[PATCH v6 5/5]: mtdoops: refactor as a kmsg_dumper

From: Simon Kagstrom
Date: Wed Oct 14 2009 - 09:43:55 EST

The last messages which happens before a crash might contain interesting
information about the crash. This patch reworks mtdoops using the
kmsg_dumper support instead of a console, which simplifies the code and
also includes the messages before the oops started.

On oops callbacks, the MTD device write is scheduled in a work queue (to
be able to use the regular mtd->write call), while panics call
mtd->panic_write directly. Thus, if panic_on_oops is set, the oops will
be written out during the panic.

A parameter to specify which mtd device to use (number or name), as well
as a flag, writable at runtime, to toggle wheter to dump oopses or only
panics (since oopses can often be handled by regular syslog).

Signed-off-by: Simon Kagstrom <simon.kagstrom@xxxxxxxxxxxxxx>
Reviewed-by: Anders Grafstrom <anders.grafstrom@xxxxxxxxxxxxxx>
---
ChangeLog:
Review comments from Anders GrafstrÃm and myself:
* Fix mtddev and dump_oops parameter permissions (dump_oops is
now runtime-settable)
* Style cleanup here and there
* Add a MTDOOPS_HEADER_SIZE define instead of hardcoding the size
* Fix a double-free on unregistration
* Rework the patch according to patch 4
* Fix output problems for some conditions

drivers/mtd/mtdoops.c | 207 ++++++++++++++++++++-----------------------------
1 files changed, 84 insertions(+), 123 deletions(-)

diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index 2870a11..817265d 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -29,18 +29,31 @@
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/delay.h>
-#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/mtd/mtd.h>
+#include <linux/kmsg_dump.h>

#define MTDOOPS_KERNMSG_MAGIC 0x5d005d00
+#define MTDOOPS_HEADER_SIZE 8

static unsigned long record_size = 4096;
module_param(record_size, ulong, 0400);
MODULE_PARM_DESC(record_size,
"record size for MTD OOPS pages in bytes (default 4096)");

+static char mtddev[80];
+module_param_string(mtddev, mtddev, 80, 0400);
+MODULE_PARM_DESC(mtddev,
+ "name or index number of the MTD device to use");
+
+static int dump_oops = 1;
+module_param(dump_oops, int, 0600);
+MODULE_PARM_DESC(dump_oops,
+ "set to 1 to dump oopses, 0 to only dump panics (default 1)");
+
static struct mtdoops_context {
+ struct kmsg_dumper dump;
+
int mtd_index;
struct work_struct work_erase;
struct work_struct work_write;
@@ -49,14 +62,9 @@ static struct mtdoops_context {
int nextpage;
int nextcount;
unsigned long *oops_page_used;
- char *name;
+ const char *name;

void *oops_buf;
-
- /* writecount and disabling ready are spin lock protected */
- spinlock_t writecount_lock;
- int ready;
- int writecount;
} oops_cxt;

static void mark_page_used(struct mtdoops_context *cxt, int page)
@@ -138,7 +146,6 @@ static void mtdoops_inc_counter(struct mtdoops_context *cxt)

printk(KERN_DEBUG "mtdoops: ready %d, %d (no erase)\n",
cxt->nextpage, cxt->nextcount);
- cxt->ready = 1;
}

/* Scheduled work - when we can't proceed without erasing a block */
@@ -187,7 +194,6 @@ badblock:
if (ret >= 0) {
printk(KERN_DEBUG "mtdoops: ready %d, %d\n",
cxt->nextpage, cxt->nextcount);
- cxt->ready = 1;
return;
}

@@ -205,11 +211,13 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
{
struct mtd_info *mtd = cxt->mtd;
size_t retlen;
+ u32 *hdr;
int ret;

- if (cxt->writecount < record_size)
- memset(cxt->oops_buf + cxt->writecount, 0xff,
- record_size - cxt->writecount);
+ /* Add mtdoops header to the buffer */
+ hdr = cxt->oops_buf;
+ hdr[0] = cxt->nextcount;
+ hdr[1] = MTDOOPS_KERNMSG_MAGIC;

if (panic)
ret = mtd->panic_write(mtd, cxt->nextpage * record_size,
@@ -218,17 +226,15 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
ret = mtd->write(mtd, cxt->nextpage * record_size,
record_size, &retlen, cxt->oops_buf);

- cxt->writecount = 0;
-
if (retlen != record_size || ret < 0)
printk(KERN_ERR "mtdoops: write failure at %ld (%td of %ld written), error %d\n",
cxt->nextpage * record_size, retlen, record_size, ret);
mark_page_used(cxt, cxt->nextpage);
+ memset(cxt->oops_buf, 0xff, record_size);

mtdoops_inc_counter(cxt);
}

-
static void mtdoops_workfunc_write(struct work_struct *work)
{
struct mtdoops_context *cxt =
@@ -247,10 +253,13 @@ static void find_next_position(struct mtdoops_context *cxt)
for (page = 0; page < cxt->oops_pages; page++) {
/* Assume the page is used */
mark_page_used(cxt, page);
- ret = mtd->read(mtd, page * record_size, 8, &retlen, (u_char *) &count[0]);
- if (retlen != 8 || (ret < 0 && ret != -EUCLEAN)) {
- printk(KERN_ERR "mtdoops: read failure at %ld (%td of 8 read), err %d\n",
- page * record_size, retlen, ret);
+ ret = mtd->read(mtd, page * record_size, MTDOOPS_HEADER_SIZE,
+ &retlen, (u_char *) &count[0]);
+ if (retlen != MTDOOPS_HEADER_SIZE ||
+ (ret < 0 && ret != -EUCLEAN)) {
+ printk(KERN_ERR "mtdoops: read failure at %ld (%td of %d read), err %d\n",
+ page * record_size, retlen,
+ MTDOOPS_HEADER_SIZE, ret);
continue;
}

@@ -287,7 +296,6 @@ static void find_next_position(struct mtdoops_context *cxt)
} else {
printk(KERN_DEBUG "mtdoops: ready %d, %d (clean)\n",
cxt->nextpage, cxt->nextcount);
- cxt->ready = 1;
}
return;
}
@@ -298,6 +306,41 @@ static void find_next_position(struct mtdoops_context *cxt)
mtdoops_inc_counter(cxt);
}

+static void mtdoops_do_dump(struct kmsg_dumper *dump,
+ enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
+ const char *s2, unsigned long l2)
+{
+ struct mtdoops_context *cxt = dump->priv;
+ unsigned long s1_start, s2_start;
+ unsigned long l1_cpy, l2_cpy;
+ char *dst;
+
+ /* Only dump oopses if dump_oops is set */
+ if (reason == kmsg_dump_oops && !dump_oops)
+ return;
+
+ dst = cxt->oops_buf + MTDOOPS_HEADER_SIZE; /* Skip the header */
+ l2_cpy = min(l2, record_size - MTDOOPS_HEADER_SIZE);
+ l1_cpy = min(l1, record_size - MTDOOPS_HEADER_SIZE - l2_cpy);
+
+ s2_start = l2 - l2_cpy;
+ s1_start = l1 - l1_cpy;
+
+ memcpy(dst, s1 + s1_start, l1_cpy);
+ memcpy(dst + l1_cpy, s2 + s2_start, l2_cpy);
+
+ /* Panics must be written immediately */
+ if (reason == kmsg_dump_panic) {
+ if (!cxt->mtd->panic_write)
+ printk(KERN_ERR "mtdoops: Cannot write from panic without panic_write\n");
+ else
+ mtdoops_write(cxt, 1);
+ return;
+ }
+
+ /* For other cases, schedule work to write it "nicely" */
+ schedule_work(&cxt->work_write);
+}

static void mtdoops_notify_add(struct mtd_info *mtd)
{
@@ -339,6 +382,8 @@ static void mtdoops_notify_add(struct mtd_info *mtd)

find_next_position(cxt);

+ cxt->dump.dump = mtdoops_do_dump;
+ register_kmsg_dumper(&cxt->dump, cxt);
printk(KERN_INFO "mtdoops: Attached to MTD device %d\n", mtd->index);
}

@@ -349,116 +394,27 @@ static void mtdoops_notify_remove(struct mtd_info *mtd)
if (mtd->index != cxt->mtd_index || cxt->mtd_index < 0)
return;

+ unregister_kmsg_dumper(&cxt->dump);
cxt->mtd = NULL;
flush_scheduled_work();
}

-static void mtdoops_console_sync(void)
-{
- struct mtdoops_context *cxt = &oops_cxt;
- struct mtd_info *mtd = cxt->mtd;
- unsigned long flags;
-
- if (!cxt->ready || !mtd || cxt->writecount == 0)
- return;
-
- /*
- * Once ready is 0 and we've held the lock no further writes to the
- * buffer will happen
- */
- spin_lock_irqsave(&cxt->writecount_lock, flags);
- if (!cxt->ready) {
- spin_unlock_irqrestore(&cxt->writecount_lock, flags);
- return;
- }
- cxt->ready = 0;
- spin_unlock_irqrestore(&cxt->writecount_lock, flags);
-
- if (mtd->panic_write && (in_interrupt() || panic_on_oops))
- /* Interrupt context, we're going to panic so try and log */
- mtdoops_write(cxt, 1);
- else
- schedule_work(&cxt->work_write);
-}
-
-static void
-mtdoops_console_write(struct console *co, const char *s, unsigned int count)
-{
- struct mtdoops_context *cxt = co->data;
- struct mtd_info *mtd = cxt->mtd;
- unsigned long flags;
-
- if (!oops_in_progress) {
- mtdoops_console_sync();
- return;
- }
-
- if (!cxt->ready || !mtd)
- return;
-
- /* Locking on writecount ensures sequential writes to the buffer */
- spin_lock_irqsave(&cxt->writecount_lock, flags);
-
- /* Check ready status didn't change whilst waiting for the lock */
- if (!cxt->ready) {
- spin_unlock_irqrestore(&cxt->writecount_lock, flags);
- return;
- }
-
- if (cxt->writecount == 0) {
- u32 *stamp = cxt->oops_buf;
- *stamp++ = cxt->nextcount;
- *stamp = MTDOOPS_KERNMSG_MAGIC;
- cxt->writecount = 8;
- }
-
- if (count + cxt->writecount > record_size)
- count = record_size - cxt->writecount;
-
- memcpy(cxt->oops_buf + cxt->writecount, s, count);
- cxt->writecount += count;
-
- spin_unlock_irqrestore(&cxt->writecount_lock, flags);
-
- if (cxt->writecount == record_size)
- mtdoops_console_sync();
-}
-
-static int __init mtdoops_console_setup(struct console *co, char *options)
-{
- struct mtdoops_context *cxt = co->data;
-
- if (cxt->mtd_index != -1 || cxt->name)
- return -EBUSY;
- if (options) {
- cxt->name = kstrdup(options, GFP_KERNEL);
- return 0;
- }
- if (co->index == -1)
- return -EINVAL;
-
- cxt->mtd_index = co->index;
- return 0;
-}

static struct mtd_notifier mtdoops_notifier = {
.add = mtdoops_notify_add,
.remove = mtdoops_notify_remove,
};

-static struct console mtdoops_console = {
- .name = "ttyMTD",
- .write = mtdoops_console_write,
- .setup = mtdoops_console_setup,
- .unblank = mtdoops_console_sync,
- .index = -1,
- .data = &oops_cxt,
-};
-
-static int __init mtdoops_console_init(void)
+static int __init mtdoops_init(void)
{
struct mtdoops_context *cxt = &oops_cxt;
+ int mtd_index;
+ char *endp;

+ if (strlen(mtddev) == 0) {
+ printk(KERN_ERR "mtdoops: mtd device must be supplied\n");
+ return -EINVAL;
+ }
if ((record_size & 4095) != 0) {
printk(KERN_ERR "mtdoops: record_size must be a multiple of 4096\n");
return -EINVAL;
@@ -467,36 +423,41 @@ static int __init mtdoops_console_init(void)
printk(KERN_ERR "mtdoops: record_size must be over 4096 bytes\n");
return -EINVAL;
}
+
+ /* Setup the MTD device to use */
+ cxt->name = mtddev;
cxt->mtd_index = -1;
+ mtd_index = simple_strtoul(mtddev, &endp, 0);
+ if (endp != mtddev)
+ cxt->mtd_index = mtd_index;
+
cxt->oops_buf = vmalloc(record_size);
if (!cxt->oops_buf) {
printk(KERN_ERR "mtdoops: failed to allocate buffer workspace\n");
return -ENOMEM;
}
+ memset(cxt->oops_buf, 0xff, record_size);

- spin_lock_init(&cxt->writecount_lock);
INIT_WORK(&cxt->work_erase, mtdoops_workfunc_erase);
INIT_WORK(&cxt->work_write, mtdoops_workfunc_write);

- register_console(&mtdoops_console);
register_mtd_user(&mtdoops_notifier);
return 0;
}

-static void __exit mtdoops_console_exit(void)
+static void __exit mtdoops_exit(void)
{
struct mtdoops_context *cxt = &oops_cxt;

unregister_mtd_user(&mtdoops_notifier);
- unregister_console(&mtdoops_console);
kfree(cxt->name);
vfree(cxt->oops_buf);
vfree(cxt->oops_page_used);
}


-subsys_initcall(mtdoops_console_init);
-module_exit(mtdoops_console_exit);
+module_init(mtdoops_init);
+module_exit(mtdoops_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Richard Purdie <rpurdie@xxxxxxxxxxxxxx>");
--
1.6.0.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/