dm integrity: optimize writing dm-bufio buffers that are partially changed

Rather than write the entire dm-bufio buffer when only a subset is
changed, improve dm-bufio (and dm-integrity) by only writing the subset
of the buffer that changed.

Update dm-integrity to make use of dm-bufio's new
dm_bufio_mark_partial_buffer_dirty() interface.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/md/dm-bufio.h b/drivers/md/dm-bufio.h
index b6d8f53ec15b..be732d3f8611 100644
--- a/drivers/md/dm-bufio.h
+++ b/drivers/md/dm-bufio.h
@@ -94,6 +94,15 @@ void dm_bufio_release(struct dm_buffer *b);
 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b);
 
 /*
+ * Mark a part of the buffer dirty.
+ *
+ * The specified part of the buffer is scheduled to be written. dm-bufio may
+ * write the specified part of the buffer or it may write a larger superset.
+ */
+void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
+					unsigned start, unsigned end);
+
+/*
  * Initiate writing of dirty buffers, without waiting for completion.
  */
 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c);