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Date: Tue, 3 Jul 2012 23:35:47 +0000
From: Seiji Aguchi <seiji.aguchi@....com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
"mikew@...gle.com" <mikew@...gle.com>,
"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
"dzickus@...hat.com" <dzickus@...hat.com>
CC: "dle-develop@...ts.sourceforge.net"
<dle-develop@...ts.sourceforge.net>,
Satoru Moriya <satoru.moriya@....com>
Subject: [RFC][PATCH 2/2] write callback: Check if existing entry is erasable
This patch introduces a following rule checking if an existing entry in NVRAM are erasable to avoid missing
a critical message ,such as panic, before an user check it.
- In case where an existing entry is panic or emergency
- It is not erasable because if panic/emergency event is lost, we have no way to detect
the root cause. We shouldn't overwrite them for any reason.
- In case where an existing entry is oops/shutdown/halt/poweroff
- It is erasable if an error ,panic, emergency or oops, happen in new event.
- Oops is erasable because system may still be running and its message may be saved
into /var/log/messages.
- Also, normal event ,shutdown/halt/poweroff, is erasable because error message is
more important than normal message.
- In case where an existing entry is unknown event
- It is erasable because any event supported by pstore outweighs unsupported events.
Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>
---
drivers/firmware/efivars.c | 48 +++++++++++++++++++++++++++++++++++++++++++-
fs/pstore/platform.c | 4 +-
include/linux/pstore.h | 5 ++++
3 files changed, 54 insertions(+), 3 deletions(-)
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c index 4929254..54d9bc6 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -685,6 +685,45 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
return 0;
}
+
+static bool can_erase_entry(struct efivar_entry *entry, enum kmsg_dump_reason
+ new_reason)
+{
+ int prev_reason = 0;
+ const char *prev_why;
+ bool is_erasable = 0;
+
+ /* Get a reason of previous message */
+ while (1) {
+ prev_why = pstore_get_reason_str(prev_reason);
+ if (!strncmp(entry->var.Data, prev_why, strlen(prev_why)))
+ break;
+ prev_reason++;
+ }
+
+ /* check if exisiting message is erasable */
+
+ switch (prev_reason) {
+ case KMSG_DUMP_PANIC:
+ case KMSG_DUMP_EMERG:
+ /* Never erase panic or emergency message */
+ break;
+ case KMSG_DUMP_OOPS:
+ case KMSG_DUMP_RESTART:
+ case KMSG_DUMP_HALT:
+ case KMSG_DUMP_POWEROFF:
+ /* Can erase if new one is error message */
+ if (new_reason <= KMSG_DUMP_EMERG)
+ is_erasable = 1;
+ break;
+ default:
+ /* Can erase unknown message */
+ is_erasable = 1;
+ }
+
+ return is_erasable;
+}
+
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) @@ -706,7 +745,7 @@ static int efi_pstore_write(enum pstore_type_id type,
efi_name[i] = stub_name[i];
/*
- * Clean up any entries with the same name
+ * Search for erasable entry
*/
list_for_each_entry(entry, &efivars->list, list) { @@ -721,6 +760,13 @@ static int efi_pstore_write(enum pstore_type_id type,
if (entry->var.VariableName[utf16_strlen(efi_name)] == 0)
continue;
+ if (!can_erase_entry(entry, reason)) {
+ /* return without writing new entry */
+ spin_unlock(&efivars->lock);
+ *id = part;
+ return ret;
+ }
+
/* found */
found = entry;
efivars->ops->set_variable(entry->var.VariableName,
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c index 03ce7a9..32715eb 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -68,7 +68,7 @@ void pstore_set_kmsg_bytes(int bytes)
/* Tag each group of saved records with a sequence number */
static int oopscount;
-static const char *get_reason_str(enum kmsg_dump_reason reason)
+const char *pstore_get_reason_str(enum kmsg_dump_reason reason)
{
switch (reason) {
case KMSG_DUMP_PANIC:
@@ -104,7 +104,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
int is_locked = 0;
int ret;
- why = get_reason_str(reason);
+ why = pstore_get_reason_str(reason);
if (in_nmi()) {
is_locked = spin_trylock(&psinfo->buf_lock); diff --git a/include/linux/pstore.h b/include/linux/pstore.h index e1461e1..e9347e9 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -54,12 +54,17 @@ struct pstore_info {
#ifdef CONFIG_PSTORE
extern int pstore_register(struct pstore_info *);
+extern const char *pstore_get_reason_str(enum kmsg_dump_reason reason);
#else
static inline int
pstore_register(struct pstore_info *psi) {
return -ENODEV;
}
+static const char *pstore_get_reason_str(enum kmsg_dump_reason reason)
+{
+ return NULL;
+}
#endif
#endif /*_LINUX_PSTORE_H*/
--
1.7.1
--
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