[PATCH] Avoid io queue in dm-crypt

[Richard Kralovic]

Process io requests from the calling process, not from the io queue. Should
improve cfq scheduler behaviour with dm-crypt.

Signed-off-by: Richard Kralovic <riso@xxxxxx>
---
 drivers/md/dm-crypt.c |   42 +++++++++++++-----------------------------
 1 files changed, 13 insertions(+), 29 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 368e8e9..7e2d3a5 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -22,6 +22,7 @@
 #include <linux/scatterlist.h>
 #include <asm/page.h>
 #include <asm/unaligned.h>
+#include <linux/semaphore.h>
 
 #include <linux/device-mapper.h>
 
@@ -57,6 +58,7 @@ struct dm_crypt_io {
 	int error;
 	sector_t sector;
 	struct dm_crypt_io *base_io;
+	struct semaphore notify;
 };
 
 struct dm_crypt_request {
@@ -104,7 +106,6 @@ struct crypt_config {
 	mempool_t *page_pool;
 	struct bio_set *bs;
 
-	struct workqueue_struct *io_queue;
 	struct workqueue_struct *crypt_queue;
 
 	char *cipher;
@@ -728,26 +729,16 @@ static void kcryptd_io_write(struct dm_crypt_io *io)
 	generic_make_request(clone);
 }
 
-static void kcryptd_io(struct work_struct *work)
+static void kcryptd_io(struct dm_crypt_io *io)
 {
-	struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
-
 	if (bio_data_dir(io->base_bio) == READ)
 		kcryptd_io_read(io);
 	else
 		kcryptd_io_write(io);
 }
 
-static void kcryptd_queue_io(struct dm_crypt_io *io)
-{
-	struct crypt_config *cc = io->target->private;
-
-	INIT_WORK(&io->work, kcryptd_io);
-	queue_work(cc->io_queue, &io->work);
-}
-
 static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io,
-					  int error, int async)
+					  int error)
 {
 	struct bio *clone = io->ctx.bio_out;
 	struct crypt_config *cc = io->target->private;
@@ -765,10 +756,7 @@ static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io,
 
 	clone->bi_sector = cc->start + io->sector;
 
-	if (async)
-		kcryptd_queue_io(io);
-	else
-		generic_make_request(clone);
+	up(&io->notify);
 }
 
 static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
@@ -811,7 +799,7 @@ static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
 
 		/* Encryption was already finished, submit io now */
 		if (crypt_finished) {
-			kcryptd_crypt_write_io_submit(io, r, 0);
+			kcryptd_crypt_write_io_submit(io, r);
 
 			/*
 			 * If there was an error, do not try next fragments.
@@ -909,13 +897,12 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
 	if (bio_data_dir(io->base_bio) == READ)
 		kcryptd_crypt_read_done(io, error);
 	else
-		kcryptd_crypt_write_io_submit(io, error, 1);
+		kcryptd_crypt_write_io_submit(io, error);
 }
 
 static void kcryptd_crypt(struct work_struct *work)
 {
 	struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
-
 	if (bio_data_dir(io->base_bio) == READ)
 		kcryptd_crypt_read_convert(io);
 	else
@@ -1005,8 +992,6 @@ static void crypt_dtr(struct dm_target *ti)
 	if (!cc)
 		return;
 
-	if (cc->io_queue)
-		destroy_workqueue(cc->io_queue);
 	if (cc->crypt_queue)
 		destroy_workqueue(cc->crypt_queue);
 
@@ -1252,11 +1237,6 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	cc->start = tmpll;
 
 	ret = -ENOMEM;
-	cc->io_queue = create_singlethread_workqueue("kcryptd_io");
-	if (!cc->io_queue) {
-		ti->error = "Couldn't create kcryptd io queue";
-		goto bad;
-	}
 
 	cc->crypt_queue = create_singlethread_workqueue("kcryptd");
 	if (!cc->crypt_queue) {
@@ -1287,9 +1267,13 @@ static int crypt_map(struct dm_target *ti, struct bio *bio,
 	io = crypt_io_alloc(ti, bio, dm_target_offset(ti, bio->bi_sector));
 
 	if (bio_data_dir(io->base_bio) == READ)
-		kcryptd_queue_io(io);
-	else
+		kcryptd_io(io);
+	else {
+		sema_init(&io->notify, 0);
 		kcryptd_queue_crypt(io);
+		down(&io->notify);
+		kcryptd_io(io);
+	}
 
 	return DM_MAPIO_SUBMITTED;
 }
-- 
1.7.2.3




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