Subject: Re: [PATCH 3/3] powerpc/pseries: Support compression of oops text via pstore

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sat, 01 Jun 2013 14:54:15 +1000

On Fri, 2013-04-26 at 15:26 +0530, Aruna Balakrishnaiah wrote:
> The patch set supports compression of oops messages while writing to NVRAM,
> this helps in capturing more of oops data to lnx,oops-log. The pstore file
> for oops messages will be in decompressed format making it readable.
> 
> In case compression fails, the patch takes care of copying the header added
> by pstore and last oops_data_sz bytes of big_oops_buf to NVRAM so that we
> have recent oops messages in lnx,oops-log.
> 
> In case decompression fails, it will result in absence of oops file but still
> have files (in /dev/pstore) for other partitions.

Any reason that isn't handled by pstore itself rather than here ? Ie
make a flag indicating that the partition supports compression and have
pstore do it (so we don't compress everything such as ofw common etc...)

Cheers,
Ben.

> 
> Signed-off-by: Aruna Balakrishnaiah <[email-masked]>
> ---
>  arch/powerpc/platforms/pseries/nvram.c |  132 +++++++++++++++++++++++++++++---
>  1 file changed, 118 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/nvram.c b/arch/powerpc/platforms/pseries/nvram.c
> index 0159d74..b5ba5e2 100644
> --- a/arch/powerpc/platforms/pseries/nvram.c
> +++ b/arch/powerpc/platforms/pseries/nvram.c
> @@ -539,6 +539,65 @@ static int zip_oops(size_t text_len)
>  }
>  
>  #ifdef CONFIG_PSTORE
> +/* Derived from logfs_uncompress */
> +int nvram_decompress(void *in, void *out, size_t inlen, size_t outlen)
> +{
> +	int err, ret;
> +
> +	ret = -EIO;
> +	err = zlib_inflateInit(&stream);
> +	if (err != Z_OK)
> +		goto error;
> +
> +	stream.next_in = in;
> +	stream.avail_in = inlen;
> +	stream.total_in = 0;
> +	stream.next_out = out;
> +	stream.avail_out = outlen;
> +	stream.total_out = 0;
> +
> +	err = zlib_inflate(&stream, Z_FINISH);
> +	if (err != Z_STREAM_END)
> +		goto error;
> +
> +	err = zlib_inflateEnd(&stream);
> +	if (err != Z_OK)
> +		goto error;
> +
> +	ret = stream.total_out;
> +error:
> +	return ret;
> +}
> +
> +static int unzip_oops(char *oops_buf, char *big_buf)
> +{
> +	struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
> +	u64 timestamp = oops_hdr->timestamp;
> +	char *big_oops_data = NULL;
> +	char *oops_data_buf = NULL;
> +	size_t big_oops_data_sz;
> +	int unzipped_len;
> +
> +	big_oops_data = big_buf + sizeof(struct oops_log_info);
> +	big_oops_data_sz = big_oops_buf_sz - sizeof(struct oops_log_info);
> +	oops_data_buf = oops_buf + sizeof(struct oops_log_info);
> +
> +	unzipped_len = nvram_decompress(oops_data_buf, big_oops_data,
> +					oops_hdr->report_length,
> +					big_oops_data_sz);
> +
> +	if (unzipped_len < 0) {
> +		pr_err("nvram: decompression failed; returned %d\n",
> +								unzipped_len);
> +		return -1;
> +	}
> +	oops_hdr = (struct oops_log_info *)big_buf;
> +	oops_hdr->version = OOPS_HDR_VERSION;
> +	oops_hdr->report_length = (u16) unzipped_len;
> +	oops_hdr->timestamp = timestamp;
> +	return 0;
> +}
> +
>  static int nvram_pstore_open(struct pstore_info *psi)
>  {
>  	/* Reset the iterator to start reading partitions again */
> @@ -567,6 +626,7 @@ static int nvram_pstore_write(enum pstore_type_id type,
>  				size_t size, struct pstore_info *psi)
>  {
>  	int rc;
> +	unsigned int err_type = ERR_TYPE_KERNEL_PANIC;
>  	struct oops_log_info *oops_hdr = (struct oops_log_info *) oops_buf;
>  
>  	/* part 1 has the recent messages from printk buffer */
> @@ -577,8 +637,31 @@ static int nvram_pstore_write(enum pstore_type_id type,
>  	oops_hdr->version = OOPS_HDR_VERSION;
>  	oops_hdr->report_length = (u16) size;
>  	oops_hdr->timestamp = get_seconds();
> +
> +	if (big_oops_buf) {
> +		rc = zip_oops(size);
> +		/*
> +		 * If compression fails copy recent log messages from
> +		 * big_oops_buf to oops_data.
> +		 */
> +		if (rc != 0) {
> +			int hsize = pstore_get_header_size();
> +			size_t diff = size - oops_data_sz + hsize;
> +
> +			if (size > oops_data_sz) {
> +				memcpy(oops_data, big_oops_buf, hsize);
> +				memcpy(oops_data + hsize, big_oops_buf + diff,
> +					oops_data_sz - hsize);
> +
> +				oops_hdr->report_length = (u16) oops_data_sz;
> +			} else
> +				memcpy(oops_data, big_oops_buf, size);
> +		} else
> +			err_type = ERR_TYPE_KERNEL_PANIC_GZ;
> +	}
> +
>  	rc = nvram_write_os_partition(&oops_log_partition, oops_buf,
> -		(int) (sizeof(*oops_hdr) + size), ERR_TYPE_KERNEL_PANIC,
> +		(int) (sizeof(*oops_hdr) + oops_hdr->report_length), err_type,
>  		count);
>  
>  	if (rc != 0)
> @@ -600,10 +683,11 @@ static ssize_t nvram_pstore_read(u64 *id, enum pstore_type_id *type,
>  	struct oops_log_info *oops_hdr;
>  	unsigned int err_type, id_no, size = 0;
>  	struct nvram_os_partition *part = NULL;
> -	char *buff = NULL;
> -	int sig = 0;
> +	char *buff = NULL, *big_buff = NULL;
> +	int rc, sig = 0;
>  	loff_t p;
>  
> +read_partition:
>  	read_type++;
>  
>  	switch (nvram_type_ids[read_type]) {
> @@ -666,6 +750,25 @@ static ssize_t nvram_pstore_read(u64 *id, enum pstore_type_id *type,
>  	if (nvram_type_ids[read_type] == PSTORE_TYPE_DMESG) {
>  		oops_hdr = (struct oops_log_info *)buff;
>  		*buf = buff + sizeof(*oops_hdr);
> +
> +		if (err_type == ERR_TYPE_KERNEL_PANIC_GZ) {
> +			big_buff = kmalloc(big_oops_buf_sz, GFP_KERNEL);
> +			if (!big_buff)
> +				return -ENOMEM;
> +
> +			rc = unzip_oops(buff, big_buff);
> +
> +			if (rc != 0) {
> +				kfree(buff);
> +				kfree(big_buff);
> +				goto read_partition;
> +			}
> +
> +			oops_hdr = (struct oops_log_info *)big_buff;
> +			*buf = big_buff + sizeof(*oops_hdr);
> +			kfree(buff);
> +		}
> +
>  		time->tv_sec = oops_hdr->timestamp;
>  		time->tv_nsec = 0;
>  		return oops_hdr->report_length;
> @@ -687,17 +790,18 @@ static int nvram_pstore_init(void)
>  {
>  	int rc = 0;
>  
> -	nvram_pstore_info.buf = oops_data;
> -	nvram_pstore_info.bufsize = oops_data_sz;
> +	if (big_oops_buf) {
> +		nvram_pstore_info.buf = big_oops_buf;
> +		nvram_pstore_info.bufsize = big_oops_buf_sz;
> +	} else {
> +		nvram_pstore_info.buf = oops_data;
> +		nvram_pstore_info.bufsize = oops_data_sz;
> +	}
>  
>  	rc = pstore_register(&nvram_pstore_info);
>  	if (rc != 0)
>  		pr_err("nvram: pstore_register() failed, defaults to "
>  				"kmsg_dump; returned %d\n", rc);
> -	else
> -		/*TODO: Support compression when pstore is configured */
> -		pr_info("nvram: Compression of oops text supported only when "
> -				"pstore is not configured");
>  
>  	return rc;
>  }
> @@ -731,11 +835,6 @@ static void __init nvram_init_oops_partition(int rtas_partition_exists)
>  	oops_data = oops_buf + sizeof(struct oops_log_info);
>  	oops_data_sz = oops_log_partition.size - sizeof(struct oops_log_info);
>  
> -	rc = nvram_pstore_init();
> -
> -	if (!rc)
> -		return;
> -
>  	/*
>  	 * Figure compression (preceded by elimination of each line's <n>
>  	 * severity prefix) will reduce the oops/panic report to at most
> @@ -759,6 +858,11 @@ static void __init nvram_init_oops_partition(int rtas_partition_exists)
>  		stream.workspace = NULL;
>  	}
>  
> +	rc = nvram_pstore_init();
> +
> +	if (!rc)
> +		return;
> +
>  	rc = kmsg_dump_register(&nvram_kmsg_dumper);
>  	if (rc != 0) {
>  		pr_err("nvram: kmsg_dump_register() failed; returned %d\n", rc);
> 
> --
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