dm raid1: split touched state into two

Split the variable "touched" into two, "touched_dirtied" and
"touched_cleaned", set when some region was dirtied or cleaned.

This will be used to optimize flushes.

After a transition from "dirty" to "clean" state we don't have flush hardware
cache on the log device. After a transition from "clean" to "dirty" the cache
must be flushed.

Before a transition from "clean" to "dirty" state we don't have to flush all
the raid legs. Before a transition from "dirty" to "clean" we must flush all
the legs to make sure that they are really in sync.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 9443896ede07..31dc33df95c7 100644
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -208,7 +208,8 @@ struct log_header {
 
 struct log_c {
         struct dm_target *ti;
-        int touched;
+        int touched_dirtied;
+        int touched_cleaned;
         uint32_t region_size;
         unsigned int region_count;
         region_t sync_count;
@@ -253,14 +254,14 @@ static inline void log_set_bit(struct log_c *l,
                                uint32_t *bs, unsigned bit)
 {
         ext2_set_bit(bit, (unsigned long *) bs);
-        l->touched = 1;
+        l->touched_cleaned = 1;
 }
 
 static inline void log_clear_bit(struct log_c *l,
                                  uint32_t *bs, unsigned bit)
 {
         ext2_clear_bit(bit, (unsigned long *) bs);
-        l->touched = 1;
+        l->touched_dirtied = 1;
 }
 
 /*----------------------------------------------------------------
@@ -378,7 +379,8 @@ static int create_log_context(struct dm_dirty_log *log, struct dm_target *ti,
         }
 
         lc->ti = ti;
-        lc->touched = 0;
+        lc->touched_dirtied = 0;
+        lc->touched_cleaned = 0;
         lc->region_size = region_size;
         lc->region_count = region_count;
         lc->sync = sync;
@@ -660,14 +662,16 @@ static int disk_flush(struct dm_dirty_log *log)
         struct log_c *lc = (struct log_c *) log->context;
 
         /* only write if the log has changed */
-        if (!lc->touched)
+        if (!lc->touched_cleaned && !lc->touched_dirtied)
                 return 0;
 
         r = rw_header(lc, WRITE);
         if (r)
                 fail_log_device(lc);
-        else
-                lc->touched = 0;
+        else {
+                lc->touched_dirtied = 0;
+                lc->touched_cleaned = 0;
+        }
 
         return r;
 }