pstore: enhancement for pstore write interface

pstore: enhancement for pstore write interface

[Chen Gong]

[PATCH 1/2] pstore: change the purpose of return value for pstore
[PATCH 2/2] pstore: update the policy of the UEFI-based backend

These two patches are for pstore write interface enhancement.
The 1st one updates the original write interface to return a valid
write result. The 2nd one updates the UEFI-based pstore backend
write policy. For the 2nd one, though Matthew current design is to
reduce UEFI variable space usage, but I think it is still too strict
as a log storage. :-)

[PATCH 1/2] pstore: change the purpose of return value for pstore write operation

[Chen Gong]

currently pstore write interface employs record id as return
value, but it is not enough because it can't tell caller if
the write operation is successful. To get this purpose, change
the return value from record id to new meaning.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
---
 drivers/acpi/apei/erst.c   |   10 ++++++----
 drivers/firmware/efivars.c |   17 +++++++++--------
 fs/pstore/platform.c       |   11 ++++++-----
 include/linux/pstore.h     |    4 ++--
 4 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
index 2ca59dc..d498cd7 100644
--- a/drivers/acpi/apei/erst.c
+++ b/drivers/acpi/apei/erst.c
@@ -933,7 +933,7 @@ 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,
 			   struct timespec *time, struct pstore_info *psi);
-static u64 erst_writer(enum pstore_type_id type, unsigned int part,
+static int erst_writer(enum pstore_type_id type, u64 *id, unsigned int part,
 		       size_t size, struct pstore_info *psi);
 static int erst_clearer(enum pstore_type_id type, u64 id,
 			struct pstore_info *psi);
@@ -1040,11 +1040,12 @@ out:
 	return (rc < 0) ? rc : (len - sizeof(*rcd));
 }
 
-static u64 erst_writer(enum pstore_type_id type, unsigned int part,
+static int erst_writer(enum pstore_type_id type, u64 *id, unsigned int part,
 		       size_t size, struct pstore_info *psi)
 {
 	struct cper_pstore_record *rcd = (struct cper_pstore_record *)
 					(erst_info.buf - sizeof(*rcd));
+	int ret;
 
 	memset(rcd, 0, sizeof(*rcd));
 	memcpy(rcd->hdr.signature, CPER_SIG_RECORD, CPER_SIG_SIZE);
@@ -1079,9 +1080,10 @@ static u64 erst_writer(enum pstore_type_id type, unsigned int part,
 	}
 	rcd->sec_hdr.section_severity = CPER_SEV_FATAL;
 
-	erst_write(&rcd->hdr);
+	ret = erst_write(&rcd->hdr);
+	*id = rcd->hdr.record_id;
 
-	return rcd->hdr.record_id;
+	return ret;
 }
 
 static int erst_clearer(enum pstore_type_id type, u64 id,
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index eb80b54..fe07673 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -490,8 +490,8 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 	return 0;
 }
 
-static u64 efi_pstore_write(enum pstore_type_id type, unsigned int part,
-			    size_t size, struct pstore_info *psi)
+static int efi_pstore_write(enum pstore_type_id type, u64 *id,
+		unsigned int part, size_t size, struct pstore_info *psi)
 {
 	char name[DUMP_NAME_LEN];
 	char stub_name[DUMP_NAME_LEN];
@@ -499,7 +499,7 @@ static u64 efi_pstore_write(enum pstore_type_id type, unsigned int part,
 	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
 	struct efivars *efivars = psi->data;
 	struct efivar_entry *entry, *found = NULL;
-	int i;
+	int i, ret = 0;
 
 	sprintf(stub_name, "dump-type%u-%u-", type, part);
 	sprintf(name, "%s%lu", stub_name, get_seconds());
@@ -548,18 +548,19 @@ static u64 efi_pstore_write(enum pstore_type_id type, unsigned int part,
 		efivar_unregister(found);
 
 	if (size)
-		efivar_create_sysfs_entry(efivars,
+		ret = efivar_create_sysfs_entry(efivars,
 					  utf16_strsize(efi_name,
 							DUMP_NAME_LEN * 2),
 					  efi_name, &vendor);
 
-	return part;
+	*id = part;
+	return ret;
 };
 
 static int efi_pstore_erase(enum pstore_type_id type, u64 id,
 			    struct pstore_info *psi)
 {
-	efi_pstore_write(type, id, 0, psi);
+	efi_pstore_write(type, &id, (unsigned int)id, 0, psi);
 
 	return 0;
 }
@@ -580,8 +581,8 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 	return -1;
 }
 
-static u64 efi_pstore_write(enum pstore_type_id type, unsigned int part,
-			    size_t size, struct pstore_info *psi)
+static int efi_pstore_write(enum pstore_type_id type, u64 *id,
+		unsigned int part, size_t size, struct pstore_info *psi)
 {
 	return 0;
 }
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index c5300ec..633c0e5 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -69,7 +69,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 	unsigned long	size, total = 0;
 	char		*dst, *why;
 	u64		id;
-	int		hsize;
+	int		hsize, ret;
 	unsigned int	part = 1;
 
 	if (reason < ARRAY_SIZE(reason_str))
@@ -97,9 +97,9 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		memcpy(dst, s1 + s1_start, l1_cpy);
 		memcpy(dst + l1_cpy, s2 + s2_start, l2_cpy);
 
-		id = psinfo->write(PSTORE_TYPE_DMESG, part,
+		ret = psinfo->write(PSTORE_TYPE_DMESG, &id, part,
 				   hsize + l1_cpy + l2_cpy, psinfo);
-		if (reason == KMSG_DUMP_OOPS && pstore_is_mounted())
+		if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
 			pstore_mkfile(PSTORE_TYPE_DMESG, psinfo->name, id,
 				      psinfo->buf, hsize + l1_cpy + l2_cpy,
 				      CURRENT_TIME, psinfo);
@@ -198,6 +198,7 @@ out:
 int pstore_write(enum pstore_type_id type, char *buf, size_t size)
 {
 	u64	id;
+	int	ret;
 
 	if (!psinfo)
 		return -ENODEV;
@@ -207,8 +208,8 @@ int pstore_write(enum pstore_type_id type, char *buf, size_t size)
 
 	mutex_lock(&psinfo->buf_mutex);
 	memcpy(psinfo->buf, buf, size);
-	id = psinfo->write(type, 0, size, psinfo);
-	if (pstore_is_mounted())
+	ret = psinfo->write(type, &id, 0, size, psinfo);
+	if (ret == 0 && pstore_is_mounted())
 		pstore_mkfile(PSTORE_TYPE_DMESG, psinfo->name, id, psinfo->buf,
 			      size, CURRENT_TIME, psinfo);
 	mutex_unlock(&psinfo->buf_mutex);
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index cc03bbf..976a3db 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -39,8 +39,8 @@ struct pstore_info {
 	int		(*close)(struct pstore_info *psi);
 	ssize_t		(*read)(u64 *id, enum pstore_type_id *type,
 			struct timespec *time, struct pstore_info *psi);
-	u64		(*write)(enum pstore_type_id type, unsigned int part,
-			size_t size, struct pstore_info *psi);
+	int		(*write)(enum pstore_type_id type, u64 *id,
+			unsigned int part, size_t size, struct pstore_info *psi);
 	int		(*erase)(enum pstore_type_id type, u64 id,
 			struct pstore_info *psi);
 	void		*data;
-- 
1.7.7.rc0.70.g82660

[PATCH 2/2] pstore: update the policy of the UEFI-based backend

[Chen Gong]

UEFI-based backend only employs one group records to save
dumped information, which means new log will overwrite old one.
It doesn't make sense because in fact the older log is nearer
to the truth. Update its policy to comply with ERST logic.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
---
 drivers/firmware/efivars.c |  108 +++++++++++++++++++++++++------------------
 1 files changed, 63 insertions(+), 45 deletions(-)

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index fe07673..f33302d 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -463,8 +463,7 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 	struct efivars *efivars = psi->data;
 	char name[DUMP_NAME_LEN];
 	int i;
-	unsigned int part, size;
-	unsigned long time;
+	unsigned int size;
 
 	while (&efivars->walk_entry->list != &efivars->list) {
 		if (!efi_guidcmp(efivars->walk_entry->var.VendorGuid,
@@ -472,9 +471,8 @@ 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) {
-				*id = part;
-				timespec->tv_sec = time;
+			if (sscanf(name, "dump-type%u-%llu", type, id) == 2) {
+				timespec->tv_sec = *id;
 				timespec->tv_nsec = 0;
 				get_var_data_locked(efivars, &efivars->walk_entry->var);
 				size = efivars->walk_entry->var.DataSize;
@@ -494,24 +492,59 @@ static int efi_pstore_write(enum pstore_type_id type, u64 *id,
 		unsigned int part, 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;
+	efi_status_t status = EFI_NOT_FOUND;
+	int i, ret;
+	unsigned int time;
+
+	if (size == 0)
+		return -1;
+
+	time = get_seconds();
+	/* assume time + part = monotonic increasing */
+	*id = time + part;
+	sprintf(name, "dump-type%u-%llu", type, *id);
+
+	spin_lock(&efivars->lock);
+
+	for (i = 0; i < DUMP_NAME_LEN; i++)
+		efi_name[i] = name[i];
+
+	status = efivars->ops->set_variable(efi_name, &vendor,
+		PSTORE_EFI_ATTRIBUTES, size, psi->buf);
+	spin_unlock(&efivars->lock);
+
+	if (status != EFI_SUCCESS) {
+		printk(KERN_WARNING "efivars: set_variable() failed: "
+			"status=%lx\n", status);
+		return -EIO;
+	}
+
+	ret = efivar_create_sysfs_entry(efivars,
+		utf16_strsize(efi_name, DUMP_NAME_LEN * 2), efi_name, &vendor);
+
+	return ret;
+};
+
+static int efi_pstore_erase(enum pstore_type_id type, u64 id,
+			    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;
-
-	sprintf(stub_name, "dump-type%u-%u-", type, part);
-	sprintf(name, "%s%lu", stub_name, get_seconds());
+	efi_status_t status = EFI_NOT_FOUND;
+	int i;
 
-	spin_lock(&efivars->lock);
+	sprintf(stub_name, "dump-type%u-%llu", type, id);
 
 	for (i = 0; i < DUMP_NAME_LEN; i++)
 		efi_name[i] = stub_name[i];
 
-	/*
-	 * Clean up any entries with the same name
-	 */
+	spin_lock(&efivars->lock);
 
 	list_for_each_entry(entry, &efivars->list, list) {
 		get_var_data_locked(efivars, &entry->var);
@@ -521,46 +554,31 @@ static int efi_pstore_write(enum pstore_type_id type, u64 *id,
 		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;
-		efivars->ops->set_variable(entry->var.VariableName,
-					   &entry->var.VendorGuid,
-					   PSTORE_EFI_ATTRIBUTES,
-					   0, NULL);
+		break;
 	}
 
-	if (found)
-		list_del(&found->list);
-
-	for (i = 0; i < DUMP_NAME_LEN; i++)
-		efi_name[i] = name[i];
+	if (!found) {
+		spin_unlock(&efivars->lock);
+		return -EINVAL;
+	}
 
-	efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
-				   size, psi->buf);
+	status = efivars->ops->set_variable(entry->var.VariableName,
+				   &entry->var.VendorGuid,
+				   PSTORE_EFI_ATTRIBUTES,
+				   0, NULL);
+	if (status != EFI_SUCCESS) {
+		printk(KERN_WARNING "efivars: set_variable() failed: "
+			"status=%lx\n", status);
+		spin_unlock(&efivars->lock);
+		return -EIO;
+	}
 
+	list_del(&found->list);
 	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, &id, (unsigned int)id, 0, psi);
+	efivar_unregister(found);
 
 	return 0;
 }
-- 
1.7.7.rc0.70.g82660

Re: [PATCH 2/2] pstore: update the policy of the UEFI-based backend

[Matthew Garrett]

I don't think this is reasonable. EFI variable space is a shared 
resource. We have no idea what the failure modes of entirely filling it 
would be. If we're going to store multiple records then at the very 
least we need to use QueryVariableInfo() to identify how much space 
there is left, and if it's a 2.1 or later system then we ideally need to 
store these as EFI_VARIABLE_HARDWARE_ERROR_RECORD rather than just plain 
runtime variables. The reason the current implementation doesn't do that 
is that there's still hardware floating around that implements EFI 1.10 
rather than UEFI 2.0

-- 
Matthew Garrett | mjg59@srcf.ucam.org