Subject: Re: [PATCH 1/6] nvram: Generalize code for OS partitions in NVRAM

From: Jim Keniston <[email-masked]>
Date: Wed, 09 Feb 2011 14:43:13 -0800

On Mon, 2011-02-07 at 15:57 +1100, Benjamin Herrenschmidt wrote:
> On Sat, 2010-11-13 at 20:15 -0800, Jim Keniston wrote:
> > Adapt the functions used to create and write to the RTAS-log partition
> > to work with any OS-type partition.
> > 
> > Signed-off-by: Jim Keniston <[email-masked]>
> > ---
> 
> Overall pretty good (sorry for taking that long to review, I've been
> swamped down). Just a handful of minor nits:

I've appended an updated patch, which addresses your comments and also
applies to 2.6.38-rc4, rather than to your kernel as it stood on Nov.
13.  See below for responses to comments.

> 
> > +/*
> > + * Per the criteria passed via nvram_remove_partition(), should this
> > + * partition be removed?  1=remove, 0=keep
> > + */
> > +static int nvram_condemn_partition(struct nvram_partition *part,
> > +		const char *name, int sig, const char *exceptions[])
> 
> As "fun" as this name is, it didn't help me understand what the function
> was about until I read the code for the next one :-)
> 
> What about instead something like nvram_can_remove_partition() or
> something a bit more explicit like that ?

Done.

...
>  .../...
> 
> > +static const char *valid_os_partitions[] = {
> > +	"ibm,rtas-log",
> > +	NULL
> > +};
> 
> Can you pick a name that will be less confusing in the global
> symbol table ? Something like "pseries_nvram_os_partitions"

Done.

> or whatever shorter you can come up with which doesn't suck ?
> 
> Also, should we move that "os partition" core out of pseries ?
> 
> Looks like it will be useful for a few other platforms, I'd like
> to move that to a more generically useful location in arch/powerpc
> but that's not a blocker for this series but something to do next
> maybe ?

I haven't tried to do that reorganization.

> 
> In that case "struct os_partition" should also find itself a better
> name, maybe struct nvram_os_partition ?

Done.

...
> >  	if (rc <= 0) {
> > -		printk(KERN_ERR "nvram_write_error_log: Failed nvram_write (%d)\n", rc);
> > +		printk(KERN_ERR "nvram_write_os_partition: Failed nvram_write (%d)\n", rc);
> >  		return rc;
> >  	}
> >  	
> >  	return 0;
> >  }
> 
> While at it, turn these into pr_err and use __FUNCTION__ or __func__

Done.  However, I didn't convert any printks in functions that I wasn't
otherwise changing.

> 
> > +int nvram_write_error_log(char * buff, int length,
> > +                          unsigned int err_type, unsigned int error_log_cnt)
> > +{
> > +	return nvram_write_os_partition(&rtas_log_partition, buff, length,
> > +						err_type, error_log_cnt);
> > +}
> 
> That's a candidate for a static inline in a .h

Maybe, but in my next patch this function adjusts a static variable, so
I figure that putting it in a header would be messy.

Here's my revised patch.
Jim
=====
Generalize code for OS partitions in NVRAM

Adapt the functions used to create and write to the RTAS-log partition
to work with any OS-type partition.

Signed-off-by: Jim Keniston <[email-masked]>
---

 arch/powerpc/include/asm/nvram.h       |    3 -
 arch/powerpc/kernel/nvram_64.c         |   31 ++++++-
 arch/powerpc/platforms/pseries/nvram.c |  143 +++++++++++++++++++-------------
 3 files changed, 113 insertions(+), 64 deletions(-)

diff --git a/arch/powerpc/include/asm/nvram.h b/arch/powerpc/include/asm/nvram.h
index 92efe67..9d1aafe 100644
--- a/arch/powerpc/include/asm/nvram.h
+++ b/arch/powerpc/include/asm/nvram.h
@@ -51,7 +51,8 @@ static inline int mmio_nvram_init(void)
 extern int __init nvram_scan_partitions(void);
 extern loff_t nvram_create_partition(const char *name, int sig,
 				     int req_size, int min_size);
-extern int nvram_remove_partition(const char *name, int sig);
+extern int nvram_remove_partition(const char *name, int sig,
+					const char *exceptions[]);
 extern int nvram_get_partition_size(loff_t data_index);
 extern loff_t nvram_find_partition(const char *name, int sig, int *out_size);
 
diff --git a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c
index bb12b32..bec1e93 100644
--- a/arch/powerpc/kernel/nvram_64.c
+++ b/arch/powerpc/kernel/nvram_64.c
@@ -237,22 +237,45 @@ static unsigned char __init nvram_checksum(struct nvram_header *p)
 	return c_sum;
 }
 
+/*
+ * Per the criteria passed via nvram_remove_partition(), should this
+ * partition be removed?  1=remove, 0=keep
+ */
+static int nvram_can_remove_partition(struct nvram_partition *part,
+		const char *name, int sig, const char *exceptions[])
+{
+	if (part->header.signature != sig)
+		return 0;
+	if (name) {
+		if (strncmp(name, part->header.name, 12))
+			return 0;
+	} else if (exceptions) {
+		const char **except;
+		for (except = exceptions; *except; except++) {
+			if (!strncmp(*except, part->header.name, 12))
+				return 0;
+		}
+	}
+	return 1;
+}
+
 /**
  * nvram_remove_partition - Remove one or more partitions in nvram
  * @name: name of the partition to remove, or NULL for a
  *        signature only match
  * @sig: signature of the partition(s) to remove
+ * @exceptions: When removing all partitions with a matching signature,
+ *        leave these alone.
  */
 
-int __init nvram_remove_partition(const char *name, int sig)
+int __init nvram_remove_partition(const char *name, int sig,
+						const char *exceptions[])
 {
 	struct nvram_partition *part, *prev, *tmp;
 	int rc;
 
 	list_for_each_entry(part, &nvram_partitions, partition) {
-		if (part->header.signature != sig)
-			continue;
-		if (name && strncmp(name, part->header.name, 12))
+		if (!nvram_can_remove_partition(part, name, sig, exceptions))
 			continue;
 
 		/* Make partition a free partition */
diff --git a/arch/powerpc/platforms/pseries/nvram.c b/arch/powerpc/platforms/pseries/nvram.c
index 7e828ba..befb41b 100644
--- a/arch/powerpc/platforms/pseries/nvram.c
+++ b/arch/powerpc/platforms/pseries/nvram.c
@@ -30,17 +30,30 @@ static int nvram_fetch, nvram_store;
 static char nvram_buf[NVRW_CNT];	/* assume this is in the first 4GB */
 static DEFINE_SPINLOCK(nvram_lock);
 
-static long nvram_error_log_index = -1;
-static long nvram_error_log_size = 0;
-
 struct err_log_info {
 	int error_type;
 	unsigned int seq_num;
 };
-#define NVRAM_MAX_REQ		2079
-#define NVRAM_MIN_REQ		1055
 
-#define NVRAM_LOG_PART_NAME	"ibm,rtas-log"
+struct nvram_os_partition {
+	const char *name;
+	int req_size;	/* desired size, in bytes */
+	int min_size;	/* minimum acceptable size (0 means req_size) */
+	long size;	/* size of data portion of partition */
+	long index;	/* offset of data portion of partition */
+};
+
+static struct nvram_os_partition rtas_log_partition = {
+	.name = "ibm,rtas-log",
+	.req_size = 2079,
+	.min_size = 1055,
+	.index = -1
+};
+
+static const char *pseries_nvram_os_partitions[] = {
+	"ibm,rtas-log",
+	NULL
+};
 
 static ssize_t pSeries_nvram_read(char *buf, size_t count, loff_t *index)
 {
@@ -134,7 +147,7 @@ static ssize_t pSeries_nvram_get_size(void)
 }

-/* nvram_write_error_log
+/* nvram_write_os_partition, nvram_write_error_log
  *
  * We need to buffer the error logs into nvram to ensure that we have
  * the failure information to decode.  If we have a severe error there
@@ -156,48 +169,55 @@ static ssize_t pSeries_nvram_get_size(void)
  * The 'data' section would look like (in bytes):
  * +--------------+------------+-----------------------------------+
  * | event_logged | sequence # | error log                         |
- * |0            3|4          7|8            nvram_error_log_size-1|
+ * |0            3|4          7|8                  error_log_size-1|
  * +--------------+------------+-----------------------------------+
  *
  * event_logged: 0 if event has not been logged to syslog, 1 if it has
  * sequence #: The unique sequence # for each event. (until it wraps)
  * error log: The error log from event_scan
  */
-int nvram_write_error_log(char * buff, int length,
-                          unsigned int err_type, unsigned int error_log_cnt)
+int nvram_write_os_partition(struct nvram_os_partition *part, char * buff,
+		int length, unsigned int err_type, unsigned int error_log_cnt)
 {
 	int rc;
 	loff_t tmp_index;
 	struct err_log_info info;
 	
-	if (nvram_error_log_index == -1) {
+	if (part->index == -1) {
 		return -ESPIPE;
 	}
 
-	if (length > nvram_error_log_size) {
-		length = nvram_error_log_size;
+	if (length > part->size) {
+		length = part->size;
 	}
 
 	info.error_type = err_type;
 	info.seq_num = error_log_cnt;
 
-	tmp_index = nvram_error_log_index;
+	tmp_index = part->index;
 
 	rc = ppc_md.nvram_write((char *)&info, sizeof(struct err_log_info), &tmp_index);
 	if (rc <= 0) {
-		printk(KERN_ERR "nvram_write_error_log: Failed nvram_write (%d)\n", rc);
+		pr_err("%s: Failed nvram_write (%d)\n", __FUNCTION__, rc);
 		return rc;
 	}
 
 	rc = ppc_md.nvram_write(buff, length, &tmp_index);
 	if (rc <= 0) {
-		printk(KERN_ERR "nvram_write_error_log: Failed nvram_write (%d)\n", rc);
+		pr_err("%s: Failed nvram_write (%d)\n", __FUNCTION__, rc);
 		return rc;
 	}
 	
 	return 0;
 }
 
+int nvram_write_error_log(char * buff, int length,
+                          unsigned int err_type, unsigned int error_log_cnt)
+{
+	return nvram_write_os_partition(&rtas_log_partition, buff, length,
+						err_type, error_log_cnt);
+}
+
 /* nvram_read_error_log
  *
  * Reads nvram for error log for at most 'length'
@@ -209,13 +229,13 @@ int nvram_read_error_log(char * buff, int length,
 	loff_t tmp_index;
 	struct err_log_info info;
 	
-	if (nvram_error_log_index == -1)
+	if (rtas_log_partition.index == -1)
 		return -1;
 
-	if (length > nvram_error_log_size)
-		length = nvram_error_log_size;
+	if (length > rtas_log_partition.size)
+		length = rtas_log_partition.size;
 
-	tmp_index = nvram_error_log_index;
+	tmp_index = rtas_log_partition.index;
 
 	rc = ppc_md.nvram_read((char *)&info, sizeof(struct err_log_info), &tmp_index);
 	if (rc <= 0) {
@@ -244,10 +264,10 @@ int nvram_clear_error_log(void)
 	int clear_word = ERR_FLAG_ALREADY_LOGGED;
 	int rc;
 
-	if (nvram_error_log_index == -1)
+	if (rtas_log_partition.index == -1)
 		return -1;
 
-	tmp_index = nvram_error_log_index;
+	tmp_index = rtas_log_partition.index;
 	
 	rc = ppc_md.nvram_write((char *)&clear_word, sizeof(int), &tmp_index);
 	if (rc <= 0) {
@@ -258,23 +278,25 @@ int nvram_clear_error_log(void)
 	return 0;
 }
 
-/* pseries_nvram_init_log_partition
+/* pseries_nvram_init_os_partition
  *
- * This will setup the partition we need for buffering the
- * error logs and cleanup partitions if needed.
+ * This sets up a partition with an "OS" signature.
  *
  * The general strategy is the following:
- * 1.) If there is log partition large enough then use it.
- * 2.) If there is none large enough, search
- * for a free partition that is large enough.
- * 3.) If there is not a free partition large enough remove 
- * _all_ OS partitions and consolidate the space.
- * 4.) Will first try getting a chunk that will satisfy the maximum
- * error log size (NVRAM_MAX_REQ).
- * 5.) If the max chunk cannot be allocated then try finding a chunk
- * that will satisfy the minum needed (NVRAM_MIN_REQ).
+ * 1.) If a partition with the indicated name already exists...
+ *	- If it's large enough, use it.
+ *	- Otherwise, recycle it and keep going.
+ * 2.) Search for a free partition that is large enough.
+ * 3.) If there's not a free partition large enough, recycle any obsolete
+ * OS partitions and try again.
+ * 4.) Will first try getting a chunk that will satisfy the requested size.
+ * 5.) If a chunk of the requested size cannot be allocated, then try finding
+ * a chunk that will satisfy the minum needed.
+ *
+ * Returns 0 on success, else -1.
  */
-static int __init pseries_nvram_init_log_partition(void)
+static int __init pseries_nvram_init_os_partition(struct nvram_os_partition
+									*part)
 {
 	loff_t p;
 	int size;
@@ -282,47 +304,50 @@ static int __init pseries_nvram_init_log_partition(void)
 	/* Scan nvram for partitions */
 	nvram_scan_partitions();
 
-	/* Lookg for ours */
-	p = nvram_find_partition(NVRAM_LOG_PART_NAME, NVRAM_SIG_OS, &size);
+	/* Look for ours */
+	p = nvram_find_partition(part->name, NVRAM_SIG_OS, &size);
 
 	/* Found one but too small, remove it */
-	if (p && size < NVRAM_MIN_REQ) {
-		pr_info("nvram: Found too small "NVRAM_LOG_PART_NAME" partition"
-			",removing it...");
-		nvram_remove_partition(NVRAM_LOG_PART_NAME, NVRAM_SIG_OS);
+	if (p && size < part->min_size) {
+		pr_info("nvram: Found too small %s partition,"
+					" removing it...\n", part->name);
+		nvram_remove_partition(part->name, NVRAM_SIG_OS, NULL);
 		p = 0;
 	}
 
 	/* Create one if we didn't find */
 	if (!p) {
-		p = nvram_create_partition(NVRAM_LOG_PART_NAME, NVRAM_SIG_OS,
-					   NVRAM_MAX_REQ, NVRAM_MIN_REQ);
-		/* No room for it, try to get rid of any OS partition
-		 * and try again
-		 */
+		p = nvram_create_partition(part->name, NVRAM_SIG_OS,
+					part->req_size, part->min_size);
 		if (p == -ENOSPC) {
-			pr_info("nvram: No room to create "NVRAM_LOG_PART_NAME
-				" partition, deleting all OS partitions...");
-			nvram_remove_partition(NULL, NVRAM_SIG_OS);
-			p = nvram_create_partition(NVRAM_LOG_PART_NAME,
-						   NVRAM_SIG_OS, NVRAM_MAX_REQ,
-						   NVRAM_MIN_REQ);
+			pr_info("nvram: No room to create %s partition, "
+				"deleting any obsolete OS partitions...\n",
+				part->name);
+			nvram_remove_partition(NULL, NVRAM_SIG_OS,
+						pseries_nvram_os_partitions);
+			p = nvram_create_partition(part->name, NVRAM_SIG_OS,
+					part->req_size, part->min_size);
 		}
 	}
 
 	if (p <= 0) {
-		pr_err("nvram: Failed to find or create "NVRAM_LOG_PART_NAME
-		       " partition, err %d\n", (int)p);
-		return 0;
+		pr_err("nvram: Failed to find or create %s"
+		       " partition, err %d\n", part->name, (int)p);
+		return -1;
 	}
 
-	nvram_error_log_index = p;
-	nvram_error_log_size = nvram_get_partition_size(p) -
-		sizeof(struct err_log_info);
+	part->index = p;
+	part->size = nvram_get_partition_size(p) - sizeof(struct err_log_info);
 	
 	return 0;
 }
-machine_arch_initcall(pseries, pseries_nvram_init_log_partition);
+
+static int __init pseries_nvram_init_log_partitions(void)
+{
+	(void) pseries_nvram_init_os_partition(&rtas_log_partition);
+	return 0;
+}
+machine_arch_initcall(pseries, pseries_nvram_init_log_partitions);
 
 int __init pSeries_nvram_init(void)
 {