This is an enabler patch for cluster mirroring.
Mirroring can be used in a cluster if the log is cluster-aware.
However, to properly handle write/recovery conflicts from different
machines we must mark and clear regions that are in the RH_NOSYNC state.
This patch adds that capability. However, it is possible to get a
situation where a "double mark" happens on a region:
1) mark region in rh_inc
2) rh_dec decrements pending count
3) mark before clear (rh_inc runs before rh_update_states)
The double mark isn't really a problem and is already handled by the
currently logging implementations... but it isn't something that has
happened before.
Comments welcome,
brassow
Index: linux-2.6.22-rc1-mm1/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.22-rc1-mm1.orig/drivers/md/dm-raid1.c
+++ linux-2.6.22-rc1-mm1/drivers/md/dm-raid1.c
@@ -425,8 +425,8 @@ static void rh_update_states(struct regi
* any more locking.
*/
list_for_each_entry_safe (reg, next, &recovered, list) {
- rh->log->type->clear_region(rh->log, reg->key);
complete_resync_work(reg, 1);
+ rh->log->type->clear_region(rh->log, reg->key);
mempool_free(reg, rh->region_pool);
}
@@ -448,13 +448,14 @@ static void rh_update_states(struct regi
static void rh_inc(struct region_hash *rh, region_t region)
{
+ int r;
struct region *reg;
read_lock(&rh->hash_lock);
reg = __rh_find(rh, region);
spin_lock_irq(&rh->region_lock);
- atomic_inc(®->pending);
+ r = atomic_inc_return(®->pending);
if (reg->state == RH_CLEAN) {
reg->state = RH_DIRTY;
@@ -462,6 +463,11 @@ static void rh_inc(struct region_hash *r
spin_unlock_irq(&rh->region_lock);
rh->log->type->mark_region(rh->log, reg->key);
+ } else if ((reg->state == RH_NOSYNC) && (r == 1)) {
+ list_del_init(®->list); /* take off the clean list */
+ spin_unlock_irq(&rh->region_lock);
+
+ rh->log->type->mark_region(rh->log, reg->key);
} else
spin_unlock_irq(&rh->region_lock);
@@ -493,20 +499,16 @@ static void rh_dec(struct region_hash *r
* There is no pending I/O for this region.
* We can move the region to corresponding list for next action.
* At this point, the region is not yet connected to any list.
- *
- * If the state is RH_NOSYNC, the region should be kept off
- * from clean list.
- * The hash entry for RH_NOSYNC will remain in memory
- * until the region is recovered or the map is reloaded.
*/
- /* do nothing for RH_NOSYNC */
if (reg->state == RH_RECOVERING) {
list_add_tail(®->list, &rh->quiesced_regions);
} else if (reg->state == RH_DIRTY) {
reg->state = RH_CLEAN;
list_add(®->list, &rh->clean_regions);
- }
+ } else if (reg->state == RH_NOSYNC)
+ list_add(®->list, &rh->clean_regions);
+
should_wake = 1;
}
spin_unlock_irqrestore(&rh->region_lock, flags);
Index: linux-2.6.22-rc1-mm1/drivers/md/dm-log.c
===================================================================
--- linux-2.6.22-rc1-mm1.orig/drivers/md/dm-log.c
+++ linux-2.6.22-rc1-mm1/drivers/md/dm-log.c
@@ -579,7 +579,10 @@ static void core_mark_region(struct dirt
static void core_clear_region(struct dirty_log *log, region_t region)
{
struct log_c *lc = (struct log_c *) log->context;
- log_set_bit(lc, lc->clean_bits, region);
+
+ /* Only clear the region if it is also in sync */
+ if (log_test_bit(lc->sync_bits, region))
+ log_set_bit(lc, lc->clean_bits, region);
}
static int core_get_resync_work(struct dirty_log *log, region_t *region)
Index: linux-2.6.22-rc1-mm1/drivers/md/dm-log.h
===================================================================
--- linux-2.6.22-rc1-mm1.orig/drivers/md/dm-log.h
+++ linux-2.6.22-rc1-mm1/drivers/md/dm-log.h
@@ -72,6 +72,9 @@ struct dirty_log_type {
* block, though for performance reasons blocking should
* be extremely rare (eg, allocating another chunk of
* memory for some reason).
+ *
+ * clear_region will only clear the region if it
+ * is also in-sync.
*/
void (*mark_region)(struct dirty_log *log, region_t region);
void (*clear_region)(struct dirty_log *log, region_t region);
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
