dm log: add flush_header function

Introduce flush_header and use it to flush the log device.

Note that we don't have to flush if all the regions transition
from "dirty" to "clean" state.

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

1 files changed, 22 insertions, 1 deletions

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 31dc33df95c7..6b23631db5b5 100644
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -288,6 +288,19 @@ static int rw_header(struct log_c *lc, int rw)
         return dm_io(&lc->io_req, 1, &lc->header_location, NULL);
 }
 
+static int flush_header(struct log_c *lc)
+{
+        struct dm_io_region null_location = {
+                .bdev = lc->header_location.bdev,
+                .sector = 0,
+                .count = 0,
+        };
+
+        lc->io_req.bi_rw = WRITE_BARRIER;
+
+        return dm_io(&lc->io_req, 1, &null_location, NULL);
+}
+
 static int read_header(struct log_c *log)
 {
         int r;
@@ -616,6 +629,8 @@ static int disk_resume(struct dm_dirty_log *log)
 
         /* write the new header */
         r = rw_header(lc, WRITE);
+        if (!r)
+                r = flush_header(lc);
         if (r) {
                 DMWARN("%s: Failed to write header on dirty region log device",
                        lc->log_dev->name);
@@ -669,7 +684,13 @@ static int disk_flush(struct dm_dirty_log *log)
         if (r)
                 fail_log_device(lc);
         else {
-                lc->touched_dirtied = 0;
+                if (lc->touched_dirtied) {
+                        r = flush_header(lc);
+                        if (r)
+                                fail_log_device(lc);
+                        else
+                                lc->touched_dirtied = 0;
+                }
                 lc->touched_cleaned = 0;
         }