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Wong" , Randy Dunlap , Jeff Layton , Amir Goldstein , Jonathan Cameron , Stefan Hajnoczi , Joanne Koong , Josef Bacik , Bagas Sanjaya , James Morse , Fuad Tabba , Sean Christopherson , Shivank Garg , Ackerley Tng , Gregory Price , Aravind Ramesh , Ajay Joshi , venkataravis@micron.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH V2 1/2] daxctl: Add support for famfs mode Date: Wed, 14 Jan 2026 15:45:18 -0600 Message-ID: <20260114214519.29999-2-john@groves.net> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260114214519.29999-1-john@groves.net> References: <20260114153133.29420.compound@groves.net> <20260114214519.29999-1-john@groves.net> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: John Groves 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 --- 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