diff mbox series

[v3,1/2] ndctl/namespace:Fix multiple issues with write-infoblock

Message ID 20220426172056.122789-2-tsahu@linux.ibm.com (mailing list archive)
State New
Headers show
Series ndctl/namespace:Fix and improve write-infoblock | expand

Commit Message

Tarun Sahu April 26, 2022, 5:20 p.m. UTC
Write-infoblock command has the below issues,
1 - Oerwriting the existing alignment value with the default value when
      not passed as parameter.
2 - Changing the mode of the namespace to fsdax when -m not specified
3 - Incorrectly updating the uuid and parent_uuid if corresponding
parameter is not specified

Considering the above three issues, we first needed to read the
original infoblock if available, and update the align, uuid, parent_uuid
to its original value while writing the infoblock if corresponding
parameter is not passed.

This will resolve the 1, 3 issues. To resolve 2, instead of setting
the value of param.mode to fsdax by default, set it to unknown and
fetch the value of namespace mode type while reading the namespace info
and update only the parameter passed related to the namespace mode.

Originally the file-read-infoblock function read the infoblock in
binary or json format based on parameter -j (passed or not).
By default getting json and parsing the original values is one of
the way to resolve the issue, but it will create complexity in
functionality as everytime, there is a need to update the parameter,
the type of namespace mode will have to be checked that is too by
reading the signature values of infoblock.
(ref: parse_namespace_infoblock) as namespace is disabled for
read/write infoblock command.

Instead, To make the process easier and to support future adaptability
for incoming issues or feature, where details of namespace infoblock,
mode, offset in backup infoblock is required in general for fsdax,
devdax, or sector mode, I created a new structure which store,
buffer of infoblock, mode of infoblock, and offset value at which the
infoblock is available in buffer. (struct ns_info)

struct ns_info{
    void *ns_sb_buf;
    enum ndctl_namespace_mode mode;
    size_t offset;
}

There is one constructor ns_info_init(struct ns_info *ns_info) which
allocate INFOBLOCK_SZ bytes of memory to ns_info->ns_sb_buf. This buf
once allocated, can be reused in file_read_infoblock,
file_write_infoblock, write_pfn_sb, parse_namespace_infoblock, without
worrying about creating buf and freeing buf at many places for the same
purpose/task. this structure can also store the infoblock data in this
buffer, which can be checked for its original values to update it while
writing the infoblock.

There is one destructor ns_info_destroy(struct ns_info *ns_info) which
free the buffer, allocated at the time of ns_info_init(struct ns_info).

Signed-off-by: Tarun Sahu <tsahu@linux.ibm.com>
---
 ndctl/namespace.c | 253 +++++++++++++++++++++++++++++++---------------
 1 file changed, 170 insertions(+), 83 deletions(-)

This patch change the declaration of following functions to pass
ns_info,

file_read_infoblock()
file_write_infoblock()
parse_namespace_infoblock()
write_pfn_sb()

Before and after the patch results:
Before:: (namespace2.0 is disabled and is of type devdax)
$ ./ndctl read-infoblock namespace2.0 -j
[
  {
    "dev":"namespace2.0",
    "signature":"NVDIMM_DAX_INFO",
    "uuid":"4a9b5f94-0710-499c-9125-ff9edf2500fe",
    "parent_uuid":"06bedb5d-3685-43c0-b6d7-c7e9d43c3887",
    "flags":0,
    "version":"1.4",
    "dataoff":16777216,
    "npfns":245504,
    "mode":2,
    "start_pad":0,
    "end_trunc":0,
    "align":16777216,
    "page_size":65536,
    "page_struct_size":64
  }
]
read 1 infoblock

$ ./ndctl write-infoblock namespace2.0 -m devdax -M dev
wrote 1 infoblock

$ ./ndctl read-infoblock namespace2.0 -j
[
  {
    "dev":"namespace2.0",
    "signature":"NVDIMM_DAX_INFO",
    "uuid":"fbd36f27-a5d7-4b7a-8414-8367195450da",
    "parent_uuid":"06bedb5d-3685-43c0-b6d7-c7e9d43c3887",
    "flags":0,
    "version":"1.4",
    "dataoff":16777216,
    "npfns":245504,
    "mode":2,
    "start_pad":0,
    "end_trunc":0,
    "align":65536,
    "page_size":65536,
    "page_struct_size":64
  }
]
read 1 infoblock

After:: (namespace2.0 is disabled and is of type devdax)
$ ./ndctl read-infoblock namespace2.0 -j
[
  {
    "dev":"namespace2.0",
    "signature":"NVDIMM_DAX_INFO",
    "uuid":"0867d20c-f097-4043-b4dd-7e8b26e99b05",
    "parent_uuid":"85a6e354-077a-4140-b6c0-4b5d0393951b",
    "flags":0,
    "version":"1.4",
    "dataoff":16777216,
    "npfns":245504,
    "mode":2,
    "start_pad":0,
    "end_trunc":0,
    "align":16777216,
    "page_size":65536,
    "page_struct_size":64
  }
]
read 1 infoblock

(align is not passed)
$ ./ndctl write-infoblock namespace2.0 -m devdax -M dev
wrote 1 infoblock

$ ./ndctl read-infoblock namespace2.0 -j
[
  {
    "dev":"namespace2.0",
    "signature":"NVDIMM_DAX_INFO",
    "uuid":"0867d20c-f097-4043-b4dd-7e8b26e99b05",
    "parent_uuid":"85a6e354-077a-4140-b6c0-4b5d0393951b",
    "flags":0,
    "version":"1.4",
    "dataoff":16777216,
    "npfns":245504,
    "mode":2,
    "start_pad":0,
    "end_trunc":0,
    "align":16777216,
    "page_size":65536,
    "page_struct_size":64
  }
]
read 1 infoblock

align value is retained.

similiary can be tested for uuid and parent_uuid.

$ ./ndctl read-infoblock namespace2.0 -j
Before:
[
  {
    "dev":"namespace2.0",
    "signature":"BTT_ARENA_INFO",
    "uuid":"a989fda3-d6fd-41eb-b621-d773d1e9c177",
    "parent_uuid":"80e131f6-d168-4c27-9152-b4f13106dba6",
    "flags":0,
    "version":"2.0",
    "external_lbasize":4096,
    "external_nlba":3928060,
    "internal_lbasize":4096,
    "internal_nlba":3928316,
    "nfree":256,
    "infosize":4096,
    "nextoff":0,
    "dataoff":4096,
    "mapoff":16090394624,
    "logoff":16106106880,
    "info2off":16106123264
  }
]
read 1 infoblock

$ ./ndctl write-infoblock namespace2.0
wrote 1 infoblock

$ ./ndctl read-infoblock namespace2.0 -j
[
  {
    "dev":"namespace2.0",
    "signature":"NVDIMM_PFN_INFO",
    "uuid":"b04b59de-290f-45da-956c-4364a77175ce",
    "parent_uuid":"80e131f6-d168-4c27-9152-b4f13106dba6",
    "flags":0,
    "version":"1.4",
    "dataoff":16777216,
    "npfns":245504,
    "mode":2,
    "start_pad":0,
    "end_trunc":0,
    "align":65536,
    "page_size":65536,
    "page_struct_size":64
  }
]
read 1 infoblock

After:
$ ./ndctl read-infoblock namespace2.0 -j
[
  {
    "dev":"namespace2.0",
    "signature":"BTT_ARENA_INFO",
    "uuid":"2c9cd4b6-3091-466c-9ad9-30745e328ddd",
    "parent_uuid":"8e810770-a135-4d64-8e65-e09984b7b33b",
    "flags":0,
    "version":"2.0",
    "external_lbasize":4096,
    "external_nlba":3928060,
    "internal_lbasize":4096,
    "internal_nlba":3928316,
    "nfree":256,
    "infosize":4096,
    "nextoff":0,
    "dataoff":4096,
    "mapoff":16090394624,
    "logoff":16106106880,
    "info2off":16106123264
  }
]
read 1 infoblock

$ ./ndctl write-infoblock namespace2.0
error checking infoblocks: Invalid argument
wrote 0 infoblocks

$ ./ndctl read-infoblock namespace2.0 -j
[
  {
    "dev":"namespace2.0",
    "signature":"BTT_ARENA_INFO",
    "uuid":"2c9cd4b6-3091-466c-9ad9-30745e328ddd",
    "parent_uuid":"8e810770-a135-4d64-8e65-e09984b7b33b",
    "flags":0,
    "version":"2.0",
    "external_lbasize":4096,
    "external_nlba":3928060,
    "internal_lbasize":4096,
    "internal_nlba":3928316,
    "nfree":256,
    "infosize":4096,
    "nextoff":0,
    "dataoff":4096,
    "mapoff":16090394624,
    "logoff":16106106880,
    "info2off":16106123264
  }
]
read 1 infoblock

Sector mode hasn't been changed to fsdax, as parameter -m
is not passed explicitly to ask the change.

Similiarly can be tested with devdax type namespace.

As this patch resolves only bug issues, next patch in this series
work on support to write-infoblock for sector mode. So for sector
mode, instead of getting the following output

error checking infoblocks: Invalid argument
wrote 0 infoblocks

we will get
wrote 1 infoblock

Comments

Shivaprasad G Bhat May 24, 2022, 5:47 a.m. UTC | #1
On 4/26/22 22:50, Tarun Sahu wrote:
> Write-infoblock command has the below issues,
> 1 - Oerwriting the existing alignment value with the default value when
>        not passed as parameter.
> 2 - Changing the mode of the namespace to fsdax when -m not specified
> 3 - Incorrectly updating the uuid and parent_uuid if corresponding
> parameter is not specified

<snip>

> diff --git a/ndctl/namespace.c b/ndctl/namespace.c
> index 257b58c..cca9a51 100644
> --- a/ndctl/namespace.c
> +++ b/ndctl/namespace.c

<snip>

> @@ -2026,12 +2105,10 @@ static int namespace_rw_infoblock(struct ndctl_namespace *ndns,
>   		struct read_infoblock_ctx *ri_ctx, int write)
>   {
>   	int rc;
> -	uuid_t uuid;
> -	char str[40];
>   	char path[50];
> -	const char *save;
>   	const char *cmd = write ? "write-infoblock" : "read-infoblock";
>   	const char *devname = ndctl_namespace_get_devname(ndns);
> +	struct ns_info ns_info;
>   
>   	if (ndctl_namespace_is_active(ndns)) {
>   		pr_verbose("%s: %s enabled, must be disabled\n", cmd, devname);
> @@ -2045,21 +2122,22 @@ static int namespace_rw_infoblock(struct ndctl_namespace *ndns,
>   		goto out;

This would lead to calling ns_info_destroy() on uninitialized ns_info, 
and ns_info->ns_sb_buf would have junk value.

With that fixed,

Reviewed-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>

>   	}
>   
> -	save = param.parent_uuid;
> -	if (!param.parent_uuid) {
> -		ndctl_namespace_get_uuid(ndns, uuid);
> -		uuid_unparse(uuid, str);
> -		param.parent_uuid = str;
> -	}
> -
>   	sprintf(path, "/dev/%s", ndctl_namespace_get_block_device(ndns));
> -	if (write) {
> +	if (ns_info_init(&ns_info) != 0)
> +		goto out;
> +
> +	rc = file_read_infoblock(path, ndns, ri_ctx, &ns_info);
> +	if (!rc && write) {
>   		unsigned long long align;
>   		bool align_provided = true;
>   
>   		if (!param.align) {
>   			align = ndctl_get_default_alignment(ndns);
> -
> +			if (ns_info.mode == NDCTL_NS_MODE_FSDAX ||
> +					ns_info.mode == NDCTL_NS_MODE_DEVDAX) {
> +				align = ((struct pfn_sb *)(ns_info.ns_sb_buf + ns_info.offset))->
> +					align;
> +			}
>   			if (asprintf((char **)&param.align, "%llu", align) < 0) {
>   				rc = -EINVAL;
>   				goto out;
> @@ -2078,18 +2156,16 @@ static int namespace_rw_infoblock(struct ndctl_namespace *ndns,
>   				rc = -EINVAL;
>   			}
>   		}
> -
>   		if (!rc)
> -			rc = file_write_infoblock(path);
> +			rc = file_write_infoblock(path, &ns_info);
>   
>   		if (!align_provided) {
>   			free((char *)param.align);
>   			param.align = NULL;
>   		}
> -	} else
> -		rc = file_read_infoblock(path, ndns, ri_ctx);
> -	param.parent_uuid = save;
> +	}
>   out:
> +	ns_info_destroy(&ns_info);
>   	ndctl_namespace_set_raw_mode(ndns, 0);
>   	ndctl_namespace_disable_invalidate(ndns);
>   	return rc;
Shivaprasad G Bhat May 24, 2022, 6:09 a.m. UTC | #2
One more comment..

On 4/26/22 22:50, Tarun Sahu wrote:
> Write-infoblock command has the below issues,
> 1 - Oerwriting the existing alignment value with the default value when
>        not passed as parameter.
> 2 - Changing the mode of the namespace to fsdax when -m not specified
> 3 - Incorrectly updating the uuid and parent_uuid if corresponding

<snip>
> ---
>   ndctl/namespace.c | 253 +++++++++++++++++++++++++++++++---------------
>   1 file changed, 170 insertions(+), 83 deletions(-)
<snip>
> 
> diff --git a/ndctl/namespace.c b/ndctl/namespace.c
> index 257b58c..cca9a51 100644
> --- a/ndctl/namespace.c
> +++ b/ndctl/namespace.c

<snip>

> @@ -2121,11 +2197,17 @@ static int do_xaction_namespace(const char *namespace,
>   		}
>   
>   		if (param.infile || !namespace) {
> -			rc = file_read_infoblock(param.infile, NULL, &ri_ctx);
> -			if (ri_ctx.jblocks)
> -				util_display_json_array(ri_ctx.f_out, ri_ctx.jblocks, 0);
> -			if (rc >= 0)
> -				(*processed)++;
> +			struct ns_info ns_info;

Move this to the beginning of the block.

> +
> +			rc = ns_info_init(&ns_info);
> +			if (!rc) {
> +				rc = file_read_infoblock(param.infile, NULL, &ri_ctx, &ns_info);
> +				if (ri_ctx.jblocks)
> +					util_display_json_array(ri_ctx.f_out, ri_ctx.jblocks, 0);
> +				if (rc >= 0)
> +					(*processed)++;
> +			}
> +			ns_info_destroy(&ns_info);
>   			return rc;
>   		}
>   	}

Thanks,
Shivaprasad
diff mbox series

Patch

diff --git a/ndctl/namespace.c b/ndctl/namespace.c
index 257b58c..cca9a51 100644
--- a/ndctl/namespace.c
+++ b/ndctl/namespace.c
@@ -62,6 +62,12 @@  static struct parameters {
 	.autorecover = true,
 };
 
+struct ns_info {
+	void *ns_sb_buf;
+	enum ndctl_namespace_mode mode;
+	size_t offset;
+};
+
 const char *cmd_name = "namespace";
 
 void builtin_xaction_namespace_reset(void)
@@ -256,7 +262,7 @@  static int set_defaults(enum device_action action)
 			break;
 		}
 	} else if (action == ACTION_WRITE_INFOBLOCK) {
-		param.mode = "fsdax";
+		param.mode = "unknown";
 	} else if (!param.reconfig && param.type) {
 		if (strcmp(param.type, "pmem") == 0)
 			param.mode = "fsdax";
@@ -1750,70 +1756,105 @@  err:
 
 #define INFOBLOCK_SZ SZ_8K
 
-static int parse_namespace_infoblock(char *_buf, struct ndctl_namespace *ndns,
+static int ns_info_init(struct ns_info *ns_info)
+{
+	char *buf = NULL;
+
+	if (!ns_info)
+		return -EINVAL;
+	buf = calloc(1, INFOBLOCK_SZ);
+	if (!buf)
+		return -ENOMEM;
+	ns_info->ns_sb_buf = buf;
+	ns_info->mode = NDCTL_NS_MODE_UNKNOWN;
+	return 0;
+}
+
+static void ns_info_destroy(struct ns_info *ns_info)
+{
+	if (ns_info && ns_info->ns_sb_buf)
+		free(ns_info->ns_sb_buf);
+}
+
+static int parse_namespace_infoblock(struct ns_info *ns_info, struct ndctl_namespace *ndns,
 		const char *path, struct read_infoblock_ctx *ri_ctx)
 {
 	int rc;
-	void *buf = _buf;
+	void *buf = ns_info->ns_sb_buf;
 	unsigned long flags = param.human ? UTIL_JSON_HUMAN : 0;
 	struct btt_sb *btt1_sb = buf + SZ_4K, *btt2_sb = buf;
-	struct json_object *jblock = NULL, *jblocks = ri_ctx->jblocks;
+	struct json_object *jblock = NULL, *jblocks = NULL;
 	struct pfn_sb *pfn_sb = buf + SZ_4K, *dax_sb = buf + SZ_4K;
 
-	if (!param.json && !param.human) {
-		rc = fwrite(buf, 1, INFOBLOCK_SZ, ri_ctx->f_out);
-		if (rc != INFOBLOCK_SZ)
-			return -EIO;
-		fflush(ri_ctx->f_out);
-		return 0;
-	}
+	if (ri_ctx) {
+		jblocks = ri_ctx->jblocks;
 
-	if (!jblocks) {
-		jblocks = json_object_new_array();
-		if (!jblocks)
-			return -ENOMEM;
-		ri_ctx->jblocks = jblocks;
+		if (!param.json && !param.human) {
+			rc = fwrite(buf, 1, INFOBLOCK_SZ, ri_ctx->f_out);
+			if (rc != INFOBLOCK_SZ)
+				return -EIO;
+			fflush(ri_ctx->f_out);
+			return 0;
+		}
+
+		if (!jblocks) {
+			jblocks = json_object_new_array();
+			if (!jblocks)
+				return -ENOMEM;
+			ri_ctx->jblocks = jblocks;
+		}
 	}
 
 	if (memcmp(btt1_sb->signature, BTT_SIG, BTT_SIG_LEN) == 0) {
-		jblock = btt_parse(btt1_sb, ndns, path, flags);
-		if (jblock)
-			json_object_array_add(jblocks, jblock);
+		ns_info->offset = BTT1_START_OFFSET;
+		ns_info->mode = NDCTL_NS_MODE_SECTOR;
+		if (ri_ctx) {
+			jblock = btt_parse(btt1_sb, ndns, path, flags);
+			if (jblock)
+				json_object_array_add(jblocks, jblock);
+		}
 	}
 
 	if (memcmp(btt2_sb->signature, BTT_SIG, BTT_SIG_LEN) == 0) {
-		jblock = btt_parse(btt2_sb, ndns, path, flags);
-		if (jblock)
-			json_object_array_add(jblocks, jblock);
+		ns_info->offset = BTT2_START_OFFSET;
+		ns_info->mode = NDCTL_NS_MODE_SECTOR;
+		if (ri_ctx) {
+			jblock = btt_parse(btt2_sb, ndns, path, flags);
+			if (jblock)
+				json_object_array_add(jblocks, jblock);
+		}
 	}
 
 	if (memcmp(pfn_sb->signature, PFN_SIG, PFN_SIG_LEN) == 0) {
-		jblock = pfn_parse(pfn_sb, ndns, path, flags);
-		if (jblock)
-			json_object_array_add(jblocks, jblock);
+		ns_info->offset = SZ_4K;
+		ns_info->mode = NDCTL_NS_MODE_FSDAX;
+		if (ri_ctx) {
+			jblock = pfn_parse(pfn_sb, ndns, path, flags);
+			if (jblock)
+				json_object_array_add(jblocks, jblock);
+		}
 	}
 
 	if (memcmp(dax_sb->signature, DAX_SIG, PFN_SIG_LEN) == 0) {
-		jblock = pfn_parse(dax_sb, ndns, path, flags);
-		if (jblock)
-			json_object_array_add(jblocks, jblock);
+		ns_info->offset = SZ_4K;
+		ns_info->mode = NDCTL_NS_MODE_DEVDAX;
+		if (ri_ctx) {
+			jblock = pfn_parse(dax_sb, ndns, path, flags);
+			if (jblock)
+				json_object_array_add(jblocks, jblock);
+		}
 	}
 
 	return 0;
 }
 
 static int file_read_infoblock(const char *path, struct ndctl_namespace *ndns,
-		struct read_infoblock_ctx *ri_ctx)
+		struct read_infoblock_ctx *ri_ctx, struct ns_info *ns_info)
 {
 	const char *devname = ndns ? ndctl_namespace_get_devname(ndns) : "";
 	const char *cmd = "read-infoblock";
-	void *buf = NULL;
 	int fd = -1, rc;
 
-	buf = calloc(1, INFOBLOCK_SZ);
-	if (!buf)
-		return -ENOMEM;
-
 	if (!path) {
 		fd = STDIN_FILENO;
 		path = "<stdin>";
@@ -1827,7 +1868,7 @@  static int file_read_infoblock(const char *path, struct ndctl_namespace *ndns,
 		goto out;
 	}
 
-	rc = read(fd, buf, INFOBLOCK_SZ);
+	rc = read(fd, ns_info->ns_sb_buf, INFOBLOCK_SZ);
 	if (rc < INFOBLOCK_SZ) {
 		pr_verbose("%s: %s failed to read %s: %s\n",
 				cmd, devname, path, strerror(errno));
@@ -1837,10 +1878,8 @@  static int file_read_infoblock(const char *path, struct ndctl_namespace *ndns,
 			rc = -EIO;
 		goto out;
 	}
-
-	rc = parse_namespace_infoblock(buf, ndns, path, ri_ctx);
+	rc = parse_namespace_infoblock(ns_info, ndns, path, ri_ctx);
 out:
-	free(buf);
 	if (fd >= 0 && fd != STDIN_FILENO)
 		close(fd);
 	return rc;
@@ -1857,10 +1896,10 @@  static unsigned long PHYS_PFN(unsigned long long phys)
 
 /* Derived from nd_pfn_init() in kernel version v5.5 */
 static int write_pfn_sb(int fd, unsigned long long size, const char *sig,
-		void *buf)
+		struct ns_info *ns_info)
 {
 	unsigned long npfns, align, pfn_align;
-	struct pfn_sb *pfn_sb = buf + SZ_4K;
+	struct pfn_sb *pfn_sb = ns_info->ns_sb_buf + SZ_4K;
 	unsigned long long start, offset;
 	uuid_t uuid, parent_uuid;
 	u32 end_trunc, start_pad;
@@ -1874,24 +1913,60 @@  static int write_pfn_sb(int fd, unsigned long long size, const char *sig,
 	align = max(pfn_align, SUBSECTION_SIZE);
 	if (param.uuid)
 		uuid_parse(param.uuid, uuid);
-	else
-		uuid_generate(uuid);
-
+	else {
+		switch (ns_info->mode) {
+		case NDCTL_NS_MODE_FSDAX:
+		case NDCTL_NS_MODE_DEVDAX:
+			memcpy(uuid,
+				((struct pfn_sb *)(ns_info->ns_sb_buf + ns_info->offset))->uuid,
+				sizeof(uuid_t));
+			break;
+		case NDCTL_NS_MODE_SECTOR:
+			memcpy(uuid,
+				((struct btt_sb *)(ns_info->ns_sb_buf + ns_info->offset))->uuid,
+				sizeof(uuid_t));
+			break;
+		default:
+			uuid_generate(uuid);
+			break;
+		}
+	}
 	if (param.parent_uuid)
 		uuid_parse(param.parent_uuid, parent_uuid);
-	else
-		memset(parent_uuid, 0, sizeof(uuid_t));
+	else {
+		switch (ns_info->mode) {
+		case NDCTL_NS_MODE_FSDAX:
+		case NDCTL_NS_MODE_DEVDAX:
+			memcpy(parent_uuid,
+				((struct pfn_sb *)(ns_info->ns_sb_buf + ns_info->offset))
+				->parent_uuid, sizeof(uuid_t));
+			break;
+		case NDCTL_NS_MODE_SECTOR:
+			memcpy(parent_uuid,
+				((struct btt_sb *)(ns_info->ns_sb_buf + ns_info->offset))
+				->parent_uuid, sizeof(uuid_t));
+			break;
+		default:
+			memset(parent_uuid, 0, sizeof(uuid_t));
+			break;
+		}
+	}
 
 	if (strcmp(param.map, "dev") == 0)
 		mode = PFN_MODE_PMEM;
 	else
 		mode = PFN_MODE_RAM;
 
+	// If originally the namespace was of sector type with backup
+	// infoblock offset 0, resetting those bits.
+	memset(ns_info->ns_sb_buf, 0, SZ_4K);
+
 	/*
 	 * Unlike the kernel implementation always set start_pad and
 	 * end_trunc relative to the specified --offset= option to allow
 	 * testing legacy / "buggy" configurations.
 	 */
+
 	start_pad = ALIGN(start, align) - start;
 	end_trunc = start + size - ALIGN_DOWN(start + size, align);
 	if (mode == PFN_MODE_PMEM) {
@@ -1933,17 +2008,16 @@  static int write_pfn_sb(int fd, unsigned long long size, const char *sig,
 	checksum = fletcher64(pfn_sb, sizeof(*pfn_sb), 0);
 	pfn_sb->checksum = cpu_to_le64(checksum);
 
-	rc = write(fd, buf, INFOBLOCK_SZ);
+	rc = write(fd, ns_info->ns_sb_buf, INFOBLOCK_SZ);
 	if (rc < INFOBLOCK_SZ)
 		return -EIO;
 	return 0;
 }
 
-static int file_write_infoblock(const char *path)
+static int file_write_infoblock(const char *path, struct ns_info *ns_info)
 {
 	unsigned long long size = parse_size64(param.size);
 	int fd = -1, rc;
-	void *buf;
 
 	if (param.std_out)
 		fd = STDOUT_FILENO;
@@ -1980,25 +2054,30 @@  static int file_write_infoblock(const char *path)
 		}
 	}
 
-	buf = calloc(INFOBLOCK_SZ, 1);
-	if (!buf) {
-		rc = -ENOMEM;
-		goto out;
-	}
-
 	switch (util_nsmode(param.mode)) {
 	case NDCTL_NS_MODE_FSDAX:
-		rc = write_pfn_sb(fd, size, PFN_SIG, buf);
+		rc = write_pfn_sb(fd, size, PFN_SIG, ns_info);
 		break;
 	case NDCTL_NS_MODE_DEVDAX:
-		rc = write_pfn_sb(fd, size, DAX_SIG, buf);
+		rc = write_pfn_sb(fd, size, DAX_SIG, ns_info);
+		break;
+	case NDCTL_NS_MODE_UNKNOWN:
+		switch (ns_info->mode) {
+		case NDCTL_NS_MODE_FSDAX:
+			rc = write_pfn_sb(fd, size, PFN_SIG, ns_info);
+			break;
+		case NDCTL_NS_MODE_DEVDAX:
+			rc = write_pfn_sb(fd, size, DAX_SIG, ns_info);
+			break;
+		default:
+			rc = -EINVAL;
+			break;
+		}
 		break;
 	default:
 		rc = -EINVAL;
 		break;
 	}
-
-	free(buf);
 out:
 	if (fd >= 0 && fd != STDOUT_FILENO)
 		close(fd);
@@ -2026,12 +2105,10 @@  static int namespace_rw_infoblock(struct ndctl_namespace *ndns,
 		struct read_infoblock_ctx *ri_ctx, int write)
 {
 	int rc;
-	uuid_t uuid;
-	char str[40];
 	char path[50];
-	const char *save;
 	const char *cmd = write ? "write-infoblock" : "read-infoblock";
 	const char *devname = ndctl_namespace_get_devname(ndns);
+	struct ns_info ns_info;
 
 	if (ndctl_namespace_is_active(ndns)) {
 		pr_verbose("%s: %s enabled, must be disabled\n", cmd, devname);
@@ -2045,21 +2122,22 @@  static int namespace_rw_infoblock(struct ndctl_namespace *ndns,
 		goto out;
 	}
 
-	save = param.parent_uuid;
-	if (!param.parent_uuid) {
-		ndctl_namespace_get_uuid(ndns, uuid);
-		uuid_unparse(uuid, str);
-		param.parent_uuid = str;
-	}
-
 	sprintf(path, "/dev/%s", ndctl_namespace_get_block_device(ndns));
-	if (write) {
+	if (ns_info_init(&ns_info) != 0)
+		goto out;
+
+	rc = file_read_infoblock(path, ndns, ri_ctx, &ns_info);
+	if (!rc && write) {
 		unsigned long long align;
 		bool align_provided = true;
 
 		if (!param.align) {
 			align = ndctl_get_default_alignment(ndns);
-
+			if (ns_info.mode == NDCTL_NS_MODE_FSDAX ||
+					ns_info.mode == NDCTL_NS_MODE_DEVDAX) {
+				align = ((struct pfn_sb *)(ns_info.ns_sb_buf + ns_info.offset))->
+					align;
+			}
 			if (asprintf((char **)&param.align, "%llu", align) < 0) {
 				rc = -EINVAL;
 				goto out;
@@ -2078,18 +2156,16 @@  static int namespace_rw_infoblock(struct ndctl_namespace *ndns,
 				rc = -EINVAL;
 			}
 		}
-
 		if (!rc)
-			rc = file_write_infoblock(path);
+			rc = file_write_infoblock(path, &ns_info);
 
 		if (!align_provided) {
 			free((char *)param.align);
 			param.align = NULL;
 		}
-	} else
-		rc = file_read_infoblock(path, ndns, ri_ctx);
-	param.parent_uuid = save;
+	}
 out:
+	ns_info_destroy(&ns_info);
 	ndctl_namespace_set_raw_mode(ndns, 0);
 	ndctl_namespace_disable_invalidate(ndns);
 	return rc;
@@ -2121,11 +2197,17 @@  static int do_xaction_namespace(const char *namespace,
 		}
 
 		if (param.infile || !namespace) {
-			rc = file_read_infoblock(param.infile, NULL, &ri_ctx);
-			if (ri_ctx.jblocks)
-				util_display_json_array(ri_ctx.f_out, ri_ctx.jblocks, 0);
-			if (rc >= 0)
-				(*processed)++;
+			struct ns_info ns_info;
+
+			rc = ns_info_init(&ns_info);
+			if (!rc) {
+				rc = file_read_infoblock(param.infile, NULL, &ri_ctx, &ns_info);
+				if (ri_ctx.jblocks)
+					util_display_json_array(ri_ctx.f_out, ri_ctx.jblocks, 0);
+				if (rc >= 0)
+					(*processed)++;
+			}
+			ns_info_destroy(&ns_info);
 			return rc;
 		}
 	}
@@ -2133,10 +2215,15 @@  static int do_xaction_namespace(const char *namespace,
 	if (action == ACTION_WRITE_INFOBLOCK && !namespace) {
 		if (!param.align)
 			param.align = "2M";
+		struct ns_info ns_info;
 
-		rc = file_write_infoblock(param.outfile);
-		if (rc >= 0)
-			(*processed)++;
+		rc = ns_info_init(&ns_info);
+		if (!rc) {
+			rc = file_write_infoblock(param.outfile, &ns_info);
+			if (rc >= 0)
+				(*processed)++;
+		}
+		ns_info_destroy(&ns_info);
 		return rc;
 	}