[PATCH 4.19 25/44] dm cache metadata: verify cache has blocks in blocks_are_clean_separate_dirty()

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mike Snitzer <snit...@redhat.com>

commit 687cf4412a343a63928a5c9d91bdc0f522939d43 upstream.

Otherwise dm_bitset_cursor_begin() return -ENODATA.  Other calls to
dm_bitset_cursor_begin() have similar negative checks.

Fixes inability to create a cache in passthrough mode (even though doing
so makes no sense).

Fixes: 0d963b6e65 ("dm cache metadata: fix metadata2 format's 
blocks_are_clean_separate_dirty")
Cc: sta...@vger.kernel.org
Reported-by: David Teigland <teigl...@redhat.com>
Signed-off-by: Mike Snitzer <snit...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/md/dm-cache-metadata.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -930,6 +930,10 @@ static int blocks_are_clean_separate_dir
        bool dirty_flag;
        *result = true;
 
+       if (from_cblock(cmd->cache_blocks) == 0)
+               /* Nothing to do */
+               return 0;
+
        r = dm_bitset_cursor_begin(&cmd->dirty_info, cmd->dirty_root,
                                   from_cblock(cmd->cache_blocks), 
&cmd->dirty_cursor);
        if (r) {