md-cluster/bitmap: unplug bitmap to sync dirty pages to disk

This patch is doing two distinct but related things.

1. It adds bitmap_unplug() for the main bitmap (mddev->bitmap).  As bit
have been set, BITMAP_PAGE_DIRTY is set so bitmap_deamon_work() will
not write those pages out in its regular scans, only bitmap_unplug()
will.  If there are no writes to the array, bitmap_unplug() won't be
called, so we need to call it explicitly here.

2. bitmap_write_all() is a bit of a confusing interface as it doesn't
actually write anything.  The current code for writing "bitmap" works
but this change makes it a bit clearer.

Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index de28c80..4a05bac 100644 (file)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1924,14 +1924,14 @@ int bitmap_copy_from_slot(struct mddev *mddev, int slot,
 
        if (clear_bits) {
                bitmap_update_sb(bitmap);
-               /* Setting this for the ev_page should be enough.
-                * And we do not require both write_all and PAGE_DIRT either
-                */
+               /* BITMAP_PAGE_PENDING is set, but bitmap_unplug needs
+                * BITMAP_PAGE_DIRTY or _NEEDWRITE to write ... */
                for (i = 0; i < bitmap->storage.file_pages; i++)
-                       set_page_attr(bitmap, i, BITMAP_PAGE_DIRTY);
-               bitmap_write_all(bitmap);
+                       if (test_page_attr(bitmap, i, BITMAP_PAGE_PENDING))
+                               set_page_attr(bitmap, i, BITMAP_PAGE_NEEDWRITE);
                bitmap_unplug(bitmap);
        }
+       bitmap_unplug(mddev->bitmap);
        *low = lo;
        *high = hi;
 err: