Date:	Mon, 30 Jul 2012 13:45:56 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
	"mikew@...gle.com" <mikew@...gle.com>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>
CC:	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: [RFC][PATCH V3]efi_pstore: hold multiple logs to avoid losing
 critical message

This patchset avoids losing a critical message like panic in NVRAM.

Change v2 -> v3
 - Merged previous 1/3 and 2/3 patches.
 - Dropped previous a 3/3 patch.
 - Remove a kernel parameter ,efi_pstore_log_num.
 - Check if there is enough space to log with QueryVariableInfo().
 - Pass oopscount to arguments of write/erase/read callbacks
   to handle multiple events.

Change v1 -> v2

1/3
  - Freshly created to avoid overwriting entries.

2/3
  - Freshly created to handle multiple logs.
  - Add an additional change passing ctime to arguments of erase_callback.

3/3
  - This is based on previous 2/2 patch
  - Add comments to kernel/printk.h in preparation for future change 
    without considering this patch.
  - Remove infinite loop to avoid potential hang up.
  - Add CFLAGS, -Wswitch-enum and remove default case from switch sentence 
    in preparation for future change without considering this patch.
  - Change a return value to -EEXIST when an erasable entry is not found. 
  - Remove KMSG_DUMP_UNDEF from kmsg_dump_reason because no one uses it.


[Problem]
    Currently, efi_pstore driver simply overwrites existing panic messages in NVRAM.
    So, in the following scenario, we will lose 1st panic messages.

    1. kernel panics.
    2. efi_pstore is kicked and write panic messages to NVRAM.
    3. system reboots.
    4. kernel panics again before a user checks the 1st panic messages in NVRAM.

[Solution]
   To avoid losing a critical message, this patch takes an approach holding multiple
   logs.
   Also, to avoid handling out of space situation, it checks if there are enough spaces
   to write logs with QueryVariableInfo().


[Patch Descriptions]

  This patch makes efi_pstore hold multiple logs.
  Once a critical message is logged, users can see it via /dev/pstore 
  without being influenced by subsequent events.

  Specific changes are as follows.

  - Check if there are enough spaces to write logs with QueryVariableInfo().
  - Remove a logic erasing existing entries from write callback.
  - Add the logic above to erase callback.
  - Pass oopscount to arguments of write/erase/read callbacks to handle multiple events.
  - Pass ctime to arguments of erase_callback to avoid invisible entries via /dev/pstore.

 Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>
 Suggested-by: Matthew Garrett <mjg@...hat.com>

---
 drivers/acpi/apei/erst.c   |   16 ++++----
 drivers/firmware/efivars.c |   93 ++++++++++++++++++++++++++++----------------
 fs/pstore/inode.c          |    7 ++-
 fs/pstore/internal.h       |    2 +-
 fs/pstore/platform.c       |   12 +++---
 fs/pstore/ram.c            |   11 ++---
 include/linux/efi.h        |    1 +
 include/linux/pstore.h     |    6 ++-
 8 files changed, 89 insertions(+), 59 deletions(-)

diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
index e4d9d24..833a9f4 100644
--- a/drivers/acpi/apei/erst.c
+++ b/drivers/acpi/apei/erst.c
@@ -931,14 +931,14 @@ static int erst_check_table(struct acpi_table_erst *erst_tab)
 
 static int erst_open_pstore(struct pstore_info *psi);
 static int erst_close_pstore(struct pstore_info *psi);
-static ssize_t erst_reader(u64 *id, enum pstore_type_id *type,
+static ssize_t erst_reader(u64 *id, enum pstore_type_id *type, u64 *count,
 			   struct timespec *time, char **buf,
 			   struct pstore_info *psi);
 static int erst_writer(enum pstore_type_id type, enum kmsg_dump_reason reason,
-		       u64 *id, unsigned int part,
+		       u64 *id, unsigned int part, u64 count,
 		       size_t size, struct pstore_info *psi);
-static int erst_clearer(enum pstore_type_id type, u64 id,
-			struct pstore_info *psi);
+static int erst_clearer(enum pstore_type_id type, u64 id, u64 count,
+			struct timespec time, struct pstore_info *psi);
 
 static struct pstore_info erst_info = {
 	.owner		= THIS_MODULE,
@@ -987,7 +987,7 @@ static int erst_close_pstore(struct pstore_info *psi)
 	return 0;
 }
 
-static ssize_t erst_reader(u64 *id, enum pstore_type_id *type,
+static ssize_t erst_reader(u64 *id, enum pstore_type_id *type, u64 *count,
 			   struct timespec *time, char **buf,
 			   struct pstore_info *psi)
 {
@@ -1055,7 +1055,7 @@ out:
 }
 
 static int erst_writer(enum pstore_type_id type, enum kmsg_dump_reason reason,
-		       u64 *id, unsigned int part,
+		       u64 *id, unsigned int part, u64 count,
 		       size_t size, struct pstore_info *psi)
 {
 	struct cper_pstore_record *rcd = (struct cper_pstore_record *)
@@ -1101,8 +1101,8 @@ static int erst_writer(enum pstore_type_id type, enum kmsg_dump_reason reason,
 	return ret;
 }
 
-static int erst_clearer(enum pstore_type_id type, u64 id,
-			struct pstore_info *psi)
+static int erst_clearer(enum pstore_type_id type, u64 id, u64 count,
+			struct timespec time, struct pstore_info *psi)
 {
 	return erst_clear(id);
 }
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 47408e8..9966fe3 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -647,7 +647,7 @@ static int efi_pstore_close(struct pstore_info *psi)
 }
 
 static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
-			       struct timespec *timespec,
+			       u64 *count, struct timespec *timespec,
 			       char **buf, struct pstore_info *psi)
 {
 	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
@@ -655,6 +655,7 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 	char name[DUMP_NAME_LEN];
 	int i;
 	unsigned int part, size;
+	u64 cnt;
 	unsigned long time;
 
 	while (&efivars->walk_entry->list != &efivars->list) {
@@ -663,8 +664,10 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 			for (i = 0; i < DUMP_NAME_LEN; i++) {
 				name[i] = efivars->walk_entry->var.VariableName[i];
 			}
-			if (sscanf(name, "dump-type%u-%u-%lu", type, &part, &time) == 3) {
+			if (sscanf(name, "dump-type%u-%u-%llu-%lu",
+			    type, &part, &cnt, &time) == 4) {
 				*id = part;
+				*count = cnt;
 				timespec->tv_sec = time;
 				timespec->tv_nsec = 0;
 				get_var_data_locked(efivars, &efivars->walk_entry->var);
@@ -687,18 +690,62 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 
 static int efi_pstore_write(enum pstore_type_id type,
 		enum kmsg_dump_reason reason, u64 *id,
-		unsigned int part, size_t size, struct pstore_info *psi)
+		unsigned int part, u64 count, size_t size,
+		struct pstore_info *psi)
 {
 	char name[DUMP_NAME_LEN];
+	efi_char16_t efi_name[DUMP_NAME_LEN];
+	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
+	struct efivars *efivars = psi->data;
+	int i, ret = 0;
+	u64 storage_space, remaining_space, max_variable_size;
+	efi_status_t status = EFI_NOT_FOUND;
+
+	spin_lock(&efivars->lock);
+
+	status = efivars->ops->query_variable_info(PSTORE_EFI_ATTRIBUTES,
+						   &storage_space,
+						   &remaining_space,
+						   &max_variable_size);
+	if (status || remaining_space < max_variable_size) {
+		spin_unlock(&efivars->lock);
+		*id = part;
+		return -EEXIST;
+	}
+
+	sprintf(name, "dump-type%u-%u-%llu-%lu", type, part, count,
+		get_seconds());
+
+	for (i = 0; i < DUMP_NAME_LEN; i++)
+		efi_name[i] = name[i];
+
+	efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
+				   size, psi->buf);
+
+	spin_unlock(&efivars->lock);
+
+	if (size)
+		ret = efivar_create_sysfs_entry(efivars,
+					  utf16_strsize(efi_name,
+							DUMP_NAME_LEN * 2),
+					  efi_name, &vendor);
+
+	*id = part;
+	return ret;
+};
+
+static int efi_pstore_erase(enum pstore_type_id type, u64 id, u64 count,
+			    struct timespec time, struct pstore_info *psi)
+{
 	char stub_name[DUMP_NAME_LEN];
 	efi_char16_t efi_name[DUMP_NAME_LEN];
 	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
 	struct efivars *efivars = psi->data;
 	struct efivar_entry *entry, *found = NULL;
-	int i, ret = 0;
+	int i;
 
-	sprintf(stub_name, "dump-type%u-%u-", type, part);
-	sprintf(name, "%s%lu", stub_name, get_seconds());
+	sprintf(stub_name, "dump-type%u-%llu-%llu-%lu", type, id, count,
+		time.tv_sec);
 
 	spin_lock(&efivars->lock);
 
@@ -717,9 +764,6 @@ static int efi_pstore_write(enum pstore_type_id type,
 		if (utf16_strncmp(entry->var.VariableName, efi_name,
 				  utf16_strlen(efi_name)))
 			continue;
-		/* Needs to be a prefix */
-		if (entry->var.VariableName[utf16_strlen(efi_name)] == 0)
-			continue;
 
 		/* found */
 		found = entry;
@@ -732,32 +776,11 @@ static int efi_pstore_write(enum pstore_type_id type,
 	if (found)
 		list_del(&found->list);
 
-	for (i = 0; i < DUMP_NAME_LEN; i++)
-		efi_name[i] = name[i];
-
-	efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
-				   size, psi->buf);
-
 	spin_unlock(&efivars->lock);
 
 	if (found)
 		efivar_unregister(found);
 
-	if (size)
-		ret = efivar_create_sysfs_entry(efivars,
-					  utf16_strsize(efi_name,
-							DUMP_NAME_LEN * 2),
-					  efi_name, &vendor);
-
-	*id = part;
-	return ret;
-};
-
-static int efi_pstore_erase(enum pstore_type_id type, u64 id,
-			    struct pstore_info *psi)
-{
-	efi_pstore_write(type, 0, &id, (unsigned int)id, 0, psi);
-
 	return 0;
 }
 #else
@@ -771,7 +794,7 @@ static int efi_pstore_close(struct pstore_info *psi)
 	return 0;
 }
 
-static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
+static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type, u64 *count,
 			       struct timespec *timespec,
 			       char **buf, struct pstore_info *psi)
 {
@@ -780,13 +803,14 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 
 static int efi_pstore_write(enum pstore_type_id type,
 		enum kmsg_dump_reason reason, u64 *id,
-		unsigned int part, size_t size, struct pstore_info *psi)
+		unsigned int part, u64 count, size_t size,
+		struct pstore_info *psi)
 {
 	return 0;
 }
 
-static int efi_pstore_erase(enum pstore_type_id type, u64 id,
-			    struct pstore_info *psi)
+static int efi_pstore_erase(enum pstore_type_id type, u64 id, u64 count,
+			    struct timespec time, struct pstore_info *psi)
 {
 	return 0;
 }
@@ -1226,6 +1250,7 @@ efivars_init(void)
 	ops.get_variable = efi.get_variable;
 	ops.set_variable = efi.set_variable;
 	ops.get_next_variable = efi.get_next_variable;
+	ops.query_variable_info = efi.query_variable_info;
 	error = register_efivars(&__efivars, &ops, efi_kobj);
 	if (error)
 		goto err_put;
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 11a2aa2..ca1b6c9 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -48,6 +48,7 @@ struct pstore_private {
 	struct pstore_info *psi;
 	enum pstore_type_id type;
 	u64	id;
+	u64	count;
 	ssize_t	size;
 	char	data[];
 };
@@ -75,7 +76,8 @@ static int pstore_unlink(struct inode *dir, struct dentry *dentry)
 	struct pstore_private *p = dentry->d_inode->i_private;
 
 	if (p->psi->erase)
-		p->psi->erase(p->type, p->id, p->psi);
+		p->psi->erase(p->type, p->id, p->count,
+			      dentry->d_inode->i_ctime, p->psi);
 
 	return simple_unlink(dir, dentry);
 }
@@ -170,7 +172,7 @@ int pstore_is_mounted(void)
  * Load it up with "size" bytes of data from "buf".
  * Set the mtime & ctime to the date that this record was originally stored.
  */
-int pstore_mkfile(enum pstore_type_id type, char *psname, u64 id,
+int pstore_mkfile(enum pstore_type_id type, char *psname, u64 id, u64 count,
 		  char *data, size_t size, struct timespec time,
 		  struct pstore_info *psi)
 {
@@ -206,6 +208,7 @@ int pstore_mkfile(enum pstore_type_id type, char *psname, u64 id,
 		goto fail_alloc;
 	private->type = type;
 	private->id = id;
+	private->count = count;
 	private->psi = psi;
 
 	switch (type) {
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index 3bde461..d93e20e 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -1,6 +1,6 @@
 extern void	pstore_set_kmsg_bytes(int);
 extern void	pstore_get_records(int);
 extern int	pstore_mkfile(enum pstore_type_id, char *psname, u64 id,
-			      char *data, size_t size,
+			      u64 count, char *data, size_t size,
 			      struct timespec time, struct pstore_info *psi);
 extern int	pstore_is_mounted(void);
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 03ce7a9..371a184 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -66,7 +66,7 @@ void pstore_set_kmsg_bytes(int bytes)
 }
 
 /* Tag each group of saved records with a sequence number */
-static int	oopscount;
+unsigned int	oopscount;
 
 static const char *get_reason_str(enum kmsg_dump_reason reason)
 {
@@ -128,7 +128,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 			break;
 
 		ret = psinfo->write(PSTORE_TYPE_DMESG, reason, &id, part,
-				    hsize + len, psinfo);
+				    oopscount, hsize + len, psinfo);
 		if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
 			pstore_new_entry = 1;
 
@@ -202,7 +202,7 @@ void pstore_get_records(int quiet)
 	struct pstore_info *psi = psinfo;
 	char			*buf = NULL;
 	ssize_t			size;
-	u64			id;
+	u64			id, count;
 	enum pstore_type_id	type;
 	struct timespec		time;
 	int			failed = 0, rc;
@@ -214,9 +214,9 @@ void pstore_get_records(int quiet)
 	if (psi->open && psi->open(psi))
 		goto out;
 
-	while ((size = psi->read(&id, &type, &time, &buf, psi)) > 0) {
-		rc = pstore_mkfile(type, psi->name, id, buf, (size_t)size,
-				  time, psi);
+	while ((size = psi->read(&id, &type, &count, &time, &buf, psi)) > 0) {
+		rc = pstore_mkfile(type, psi->name, id, count, buf,
+				   (size_t)size, time, psi);
 		kfree(buf);
 		buf = NULL;
 		if (rc && (rc != -EEXIST || !quiet))
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 453030f..2bdd4f2 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -86,9 +86,8 @@ static int ramoops_pstore_open(struct pstore_info *psi)
 }
 
 static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
-				   struct timespec *time,
-				   char **buf,
-				   struct pstore_info *psi)
+				   u64 *count, struct timespec *time,
+				   char **buf, struct pstore_info *psi)
 {
 	ssize_t size;
 	struct ramoops_context *cxt = psi->data;
@@ -137,7 +136,7 @@ static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz)
 static int ramoops_pstore_write(enum pstore_type_id type,
 				enum kmsg_dump_reason reason,
 				u64 *id,
-				unsigned int part,
+				unsigned int part, u64 count,
 				size_t size, struct pstore_info *psi)
 {
 	struct ramoops_context *cxt = psi->data;
@@ -177,8 +176,8 @@ static int ramoops_pstore_write(enum pstore_type_id type,
 	return 0;
 }
 
-static int ramoops_pstore_erase(enum pstore_type_id type, u64 id,
-				struct pstore_info *psi)
+static int ramoops_pstore_erase(enum pstore_type_id type, u64 id, u64 count,
+				timespec time, struct pstore_info *psi)
 {
 	struct ramoops_context *cxt = psi->data;
 
diff --git a/include/linux/efi.h b/include/linux/efi.h
index ec45ccd..b19bef5 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -635,6 +635,7 @@ struct efivar_operations {
 	efi_get_variable_t *get_variable;
 	efi_get_next_variable_t *get_next_variable;
 	efi_set_variable_t *set_variable;
+	efi_query_variable_info_t *query_variable_info;
 };
 
 struct efivars {
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index e1461e1..9fd1fc8 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -42,12 +42,14 @@ struct pstore_info {
 	int		(*open)(struct pstore_info *psi);
 	int		(*close)(struct pstore_info *psi);
 	ssize_t		(*read)(u64 *id, enum pstore_type_id *type,
-			struct timespec *time, char **buf,
+			u64 *count, struct timespec *time, char **buf,
 			struct pstore_info *psi);
 	int		(*write)(enum pstore_type_id type,
 			enum kmsg_dump_reason reason, u64 *id,
-			unsigned int part, size_t size, struct pstore_info *psi);
+			unsigned int part, u64 count, size_t size,
+			struct pstore_info *psi);
 	int		(*erase)(enum pstore_type_id type, u64 id,
+			u64 count, struct timespec time,
 			struct pstore_info *psi);
 	void		*data;
 };
-- 1.7.1
--
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