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>

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 9443896..31dc33d 100644 (file)
--- 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;
 }