[dm-devel] [PATCH 18/20] dm-crypt: offload writes to thread
Mikulas Patocka
mpatocka at redhat.com
Tue Aug 21 09:09:29 UTC 2012
Submitting write bios directly in the encryption thread caused serious
performance degradation. On multiprocessor machine encryption requests
finish in a different order than they were submitted in. Consequently, write
requests would be submitted in a different order and it could cause severe
performance degradation.
This patch moves submitting write requests to a separate thread so that
the requests can be sorted before submitting.
Sorting in implemented in the next patch.
Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
---
drivers/md/dm-crypt.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 80 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 9316630..0e31454 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -49,6 +49,8 @@ struct dm_crypt_io {
int error;
sector_t sector;
+
+ struct list_head list;
};
struct dm_crypt_request {
@@ -120,6 +122,10 @@ struct crypt_config {
wait_queue_head_t crypt_thread_wait;
struct list_head crypt_thread_list;
+ struct task_struct *write_thread;
+ wait_queue_head_t write_thread_wait;
+ struct list_head write_thread_list;
+
char *cipher;
char *cipher_string;
@@ -1069,9 +1075,8 @@ static int kcryptd_io_read(struct dm_crypt_io *io)
return 0;
}
-static void kcryptd_io_write(struct work_struct *work)
+static void kcryptd_io_write(struct dm_crypt_io *io)
{
- struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
struct crypt_config *cc = io->cc;
struct bio *clone = io->bio_out;
@@ -1087,12 +1092,68 @@ static void kcryptd_io_write(struct work_struct *work)
generic_make_request(clone);
}
+static int dmcrypt_write(void *data)
+{
+ struct crypt_config *cc = data;
+ while (1) {
+ struct list_head local_list;
+ struct blk_plug plug;
+
+ DECLARE_WAITQUEUE(wait, current);
+
+ spin_lock_irq(&cc->write_thread_wait.lock);
+continue_locked:
+
+ if (!list_empty(&cc->write_thread_list))
+ goto pop_from_list;
+
+ __set_current_state(TASK_INTERRUPTIBLE);
+ __add_wait_queue(&cc->write_thread_wait, &wait);
+
+ spin_unlock_irq(&cc->write_thread_wait.lock);
+
+ if (unlikely(kthread_should_stop())) {
+ set_task_state(current, TASK_RUNNING);
+ remove_wait_queue(&cc->write_thread_wait, &wait);
+ break;
+ }
+
+ schedule();
+
+ set_task_state(current, TASK_RUNNING);
+ spin_lock_irq(&cc->write_thread_wait.lock);
+ __remove_wait_queue(&cc->write_thread_wait, &wait);
+ goto continue_locked;
+
+pop_from_list:
+ local_list = cc->write_thread_list;
+ local_list.next->prev = &local_list;
+ local_list.prev->next = &local_list;
+ INIT_LIST_HEAD(&cc->write_thread_list);
+
+ spin_unlock_irq(&cc->write_thread_wait.lock);
+
+ blk_start_plug(&plug);
+ do {
+ struct dm_crypt_io *io = container_of(local_list.next,
+ struct dm_crypt_io, list);
+ list_del(&io->list);
+ kcryptd_io_write(io);
+ } while (!list_empty(&local_list));
+ blk_finish_plug(&plug);
+ }
+ return 0;
+}
+
static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io)
{
struct crypt_config *cc = io->cc;
+ unsigned long flags;
- INIT_WORK(&io->work, kcryptd_io_write);
- queue_work(cc->io_queue, &io->work);
+ spin_lock_irqsave(&cc->write_thread_wait.lock, flags);
+ list_add_tail(&io->list, &cc->write_thread_list);
+ wake_up_locked(&cc->write_thread_wait);
+ spin_unlock_irqrestore(&cc->write_thread_wait.lock, flags);
}
static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
@@ -1299,6 +1360,9 @@ static void crypt_dtr(struct dm_target *ti)
kfree(cc->crypt_threads);
}
+ if (cc->write_thread)
+ kthread_stop(cc->write_thread);
+
if (cc->io_queue)
destroy_workqueue(cc->io_queue);
@@ -1669,6 +1733,18 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
}
}
+ init_waitqueue_head(&cc->write_thread_wait);
+ INIT_LIST_HEAD(&cc->write_thread_list);
+
+ cc->write_thread = kthread_create(dmcrypt_write, cc, "dmcrypt_write");
+ if (IS_ERR(cc->write_thread)) {
+ ret = PTR_ERR(cc->write_thread);
+ cc->write_thread = NULL;
+ ti->error = "Couldn't spawn write thread";
+ goto bad;
+ }
+ wake_up_process(cc->write_thread);
+
ti->num_flush_requests = 1;
ti->discard_zeroes_data_unsupported = true;
--
1.7.10.4
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