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>

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 31dc33df95c79ed914d0bc0b9c3f1efa62489a13..6b23631db5b56566621d1cd625e13447263738f0 100644 (file)
--- 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;
        }