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 is implemented in the next patch.
Note: it is required that a previous patch "dm-crypt: don't allocate pages
for a partial request." is applied before applying this patch. Without
that, this patch could introduce a crash.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/md/dm-crypt.c | 120 ++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 97 insertions(+), 23 deletions(-)
Index: linux-3.14/drivers/md/dm-crypt.c
===================================================================
--- linux-3.14.orig/drivers/md/dm-crypt.c 2014-04-04 21:05:40.000000000 +0200
+++ linux-3.14/drivers/md/dm-crypt.c 2014-04-04 21:06:22.000000000 +0200
@@ -18,6 +18,7 @@
#include <linux/slab.h>
#include <linux/crypto.h>
#include <linux/workqueue.h>
+#include <linux/kthread.h>
#include <linux/backing-dev.h>
#include <linux/atomic.h>
#include <linux/scatterlist.h>
@@ -58,6 +59,8 @@ struct dm_crypt_io {
atomic_t io_pending;
int error;
sector_t sector;
+
+ struct list_head list;
} CRYPTO_MINALIGN_ATTR;
struct dm_crypt_request {
@@ -128,6 +131,10 @@ struct crypt_config {
struct workqueue_struct *io_queue;
struct workqueue_struct *crypt_queue;
+ struct task_struct *write_thread;
+ wait_queue_head_t write_thread_wait;
+ struct list_head write_thread_list;
+
char *cipher;
char *cipher_string;
@@ -1141,37 +1148,89 @@ static int kcryptd_io_read(struct dm_cry
return 0;
}
+static void kcryptd_io_read_work(struct work_struct *work)
+{
+ struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
+
+ crypt_inc_pending(io);
+ if (kcryptd_io_read(io, GFP_NOIO))
+ io->error = -ENOMEM;
+ crypt_dec_pending(io);
+}
+
+static void kcryptd_queue_read(struct dm_crypt_io *io)
+{
+ struct crypt_config *cc = io->cc;
+
+ INIT_WORK(&io->work, kcryptd_io_read_work);
+ queue_work(cc->io_queue, &io->work);
+}
+
static void kcryptd_io_write(struct dm_crypt_io *io)
{
struct bio *clone = io->ctx.bio_out;
+
generic_make_request(clone);
}
-static void kcryptd_io(struct work_struct *work)
+static int dmcrypt_write(void *data)
{
- struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
+ struct crypt_config *cc = data;
+ while (1) {
+ struct list_head local_list;
+ struct blk_plug plug;
- if (bio_data_dir(io->base_bio) == READ) {
- crypt_inc_pending(io);
- if (kcryptd_io_read(io, GFP_NOIO))
- io->error = -ENOMEM;
- crypt_dec_pending(io);
- } else
- kcryptd_io_write(io);
-}
+ DECLARE_WAITQUEUE(wait, current);
-static void kcryptd_queue_io(struct dm_crypt_io *io)
-{
- struct crypt_config *cc = io->cc;
+ spin_lock_irq(&cc->write_thread_wait.lock);
+continue_locked:
- INIT_WORK(&io->work, kcryptd_io);
- queue_work(cc->io_queue, &io->work);
+ 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, int async)
+static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io)
{
struct bio *clone = io->ctx.bio_out;
struct crypt_config *cc = io->cc;
+ unsigned long flags;
if (unlikely(io->error < 0)) {
crypt_free_buffer_pages(cc, clone);
@@ -1185,10 +1244,10 @@ static void kcryptd_crypt_write_io_submi
clone->bi_iter.bi_sector = cc->start + io->sector;
- if (async)
- kcryptd_queue_io(io);
- else
- generic_make_request(clone);
+ 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)
@@ -1224,7 +1283,7 @@ static void kcryptd_crypt_write_convert(
/* Encryption was already finished, submit io now */
if (crypt_finished) {
- kcryptd_crypt_write_io_submit(io, 0);
+ kcryptd_crypt_write_io_submit(io);
io->sector = sector;
}
@@ -1284,7 +1343,7 @@ static void kcryptd_async_done(struct cr
if (bio_data_dir(io->base_bio) == READ)
kcryptd_crypt_read_done(io);
else
- kcryptd_crypt_write_io_submit(io, 1);
+ kcryptd_crypt_write_io_submit(io);
}
static void kcryptd_crypt(struct work_struct *work)
@@ -1431,6 +1490,9 @@ static void crypt_dtr(struct dm_target *
if (!cc)
return;
+ if (cc->write_thread)
+ kthread_stop(cc->write_thread);
+
if (cc->io_queue)
destroy_workqueue(cc->io_queue);
if (cc->crypt_queue)
@@ -1745,6 +1807,18 @@ static int crypt_ctr(struct dm_target *t
goto bad;
}
+ 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_bios = 1;
ti->discard_zeroes_data_unsupported = true;
@@ -1779,7 +1853,7 @@ static int crypt_map(struct dm_target *t
if (bio_data_dir(io->base_bio) == READ) {
if (kcryptd_io_read(io, GFP_NOWAIT))
- kcryptd_queue_io(io);
+ kcryptd_queue_read(io);
} else
kcryptd_queue_crypt(io);
--
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