dm: eliminate some holes data structures

Eliminate a 4-byte hole in 'struct dm_io_memory' by moving 'offset' above the
'ptr' to which it applies (size reduced from 24 to 16 bytes).  And by
association, 1-4 byte hole is eliminated in 'struct dm_io_request' (size
reduced from 56 to 48 bytes).

Eliminate all 6 4-byte holes and 1 cache-line in 'struct dm_snapshot' (size
reduced from 392 to 368 bytes).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/dm-io.h b/include/linux/dm-io.h
index b6bf17ee2f61..5c9186b93fff 100644
--- a/include/linux/dm-io.h
+++ b/include/linux/dm-io.h
@@ -37,14 +37,14 @@ enum dm_io_mem_type {
 struct dm_io_memory {
         enum dm_io_mem_type type;
 
+        unsigned offset;
+
         union {
                 struct page_list *pl;
                 struct bio_vec *bvec;
                 void *vma;
                 void *addr;
         } ptr;
-
-        unsigned offset;
 };
 
 struct dm_io_notify {