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drbd: allow parallel flushes for multi-volume resources

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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.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Lars Ellenberg 2016-06-14 00:26:19 +02:00 committed by Jens Axboe
parent 0982368bfd
commit f9ff0da564
1 changed files with 89 additions and 25 deletions
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114
drivers/block/drbd/drbd_receiver.c
View File

@ -1204,13 +1204,84 @@ static int drbd_recv_header(struct drbd_connection *connection, struct packet_in
return err;
}
/* 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)
{
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;
bio_set_op_attrs(bio, REQ_OP_FLUSH, WRITE_FLUSH);
device->flush_jif = jiffies;
set_bit(FLUSH_PENDING, &device->flags);
atomic_inc(&ctx->pending);
submit_bio(bio);
}
static void drbd_flush(struct drbd_connection *connection)
{
int rv;
struct drbd_peer_device *peer_device;
int vnr;
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 +1291,24 @@ 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);
}
}
}