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Subject: Re: [PATCH v2 03/11] pstore/blk: blkoops: support pmsg recorder
To:     Kees Cook <keescook@chromium.org>
Cc:     Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>,
        Tony Luck <tony.luck@intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mtd@lists.infradead.org
References: <1581078355-19647-1-git-send-email-liaoweixiong@allwinnertech.com>
 <1581078355-19647-4-git-send-email-liaoweixiong@allwinnertech.com>
 <202003181107.6B776F0E5F@keescook>
From:   WeiXiong Liao <liaoweixiong@allwinnertech.com>
Message-ID: <4ddb742f-7819-25e9-7bf4-49a80823d2aa@allwinnertech.com>
Date:   Sun, 22 Mar 2020 19:14:37 +0800
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hi Kees Cook,

On 2020/3/19 AM 2:13, Kees Cook wrote:
> On Fri, Feb 07, 2020 at 08:25:47PM +0800, WeiXiong Liao wrote:
>> pmsg support recorder for userspace. To enable pmsg, just make pmsg_size
>> be greater than 0 and a multiple of 4096.
>>
>> Signed-off-by: WeiXiong Liao <liaoweixiong@allwinnertech.com>
>> ---
>>  fs/pstore/Kconfig          |  12 +++
>>  fs/pstore/blkoops.c        |  11 +++
>>  fs/pstore/blkzone.c        | 229 +++++++++++++++++++++++++++++++++++++++++++--
>>  include/linux/pstore_blk.h |   4 +
>>  4 files changed, 246 insertions(+), 10 deletions(-)
>>
>> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
>> index 7a57a8edb612..bbf1fdb5eaa7 100644
>> --- a/fs/pstore/Kconfig
>> +++ b/fs/pstore/Kconfig
>> @@ -186,6 +186,18 @@ config PSTORE_BLKOOPS_DMESG_SIZE
>>  	  NOTE that, both kconfig and module parameters can configure blkoops,
>>  	  but module parameters have priority over kconfig.
>>  
>> +config PSTORE_BLKOOPS_PMSG_SIZE
>> +	int "pmsg size in kbytes for blkoops"
>> +	depends on PSTORE_BLKOOPS
>> +	depends on PSTORE_PMSG
>> +	default 64
> 
> Instead of "depends on PSTORE_PMSG", you can do:
> 
> 	default 64 if PSTORE_PMSG
> 	default 0
> 

What happens if PSTORE_BLKOOPS_PMSG_SIZE is non-zero while
PSTORE_PMSG is disabled? The pmsg recorder do not work but pstore/blk
will always allocate zone for pmsg recorder since pmsg_size is non-zero.
It waste storage space.

I think "depends on PSTORE_PMSG" is batter than "default 64 if PSTORE_PMSG",
because PSTORE_BLKOOPS_PMSG_SIZE really depends on PSTORE_PMSG.

>> +	help
>> +	  This just sets size of pmsg (pmsg_size) for pstore/blk. The size is
>> +	  in KB and must be a multiple of 4.
>> +
>> +	  NOTE that, both kconfig and module parameters can configure blkoops,
>> +	  but module parameters have priority over kconfig.
>> +
>>  config PSTORE_BLKOOPS_BLKDEV
>>  	string "block device for blkoops"
>>  	depends on PSTORE_BLKOOPS
>> diff --git a/fs/pstore/blkoops.c b/fs/pstore/blkoops.c
>> index 8027c3af8c8d..02e6e4c1f965 100644
>> --- a/fs/pstore/blkoops.c
>> +++ b/fs/pstore/blkoops.c
>> @@ -16,6 +16,10 @@
>>  module_param(dmesg_size, long, 0400);
>>  MODULE_PARM_DESC(dmesg_size, "demsg size in kbytes");
>>  
>> +static long pmsg_size = -1;
> 
> Now PSTORE_BLKOOPS_PMSG_SIZE will always be available and you can set it
> here.
> 

Note above.

>> +module_param(pmsg_size, long, 0400);
>> +MODULE_PARM_DESC(pmsg_size, "pmsg size in kbytes");
>> +
>>  static int dump_oops = -1;
>>  module_param(dump_oops, int, 0400);
>>  MODULE_PARM_DESC(total_size, "whether dump oops");
>> @@ -60,6 +64,12 @@
>>  #define DEFAULT_DMESG_SIZE 0
>>  #endif
>>  
>> +#ifdef CONFIG_PSTORE_BLKOOPS_PMSG_SIZE
>> +#define DEFAULT_PMSG_SIZE CONFIG_PSTORE_BLKOOPS_PMSG_SIZE
>> +#else
>> +#define DEFAULT_PMSG_SIZE 0
>> +#endif
> 
> And drop this.
> 

Note above.

>> +
>>  #ifdef CONFIG_PSTORE_BLKOOPS_DUMP_OOPS
>>  #define DEFAULT_DUMP_OOPS CONFIG_PSTORE_BLKOOPS_DUMP_OOPS
>>  #else
>> @@ -113,6 +123,7 @@ int blkoops_register_device(struct blkoops_device *bo_dev)
>>  	}
>>  
>>  	verify_size(dmesg_size, DEFAULT_DMESG_SIZE, 4096);
>> +	verify_size(pmsg_size, DEFAULT_PMSG_SIZE, 4096);
>>  #undef verify_size
>>  	dump_oops = !!(dump_oops < 0 ? DEFAULT_DUMP_OOPS : dump_oops);
>>  
>> diff --git a/fs/pstore/blkzone.c b/fs/pstore/blkzone.c
>> index f77f612b50ba..a3464252d52e 100644
>> --- a/fs/pstore/blkzone.c
>> +++ b/fs/pstore/blkzone.c
>> @@ -24,12 +24,14 @@
>>   *
>>   * @sig: signature to indicate header (BLK_SIG xor BLKZONE-type value)
>>   * @datalen: length of data in @data
>> + * @start: offset into @data where the beginning of the stored bytes begin
>>   * @data: zone data.
>>   */
>>  struct blkz_buffer {
>>  #define BLK_SIG (0x43474244) /* DBGC */
>>  	uint32_t sig;
>>  	atomic_t datalen;
>> +	atomic_t start;
>>  	uint8_t data[];
>>  };
>>  
>> @@ -85,8 +87,10 @@ struct blkz_zone {
>>  
>>  struct blkz_context {
>>  	struct blkz_zone **dbzs;	/* dmesg block zones */
>> +	struct blkz_zone *pbz;		/* Pmsg block zone */
>>  	unsigned int dmesg_max_cnt;
>>  	unsigned int dmesg_read_cnt;
>> +	unsigned int pmsg_read_cnt;
>>  	unsigned int dmesg_write_cnt;
>>  	/*
>>  	 * the counter should be recovered when recover.
>> @@ -119,6 +123,11 @@ static inline int buffer_datalen(struct blkz_zone *zone)
>>  	return atomic_read(&zone->buffer->datalen);
>>  }
>>  
>> +static inline int buffer_start(struct blkz_zone *zone)
>> +{
>> +	return atomic_read(&zone->buffer->start);
>> +}
>> +
>>  static inline bool is_on_panic(void)
>>  {
>>  	struct blkz_context *cxt = &blkz_cxt;
>> @@ -410,6 +419,69 @@ static int blkz_recover_dmesg(struct blkz_context *cxt)
>>  	return ret;
>>  }
>>  
>> +static int blkz_recover_pmsg(struct blkz_context *cxt)
>> +{
>> +	struct blkz_info *info = cxt->bzinfo;
>> +	struct blkz_buffer *oldbuf;
>> +	struct blkz_zone *zone = NULL;
>> +	int ret = 0;
>> +	ssize_t rcnt, len;
>> +
>> +	zone = cxt->pbz;
>> +	if (!zone || zone->oldbuf)
>> +		return 0;
>> +
>> +	if (is_on_panic())
>> +		goto out;
>> +
>> +	if (unlikely(!info->read))
>> +		return -EINVAL;
>> +
>> +	len = zone->buffer_size + sizeof(*oldbuf);
>> +	oldbuf = kzalloc(len, GFP_KERNEL);
>> +	if (!oldbuf)
>> +		return -ENOMEM;
>> +
>> +	rcnt = info->read((char *)oldbuf, len, zone->off);
>> +	if (rcnt != len) {
>> +		pr_debug("recover pmsg failed\n");
>> +		ret = (int)rcnt < 0 ? (int)rcnt : -EIO;
>> +		goto free_oldbuf;
>> +	}
>> +
>> +	if (oldbuf->sig != zone->buffer->sig) {
>> +		pr_debug("no valid data in zone %s\n", zone->name);
>> +		goto free_oldbuf;
>> +	}
>> +
>> +	if (zone->buffer_size < atomic_read(&oldbuf->datalen) ||
>> +		zone->buffer_size < atomic_read(&oldbuf->start)) {
>> +		pr_info("found overtop zone: %s: off %lu, size %zu\n",
>> +				zone->name, zone->off, zone->buffer_size);
>> +		goto free_oldbuf;
>> +	}
>> +
>> +	if (!atomic_read(&oldbuf->datalen)) {
>> +		pr_debug("found erased zone: %s: id 0, off %lu, size %zu, datalen %d\n",
>> +				zone->name, zone->off, zone->buffer_size,
>> +				atomic_read(&oldbuf->datalen));
>> +		kfree(oldbuf);
>> +		goto out;
>> +	}
>> +
>> +	pr_debug("found nice zone: %s: id 0, off %lu, size %zu, datalen %d\n",
>> +			zone->name, zone->off, zone->buffer_size,
>> +			atomic_read(&oldbuf->datalen));
>> +	zone->oldbuf = oldbuf;
>> +out:
>> +	blkz_flush_dirty_zone(zone);
>> +	return 0;
>> +
>> +free_oldbuf:
>> +	kfree(oldbuf);
>> +	return ret;
>> +}
>> +
>>  static inline int blkz_recovery(struct blkz_context *cxt)
>>  {
>>  	int ret = -EBUSY;
>> @@ -421,6 +493,10 @@ static inline int blkz_recovery(struct blkz_context *cxt)
>>  	if (ret)
>>  		goto recover_fail;
>>  
>> +	ret = blkz_recover_pmsg(cxt);
>> +	if (ret)
>> +		goto recover_fail;
>> +
>>  	pr_debug("recover end!\n");
>>  	atomic_set(&cxt->recovered, 1);
>>  	return 0;
>> @@ -435,9 +511,17 @@ static int blkz_pstore_open(struct pstore_info *psi)
>>  	struct blkz_context *cxt = psi->data;
>>  
>>  	cxt->dmesg_read_cnt = 0;
>> +	cxt->pmsg_read_cnt = 0;
>>  	return 0;
>>  }
>>  
>> +static inline bool blkz_old_ok(struct blkz_zone *zone)
>> +{
>> +	if (zone && zone->oldbuf && atomic_read(&zone->oldbuf->datalen))
>> +		return true;
>> +	return false;
>> +}
>> +
>>  static inline bool blkz_ok(struct blkz_zone *zone)
>>  {
>>  	if (zone && zone->buffer && buffer_datalen(zone))
>> @@ -455,6 +539,25 @@ static inline int blkz_dmesg_erase(struct blkz_context *cxt,
>>  	return blkz_zone_write(zone, FLUSH_META, NULL, 0, 0);
>>  }
>>  
>> +static inline int blkz_pmsg_erase(struct blkz_context *cxt,
>> +		struct blkz_zone *zone)
>> +{
>> +	if (unlikely(!blkz_old_ok(zone)))
>> +		return 0;
>> +
>> +	kfree(zone->oldbuf);
>> +	zone->oldbuf = NULL;
>> +	/*
>> +	 * if there are new data in zone buffer, that means the old data
>> +	 * are already invalid. It is no need to flush 0 (erase) to
>> +	 * block device.
>> +	 */
>> +	if (!buffer_datalen(zone))
>> +		return blkz_zone_write(zone, FLUSH_META, NULL, 0, 0);
>> +	blkz_flush_dirty_zone(zone);
>> +	return 0;
>> +}
>> +
>>  static int blkz_pstore_erase(struct pstore_record *record)
>>  {
>>  	struct blkz_context *cxt = record->psi->data;
>> @@ -462,6 +565,8 @@ static int blkz_pstore_erase(struct pstore_record *record)
>>  	switch (record->type) {
>>  	case PSTORE_TYPE_DMESG:
>>  		return blkz_dmesg_erase(cxt, cxt->dbzs[record->id]);
>> +	case PSTORE_TYPE_PMSG:
>> +		return blkz_pmsg_erase(cxt, cxt->pbz);
>>  	default:
>>  		return -EINVAL;
>>  	}
>> @@ -482,8 +587,10 @@ static void blkz_write_kmsg_hdr(struct blkz_zone *zone,
>>  	hdr->reason = record->reason;
>>  	if (hdr->reason == KMSG_DUMP_OOPS)
>>  		hdr->counter = ++cxt->oops_counter;
>> -	else
>> +	else if (hdr->reason == KMSG_DUMP_PANIC)
>>  		hdr->counter = ++cxt->panic_counter;
>> +	else
>> +		hdr->counter = 0;
>>  }
>>  
>>  static inline int notrace blkz_dmesg_write_do(struct blkz_context *cxt,
>> @@ -546,6 +653,55 @@ static int notrace blkz_dmesg_write(struct blkz_context *cxt,
>>  	return 0;
>>  }
>>  
>> +static int notrace blkz_pmsg_write(struct blkz_context *cxt,
>> +		struct pstore_record *record)
>> +{
>> +	struct blkz_zone *zone;
>> +	size_t start, rem;
>> +	int cnt = record->size;
>> +	bool is_full_data = false;
>> +	char *buf = record->buf;
>> +
>> +	zone = cxt->pbz;
>> +	if (!zone)
>> +		return -ENOSPC;
>> +
>> +	if (atomic_read(&zone->buffer->datalen) >= zone->buffer_size)
>> +		is_full_data = true;
>> +
>> +	if (unlikely(cnt > zone->buffer_size)) {
>> +		buf += cnt - zone->buffer_size;
>> +		cnt = zone->buffer_size;
>> +	}
>> +
>> +	start = buffer_start(zone);
>> +	rem = zone->buffer_size - start;
>> +	if (unlikely(rem < cnt)) {
>> +		blkz_zone_write(zone, FLUSH_PART, buf, rem, start);
>> +		buf += rem;
>> +		cnt -= rem;
>> +		start = 0;
>> +		is_full_data = true;
>> +	}
>> +
>> +	atomic_set(&zone->buffer->start, cnt + start);
>> +	blkz_zone_write(zone, FLUSH_PART, buf, cnt, start);
>> +
>> +	/**
>> +	 * blkz_zone_write will set datalen as start + cnt.
>> +	 * It work if actual data length lesser than buffer size.
>> +	 * If data length greater than buffer size, pmsg will rewrite to
>> +	 * beginning of zone, which make buffer->datalen wrongly.
>> +	 * So we should reset datalen as buffer size once actual data length
>> +	 * greater than buffer size.
>> +	 */
>> +	if (is_full_data) {
>> +		atomic_set(&zone->buffer->datalen, zone->buffer_size);
>> +		blkz_zone_write(zone, FLUSH_META, NULL, 0, 0);
>> +	}
>> +	return 0;
>> +}
>> +
>>  static int notrace blkz_pstore_write(struct pstore_record *record)
>>  {
>>  	struct blkz_context *cxt = record->psi->data;
>> @@ -557,6 +713,8 @@ static int notrace blkz_pstore_write(struct pstore_record *record)
>>  	switch (record->type) {
>>  	case PSTORE_TYPE_DMESG:
>>  		return blkz_dmesg_write(cxt, record);
>> +	case PSTORE_TYPE_PMSG:
>> +		return blkz_pmsg_write(cxt, record);
>>  	default:
>>  		return -EINVAL;
>>  	}
>> @@ -573,6 +731,13 @@ static struct blkz_zone *blkz_read_next_zone(struct blkz_context *cxt)
>>  			return zone;
>>  	}
>>  
>> +	if (cxt->pmsg_read_cnt == 0) {
>> +		cxt->pmsg_read_cnt++;
>> +		zone = cxt->pbz;
>> +		if (blkz_old_ok(zone))
>> +			return zone;
>> +	}
>> +
>>  	return NULL;
>>  }
>>  
>> @@ -611,7 +776,8 @@ static ssize_t blkz_dmesg_read(struct blkz_zone *zone,
>>  		char *buf = kasprintf(GFP_KERNEL,
>>  				"%s: Total %d times\n",
>>  				record->reason == KMSG_DUMP_OOPS ? "Oops" :
>> -				"Panic", record->count);
>> +				record->reason == KMSG_DUMP_PANIC ? "Panic" :
>> +				"Unknown", record->count);
> 
> Please use get_reason_str() here.
> 

get_reason_str() is marked 'static' on platform.c and pstore/blk only
support oops
and panic, it's no need to check more reason number.

>>  		hlen = strlen(buf);
>>  		record->buf = krealloc(buf, hlen + size, GFP_KERNEL);
>>  		if (!record->buf) {
>> @@ -633,6 +799,29 @@ static ssize_t blkz_dmesg_read(struct blkz_zone *zone,
>>  	return size + hlen;
>>  }
>>  
>> +static ssize_t blkz_pmsg_read(struct blkz_zone *zone,
>> +		struct pstore_record *record)
>> +{
>> +	size_t size, start;
>> +	struct blkz_buffer *buf;
>> +
>> +	buf = (struct blkz_buffer *)zone->oldbuf;
>> +	if (!buf)
>> +		return READ_NEXT_ZONE;
>> +
>> +	size = atomic_read(&buf->datalen);
>> +	start = atomic_read(&buf->start);
>> +
>> +	record->buf = kmalloc(size, GFP_KERNEL);
>> +	if (!record->buf)
>> +		return -ENOMEM;
>> +
>> +	memcpy(record->buf, buf->data + start, size - start);
>> +	memcpy(record->buf + size - start, buf->data, start);
>> +
>> +	return size;
>> +}
>> +
>>  static ssize_t blkz_pstore_read(struct pstore_record *record)
>>  {
>>  	struct blkz_context *cxt = record->psi->data;
>> @@ -657,6 +846,9 @@ static ssize_t blkz_pstore_read(struct pstore_record *record)
>>  		blkz_read = blkz_dmesg_read;
>>  		record->id = cxt->dmesg_read_cnt - 1;
>>  		break;
>> +	case PSTORE_TYPE_PMSG:
>> +		blkz_read = blkz_pmsg_read;
>> +		break;
>>  	default:
>>  		goto next_zone;
>>  	}
>> @@ -712,8 +904,10 @@ static struct blkz_zone *blkz_init_zone(enum pstore_type_id type,
>>  	zone->type = type;
>>  	zone->buffer_size = size - sizeof(struct blkz_buffer);
>>  	zone->buffer->sig = type ^ BLK_SIG;
>> +	zone->oldbuf = NULL;
>>  	atomic_set(&zone->dirty, 0);
>>  	atomic_set(&zone->buffer->datalen, 0);
>> +	atomic_set(&zone->buffer->start, 0);
>>  
>>  	*off += size;
>>  
>> @@ -798,17 +992,26 @@ static int blkz_cut_zones(struct blkz_context *cxt)
>>  	struct blkz_info *info = cxt->bzinfo;
>>  	unsigned long off = 0;
>>  	int err;
>> -	size_t size;
>> +	size_t off_size = 0;
>>  
>> -	size = info->total_size;
>> -	cxt->dbzs = blkz_init_zones(PSTORE_TYPE_DMESG, &off, size,
>> +	off_size += info->pmsg_size;
>> +	cxt->pbz = blkz_init_zone(PSTORE_TYPE_PMSG, &off, info->pmsg_size);
>> +	if (IS_ERR(cxt->pbz)) {
>> +		err = PTR_ERR(cxt->pbz);
>> +		goto fail_out;
>> +	}
>> +
>> +	cxt->dbzs = blkz_init_zones(PSTORE_TYPE_DMESG, &off,
>> +			info->total_size - off_size,
>>  			info->dmesg_size, &cxt->dmesg_max_cnt);
>>  	if (IS_ERR(cxt->dbzs)) {
>>  		err = PTR_ERR(cxt->dbzs);
>> -		goto fail_out;
>> +		goto free_pmsg;
>>  	}
>>  
>>  	return 0;
>> +free_pmsg:
>> +	blkz_free_zone(&cxt->pbz);
>>  fail_out:
>>  	return err;
>>  }
>> @@ -824,7 +1027,7 @@ int blkz_register(struct blkz_info *info)
>>  		return -EINVAL;
>>  	}
>>  
>> -	if (!info->dmesg_size) {
>> +	if (!info->dmesg_size && !info->pmsg_size) {
>>  		pr_warn("at least one of the records be non-zero\n");
>>  		return -EINVAL;
>>  	}
>> @@ -851,6 +1054,7 @@ int blkz_register(struct blkz_info *info)
>>  
>>  	check_size(total_size, 4096);
>>  	check_size(dmesg_size, SECTOR_SIZE);
>> +	check_size(pmsg_size, SECTOR_SIZE);
>>  
>>  #undef check_size
>>  
>> @@ -882,6 +1086,7 @@ int blkz_register(struct blkz_info *info)
>>  	pr_debug("register %s with properties:\n", info->name);
>>  	pr_debug("\ttotal size : %ld Bytes\n", info->total_size);
>>  	pr_debug("\tdmesg size : %ld Bytes\n", info->dmesg_size);
>> +	pr_debug("\tpmsg size : %ld Bytes\n", info->pmsg_size);
>>  
>>  	err = blkz_cut_zones(cxt);
>>  	if (err) {
>> @@ -900,11 +1105,14 @@ int blkz_register(struct blkz_info *info)
>>  	}
>>  	cxt->pstore.data = cxt;
>>  	if (info->dmesg_size)
>> -		cxt->pstore.flags = PSTORE_FLAGS_DMESG;
>> +		cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
>> +	if (info->pmsg_size)
>> +		cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
>>  
>> -	pr_info("Registered %s as blkzone backend for %s%s\n", info->name,
>> +	pr_info("Registered %s as blkzone backend for %s%s%s\n", info->name,
>>  			cxt->dbzs && cxt->bzinfo->dump_oops ? "Oops " : "",
>> -			cxt->dbzs && cxt->bzinfo->panic_write ? "Panic " : "");
>> +			cxt->dbzs && cxt->bzinfo->panic_write ? "Panic " : "",
>> +			cxt->pbz ? "Pmsg" : "");
> 
> I'd switch to leading spaces so can leave these strings unchanged as you
> add them:
> 
> 	for%s%s%s\n", info->name,
> 		cxt->dbzs && cxt->bzinfo->dump_oops ? " Oops" : "",
> 		cxt->dbzs && cxt->bzinfo->panic_write ? " Panic" : "",
> 		cxt->pbz ? " Pmsg" : "");
> 
> etc

That's a good idea.

> 
>>  
>>  	err = pstore_register(&cxt->pstore);
>>  	if (err) {
>> @@ -940,6 +1148,7 @@ void blkz_unregister(struct blkz_info *info)
>>  	spin_unlock(&cxt->bzinfo_lock);
>>  
>>  	blkz_free_zones(&cxt->dbzs, &cxt->dmesg_max_cnt);
>> +	blkz_free_zone(&cxt->pbz);
>>  }
>>  EXPORT_SYMBOL_GPL(blkz_unregister);
>>  
>> diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
>> index 589d276fa4e4..af06be25bd01 100644
>> --- a/include/linux/pstore_blk.h
>> +++ b/include/linux/pstore_blk.h
>> @@ -19,6 +19,9 @@
>>   * @dmesg_size:
>>   *	The size of each zones for dmesg (oops & panic). Zero means disabled,
>>   *	otherwise, it must be multiple of SECTOR_SIZE(512 Bytes).
>> + * @pmsg_size:
>> + *	The size of zone for pmsg. Zero means disabled, othewise, it must be
>> + *	multiple of SECTOR_SIZE(512).
>>   * @dump_oops:
>>   *	Dump oops and panic log or only panic.
>>   * @read, @write:
>> @@ -50,6 +53,7 @@ struct blkz_info {
>>  
>>  	unsigned long total_size;
>>  	unsigned long dmesg_size;
>> +	unsigned long pmsg_size;
>>  	int dump_oops;
>>  	blkz_read_op read;
>>  	blkz_write_op write;
>> -- 
>> 1.9.1
>>
> 

-- 
WeiXiong Liao