drbd: remove struct drbd_tl_epoch objects (barrier works)
cherry-picked and adapted from drbd 9 devel branch
DRBD requests (struct drbd_request) are already on the per resource
transfer log list, and carry their epoch number. We do not need to
additionally link them on other ring lists in other structs.
The drbd sender thread can recognize itself when to send a P_BARRIER,
by tracking the currently processed epoch, and how many writes
have been processed for that epoch.
If the epoch of the request to be processed does not match the currently
processed epoch, any writes have been processed in it, a P_BARRIER for
this last processed epoch is send out first.
The new epoch then becomes the currently processed epoch.
To not get stuck in drbd_al_begin_io() waiting for P_BARRIER_ACK,
the sender thread also needs to handle the case when the current
epoch was closed already, but no new requests are queued yet,
and send out P_BARRIER as soon as possible.
This is done by comparing the per resource "current transfer log epoch"
(tconn->current_tle_nr) with the per connection "currently processed
epoch number" (tconn->send.current_epoch_nr), while waiting for
new requests to be processed in wait_for_work().
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index c0d0de5..309c121 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -562,12 +562,16 @@
struct bio *private_bio;
struct drbd_interval i;
- unsigned int epoch; /* barrier_nr */
- /* barrier_nr: used to check on "completion" whether this req was in
+ /* epoch: used to check on "completion" whether this req was in
* the current epoch, and we therefore have to close it,
- * starting a new epoch...
+ * causing a p_barrier packet to be send, starting a new epoch.
+ *
+ * This corresponds to "barrier" in struct p_barrier[_ack],
+ * and to "barrier_nr" in struct drbd_epoch (and various
+ * comments/function parameters/local variable names).
*/
+ unsigned int epoch;
struct list_head tl_requests; /* ring list in the transfer log */
struct bio *master_bio; /* master bio pointer */
@@ -575,14 +579,6 @@
unsigned long start_time;
};
-struct drbd_tl_epoch {
- struct drbd_work w;
- struct list_head requests; /* requests before */
- struct drbd_tl_epoch *next; /* pointer to the next barrier */
- unsigned int br_number; /* the barriers identifier. */
- int n_writes; /* number of requests attached before this barrier */
-};
-
struct drbd_epoch {
struct drbd_tconn *tconn;
struct list_head list;
@@ -845,11 +841,8 @@
unsigned int ko_count;
spinlock_t req_lock;
- struct drbd_tl_epoch *unused_spare_tle; /* for pre-allocation */
- struct drbd_tl_epoch *newest_tle;
- struct drbd_tl_epoch *oldest_tle;
- struct list_head out_of_sequence_requests;
- struct list_head barrier_acked_requests;
+
+ struct list_head transfer_log; /* all requests not yet fully processed */
struct crypto_hash *cram_hmac_tfm;
struct crypto_hash *integrity_tfm; /* checksums we compute, updates protected by tconn->data->mutex */
@@ -859,18 +852,36 @@
void *int_dig_in;
void *int_dig_vv;
+ /* receiver side */
struct drbd_epoch *current_epoch;
spinlock_t epoch_lock;
unsigned int epochs;
enum write_ordering_e write_ordering;
atomic_t current_tle_nr; /* transfer log epoch number */
+ unsigned current_tle_writes; /* writes seen within this tl epoch */
unsigned long last_reconnect_jif;
struct drbd_thread receiver;
struct drbd_thread worker;
struct drbd_thread asender;
cpumask_var_t cpu_mask;
+
+ /* sender side */
struct drbd_work_queue sender_work;
+
+ struct {
+ /* whether this sender thread
+ * has processed a single write yet. */
+ bool seen_any_write_yet;
+
+ /* Which barrier number to send with the next P_BARRIER */
+ int current_epoch_nr;
+
+ /* how many write requests have been sent
+ * with req->epoch == current_epoch_nr.
+ * If none, no P_BARRIER will be sent. */
+ unsigned current_epoch_writes;
+ } send;
};
struct drbd_conf {
@@ -1054,7 +1065,6 @@
extern void tl_release(struct drbd_tconn *, unsigned int barrier_nr,
unsigned int set_size);
extern void tl_clear(struct drbd_tconn *);
-extern void _tl_add_barrier(struct drbd_tconn *, struct drbd_tl_epoch *);
extern void drbd_free_sock(struct drbd_tconn *tconn);
extern int drbd_send(struct drbd_tconn *tconn, struct socket *sock,
void *buf, size_t size, unsigned msg_flags);
@@ -1460,7 +1470,6 @@
extern int w_send_write_hint(struct drbd_work *, int);
extern int w_make_resync_request(struct drbd_work *, int);
extern int w_send_dblock(struct drbd_work *, int);
-extern int w_send_barrier(struct drbd_work *, int);
extern int w_send_read_req(struct drbd_work *, int);
extern int w_prev_work_done(struct drbd_work *, int);
extern int w_e_reissue(struct drbd_work *, int);
