From ad3fc798800fb7ca04c1dfc439dba946818048d8 Mon Sep 17 00:00:00 2001
From: Guoqing Jiang <jgq516@gmail.com>
Date: Tue, 25 May 2021 17:46:16 +0800
Subject: [PATCH] md: revert io stats accounting
Git-commit: ad3fc798800fb7ca04c1dfc439dba946818048d8
Patch-mainline: v5.14-rc1
References: git-fixes

The commit 41d2d848e5c0 ("md: improve io stats accounting") could cause
double fault problem per the report [1], and also it is not correct to
change ->bi_end_io if md don't own it, so let's revert it.

And io stats accounting will be replemented in later commits.

[1]. https://lore.kernel.org/linux-raid/3bf04253-3fad-434a-63a7-20214e38cf26@gmail.com/T/#t

(Coly Li: Not revert mddev.md_io_pool to keep KABI consistency)

Fixes: 41d2d848e5c0 ("md: improve io stats accounting")
Signed-off-by: Guoqing Jiang <jiangguoqing@kylinos.cn>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Coly Li <colyli@suse.de>
---
 drivers/md/md.c |   45 ---------------------------------------------
 drivers/md/md.h |    1 +
 2 files changed, 1 insertion(+), 45 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -465,29 +465,6 @@ check_suspended:
 }
 EXPORT_SYMBOL(md_handle_request);
 
-struct md_io {
-	struct mddev *mddev;
-	bio_end_io_t *orig_bi_end_io;
-	void *orig_bi_private;
-	unsigned long start_time;
-};
-
-static void md_end_io(struct bio *bio)
-{
-	struct md_io *md_io = bio->bi_private;
-	struct mddev *mddev = md_io->mddev;
-
-	disk_end_io_acct(mddev->gendisk, bio_op(bio), md_io->start_time);
-
-	bio->bi_end_io = md_io->orig_bi_end_io;
-	bio->bi_private = md_io->orig_bi_private;
-
-	mempool_free(md_io, &mddev->md_io_pool);
-
-	if (bio->bi_end_io)
-		bio->bi_end_io(bio);
-}
-
 static blk_qc_t md_submit_bio(struct bio *bio)
 {
 	const int rw = bio_data_dir(bio);
@@ -512,22 +489,6 @@ static blk_qc_t md_submit_bio(struct bio
 		return BLK_QC_T_NONE;
 	}
 
-	if (bio->bi_end_io != md_end_io) {
-		struct md_io *md_io;
-
-		md_io = mempool_alloc(&mddev->md_io_pool, GFP_NOIO);
-		md_io->mddev = mddev;
-		md_io->orig_bi_end_io = bio->bi_end_io;
-		md_io->orig_bi_private = bio->bi_private;
-
-		bio->bi_end_io = md_end_io;
-		bio->bi_private = md_io;
-
-		md_io->start_time = disk_start_io_acct(mddev->gendisk,
-						       bio_sectors(bio),
-						       bio_op(bio));
-	}
-
 	/* bio could be mergeable after passing to underlayer */
 	bio->bi_opf &= ~REQ_NOMERGE;
 
@@ -5651,7 +5612,6 @@ static void md_free(struct kobject *ko)
 
 	bioset_exit(&mddev->bio_set);
 	bioset_exit(&mddev->sync_set);
-	mempool_exit(&mddev->md_io_pool);
 	kfree(mddev);
 }
 
@@ -5747,11 +5707,6 @@ static int md_alloc(dev_t dev, char *nam
 		 */
 		mddev->hold_active = UNTIL_STOP;
 
-	error = mempool_init_kmalloc_pool(&mddev->md_io_pool, BIO_POOL_SIZE,
-					  sizeof(struct md_io));
-	if (error)
-		goto abort;
-
 	error = -ENOMEM;
 	mddev->queue = blk_alloc_queue(NUMA_NO_NODE);
 	if (!mddev->queue)
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -490,6 +490,7 @@ struct mddev {
 	struct bio_set			sync_set; /* for sync operations like
 						   * metadata and bitmap writes
 						   */
+	/* keep it for KABI consistency */
 	mempool_t			md_io_pool;
 
 	/* Generic flush handling.