mtd: mtdoops: keep track of used/unused 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>
Reviewed-by: Anders Grafstrom <anders.grafstrom@netinsight.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index c383add..06c5382 100644 (file)
--- 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;
+       unsigned long *oops_page_used;
        char *name;
 
        void *oops_buf;
@@ -54,18 +55,38 @@ static struct mtdoops_context {
        int writecount;
 } oops_cxt;
 
+static void mark_page_used(struct mtdoops_context *cxt, int page)
+{
+       set_bit(page, cxt->oops_page_used);
+}
+
+static void mark_page_unused(struct mtdoops_context *cxt, int page)
+{
+       clear_bit(page, cxt->oops_page_used);
+}
+
+static int page_is_used(struct mtdoops_context *cxt, int page)
+{
+       return test_bit(page, cxt->oops_page_used);
+}
+
 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 +111,15 @@ 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 +127,7 @@ 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 +178,7 @@ 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 +219,7 @@ 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 +241,8 @@ 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 +250,8 @@ static void find_next_position(struct mtdoops_context *cxt)
                        continue;
                }
 
+               if (count[0] == 0xffffffff && count[1] == 0xffffffff)
+                       mark_page_unused(cxt, page);
                if (count[1] != MTDOOPS_KERNMSG_MAGIC)
                        continue;
                if (count[0] == 0xffffffff)
@@ -273,6 +288,9 @@ 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;
@@ -292,6 +310,13 @@ 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,
+                       BITS_PER_LONG));
+       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;
@@ -444,6 +469,7 @@ static void __exit mtdoops_console_exit(void)
        unregister_console(&mtdoops_console);
        kfree(cxt->name);
        vfree(cxt->oops_buf);
+       vfree(cxt->oops_page_used);
 }