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path: root/drivers/block/drbd/drbd_req.c
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Diffstat (limited to 'drivers/block/drbd/drbd_req.c')
-rw-r--r--drivers/block/drbd/drbd_req.c30
1 files changed, 26 insertions, 4 deletions
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 910335c3092..0bb1e41f136 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -834,7 +834,15 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, uns
req->private_bio = NULL;
}
if (rw == WRITE) {
- remote = 1;
+ /* Need to replicate writes. Unless it is an empty flush,
+ * which is better mapped to a DRBD P_BARRIER packet,
+ * also for drbd wire protocol compatibility reasons. */
+ if (unlikely(size == 0)) {
+ /* The only size==0 bios we expect are empty flushes. */
+ D_ASSERT(bio->bi_rw & REQ_FLUSH);
+ remote = 0;
+ } else
+ remote = 1;
} else {
/* READ || READA */
if (local) {
@@ -870,8 +878,11 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, uns
* extent. This waits for any resync activity in the corresponding
* resync extent to finish, and, if necessary, pulls in the target
* extent into the activity log, which involves further disk io because
- * of transactional on-disk meta data updates. */
- if (rw == WRITE && local && !test_bit(AL_SUSPENDED, &mdev->flags)) {
+ * of transactional on-disk meta data updates.
+ * Empty flushes don't need to go into the activity log, they can only
+ * flush data for pending writes which are already in there. */
+ if (rw == WRITE && local && size
+ && !test_bit(AL_SUSPENDED, &mdev->flags)) {
req->rq_state |= RQ_IN_ACT_LOG;
drbd_al_begin_io(mdev, sector);
}
@@ -994,7 +1005,10 @@ allocate_barrier:
if (rw == WRITE && _req_conflicts(req))
goto fail_conflicting;
- list_add_tail(&req->tl_requests, &mdev->newest_tle->requests);
+ /* no point in adding empty flushes to the transfer log,
+ * they are mapped to drbd barriers already. */
+ if (likely(size!=0))
+ list_add_tail(&req->tl_requests, &mdev->newest_tle->requests);
/* NOTE remote first: to get the concurrent write detection right,
* we must register the request before start of local IO. */
@@ -1014,6 +1028,14 @@ allocate_barrier:
mdev->net_conf->on_congestion != OC_BLOCK && mdev->agreed_pro_version >= 96)
maybe_pull_ahead(mdev);
+ /* If this was a flush, queue a drbd barrier/start a new epoch.
+ * Unless the current epoch was empty anyways, or we are not currently
+ * replicating, in which case there is no point. */
+ if (unlikely(bio->bi_rw & REQ_FLUSH)
+ && mdev->newest_tle->n_writes
+ && drbd_should_do_remote(mdev->state))
+ queue_barrier(mdev);
+
spin_unlock_irq(&mdev->req_lock);
kfree(b); /* if someone else has beaten us to it... */