[PATCH 2/2] dm-bufio: all dm_bufio_client share the same dm_io_client.

[LongPing Wei <weilongping@xxxxxxxx>]

The size of biovec's memory of one dm_io_client will be
reserved_bio_based_ios(default value is 16) * 4KiB memory.
When the number of dm-bufio(dm-verity) devices is dozens,
the total memory size will be several MiBs.

The number of dm-bufio(dm-verity) devices is 59 on my test device,
and the size of biovec's memory here will be 3.87MiB.

This commit will reduce the memory usage of dm-bufio
by making all dm_bufio_client share the same dm_io_client.

Fixes: 95d402f057f2e ("dm: add bufio")

Signed-off-by: LongPing Wei <weilongping@xxxxxxxx>
---
 drivers/md/dm-bufio.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index f0b5a6931161..5aa53b06112d 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -70,6 +70,8 @@
 
 #define SCAN_RESCHED_CYCLE	16
 
+static struct dm_io_client *bufio_io_client;
+
 /*--------------------------------------------------------------*/
 
 /*
@@ -992,7 +994,6 @@ struct dm_bufio_client {
 	void (*write_callback)(struct dm_buffer *buf);
 	struct kmem_cache *slab_buffer;
 	struct kmem_cache *slab_cache;
-	struct dm_io_client *dm_io;
 
 	struct list_head reserved_buffers;
 	unsigned int need_reserved_buffers;
@@ -1311,7 +1312,7 @@ static void use_dmio(struct dm_buffer *b, enum req_op op, sector_t sector,
 		.bi_opf = op,
 		.notify.fn = dmio_complete,
 		.notify.context = b,
-		.client = b->c->dm_io,
+		.client = bufio_io_client,
 	};
 	struct dm_io_region region = {
 		.bdev = b->c->bdev,
@@ -2197,7 +2198,7 @@ int dm_bufio_issue_flush(struct dm_bufio_client *c)
 		.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC,
 		.mem.type = DM_IO_KMEM,
 		.mem.ptr.addr = NULL,
-		.client = c->dm_io,
+		.client = bufio_io_client,
 	};
 	struct dm_io_region io_reg = {
 		.bdev = c->bdev,
@@ -2221,7 +2222,7 @@ int dm_bufio_issue_discard(struct dm_bufio_client *c, sector_t block, sector_t c
 		.bi_opf = REQ_OP_DISCARD | REQ_SYNC,
 		.mem.type = DM_IO_KMEM,
 		.mem.ptr.addr = NULL,
-		.client = c->dm_io,
+		.client = bufio_io_client,
 	};
 	struct dm_io_region io_reg = {
 		.bdev = c->bdev,
@@ -2310,7 +2311,7 @@ EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
 
 struct dm_io_client *dm_bufio_get_dm_io_client(struct dm_bufio_client *c)
 {
-	return c->dm_io;
+	return bufio_io_client;
 }
 EXPORT_SYMBOL_GPL(dm_bufio_get_dm_io_client);
 
@@ -2530,12 +2531,6 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
 	init_waitqueue_head(&c->free_buffer_wait);
 	c->async_write_error = 0;
 
-	c->dm_io = dm_io_client_create();
-	if (IS_ERR(c->dm_io)) {
-		r = PTR_ERR(c->dm_io);
-		goto bad_dm_io;
-	}
-
 	if (block_size <= KMALLOC_MAX_SIZE && !is_power_of_2(block_size)) {
 		unsigned int align = min(1U << __ffs(block_size), (unsigned int)PAGE_SIZE);
 
@@ -2606,8 +2601,6 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
 	}
 	kmem_cache_destroy(c->slab_cache);
 	kmem_cache_destroy(c->slab_buffer);
-	dm_io_client_destroy(c->dm_io);
-bad_dm_io:
 	mutex_destroy(&c->lock);
 	if (c->no_sleep)
 		static_branch_dec(&no_sleep_enabled);
@@ -2657,7 +2650,6 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)
 	cache_destroy(&c->cache);
 	kmem_cache_destroy(c->slab_cache);
 	kmem_cache_destroy(c->slab_buffer);
-	dm_io_client_destroy(c->dm_io);
 	mutex_destroy(&c->lock);
 	if (c->no_sleep)
 		static_branch_dec(&no_sleep_enabled);
@@ -2944,6 +2936,15 @@ static int __init dm_bufio_init(void)
 	if (!dm_bufio_wq)
 		return -ENOMEM;
 
+	bufio_io_client = dm_io_client_create();
+	if (IS_ERR(bufio_io_client)) {
+		int r = PTR_ERR(bufio_io_client);
+		bufio_io_client = NULL;
+		DMERR("Cannot allocate dm io");
+		destroy_workqueue(dm_bufio_wq);
+		return r;
+	}
+
 	INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn);
 	INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup);
 	queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
-- 
2.34.1