dm dust: add limited write failure mode

Add a limited write failure mode which allows a write to a block to fail
a specified amount of times, prior to remapping.  The "addbadblock"
message is extended to allow specifying the limited number of times a
write fails.

Example: add bad block on block 60, with 5 write failures:
  dmsetup message 0 dust1 addbadblock 60 5

The write failure counter will be printed for newly added bad blocks.

Signed-off-by: Bryan Gurney <bgurney@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-dust.c b/drivers/md/dm-dust.c
index 9a926a7..eb37584 100644 (file)
--- a/drivers/md/dm-dust.c
+++ b/drivers/md/dm-dust.c
@@ -17,6 +17,7 @@
 struct badblock {
        struct rb_node node;
        sector_t bb;
+       unsigned char wr_fail_cnt;
 };
 
 struct dust_device {
@@ -101,7 +102,8 @@ static int dust_remove_block(struct dust_device *dd, unsigned long long block)
        return 0;
 }
 
-static int dust_add_block(struct dust_device *dd, unsigned long long block)
+static int dust_add_block(struct dust_device *dd, unsigned long long block,
+                         unsigned char wr_fail_cnt)
 {
        struct badblock *bblock;
        unsigned long flags;
@@ -115,6 +117,7 @@ static int dust_add_block(struct dust_device *dd, unsigned long long block)
 
        spin_lock_irqsave(&dd->dust_lock, flags);
        bblock->bb = block;
+       bblock->wr_fail_cnt = wr_fail_cnt;
        if (!dust_rb_insert(&dd->badblocklist, bblock)) {
                if (!dd->quiet_mode) {
                        DMERR("%s: block %llu already in badblocklist",
@@ -126,8 +129,10 @@ static int dust_add_block(struct dust_device *dd, unsigned long long block)
        }
 
        dd->badblock_count++;
-       if (!dd->quiet_mode)
-               DMINFO("%s: badblock added at block %llu", __func__, block);
+       if (!dd->quiet_mode) {
+               DMINFO("%s: badblock added at block %llu with write fail count %hhu",
+                      __func__, block, wr_fail_cnt);
+       }
        spin_unlock_irqrestore(&dd->dust_lock, flags);
 
        return 0;
@@ -175,10 +180,15 @@ static int dust_map_read(struct dust_device *dd, sector_t thisblock,
        return r;
 }
 
-static void __dust_map_write(struct dust_device *dd, sector_t thisblock)
+static int __dust_map_write(struct dust_device *dd, sector_t thisblock)
 {
        struct badblock *bblk = dust_rb_search(&dd->badblocklist, thisblock);
 
+       if (bblk && bblk->wr_fail_cnt > 0) {
+               bblk->wr_fail_cnt--;
+               return DM_MAPIO_KILL;
+       }
+
        if (bblk) {
                rb_erase(&bblk->node, &dd->badblocklist);
                dd->badblock_count--;
@@ -189,21 +199,24 @@ static void __dust_map_write(struct dust_device *dd, sector_t thisblock)
                               (unsigned long long)thisblock);
                }
        }
+
+       return DM_MAPIO_REMAPPED;
 }
 
 static int dust_map_write(struct dust_device *dd, sector_t thisblock,
                          bool fail_read_on_bb)
 {
        unsigned long flags;
+       int ret = DM_MAPIO_REMAPPED;
 
        if (fail_read_on_bb) {
                thisblock >>= dd->sect_per_block_shift;
                spin_lock_irqsave(&dd->dust_lock, flags);
-               __dust_map_write(dd, thisblock);
+               ret = __dust_map_write(dd, thisblock);
                spin_unlock_irqrestore(&dd->dust_lock, flags);
        }
 
-       return DM_MAPIO_REMAPPED;
+       return ret;
 }
 
 static int dust_map(struct dm_target *ti, struct bio *bio)
@@ -377,6 +390,8 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
        bool invalid_msg = false;
        int r = -EINVAL;
        unsigned long long tmp, block;
+       unsigned char wr_fail_cnt;
+       unsigned int tmp_ui;
        unsigned long flags;
        char dummy;
 
@@ -422,7 +437,7 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
                }
 
                if (!strcasecmp(argv[0], "addbadblock"))
-                       r = dust_add_block(dd, block);
+                       r = dust_add_block(dd, block, 0);
                else if (!strcasecmp(argv[0], "removebadblock"))
                        r = dust_remove_block(dd, block);
                else if (!strcasecmp(argv[0], "queryblock"))
@@ -430,6 +445,30 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
                else
                        invalid_msg = true;
 
+       } else if (argc == 3) {
+               if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1)
+                       return r;
+
+               if (sscanf(argv[2], "%u%c", &tmp_ui, &dummy) != 1)
+                       return r;
+
+               block = tmp;
+               if (tmp_ui > 255) {
+                       DMERR("selected write fail count out of range");
+                       return r;
+               }
+               wr_fail_cnt = tmp_ui;
+               sector_div(size, dd->sect_per_block);
+               if (block > size) {
+                       DMERR("selected block value out of range");
+                       return r;
+               }
+
+               if (!strcasecmp(argv[0], "addbadblock"))
+                       r = dust_add_block(dd, block, wr_fail_cnt);
+               else
+                       invalid_msg = true;
+
        } else
                DMERR("invalid number of arguments '%d'", argc);