Add the ability to set the era counter maintained by the dm-cache era
policy shim to an arbitrary 32-bit value, to allow era rollback after
the underlying device is restored from a snapshot.
Signed-off-by: Morgan Mears <mmears@xxxxxxxxxx>
---
drivers/md/dm-cache-policy-era.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/drivers/md/dm-cache-policy-era.c b/drivers/md/dm-cache-policy-era.c index d4fc0b0..c4cf2ba 100644
--- a/drivers/md/dm-cache-policy-era.c
+++ b/drivers/md/dm-cache-policy-era.c
@@ -155,6 +155,26 @@ static int incr_era_counter(struct era_policy *era, const char *curr_era_str,
return r;
}
+static int set_era_counter(struct era_policy *era, const char *new_era_str,
+ era_match_fn_t dummy)
+{
+ era_t new_era_counter;
+
+ /*
+ * Set the era counter to a user-provided value, as long as it is
+ * in range.
+ */
+
+ if (kstrtou32(new_era_str, 10, &new_era_counter))
+ return -EINVAL;
+ if (new_era_counter > ERA_MAX_ERA)
+ return -EOVERFLOW;
+ era->era_counter = new_era_counter;
+ smp_wmb();
+
+ return 0;
+}
+
static void *era_cblock_to_hint(struct shim_walk_map_ctx *ctx,
dm_cblock_t cblock, dm_oblock_t oblock)
{
@@ -404,6 +424,7 @@ static int era_set_config_value(struct dm_cache_policy *p, const char *key,
struct era_policy *era = to_era_policy(p);
struct config_value_handler *vh, value_handlers[] = {
{ "increment_era_counter", incr_era_counter, NULL },
+ { "set_era_counter", set_era_counter, NULL },
{ "unmap_blocks_from_later_eras", cond_unmap_by_era, era_is_gt_value },
{ "unmap_blocks_from_this_era_and_later", cond_unmap_by_era, era_is_gte_value },
{ "unmap_blocks_from_this_era_and_earlier", cond_unmap_by_era, era_is_lte_value },
--
--
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