From: Lars Ellenberg <lars.ellenb...@linbit.com>
To maintain write-order fidelity accros all volumes in a DRBD resource,
the receiver of a P_BARRIER needs to issue flushes to all volumes.
We used to do this by calling blkdev_issue_flush(), synchronously,
one volume at a time.
We now submit all flushes to all volumes in parallel, then wait for all
completions, to reduce worst-case latencies on multi-volume resources.
Signed-off-by: Philipp Reisner <philipp.reis...@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenb...@linbit.com>
---
drivers/block/drbd/drbd_receiver.c | 113 +++++++++++++++++++++++++++++--------
1 file changed, 88 insertions(+), 25 deletions(-)
diff --git a/drivers/block/drbd/drbd_receiver.c
b/drivers/block/drbd/drbd_receiver.c
index 4cfc721..a2e7ba9 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1204,13 +1204,83 @@ static int drbd_recv_header(struct drbd_connection
*connection, struct packet_in
return err;
}
-static void drbd_flush(struct drbd_connection *connection)
+/* This is blkdev_issue_flush, but asynchronous.
+ * We want to submit to all component volumes in parallel,
+ * then wait for all completions.
+ */
+struct issue_flush_context {
+ atomic_t pending;
+ int error;
+ struct completion done;
+};
+struct one_flush_context {
+ struct drbd_device *device;
+ struct issue_flush_context *ctx;
+};
+
+void one_flush_endio(struct bio *bio)
{
- int rv;
- struct drbd_peer_device *peer_device;
- int vnr;
+ struct one_flush_context *octx = bio->bi_private;
+ struct drbd_device *device = octx->device;
+ struct issue_flush_context *ctx = octx->ctx;
+
+ if (bio->bi_error) {
+ ctx->error = bio->bi_error;
+ drbd_info(device, "local disk FLUSH FAILED with status %d\n",
bio->bi_error);
+ }
+ kfree(octx);
+ bio_put(bio);
+
+ clear_bit(FLUSH_PENDING, &device->flags);
+ put_ldev(device);
+ kref_put(&device->kref, drbd_destroy_device);
+
+ if (atomic_dec_and_test(&ctx->pending))
+ complete(&ctx->done);
+}
+
+static void submit_one_flush(struct drbd_device *device, struct
issue_flush_context *ctx)
+{
+ struct bio *bio = bio_alloc(GFP_NOIO, 0);
+ struct one_flush_context *octx = kmalloc(sizeof(*octx), GFP_NOIO);
+ if (!bio || !octx) {
+ drbd_warn(device, "Could not allocate a bio, CANNOT ISSUE
FLUSH\n");
+ /* FIXME: what else can I do now? disconnecting or detaching
+ * really does not help to improve the state of the world,
either.
+ */
+ kfree(octx);
+ if (bio)
+ bio_put(bio);
+ ctx->error = -ENOMEM;
+ put_ldev(device);
+ kref_put(&device->kref, drbd_destroy_device);
+ return;
+ }
+
+ octx->device = device;
+ octx->ctx = ctx;
+ bio->bi_bdev = device->ldev->backing_bdev;
+ bio->bi_private = octx;
+ bio->bi_end_io = one_flush_endio;
+
+ device->flush_jif = jiffies;
+ set_bit(FLUSH_PENDING, &device->flags);
+ atomic_inc(&ctx->pending);
+ submit_bio(WRITE_FLUSH, bio);
+}
+
+static void drbd_flush(struct drbd_connection *connection)
+{
if (connection->resource->write_ordering >= WO_BDEV_FLUSH) {
+ struct drbd_peer_device *peer_device;
+ struct issue_flush_context ctx;
+ int vnr;
+
+ atomic_set(&ctx.pending, 1);
+ ctx.error = 0;
+ init_completion(&ctx.done);
+
rcu_read_lock();
idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
{
struct drbd_device *device = peer_device->device;
@@ -1220,31 +1290,24 @@ static void drbd_flush(struct drbd_connection
*connection)
kref_get(&device->kref);
rcu_read_unlock();
- /* Right now, we have only this one synchronous code
path
- * for flushes between request epochs.
- * We may want to make those asynchronous,
- * or at least parallelize the flushes to the volume
devices.
- */
- device->flush_jif = jiffies;
- set_bit(FLUSH_PENDING, &device->flags);
- rv = blkdev_issue_flush(device->ldev->backing_bdev,
- GFP_NOIO, NULL);
- clear_bit(FLUSH_PENDING, &device->flags);
- if (rv) {
- drbd_info(device, "local disk flush failed with
status %d\n", rv);
- /* would rather check on EOPNOTSUPP, but that
is not reliable.
- * don't try again for ANY return value != 0
- * if (rv == -EOPNOTSUPP) */
- drbd_bump_write_ordering(connection->resource,
NULL, WO_DRAIN_IO);
- }
- put_ldev(device);
- kref_put(&device->kref, drbd_destroy_device);
+ submit_one_flush(device, &ctx);
rcu_read_lock();
- if (rv)
- break;
}
rcu_read_unlock();
+
+ /* Do we want to add a timeout,
+ * if disk-timeout is set? */
+ if (!atomic_dec_and_test(&ctx.pending))
+ wait_for_completion(&ctx.done);
+
+ if (ctx.error) {
+ /* would rather check on EOPNOTSUPP, but that is not
reliable.
+ * don't try again for ANY return value != 0
+ * if (rv == -EOPNOTSUPP) */
+ /* Any error is already reported by bio_endio callback.
*/
+ drbd_bump_write_ordering(connection->resource, NULL,
WO_DRAIN_IO);
+ }
}
}
--
1.9.1
