drbd: announce FLUSH/FUA capability to upper layers

Unconditionally announce FLUSH/FUA to upper layers.
If the lower layers on either node do not actually support this,
generic_make_request() will deal with it.

If this causes performance regressions on your setup,
make sure there are no volatile caches involved,
and mount -o nobarrier or equivalent.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 16 insertions, 5 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 83d99133f94b..c74ca2df7431 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -277,6 +277,9 @@ static void drbd_pp_free(struct drbd_conf *mdev, struct page *page, int is_net)
         atomic_t *a = is_net ? &mdev->pp_in_use_by_net : &mdev->pp_in_use;
         int i;
 
+        if (page == NULL)
+                return;
+
         if (drbd_pp_vacant > (DRBD_MAX_BIO_SIZE/PAGE_SIZE)*minor_count)
                 i = page_chain_free(page);
         else {
@@ -316,7 +319,7 @@ struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
                                      gfp_t gfp_mask) __must_hold(local)
 {
         struct drbd_epoch_entry *e;
-        struct page *page;
+        struct page *page = NULL;
         unsigned nr_pages = (data_size + PAGE_SIZE -1) >> PAGE_SHIFT;
 
         if (drbd_insert_fault(mdev, DRBD_FAULT_AL_EE))
@@ -329,9 +332,11 @@ struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
                 return NULL;
         }
 
-        page = drbd_pp_alloc(mdev, nr_pages, (gfp_mask & __GFP_WAIT));
-        if (!page)
-                goto fail;
+        if (data_size) {
+                page = drbd_pp_alloc(mdev, nr_pages, (gfp_mask & __GFP_WAIT));
+                if (!page)
+                        goto fail;
+        }
 
         INIT_HLIST_NODE(&e->collision);
         e->epoch = NULL;
@@ -1270,7 +1275,6 @@ read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __
 
         data_size -= dgs;
 
-        ERR_IF(data_size == 0) return NULL;
         ERR_IF(data_size &  0x1ff) return NULL;
         ERR_IF(data_size >  DRBD_MAX_BIO_SIZE) return NULL;
 
@@ -1291,6 +1295,9 @@ read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __
         if (!e)
                 return NULL;
 
+        if (!data_size)
+                return e;
+
         ds = data_size;
         page = e->pages;
         page_chain_for_each(page) {
@@ -1715,6 +1722,10 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 
         dp_flags = be32_to_cpu(p->dp_flags);
         rw |= wire_flags_to_bio(mdev, dp_flags);
+        if (e->pages == NULL) {
+                D_ASSERT(e->size == 0);
+                D_ASSERT(dp_flags & DP_FLUSH);
+        }
 
         if (dp_flags & DP_MAY_SET_IN_SYNC)
                 e->flags |= EE_MAY_SET_IN_SYNC;