_DEV_MODE_FAMFS,
 };
 
 struct mapping {
@@ -471,6 +472,13 @@ static const char *parse_device_options(int argc, const 
char **argv,
                                        "--no-online is incompatible with 
--mode=devdax\n");
                                rc =  -EINVAL;
                        }
+               } else if (strcmp(param.mode, "famfs") == 0) {
+                       reconfig_mode = DAXCTL_DEV_MODE_FAMFS;
+                       if (param.no_online) {
+                               fprintf(stderr,
+                                       "--no-online is incompatible with 
--mode=famfs\n");
+                               rc =  -EINVAL;
+                       }
                }
                break;
        case ACTION_CREATE:
@@ -696,8 +704,42 @@ static int disable_devdax_device(struct daxctl_dev *dev)
        int rc;
 
        if (mem) {
-               fprintf(stderr, "%s was already in system-ram mode\n",
-                       devname);
+               fprintf(stderr, "%s is in system-ram mode\n", devname);
+               return 1;
+       }
+       if (daxctl_dev_is_famfs_mode(dev)) {
+               fprintf(stderr, "%s is in famfs mode\n", devname);
+               return 1;
+       }
+       if (!daxctl_dev_is_devdax_mode(dev)) {
+               fprintf(stderr, "%s is not in devdax mode\n", devname);
+               return 1;
+       }
+       rc = daxctl_dev_disable(dev);
+       if (rc) {
+               fprintf(stderr, "%s: disable failed: %s\n",
+                       daxctl_dev_get_devname(dev), strerror(-rc));
+               return rc;
+       }
+       return 0;
+}
+
+static int disable_famfs_device(struct daxctl_dev *dev)
+{
+       struct daxctl_memory *mem = daxctl_dev_get_memory(dev);
+       const char *devname = daxctl_dev_get_devname(dev);
+       int rc;
+
+       if (mem) {
+               fprintf(stderr, "%s is in system-ram mode\n", devname);
+               return 1;
+       }
+       if (daxctl_dev_is_devdax_mode(dev)) {
+               fprintf(stderr, "%s is in devdax mode\n", devname);
+               return 1;
+       }
+       if (!daxctl_dev_is_famfs_mode(dev)) {
+               fprintf(stderr, "%s is not in famfs mode\n", devname);
                return 1;
        }
        rc = daxctl_dev_disable(dev);
@@ -711,6 +753,7 @@ static int disable_devdax_device(struct daxctl_dev *dev)
 
 static int reconfig_mode_system_ram(struct daxctl_dev *dev)
 {
+       struct daxctl_memory *mem = daxctl_dev_get_memory(dev);
        const char *devname = daxctl_dev_get_devname(dev);
        int rc, skip_enable = 0;
 
@@ -724,11 +767,21 @@ static int reconfig_mode_system_ram(struct daxctl_dev 
*dev)
        }
 
        if (daxctl_dev_is_enabled(dev)) {
-               rc = disable_devdax_device(dev);
-               if (rc < 0)
-                       return rc;
-               if (rc > 0)
+               if (mem) {
+                       /* already in system-ram mode */
                        skip_enable = 1;
+               } else if (daxctl_dev_is_famfs_mode(dev)) {
+                       rc = disable_famfs_device(dev);
+                       if (rc)
+                               return rc;
+               } else if (daxctl_dev_is_devdax_mode(dev)) {
+                       rc = disable_devdax_device(dev);
+                       if (rc)
+                               return rc;
+               } else {
+                       fprintf(stderr, "%s: unknown mode\n", devname);
+                       return -EINVAL;
+               }
        }
 
        if (!skip_enable) {
@@ -750,7 +803,7 @@ static int disable_system_ram_device(struct daxctl_dev *dev)
        int rc;
 
        if (!mem) {
-               fprintf(stderr, "%s was already in devdax mode\n", devname);
+               fprintf(stderr, "%s is not in system-ram mode\n", devname);
                return 1;
        }
 
@@ -786,12 +839,28 @@ static int disable_system_ram_device(struct daxctl_dev 
*dev)
 
 static int reconfig_mode_devdax(struct daxctl_dev *dev)
 {
+       struct daxctl_memory *mem = daxctl_dev_get_memory(dev);
+       const char *devname = daxctl_dev_get_devname(dev);
        int rc;
 
        if (daxctl_dev_is_enabled(dev)) {
-               rc = disable_system_ram_device(dev);
-               if (rc)
-                       return rc;
+               if (mem) {
+                       rc = disable_system_ram_device(dev);
+                       if (rc)
+                               return rc;
+               } else if (daxctl_dev_is_famfs_mode(dev)) {
+                       rc = disable_famfs_device(dev);
+                       if (rc)
+                               return rc;
+               } else if (daxctl_dev_is_devdax_mode(dev)) {
+                       /* already in devdax mode, just re-enable */
+                       rc = daxctl_dev_disable(dev);
+                       if (rc)
+                               return rc;
+               } else {
+                       fprintf(stderr, "%s: unknown mode\n", devname);
+                       return -EINVAL;
+               }
        }
 
        rc = daxctl_dev_enable_devdax(dev);
@@ -801,6 +870,40 @@ static int reconfig_mode_devdax(struct daxctl_dev *dev)
        return 0;
 }
 
+static int reconfig_mode_famfs(struct daxctl_dev *dev)
+{
+       struct daxctl_memory *mem = daxctl_dev_get_memory(dev);
+       const char *devname = daxctl_dev_get_devname(dev);
+       int rc;
+
+       if (daxctl_dev_is_enabled(dev)) {
+               if (mem) {
+                       fprintf(stderr,
+                               "%s is in system-ram mode, must be in devdax 
mode to convert to famfs\n",
+                               devname);
+                       return -EINVAL;
+               } else if (daxctl_dev_is_famfs_mode(dev)) {
+                       /* already in famfs mode, just re-enable */
+                       rc = daxctl_dev_disable(dev);
+                       if (rc)
+                               return rc;
+               } else if (daxctl_dev_is_devdax_mode(dev)) {
+                       rc = disable_devdax_device(dev);
+                       if (rc)
+                               return rc;
+               } else {
+                       fprintf(stderr, "%s: unknown mode\n", devname);
+                       return -EINVAL;
+               }
+       }
+
+       rc = daxctl_dev_enable_famfs(dev);
+       if (rc)
+               return rc;
+
+       return 0;
+}
+
 static int do_create(struct daxctl_region *region, long long val,
                     struct json_object **jdevs)
 {
@@ -887,6 +990,9 @@ static int do_reconfig(struct daxctl_dev *dev, enum 
dev_mode mode,
        case DAXCTL_DEV_MODE_DEVDAX:
                rc = reconfig_mode_devdax(dev);
                break;
+       case DAXCTL_DEV_MODE_FAMFS:
+               rc = reconfig_mode_famfs(dev);
+               break;
        default:
                fprintf(stderr, "%s: unknown mode requested: %d\n",
                        devname, mode);
diff --git a/daxctl/json.c b/daxctl/json.c
index 3cbce9d..01f139b 100644
--- a/daxctl/json.c
+++ b/daxctl/json.c
@@ -48,8 +48,12 @@ struct json_object *util_daxctl_dev_to_json(struct 
daxctl_dev *dev,
 
        if (mem)
                jobj = json_object_new_string("system-ram");
-       else
+       else if (daxctl_dev_is_famfs_mode(dev))
+               jobj = json_object_new_string("famfs");
+       else if (daxctl_dev_is_devdax_mode(dev))
                jobj = json_object_new_string("devdax");
+       else
+               jobj = json_object_new_string("unknown");
        if (jobj)
                json_object_object_add(jdev, "mode", jobj);
 
diff --git a/daxctl/lib/libdaxctl-private.h b/daxctl/lib/libdaxctl-private.h
index ae45311..0bb73e8 100644
--- a/daxctl/lib/libdaxctl-private.h
+++ b/daxctl/lib/libdaxctl-private.h
@@ -21,12 +21,14 @@ static const char *dax_subsystems[] = {
 enum daxctl_dev_mode {
        DAXCTL_DEV_MODE_DEVDAX = 0,
        DAXCTL_DEV_MODE_RAM,
+       DAXCTL_DEV_MODE_FAMFS,
        DAXCTL_DEV_MODE_END,
 };
 
 static const char *dax_modules[] = {
        [DAXCTL_DEV_MODE_DEVDAX] = "device_dax",
        [DAXCTL_DEV_MODE_RAM] = "kmem",
+       [DAXCTL_DEV_MODE_FAMFS] = "fsdev_dax",
 };
 
 enum memory_op {
diff --git a/daxctl/lib/libdaxctl.c b/daxctl/lib/libdaxctl.c
index b7fa0de..0a6cbfe 100644
--- a/daxctl/lib/libdaxctl.c
+++ b/daxctl/lib/libdaxctl.c
@@ -418,6 +418,78 @@ DAXCTL_EXPORT int daxctl_dev_is_system_ram_capable(struct 
daxctl_dev *dev)
        return false;
 }
 
+/*
+ * Check if device is currently in famfs mode (bound to fsdev_dax driver)
+ */
+DAXCTL_EXPORT int daxctl_dev_is_famfs_mode(struct daxctl_dev *dev)
+{
+       const char *devname = daxctl_dev_get_devname(dev);
+       struct daxctl_ctx *ctx = daxctl_dev_get_ctx(dev);
+       char *mod_path, *mod_base;
+       char path[200];
+       const int len = sizeof(path);
+
+       if (!device_model_is_dax_bus(dev))
+               return false;
+
+       if (!daxctl_dev_is_enabled(dev))
+               return false;
+
+       if (snprintf(path, len, "%s/driver", dev->dev_path) >= len) {
+               err(ctx, "%s: buffer too small!\n", devname);
+               return false;
+       }
+
+       mod_path = realpath(path, NULL);
+       if (!mod_path)
+               return false;
+
+       mod_base = basename(mod_path);
+       if (strcmp(mod_base, dax_modules[DAXCTL_DEV_MODE_FAMFS]) == 0) {
+               free(mod_path);
+               return true;
+       }
+
+       free(mod_path);
+       return false;
+}
+
+/*
+ * Check if device is currently in devdax mode (bound to device_dax driver)
+ */
+DAXCTL_EXPORT int daxctl_dev_is_devdax_mode(struct daxctl_dev *dev)
+{
+       const char *devname = daxctl_dev_get_devname(dev);
+       struct daxctl_ctx *ctx = daxctl_dev_get_ctx(dev);
+       char *mod_path, *mod_base;
+       char path[200];
+       const int len = sizeof(path);
+
+       if (!device_model_is_dax_bus(dev))
+               return false;
+
+       if (!daxctl_dev_is_enabled(dev))
+               return false;
+
+       if (snprintf(path, len, "%s/driver", dev->dev_path) >= len) {
+               err(ctx, "%s: buffer too small!\n", devname);
+               return false;
+       }
+
+       mod_path = realpath(path, NULL);
+       if (!mod_path)
+               return false;
+
+       mod_base = basename(mod_path);
+       if (strcmp(mod_base, dax_modules[DAXCTL_DEV_MODE_DEVDAX]) == 0) {
+               free(mod_path);
+               return true;
+       }
+
+       free(mod_path);
+       return false;
+}
+
 /*
  * This checks for the device to be in system-ram mode, so calling
  * daxctl_dev_get_memory() on a devdax mode device will always return NULL.
@@ -982,6 +1054,11 @@ DAXCTL_EXPORT int daxctl_dev_enable_ram(struct daxctl_dev 
*dev)
        return daxctl_dev_enable(dev, DAXCTL_DEV_MODE_RAM);
 }
 
+DAXCTL_EXPORT int daxctl_dev_enable_famfs(struct daxctl_dev *dev)
+{
+       return daxctl_dev_enable(dev, DAXCTL_DEV_MODE_FAMFS);
+}
+
 DAXCTL_EXPORT int daxctl_dev_disable(struct daxctl_dev *dev)
 {
        const char *devname = daxctl_dev_get_devname(dev);
diff --git a/daxctl/lib/libdaxctl.sym b/daxctl/lib/libdaxctl.sym
index 3098811..2a812c6 100644
--- a/daxctl/lib/libdaxctl.sym
+++ b/daxctl/lib/libdaxctl.sym
@@ -104,3 +104,10 @@ LIBDAXCTL_10 {
 global:
        daxctl_dev_is_system_ram_capable;
 } LIBDAXCTL_9;
+
+LIBDAXCTL_11 {
+global:
+       daxctl_dev_enable_famfs;
+       daxctl_dev_is_famfs_mode;
+       daxctl_dev_is_devdax_mode;
+} LIBDAXCTL_10;
diff --git a/daxctl/libdaxctl.h b/daxctl/libdaxctl.h
index 53c6bbd..84fcdb4 100644
--- a/daxctl/libdaxctl.h
+++ b/daxctl/libdaxctl.h
@@ -72,12 +72,15 @@ int daxctl_dev_is_enabled(struct daxctl_dev *dev);
 int daxctl_dev_disable(struct daxctl_dev *dev);
 int daxctl_dev_enable_devdax(struct daxctl_dev *dev);
 int daxctl_dev_enable_ram(struct daxctl_dev *dev);
+int daxctl_dev_enable_famfs(struct daxctl_dev *dev);
 int daxctl_dev_get_target_node(struct daxctl_dev *dev);
 int daxctl_dev_will_auto_online_memory(struct daxctl_dev *dev);
 int daxctl_dev_has_online_memory(struct daxctl_dev *dev);
 
 struct daxctl_memory;
 int daxctl_dev_is_system_ram_capable(struct daxctl_dev *dev);
+int daxctl_dev_is_famfs_mode(struct daxctl_dev *dev);
+int daxctl_dev_is_devdax_mode(struct daxctl_dev *dev);
 struct daxctl_memory *daxctl_dev_get_memory(struct daxctl_dev *dev);
 struct daxctl_dev *daxctl_memory_get_dev(struct daxctl_memory *mem);
 const char *daxctl_memory_get_node_path(struct daxctl_memory *mem);
-- 
2.49.0


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