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Subject[PATCH/RFC v5 2/5]: mtdoops: Keep track of used/unused mtdoops pages in an array
This patch makes mtdoops keep track of used/unused pages in an array
instead of scanning the flash after a write. The advantage with this
approach is that it avoids calling mtd->read on a panic, which is not
possible for all mtd drivers.

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
---
drivers/mtd/mtdoops.c | 72 ++++++++++++++++++++++++++++++++++++------------
1 files changed, 54 insertions(+), 18 deletions(-)
diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index c785e1a..6af340e 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -44,6 +44,7 @@ static struct mtdoops_context {
int oops_pages;
int nextpage;
int nextcount;
+ u32 *oops_page_used;
char *name;

void *oops_buf;
@@ -54,18 +55,47 @@ static struct mtdoops_context {
int writecount;
} oops_cxt;

+static void mark_page_used(struct mtdoops_context *cxt, int page)
+{
+ u32 *p = cxt->oops_page_used + page / (8 * sizeof(u32));
+ u32 idx = page % (8 * sizeof(u32));
+
+ *p = *p | (1 << idx);
+}
+
+static void mark_page_unused(struct mtdoops_context *cxt, int page)
+{
+ u32 *p = cxt->oops_page_used + page / (8 * sizeof(u32));
+ u32 idx = page % (8 * sizeof(u32));
+
+ *p = *p & ~(1 << idx);
+}
+
+static int page_is_used(struct mtdoops_context *cxt, int page)
+{
+ u32 *p = cxt->oops_page_used + page / (8 * sizeof(u32));
+ u32 idx = page % (8 * sizeof(u32));
+
+ return *p & (1 << idx);
+}
+
static void mtdoops_erase_callback(struct erase_info *done)
{
wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
wake_up(wait_q);
}

-static int mtdoops_erase_block(struct mtd_info *mtd, int offset)
+static int mtdoops_erase_block(struct mtdoops_context *cxt, int offset)
{
+ struct mtd_info *mtd = cxt->mtd;
+ u32 start_page_offset = mtd_div_by_eb(offset, mtd) * mtd->erasesize;
+ u32 start_page = start_page_offset / OOPS_PAGE_SIZE;
+ u32 erase_pages = mtd->erasesize / OOPS_PAGE_SIZE;
struct erase_info erase;
DECLARE_WAITQUEUE(wait, current);
wait_queue_head_t wait_q;
int ret;
+ int page;

init_waitqueue_head(&wait_q);
erase.mtd = mtd;
@@ -90,16 +120,15 @@ static int mtdoops_erase_block(struct mtd_info *mtd, int offset)
schedule(); /* Wait for erase to finish. */
remove_wait_queue(&wait_q, &wait);

+ /* Mark pages as unused */
+ for (page = start_page; page < start_page + erase_pages; page++)
+ mark_page_unused(cxt, page);
+
return 0;
}

static void mtdoops_inc_counter(struct mtdoops_context *cxt)
{
- struct mtd_info *mtd = cxt->mtd;
- size_t retlen;
- u32 count;
- int ret;
-
cxt->nextpage++;
if (cxt->nextpage >= cxt->oops_pages)
cxt->nextpage = 0;
@@ -107,17 +136,7 @@ static void mtdoops_inc_counter(struct mtdoops_context *cxt)
if (cxt->nextcount == 0xffffffff)
cxt->nextcount = 0;

- ret = mtd->read(mtd, cxt->nextpage * OOPS_PAGE_SIZE, 4,
- &retlen, (u_char *) &count);
- if (retlen != 4 || (ret < 0 && ret != -EUCLEAN)) {
- printk(KERN_ERR "mtdoops: read failure at %d (%td of 4 read), err %d\n",
- cxt->nextpage * OOPS_PAGE_SIZE, retlen, ret);
- schedule_work(&cxt->work_erase);
- return;
- }
-
- /* See if we need to erase the next block */
- if (count != 0xffffffff) {
+ if (page_is_used(cxt, cxt->nextpage)) {
schedule_work(&cxt->work_erase);
return;
}
@@ -168,7 +187,7 @@ badblock:
}

for (j = 0, ret = -1; (j < 3) && (ret < 0); j++)
- ret = mtdoops_erase_block(mtd, cxt->nextpage * OOPS_PAGE_SIZE);
+ ret = mtdoops_erase_block(cxt, cxt->nextpage * OOPS_PAGE_SIZE);

if (ret >= 0) {
printk(KERN_DEBUG "mtdoops: ready %d, %d\n",
@@ -209,6 +228,7 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
if (retlen != OOPS_PAGE_SIZE || ret < 0)
printk(KERN_ERR "mtdoops: write failure at %d (%td of %d written), error %d\n",
cxt->nextpage * OOPS_PAGE_SIZE, retlen, OOPS_PAGE_SIZE, ret);
+ mark_page_used(cxt, cxt->nextpage);

mtdoops_inc_counter(cxt);
}
@@ -230,6 +250,8 @@ static void find_next_position(struct mtdoops_context *cxt)
size_t retlen;

for (page = 0; page < cxt->oops_pages; page++) {
+ /* Assume the page is used */
+ mark_page_used(cxt, page);
ret = mtd->read(mtd, page * OOPS_PAGE_SIZE, 8, &retlen, (u_char *) &count[0]);
if (retlen != 8 || (ret < 0 && ret != -EUCLEAN)) {
printk(KERN_ERR "mtdoops: read failure at %d (%td of 8 read), err %d\n",
@@ -237,6 +259,8 @@ static void find_next_position(struct mtdoops_context *cxt)
continue;
}

+ if (count[0] == 0xffffffff && count[1] == 0xffffffff)
+ mark_page_unused(cxt, page);
if (count[0] == 0xffffffff)
continue;
if (count[1] != MTDOOPS_KERNMSG_MAGIC) {
@@ -283,6 +307,9 @@ static void find_next_position(struct mtdoops_context *cxt)
static void mtdoops_notify_add(struct mtd_info *mtd)
{
struct mtdoops_context *cxt = &oops_cxt;
+ u64 mtdoops_pages = mtd->size;
+
+ do_div(mtdoops_pages, OOPS_PAGE_SIZE);

if (cxt->name && !strcmp(mtd->name, cxt->name))
cxt->mtd_index = mtd->index;
@@ -302,6 +329,13 @@ static void mtdoops_notify_add(struct mtd_info *mtd)
return;
}

+ /* oops_page_used is a bit field */
+ cxt->oops_page_used = vmalloc(DIV_ROUND_UP(mtdoops_pages,
+ 8 * sizeof(u32)));
+ if (!cxt->oops_page_used) {
+ printk(KERN_ERR "Could not allocate page array\n");
+ return;
+ }
cxt->mtd = mtd;
if (mtd->size > INT_MAX)
cxt->oops_pages = INT_MAX / OOPS_PAGE_SIZE;
@@ -454,6 +488,8 @@ static void __exit mtdoops_console_exit(void)
unregister_console(&mtdoops_console);
kfree(cxt->name);
vfree(cxt->oops_buf);
+ if (cxt->oops_page_used)
+ vfree(cxt->oops_page_used);
}


--
1.6.0.4


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