diff mbox series

[v2,md-6.14,5/5] md/md-bitmap: move bitmap_{start, end}write to md upper layer

Message ID 20241218121745.2459-6-yukuai@kernel.org (mailing list archive)
State New
Headers show
Series md/md-bitmap: move bitmap_{start, end}write to md upper layer | expand

Commit Message

yukuai@kernel.org Dec. 18, 2024, 12:17 p.m. UTC 
From: Yu Kuai <yukuai3@huawei.com>

There are two BUG reports that raid5 will hang at
bitmap_startwrite([1],[2]), root cause is that bitmap start write and end
write is unbalanced. For example, handle_stripe_clean_event() doesn't
check if stripe->dev[].towrite is NULL after tag 'returnbi', and extra
bitmap_endwrite() will be called.

While reviewing raid5 code, it's found that bitmap operations can be
optimized. For example, for a 4 disks raid5, with chunksize=8k, if user
issue a IO (0 + 48k) to the array:

┌────────────────────────────────────────────────────────────┐
│chunk 0                                                     │
│      ┌────────────┬─────────────┬─────────────┬────────────┼
│  sh0 │A0: 0 + 4k  │A1: 8k + 4k  │A2: 16k + 4k │A3: P       │
│      ┼────────────┼─────────────┼─────────────┼────────────┼
│  sh1 │B0: 4k + 4k │B1: 12k + 4k │B2: 20k + 4k │B3: P       │
┼──────┴────────────┴─────────────┴─────────────┴────────────┼
│chunk 1                                                     │
│      ┌────────────┬─────────────┬─────────────┬────────────┤
│  sh2 │C0: 24k + 4k│C1: 32k + 4k │C2: P        │C3: 40k + 4k│
│      ┼────────────┼─────────────┼─────────────┼────────────┼
│  sh3 │D0: 28k + 4k│D1: 36k + 4k │D2: P        │D3: 44k + 4k│
└──────┴────────────┴─────────────┴─────────────┴────────────┘

Before this patch, 4 stripe head will be used, and each sh will attach
bio for 3 disks, and each attached bio will trigger
bitmap_startwrite() once, which means total 12 times.
 - 3 times (0 + 4k), for (A0, A1 and A2)
 - 3 times (4 + 4k), for (B0, B1 and B2)
 - 3 times (8 + 4k), for (C0, C1 and C3)
 - 3 times (12 + 4k), for (D0, D1 and D3)

After this patch, md upper layer will calculate that IO range (0 + 48k)
is corresponding to the bitmap (0 + 16k), and call bitmap_startwrite()
just once.

Noted that this patch will align bitmap ranges to the chunks, for example,
if user issue a IO (0 + 4k) to array:

- Before this patch, 1 time (0 + 4k), for A0;
- After this patch, 1 time (0 + 8k) for chunk 0;

Usually, one bitmap bit will represent more than one disk chunk, and this
doesn't have any difference. And even if user really created a array
that one chunk contain multiple bits, the overhead is that more data
will be recovered after power failure.

[1] https://lore.kernel.org/all/CAJpMwyjmHQLvm6zg1cmQErttNNQPDAAXPKM3xgTjMhbfts986Q@mail.gmail.com/
[2] https://lore.kernel.org/all/ADF7D720-5764-4AF3-B68E-1845988737AA@flyingcircus.io/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Yu Kuai <yukuai@kernel.org>
---
 drivers/md/md.c          | 29 +++++++++++++++++++++++++++++
 drivers/md/md.h          |  2 ++
 drivers/md/raid1.c       |  4 ----
 drivers/md/raid10.c      |  3 ---
 drivers/md/raid5-cache.c |  2 --
 drivers/md/raid5.c       | 24 +-----------------------
 6 files changed, 32 insertions(+), 32 deletions(-)
diff mbox series

Patch

diff --git a/drivers/md/md.c b/drivers/md/md.c
index aebe12b0ee27..c60ae2c70102 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8745,12 +8745,32 @@  void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
 }
 EXPORT_SYMBOL_GPL(md_submit_discard_bio);
 
+static void md_bitmap_start(struct mddev *mddev,
+			    struct md_io_clone *md_io_clone)
+{
+	if (mddev->pers->bitmap_sector)
+		mddev->pers->bitmap_sector(mddev, &md_io_clone->offset,
+					   &md_io_clone->sectors);
+
+	mddev->bitmap_ops->startwrite(mddev, md_io_clone->offset,
+				      md_io_clone->sectors);
+}
+
+static void md_bitmap_end(struct mddev *mddev, struct md_io_clone *md_io_clone)
+{
+	mddev->bitmap_ops->endwrite(mddev, md_io_clone->offset,
+				    md_io_clone->sectors);
+}
+
 static void md_end_clone_io(struct bio *bio)
 {
 	struct md_io_clone *md_io_clone = bio->bi_private;
 	struct bio *orig_bio = md_io_clone->orig_bio;
 	struct mddev *mddev = md_io_clone->mddev;
 
+	if (bio_data_dir(orig_bio) == WRITE && mddev->bitmap)
+		md_bitmap_end(mddev, md_io_clone);
+
 	if (bio->bi_status && !orig_bio->bi_status)
 		orig_bio->bi_status = bio->bi_status;
 
@@ -8775,6 +8795,12 @@  static void md_clone_bio(struct mddev *mddev, struct bio **bio)
 	if (blk_queue_io_stat(bdev->bd_disk->queue))
 		md_io_clone->start_time = bio_start_io_acct(*bio);
 
+	if (bio_data_dir(*bio) == WRITE && mddev->bitmap) {
+		md_io_clone->offset = (*bio)->bi_iter.bi_sector;
+		md_io_clone->sectors = bio_sectors(*bio);
+		md_bitmap_start(mddev, md_io_clone);
+	}
+
 	clone->bi_end_io = md_end_clone_io;
 	clone->bi_private = md_io_clone;
 	*bio = clone;
@@ -8793,6 +8819,9 @@  void md_free_cloned_bio(struct bio *bio)
 	struct bio *orig_bio = md_io_clone->orig_bio;
 	struct mddev *mddev = md_io_clone->mddev;
 
+	if (bio_data_dir(orig_bio) == WRITE && mddev->bitmap)
+		md_bitmap_end(mddev, md_io_clone);
+
 	if (bio->bi_status && !orig_bio->bi_status)
 		orig_bio->bi_status = bio->bi_status;
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index de6dadb9a40b..def808064ad8 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -831,6 +831,8 @@  struct md_io_clone {
 	struct mddev	*mddev;
 	struct bio	*orig_bio;
 	unsigned long	start_time;
+	sector_t	offset;
+	unsigned long	sectors;
 	struct bio	bio_clone;
 };
 
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 81dff2cea0db..b5a5766cccf7 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -422,8 +422,6 @@  static void close_write(struct r1bio *r1_bio)
 
 	if (test_bit(R1BIO_BehindIO, &r1_bio->state))
 		mddev->bitmap_ops->end_behind_write(mddev);
-	/* clear the bitmap if all writes complete successfully */
-	mddev->bitmap_ops->endwrite(mddev, r1_bio->sector, r1_bio->sectors);
 	md_write_end(mddev);
 }
 
@@ -1647,8 +1645,6 @@  static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 
 			if (test_bit(R1BIO_BehindIO, &r1_bio->state))
 				mddev->bitmap_ops->start_behind_write(mddev);
-			mddev->bitmap_ops->startwrite(mddev, r1_bio->sector,
-						      r1_bio->sectors);
 			first_clone = 0;
 		}
 
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 3dc0170125b2..2fe8e6f96057 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -428,8 +428,6 @@  static void close_write(struct r10bio *r10_bio)
 {
 	struct mddev *mddev = r10_bio->mddev;
 
-	/* clear the bitmap if all writes complete successfully */
-	mddev->bitmap_ops->endwrite(mddev, r10_bio->sector, r10_bio->sectors);
 	md_write_end(mddev);
 }
 
@@ -1517,7 +1515,6 @@  static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 	md_account_bio(mddev, &bio);
 	r10_bio->master_bio = bio;
 	atomic_set(&r10_bio->remaining, 1);
-	mddev->bitmap_ops->startwrite(mddev, r10_bio->sector, r10_bio->sectors);
 
 	for (i = 0; i < conf->copies; i++) {
 		if (r10_bio->devs[i].bio)
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index ba4f9577c737..011246e16a99 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -313,8 +313,6 @@  void r5c_handle_cached_data_endio(struct r5conf *conf,
 		if (sh->dev[i].written) {
 			set_bit(R5_UPTODATE, &sh->dev[i].flags);
 			r5c_return_dev_pending_writes(conf, &sh->dev[i]);
-			conf->mddev->bitmap_ops->endwrite(conf->mddev,
-					sh->sector, RAID5_STRIPE_SECTORS(conf));
 		}
 	}
 }
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b2fe201b599d..017439e2af03 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3578,12 +3578,6 @@  static void __add_stripe_bio(struct stripe_head *sh, struct bio *bi,
 		 * is added to a batch, STRIPE_BIT_DELAY cannot be changed
 		 * any more.
 		 */
-		set_bit(STRIPE_BITMAP_PENDING, &sh->state);
-		spin_unlock_irq(&sh->stripe_lock);
-		conf->mddev->bitmap_ops->startwrite(conf->mddev, sh->sector,
-					RAID5_STRIPE_SECTORS(conf));
-		spin_lock_irq(&sh->stripe_lock);
-		clear_bit(STRIPE_BITMAP_PENDING, &sh->state);
 		if (!sh->batch_head) {
 			sh->bm_seq = conf->seq_flush+1;
 			set_bit(STRIPE_BIT_DELAY, &sh->state);
@@ -3638,7 +3632,6 @@  handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 	BUG_ON(sh->batch_head);
 	for (i = disks; i--; ) {
 		struct bio *bi;
-		int bitmap_end = 0;
 
 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
 			struct md_rdev *rdev = conf->disks[i].rdev;
@@ -3663,8 +3656,6 @@  handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 		sh->dev[i].towrite = NULL;
 		sh->overwrite_disks = 0;
 		spin_unlock_irq(&sh->stripe_lock);
-		if (bi)
-			bitmap_end = 1;
 
 		log_stripe_write_finished(sh);
 
@@ -3679,10 +3670,6 @@  handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 			bio_io_error(bi);
 			bi = nextbi;
 		}
-		if (bitmap_end)
-			conf->mddev->bitmap_ops->endwrite(conf->mddev,
-					sh->sector, RAID5_STRIPE_SECTORS(conf));
-		bitmap_end = 0;
 		/* and fail all 'written' */
 		bi = sh->dev[i].written;
 		sh->dev[i].written = NULL;
@@ -3691,7 +3678,6 @@  handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 			sh->dev[i].page = sh->dev[i].orig_page;
 		}
 
-		if (bi) bitmap_end = 1;
 		while (bi && bi->bi_iter.bi_sector <
 		       sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
 			struct bio *bi2 = r5_next_bio(conf, bi, sh->dev[i].sector);
@@ -3725,9 +3711,6 @@  handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 				bi = nextbi;
 			}
 		}
-		if (bitmap_end)
-			conf->mddev->bitmap_ops->endwrite(conf->mddev,
-					sh->sector, RAID5_STRIPE_SECTORS(conf));
 		/* If we were in the middle of a write the parity block might
 		 * still be locked - so just clear all R5_LOCKED flags
 		 */
@@ -4076,8 +4059,7 @@  static void handle_stripe_clean_event(struct r5conf *conf,
 					bio_endio(wbi);
 					wbi = wbi2;
 				}
-				conf->mddev->bitmap_ops->endwrite(conf->mddev,
-					sh->sector, RAID5_STRIPE_SECTORS(conf));
+
 				if (head_sh->batch_head) {
 					sh = list_first_entry(&sh->batch_list,
 							      struct stripe_head,
@@ -5797,10 +5779,6 @@  static void make_discard_request(struct mddev *mddev, struct bio *bi)
 		}
 		spin_unlock_irq(&sh->stripe_lock);
 		if (conf->mddev->bitmap) {
-			for (d = 0; d < conf->raid_disks - conf->max_degraded;
-			     d++)
-				mddev->bitmap_ops->startwrite(mddev, sh->sector,
-					RAID5_STRIPE_SECTORS(conf));
 			sh->bm_seq = conf->seq_flush + 1;
 			set_bit(STRIPE_BIT_DELAY, &sh->state);
 		}