[PATCH 0/3] Fix undefined behaviour during device synchronization

md/drbd drivers use 'signed int' variable to track sync vs non-sync IO,
and judge whether sync IO needs to be throttled by signed comparison.
If the value of the variable is greater than INT_MAX or close to
INT_MAX, some undefined behavior may occur.

Fix by using 64bit signed integer type.

The v2 "md: Fix undefined behaviour in is_mddev_idle" patch
differences to v1:
- add ubsan info in message
- use 64bit signed integer type instead of long type;
- move sync_io variable form struct gendisk to struct md_rdev, and 
  modify md_sync_acct() and md_sync_acct_bio() to fit for this change.

Li Jinlin (3):
  md: Fix undefined behaviour in is_mddev_idle
  drdb: Fix undefined behaviour in drbd_rs_c_min_rate_throttle
  drdb: Remove useless variable in struct drbd_device

 drivers/block/drbd/drbd_bitmap.c   |  2 +-
 drivers/block/drbd/drbd_int.h      |  5 ++---
 drivers/block/drbd/drbd_main.c     |  3 +--
 drivers/block/drbd/drbd_receiver.c | 12 ++++++------
 drivers/block/drbd/drbd_state.c    |  1 -
 drivers/block/drbd/drbd_worker.c   |  5 ++---
 drivers/md/md.c                    |  6 +++---
 drivers/md/md.h                    | 13 +++++++++----
 drivers/md/raid1.c                 |  4 ++--
 drivers/md/raid10.c                | 24 ++++++++++++------------
 drivers/md/raid5.c                 |  4 ++--
 include/linux/genhd.h              |  1 -
 12 files changed, 40 insertions(+), 40 deletions(-)

-- 
2.27.0

When the stat aacum of the disk is greater than INT_MAX, its
value becomes negative after casting to 'int', which may lead
to overflow after subtracting a positive number. In the same
way, when the value of rs_sect_ev is greater than INT_MAX,
overflow may also occur. These situations will lead to
undefined behavior.

Otherwise, if the stat accum of the disk is close to INT_MAX
when creating md, the initial value of rs_last_events would be
set close to INT_MAX when mddev initializes IO event counters.
'curr_events - device->rs_last_events > 64' will always false
during synchronization, which may cause resync is not throttled
even if the lower device is busy.

Fix by using atomic64_t type for rs_sect_ev, and using s64 type
for curr_events/last_events.

Signed-off-by: Li Jinlin <redacted>
---
 drivers/block/drbd/drbd_bitmap.c   |  2 +-
 drivers/block/drbd/drbd_int.h      |  4 ++--
 drivers/block/drbd/drbd_main.c     |  2 +-
 drivers/block/drbd/drbd_receiver.c | 12 ++++++------
 drivers/block/drbd/drbd_worker.c   |  4 ++--
 5 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index c1f816f896a8..d580f4071622 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c

@@ -1021,7 +1021,7 @@ static void bm_page_io_async(struct drbd_bm_aio_ctx *ctx, int page_nr) __must_ho
 		submit_bio(bio);
 		/* this should not count as user activity and cause the
 		 * resync to throttle -- see drbd_rs_should_slow_down(). */
-		atomic_add(len >> 9, &device->rs_sect_ev);
+		atomic64_add(len >> 9, &device->rs_sect_ev);
 	}
 }
 

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index f27d5b0f9a0b..1b71adc07e83 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h

@@ -954,9 +954,9 @@ struct drbd_device {
 	struct mutex *state_mutex; /* either own_state_mutex or first_peer_device(device)->connection->cstate_mutex */
 	char congestion_reason;  /* Why we where congested... */
 	atomic_t rs_sect_in; /* for incoming resync data rate, SyncTarget */
-	atomic_t rs_sect_ev; /* for submitted resync data rate, both */
+	atomic64_t rs_sect_ev; /* for submitted resync data rate, both */
 	int rs_last_sect_ev; /* counter to compare with */
-	int rs_last_events;  /* counter of read or write "events" (unit sectors)
+	s64 rs_last_events;  /* counter of read or write "events" (unit sectors)
 			      * on the lower level device when we last looked. */
 	int c_sync_rate; /* current resync rate after syncer throttle magic */
 	struct fifo_buffer *rs_plan_s; /* correction values of resync planer (RCU, connection->conn_update) */

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 53ba2dddba6e..ea057bd60541 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c

@@ -1974,7 +1974,7 @@ void drbd_init_set_defaults(struct drbd_device *device)
 	atomic_set(&device->local_cnt, 0);
 	atomic_set(&device->pp_in_use_by_net, 0);
 	atomic_set(&device->rs_sect_in, 0);
-	atomic_set(&device->rs_sect_ev, 0);
+	atomic64_set(&device->rs_sect_ev, 0);
 	atomic_set(&device->ap_in_flight, 0);
 	atomic_set(&device->md_io.in_use, 0);
 

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 1f740e42e457..4b75ad3dd0cd 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c

@@ -2106,7 +2106,7 @@ static int recv_resync_read(struct drbd_peer_device *peer_device, sector_t secto
 	list_add_tail(&peer_req->w.list, &device->sync_ee);
 	spin_unlock_irq(&device->resource->req_lock);
 
-	atomic_add(pi->size >> 9, &device->rs_sect_ev);
+	atomic64_add(pi->size >> 9, &device->rs_sect_ev);
 	if (drbd_submit_peer_request(device, peer_req, REQ_OP_WRITE, 0,
 				     DRBD_FAULT_RS_WR) == 0)
 		return 0;

@@ -2792,7 +2792,7 @@ bool drbd_rs_c_min_rate_throttle(struct drbd_device *device)
 	struct gendisk *disk = device->ldev->backing_bdev->bd_disk;
 	unsigned long db, dt, dbdt;
 	unsigned int c_min_rate;
-	int curr_events;
+	s64 curr_events;
 
 	rcu_read_lock();
 	c_min_rate = rcu_dereference(device->ldev->disk_conf)->c_min_rate;

@@ -2802,8 +2802,8 @@ bool drbd_rs_c_min_rate_throttle(struct drbd_device *device)
 	if (c_min_rate == 0)
 		return false;
 
-	curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
-			atomic_read(&device->rs_sect_ev);
+	curr_events = (s64)part_stat_read_accum(disk->part0, sectors) -
+			atomic64_read(&device->rs_sect_ev);
 
 	if (atomic_read(&device->ap_actlog_cnt)
 	    || curr_events - device->rs_last_events > 64) {

@@ -3023,7 +3023,7 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
 		goto out_free_e;
 
 submit_for_resync:
-	atomic_add(size >> 9, &device->rs_sect_ev);
+	atomic64_add(size >> 9, &device->rs_sect_ev);
 
 submit:
 	update_receiver_timing_details(connection, drbd_submit_peer_request);

@@ -5019,7 +5019,7 @@ static int receive_rs_deallocated(struct drbd_connection *connection, struct pac
 		list_add_tail(&peer_req->w.list, &device->sync_ee);
 		spin_unlock_irq(&device->resource->req_lock);
 
-		atomic_add(pi->size >> 9, &device->rs_sect_ev);
+		atomic64_add(pi->size >> 9, &device->rs_sect_ev);
 		err = drbd_submit_peer_request(device, peer_req, op, 0, DRBD_FAULT_RS_WR);
 
 		if (err) {

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 64563bfdf0da..a4edd0a9c875 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c

@@ -409,7 +409,7 @@ static int read_for_csum(struct drbd_peer_device *peer_device, sector_t sector,
 	list_add_tail(&peer_req->w.list, &device->read_ee);
 	spin_unlock_irq(&device->resource->req_lock);
 
-	atomic_add(size >> 9, &device->rs_sect_ev);
+	atomic64_add(size >> 9, &device->rs_sect_ev);
 	if (drbd_submit_peer_request(device, peer_req, REQ_OP_READ, 0,
 				     DRBD_FAULT_RS_RD) == 0)
 		return 0;

@@ -1679,7 +1679,7 @@ void drbd_rs_controller_reset(struct drbd_device *device)
 	struct fifo_buffer *plan;
 
 	atomic_set(&device->rs_sect_in, 0);
-	atomic_set(&device->rs_sect_ev, 0);
+	atomic64_set(&device->rs_sect_ev, 0);
 	device->rs_in_flight = 0;
 	device->rs_last_events =
 		(int)part_stat_read_accum(disk->part0, sectors);

-- 
2.27.0

UBSAN reports this problem:

[ 5984.281385] UBSAN: Undefined behaviour in drivers/md/md.c:8175:15
[ 5984.281390] signed integer overflow:
[ 5984.281393] -2147483291 - 2072033152 cannot be represented in type 'int'
[ 5984.281400] CPU: 25 PID: 1854 Comm: md101_resync Kdump: loaded Not tainted 4.19.90
[ 5984.281404] Hardware name: Huawei TaiShan 200 (Model 5280)/BC82AMDDA
[ 5984.281406] Call trace:
[ 5984.281415]  dump_backtrace+0x0/0x310
[ 5984.281418]  show_stack+0x28/0x38
[ 5984.281425]  dump_stack+0xec/0x15c
[ 5984.281430]  ubsan_epilogue+0x18/0x84
[ 5984.281434]  handle_overflow+0x14c/0x19c
[ 5984.281439]  __ubsan_handle_sub_overflow+0x34/0x44
[ 5984.281445]  is_mddev_idle+0x338/0x3d8
[ 5984.281449]  md_do_sync+0x1bb8/0x1cf8
[ 5984.281452]  md_thread+0x220/0x288
[ 5984.281457]  kthread+0x1d8/0x1e0
[ 5984.281461]  ret_from_fork+0x10/0x18

When the stat aacum of the disk is greater than INT_MAX, its
value becomes negative after casting to 'int', which may lead
to overflow after subtracting a positive number. In the same
way, when the value of sync_io is greater than INT_MAX,
overflow may also occur. These situations will lead to
undefined behavior.

Otherwise, if the stat accum of the disk is close to INT_MAX
when creating raid arrays, the initial value of last_events
would be set close to INT_MAX when mddev initializes IO
event counters. 'curr_events - rdev->last_events > 64' will
always false during synchronization. If all the disks of mddev
are in this case, is_mddev_idle() will always return 1, which
may cause non-sync IO is very slow.

To address these problems, need to use 64bit signed integer
type for sync_io, last_events, and curr_events.

In all the drivers that come with the kernel, the sync_io
variable in struct gendisk is only used for the md driver
currently. It should be more suitable in struct md_rdev, so
add the sync_io variable in struct md_rdev, and use it to
replace. We modify md_sync_acct() and md_sync_acct_bio()
to fit for this change as well. md_sync_acct_bio() need
access to the rdev, so we set bio->bi_bdev to rdev before
calling it, and reset bio->bi_bdev to bdev in this function.

Signed-off-by: Li Jinlin <redacted>
---
 drivers/md/md.c       |  6 +++---
 drivers/md/md.h       | 13 +++++++++----
 drivers/md/raid1.c    |  4 ++--
 drivers/md/raid10.c   | 24 ++++++++++++------------
 drivers/md/raid5.c    |  4 ++--
 include/linux/genhd.h |  1 -
 6 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5111ed966947..f1b71a92801e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c

@@ -8429,14 +8429,14 @@ static int is_mddev_idle(struct mddev *mddev, int init)
 {
 	struct md_rdev *rdev;
 	int idle;
-	int curr_events;
+	s64 curr_events;
 
 	idle = 1;
 	rcu_read_lock();
 	rdev_for_each_rcu(rdev, mddev) {
 		struct gendisk *disk = rdev->bdev->bd_disk;
-		curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
-			      atomic_read(&disk->sync_io);
+		curr_events = (s64)part_stat_read_accum(disk->part0, sectors) -
+			      atomic64_read(&rdev->sync_io);
 		/* sync IO will cause sync_io to increase before the disk_stats
 		 * as sync_io is counted when a request starts, and
 		 * disk_stats is counted when it completes.

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 53ea7a6961de..584e357e0940 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h

@@ -50,7 +50,7 @@ struct md_rdev {
 
 	sector_t sectors;		/* Device size (in 512bytes sectors) */
 	struct mddev *mddev;		/* RAID array if running */
-	int last_events;		/* IO event timestamp */
+	s64 last_events;		/* IO event timestamp */
 
 	/*
 	 * If meta_bdev is non-NULL, it means that a separate device is

@@ -138,6 +138,8 @@ struct md_rdev {
 		unsigned int size;	/* Size in sectors of the PPL space */
 		sector_t sector;	/* First sector of the PPL space */
 	} ppl;
+
+	atomic64_t sync_io;		/* counter of sync IO (unit sectors) */
 };
 enum flag_bits {
 	Faulty,			/* device is known to have a fault */

@@ -549,14 +551,17 @@ static inline int mddev_trylock(struct mddev *mddev)
 }
 extern void mddev_unlock(struct mddev *mddev);
 
-static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
+static inline void md_sync_acct(struct md_rdev *rdev, unsigned long nr_sectors)
 {
-	atomic_add(nr_sectors, &bdev->bd_disk->sync_io);
+	atomic64_add(nr_sectors, &rdev->sync_io);
 }
 
 static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
 {
-	md_sync_acct(bio->bi_bdev, nr_sectors);
+	struct md_rdev *rdev = (void *)bio->bi_bdev;
+
+	bio_set_dev(bio, rdev->bdev);
+	md_sync_acct(rdev, nr_sectors);
 }
 
 struct md_personality

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 7dc8026cf6ee..74c42dabe57c 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c

@@ -2232,7 +2232,7 @@ static void sync_request_write(struct mddev *mddev, struct r1bio *r1_bio)
 
 		wbio->bi_end_io = end_sync_write;
 		atomic_inc(&r1_bio->remaining);
-		md_sync_acct(conf->mirrors[i].rdev->bdev, bio_sectors(wbio));
+		md_sync_acct(conf->mirrors[i].rdev, bio_sectors(wbio));
 
 		submit_bio_noacct(wbio);
 	}

@@ -2791,7 +2791,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
 		if (rdev && bio->bi_end_io) {
 			atomic_inc(&rdev->nr_pending);
 			bio->bi_iter.bi_sector = sector_nr + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
 			if (test_bit(FailFast, &rdev->flags))
 				bio->bi_opf |= MD_FAILFAST;
 		}

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index dde98f65bd04..fc1e6c0996de 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c

@@ -2407,7 +2407,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
 
 		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
 		atomic_inc(&r10_bio->remaining);
-		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(tbio));
+		md_sync_acct(conf->mirrors[d].rdev, bio_sectors(tbio));
 
 		if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
 			tbio->bi_opf |= MD_FAILFAST;

@@ -2430,7 +2430,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
 			bio_copy_data(tbio, fbio);
 		d = r10_bio->devs[i].devnum;
 		atomic_inc(&r10_bio->remaining);
-		md_sync_acct(conf->mirrors[d].replacement->bdev,
+		md_sync_acct(conf->mirrors[d].replacement,
 			     bio_sectors(tbio));
 		submit_bio_noacct(tbio);
 	}

@@ -2562,12 +2562,12 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
 		wbio2 = NULL;
 	if (wbio->bi_end_io) {
 		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
-		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
+		md_sync_acct(conf->mirrors[d].rdev, bio_sectors(wbio));
 		submit_bio_noacct(wbio);
 	}
 	if (wbio2) {
 		atomic_inc(&conf->mirrors[d].replacement->nr_pending);
-		md_sync_acct(conf->mirrors[d].replacement->bdev,
+		md_sync_acct(conf->mirrors[d].replacement,
 			     bio_sectors(wbio2));
 		submit_bio_noacct(wbio2);
 	}

@@ -3486,7 +3486,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 				from_addr = r10_bio->devs[j].addr;
 				bio->bi_iter.bi_sector = from_addr +
 					rdev->data_offset;
-				bio_set_dev(bio, rdev->bdev);
+				bio->bi_bdev = (void *)rdev;
 				atomic_inc(&rdev->nr_pending);
 				/* and we write to 'i' (if not in_sync) */
 

@@ -3508,7 +3508,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 					bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 					bio->bi_iter.bi_sector = to_addr
 						+ mrdev->data_offset;
-					bio_set_dev(bio, mrdev->bdev);
+					bio->bi_bdev = (void *)mrdev;
 					atomic_inc(&r10_bio->remaining);
 				} else
 					r10_bio->devs[1].bio->bi_end_io = NULL;

@@ -3529,7 +3529,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 				bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 				bio->bi_iter.bi_sector = to_addr +
 					mreplace->data_offset;
-				bio_set_dev(bio, mreplace->bdev);
+				bio->bi_bdev = (void *)mreplace;
 				atomic_inc(&r10_bio->remaining);
 				break;
 			}

@@ -3684,7 +3684,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			if (test_bit(FailFast, &rdev->flags))
 				bio->bi_opf |= MD_FAILFAST;
 			bio->bi_iter.bi_sector = sector + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
 			count++;
 
 			rdev = rcu_dereference(conf->mirrors[d].replacement);

@@ -3706,7 +3706,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			if (test_bit(FailFast, &rdev->flags))
 				bio->bi_opf |= MD_FAILFAST;
 			bio->bi_iter.bi_sector = sector + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
 			count++;
 			rcu_read_unlock();
 		}

@@ -4865,7 +4865,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
 
 	read_bio = bio_alloc_bioset(GFP_KERNEL, RESYNC_PAGES, &mddev->bio_set);
 
-	bio_set_dev(read_bio, rdev->bdev);
+	read_bio->bi_bdev = (void *)rdev;
 	read_bio->bi_iter.bi_sector = (r10_bio->devs[r10_bio->read_slot].addr
 			       + rdev->data_offset);
 	read_bio->bi_private = r10_bio;

@@ -4921,7 +4921,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
 		if (!rdev2 || test_bit(Faulty, &rdev2->flags))
 			continue;
 
-		bio_set_dev(b, rdev2->bdev);
+		b->bi_bdev = (void *)rdev2;
 		b->bi_iter.bi_sector = r10_bio->devs[s/2].addr +
 			rdev2->new_data_offset;
 		b->bi_end_io = end_reshape_write;

@@ -5016,7 +5016,7 @@ static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio)
 		}
 		atomic_inc(&rdev->nr_pending);
 		rcu_read_unlock();
-		md_sync_acct_bio(b, r10_bio->sectors);
+		md_sync_acct(rdev, r10_bio->sectors);
 		atomic_inc(&r10_bio->remaining);
 		b->bi_next = NULL;
 		submit_bio_noacct(b);

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9c1a5877cf9f..b932282ff50a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c

@@ -1167,7 +1167,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 		if (rdev) {
 			if (s->syncing || s->expanding || s->expanded
 			    || s->replacing)
-				md_sync_acct(rdev->bdev, RAID5_STRIPE_SECTORS(conf));
+				md_sync_acct(rdev, RAID5_STRIPE_SECTORS(conf));
 
 			set_bit(STRIPE_IO_STARTED, &sh->state);
 

@@ -1234,7 +1234,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 		if (rrdev) {
 			if (s->syncing || s->expanding || s->expanded
 			    || s->replacing)
-				md_sync_acct(rrdev->bdev, RAID5_STRIPE_SECTORS(conf));
+				md_sync_acct(rrdev, RAID5_STRIPE_SECTORS(conf));
 
 			set_bit(STRIPE_IO_STARTED, &sh->state);
 

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 74c410263113..6b84444111e4 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h

@@ -150,7 +150,6 @@ struct gendisk {
 	struct list_head slave_bdevs;
 #endif
 	struct timer_rand_state *random;
-	atomic_t sync_io;		/* RAID */
 	struct disk_events *ev;
 #ifdef  CONFIG_BLK_DEV_INTEGRITY
 	struct kobject integrity_kobj;

-- 
2.27.0

rs_last_sect_ev is unused since added in 1d7734a0df02, so just remove it.

Signed-off-by: Li Jinlin <redacted>
---
 drivers/block/drbd/drbd_int.h    | 1 -
 drivers/block/drbd/drbd_main.c   | 1 -
 drivers/block/drbd/drbd_state.c  | 1 -
 drivers/block/drbd/drbd_worker.c | 1 -
 4 files changed, 4 deletions(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 1b71adc07e83..a163141aff1b 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h

@@ -955,7 +955,6 @@ struct drbd_device {
 	char congestion_reason;  /* Why we where congested... */
 	atomic_t rs_sect_in; /* for incoming resync data rate, SyncTarget */
 	atomic64_t rs_sect_ev; /* for submitted resync data rate, both */
-	int rs_last_sect_ev; /* counter to compare with */
 	s64 rs_last_events;  /* counter of read or write "events" (unit sectors)
 			      * on the lower level device when we last looked. */
 	int c_sync_rate; /* current resync rate after syncer throttle magic */

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index ea057bd60541..f1fa03c69809 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c

@@ -2046,7 +2046,6 @@ void drbd_device_cleanup(struct drbd_device *device)
 	device->rs_total     =
 	device->rs_failed    = 0;
 	device->rs_last_events = 0;
-	device->rs_last_sect_ev = 0;
 	for (i = 0; i < DRBD_SYNC_MARKS; i++) {
 		device->rs_mark_left[i] = 0;
 		device->rs_mark_time[i] = 0;

diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index b8a27818ab3f..4a6c69133c62 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c

@@ -1389,7 +1389,6 @@ _drbd_set_state(struct drbd_device *device, union drbd_state ns,
 
 		set_ov_position(device, ns.conn);
 		device->rs_start = now;
-		device->rs_last_sect_ev = 0;
 		device->ov_last_oos_size = 0;
 		device->ov_last_oos_start = 0;
 

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index a4edd0a9c875..45ae4abd355a 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c

@@ -1829,7 +1829,6 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 		device->rs_failed    = 0;
 		device->rs_paused    = 0;
 		device->rs_same_csum = 0;
-		device->rs_last_sect_ev = 0;
 		device->rs_total     = tw;
 		device->rs_start     = now;
 		for (i = 0; i < DRBD_SYNC_MARKS; i++) {

-- 
2.27.0

On 12/10/21 6:17 AM, Li Jinlin wrote:

UBSAN reports this problem:

[ 5984.281385] UBSAN: Undefined behaviour in drivers/md/md.c:8175:15
[ 5984.281390] signed integer overflow:
[ 5984.281393] -2147483291 - 2072033152 cannot be represented in type 'int'
[ 5984.281400] CPU: 25 PID: 1854 Comm: md101_resync Kdump: loaded Not tainted 4.19.90
[ 5984.281404] Hardware name: Huawei TaiShan 200 (Model 5280)/BC82AMDDA
[ 5984.281406] Call trace:
[ 5984.281415]  dump_backtrace+0x0/0x310
[ 5984.281418]  show_stack+0x28/0x38
[ 5984.281425]  dump_stack+0xec/0x15c
[ 5984.281430]  ubsan_epilogue+0x18/0x84
[ 5984.281434]  handle_overflow+0x14c/0x19c
[ 5984.281439]  __ubsan_handle_sub_overflow+0x34/0x44
[ 5984.281445]  is_mddev_idle+0x338/0x3d8
[ 5984.281449]  md_do_sync+0x1bb8/0x1cf8
[ 5984.281452]  md_thread+0x220/0x288
[ 5984.281457]  kthread+0x1d8/0x1e0
[ 5984.281461]  ret_from_fork+0x10/0x18

When the stat aacum of the disk is greater than INT_MAX, its
value becomes negative after casting to 'int', which may lead
to overflow after subtracting a positive number. In the same
way, when the value of sync_io is greater than INT_MAX,
overflow may also occur. These situations will lead to
undefined behavior.

Otherwise, if the stat accum of the disk is close to INT_MAX
when creating raid arrays, the initial value of last_events
would be set close to INT_MAX when mddev initializes IO
event counters. 'curr_events - rdev->last_events > 64' will
always false during synchronization. If all the disks of mddev
are in this case, is_mddev_idle() will always return 1, which
may cause non-sync IO is very slow.

To address these problems, need to use 64bit signed integer
type for sync_io, last_events, and curr_events.

In all the drivers that come with the kernel, the sync_io
variable in struct gendisk is only used for the md driver
currently. It should be more suitable in struct md_rdev, so
add the sync_io variable in struct md_rdev, and use it to
replace. We modify md_sync_acct() and md_sync_acct_bio()
to fit for this change as well. md_sync_acct_bio() need
access to the rdev, so we set bio->bi_bdev to rdev before
calling it, and reset bio->bi_bdev to bdev in this function.

Please make that two patches, one for moving sync_io and one for
fixing the undefined behaviour.

So you are replacing a 'signed integer' (ie 32bit) calculation with a 
'signed 64-bit integer' calculation.
IE you just shifted the overflow from INT_MAX to LONG_MAX, without 
actually fixing it, or?

That look weird. bio->bi_bdev should be a 'struct gendisk', not a MD 
internal data structure.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

On 2021/12/10 15:45, Hannes Reinecke wrote:

On 12/10/21 6:17 AM, Li Jinlin wrote:

quoted

UBSAN reports this problem:

[ 5984.281385] UBSAN: Undefined behaviour in drivers/md/md.c:8175:15
[ 5984.281390] signed integer overflow:
[ 5984.281393] -2147483291 - 2072033152 cannot be represented in type 'int'
[ 5984.281400] CPU: 25 PID: 1854 Comm: md101_resync Kdump: loaded Not tainted 4.19.90
[ 5984.281404] Hardware name: Huawei TaiShan 200 (Model 5280)/BC82AMDDA
[ 5984.281406] Call trace:
[ 5984.281415]  dump_backtrace+0x0/0x310
[ 5984.281418]  show_stack+0x28/0x38
[ 5984.281425]  dump_stack+0xec/0x15c
[ 5984.281430]  ubsan_epilogue+0x18/0x84
[ 5984.281434]  handle_overflow+0x14c/0x19c
[ 5984.281439]  __ubsan_handle_sub_overflow+0x34/0x44
[ 5984.281445]  is_mddev_idle+0x338/0x3d8
[ 5984.281449]  md_do_sync+0x1bb8/0x1cf8
[ 5984.281452]  md_thread+0x220/0x288
[ 5984.281457]  kthread+0x1d8/0x1e0
[ 5984.281461]  ret_from_fork+0x10/0x18

When the stat aacum of the disk is greater than INT_MAX, its
value becomes negative after casting to 'int', which may lead
to overflow after subtracting a positive number. In the same
way, when the value of sync_io is greater than INT_MAX,
overflow may also occur. These situations will lead to
undefined behavior.

Otherwise, if the stat accum of the disk is close to INT_MAX
when creating raid arrays, the initial value of last_events
would be set close to INT_MAX when mddev initializes IO
event counters. 'curr_events - rdev->last_events > 64' will
always false during synchronization. If all the disks of mddev
are in this case, is_mddev_idle() will always return 1, which
may cause non-sync IO is very slow.

To address these problems, need to use 64bit signed integer
type for sync_io, last_events, and curr_events.

In all the drivers that come with the kernel, the sync_io
variable in struct gendisk is only used for the md driver
currently. It should be more suitable in struct md_rdev, so
add the sync_io variable in struct md_rdev, and use it to
replace. We modify md_sync_acct() and md_sync_acct_bio()
to fit for this change as well. md_sync_acct_bio() need
access to the rdev, so we set bio->bi_bdev to rdev before
calling it, and reset bio->bi_bdev to bdev in this function.

Please make that two patches, one for moving sync_io and one for
fixing the undefined behaviour.

quoted

Signed-off-by: Li Jinlin <redacted>
---
  drivers/md/md.c       |  6 +++---
  drivers/md/md.h       | 13 +++++++++----
  drivers/md/raid1.c    |  4 ++--
  drivers/md/raid10.c   | 24 ++++++++++++------------
  drivers/md/raid5.c    |  4 ++--
  include/linux/genhd.h |  1 -
  6 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5111ed966947..f1b71a92801e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c

@@ -8429,14 +8429,14 @@ static int is_mddev_idle(struct mddev *mddev, int init)
  {
  	struct md_rdev *rdev;
  	int idle;
-	int curr_events;
+	s64 curr_events;
  
  	idle = 1;
  	rcu_read_lock();
  	rdev_for_each_rcu(rdev, mddev) {
  		struct gendisk *disk = rdev->bdev->bd_disk;
-		curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
-			      atomic_read(&disk->sync_io);
+		curr_events = (s64)part_stat_read_accum(disk->part0, sectors) -
+			      atomic64_read(&rdev->sync_io);

So you are replacing a 'signed integer' (ie 32bit) calculation with a 
'signed 64-bit integer' calculation.
IE you just shifted the overflow from INT_MAX to LONG_MAX, without 
actually fixing it, or?

quoted

  		/* sync IO will cause sync_io to increase before the disk_stats
  		 * as sync_io is counted when a request starts, and
  		 * disk_stats is counted when it completes.

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 53ea7a6961de..584e357e0940 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h

@@ -50,7 +50,7 @@ struct md_rdev {
  
  	sector_t sectors;		/* Device size (in 512bytes sectors) */
  	struct mddev *mddev;		/* RAID array if running */
-	int last_events;		/* IO event timestamp */
+	s64 last_events;		/* IO event timestamp */
  
  	/*
  	 * If meta_bdev is non-NULL, it means that a separate device is

@@ -138,6 +138,8 @@ struct md_rdev {
  		unsigned int size;	/* Size in sectors of the PPL space */
  		sector_t sector;	/* First sector of the PPL space */
  	} ppl;
+
+	atomic64_t sync_io;		/* counter of sync IO (unit sectors) */
  };
  enum flag_bits {
  	Faulty,			/* device is known to have a fault */

@@ -549,14 +551,17 @@ static inline int mddev_trylock(struct mddev *mddev)
  }
  extern void mddev_unlock(struct mddev *mddev);
  
-static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
+static inline void md_sync_acct(struct md_rdev *rdev, unsigned long nr_sectors)
  {
-	atomic_add(nr_sectors, &bdev->bd_disk->sync_io);
+	atomic64_add(nr_sectors, &rdev->sync_io);
  }
  
  static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
  {
-	md_sync_acct(bio->bi_bdev, nr_sectors);
+	struct md_rdev *rdev = (void *)bio->bi_bdev;

That look weird. bio->bi_bdev should be a 'struct gendisk', not a MD 
internal data structure.

You mean a "struct block_device". right ? :)

quoted

+
+	bio_set_dev(bio, rdev->bdev);
+	md_sync_acct(rdev, nr_sectors);
  }
  
  struct md_personality

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 7dc8026cf6ee..74c42dabe57c 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c

@@ -2232,7 +2232,7 @@ static void sync_request_write(struct mddev *mddev, struct r1bio *r1_bio)
  
  		wbio->bi_end_io = end_sync_write;
  		atomic_inc(&r1_bio->remaining);
-		md_sync_acct(conf->mirrors[i].rdev->bdev, bio_sectors(wbio));
+		md_sync_acct(conf->mirrors[i].rdev, bio_sectors(wbio));
  
  		submit_bio_noacct(wbio);
  	}

@@ -2791,7 +2791,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
  		if (rdev && bio->bi_end_io) {
  			atomic_inc(&rdev->nr_pending);
  			bio->bi_iter.bi_sector = sector_nr + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
  			if (test_bit(FailFast, &rdev->flags))
  				bio->bi_opf |= MD_FAILFAST;
  		}

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index dde98f65bd04..fc1e6c0996de 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c

@@ -2407,7 +2407,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  
  		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
  		atomic_inc(&r10_bio->remaining);
-		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(tbio));
+		md_sync_acct(conf->mirrors[d].rdev, bio_sectors(tbio));
  
  		if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
  			tbio->bi_opf |= MD_FAILFAST;

@@ -2430,7 +2430,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  			bio_copy_data(tbio, fbio);
  		d = r10_bio->devs[i].devnum;
  		atomic_inc(&r10_bio->remaining);
-		md_sync_acct(conf->mirrors[d].replacement->bdev,
+		md_sync_acct(conf->mirrors[d].replacement,
  			     bio_sectors(tbio));
  		submit_bio_noacct(tbio);
  	}

@@ -2562,12 +2562,12 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  		wbio2 = NULL;
  	if (wbio->bi_end_io) {
  		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
-		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
+		md_sync_acct(conf->mirrors[d].rdev, bio_sectors(wbio));
  		submit_bio_noacct(wbio);
  	}
  	if (wbio2) {
  		atomic_inc(&conf->mirrors[d].replacement->nr_pending);
-		md_sync_acct(conf->mirrors[d].replacement->bdev,
+		md_sync_acct(conf->mirrors[d].replacement,
  			     bio_sectors(wbio2));
  		submit_bio_noacct(wbio2);
  	}

@@ -3486,7 +3486,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  				from_addr = r10_bio->devs[j].addr;
  				bio->bi_iter.bi_sector = from_addr +
  					rdev->data_offset;
-				bio_set_dev(bio, rdev->bdev);
+				bio->bi_bdev = (void *)rdev;
  				atomic_inc(&rdev->nr_pending);
  				/* and we write to 'i' (if not in_sync) */
  

@@ -3508,7 +3508,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  					bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
  					bio->bi_iter.bi_sector = to_addr
  						+ mrdev->data_offset;
-					bio_set_dev(bio, mrdev->bdev);
+					bio->bi_bdev = (void *)mrdev;
  					atomic_inc(&r10_bio->remaining);
  				} else
  					r10_bio->devs[1].bio->bi_end_io = NULL;

@@ -3529,7 +3529,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  				bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
  				bio->bi_iter.bi_sector = to_addr +
  					mreplace->data_offset;
-				bio_set_dev(bio, mreplace->bdev);
+				bio->bi_bdev = (void *)mreplace;
  				atomic_inc(&r10_bio->remaining);
  				break;
  			}

@@ -3684,7 +3684,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  			if (test_bit(FailFast, &rdev->flags))
  				bio->bi_opf |= MD_FAILFAST;
  			bio->bi_iter.bi_sector = sector + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
  			count++;
  
  			rdev = rcu_dereference(conf->mirrors[d].replacement);

@@ -3706,7 +3706,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  			if (test_bit(FailFast, &rdev->flags))
  				bio->bi_opf |= MD_FAILFAST;
  			bio->bi_iter.bi_sector = sector + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
  			count++;
  			rcu_read_unlock();
  		}

@@ -4865,7 +4865,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
  
  	read_bio = bio_alloc_bioset(GFP_KERNEL, RESYNC_PAGES, &mddev->bio_set);
  
-	bio_set_dev(read_bio, rdev->bdev);
+	read_bio->bi_bdev = (void *)rdev;
  	read_bio->bi_iter.bi_sector = (r10_bio->devs[r10_bio->read_slot].addr
  			       + rdev->data_offset);
  	read_bio->bi_private = r10_bio;

@@ -4921,7 +4921,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
  		if (!rdev2 || test_bit(Faulty, &rdev2->flags))
  			continue;
  
-		bio_set_dev(b, rdev2->bdev);
+		b->bi_bdev = (void *)rdev2;
  		b->bi_iter.bi_sector = r10_bio->devs[s/2].addr +
  			rdev2->new_data_offset;
  		b->bi_end_io = end_reshape_write;

@@ -5016,7 +5016,7 @@ static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  		}
  		atomic_inc(&rdev->nr_pending);
  		rcu_read_unlock();
-		md_sync_acct_bio(b, r10_bio->sectors);
+		md_sync_acct(rdev, r10_bio->sectors);
  		atomic_inc(&r10_bio->remaining);
  		b->bi_next = NULL;
  		submit_bio_noacct(b);

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9c1a5877cf9f..b932282ff50a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c

@@ -1167,7 +1167,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
  		if (rdev) {
  			if (s->syncing || s->expanding || s->expanded
  			    || s->replacing)
-				md_sync_acct(rdev->bdev, RAID5_STRIPE_SECTORS(conf));
+				md_sync_acct(rdev, RAID5_STRIPE_SECTORS(conf));
  
  			set_bit(STRIPE_IO_STARTED, &sh->state);
  

@@ -1234,7 +1234,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
  		if (rrdev) {
  			if (s->syncing || s->expanding || s->expanded
  			    || s->replacing)
-				md_sync_acct(rrdev->bdev, RAID5_STRIPE_SECTORS(conf));
+				md_sync_acct(rrdev, RAID5_STRIPE_SECTORS(conf));
  
  			set_bit(STRIPE_IO_STARTED, &sh->state);
  

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 74c410263113..6b84444111e4 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h

@@ -150,7 +150,6 @@ struct gendisk {
  	struct list_head slave_bdevs;
  #endif
  	struct timer_rand_state *random;
-	atomic_t sync_io;		/* RAID */
  	struct disk_events *ev;
  #ifdef  CONFIG_BLK_DEV_INTEGRITY
  	struct kobject integrity_kobj;

Cheers,

Hannes

-- 
Damien Le Moal
Western Digital Research

On 12/10/2021 3:17 PM, Damien Le Moal wrote:

On 2021/12/10 15:45, Hannes Reinecke wrote:

quoted

On 12/10/21 6:17 AM, Li Jinlin wrote:

quoted

UBSAN reports this problem:

[ 5984.281385] UBSAN: Undefined behaviour in drivers/md/md.c:8175:15
[ 5984.281390] signed integer overflow:
[ 5984.281393] -2147483291 - 2072033152 cannot be represented in type 'int'
[ 5984.281400] CPU: 25 PID: 1854 Comm: md101_resync Kdump: loaded Not tainted 4.19.90
[ 5984.281404] Hardware name: Huawei TaiShan 200 (Model 5280)/BC82AMDDA
[ 5984.281406] Call trace:
[ 5984.281415]  dump_backtrace+0x0/0x310
[ 5984.281418]  show_stack+0x28/0x38
[ 5984.281425]  dump_stack+0xec/0x15c
[ 5984.281430]  ubsan_epilogue+0x18/0x84
[ 5984.281434]  handle_overflow+0x14c/0x19c
[ 5984.281439]  __ubsan_handle_sub_overflow+0x34/0x44
[ 5984.281445]  is_mddev_idle+0x338/0x3d8
[ 5984.281449]  md_do_sync+0x1bb8/0x1cf8
[ 5984.281452]  md_thread+0x220/0x288
[ 5984.281457]  kthread+0x1d8/0x1e0
[ 5984.281461]  ret_from_fork+0x10/0x18

When the stat aacum of the disk is greater than INT_MAX, its
value becomes negative after casting to 'int', which may lead
to overflow after subtracting a positive number. In the same
way, when the value of sync_io is greater than INT_MAX,
overflow may also occur. These situations will lead to
undefined behavior.

Otherwise, if the stat accum of the disk is close to INT_MAX
when creating raid arrays, the initial value of last_events
would be set close to INT_MAX when mddev initializes IO
event counters. 'curr_events - rdev->last_events > 64' will
always false during synchronization. If all the disks of mddev
are in this case, is_mddev_idle() will always return 1, which
may cause non-sync IO is very slow.

To address these problems, need to use 64bit signed integer
type for sync_io, last_events, and curr_events.

In all the drivers that come with the kernel, the sync_io
variable in struct gendisk is only used for the md driver
currently. It should be more suitable in struct md_rdev, so
add the sync_io variable in struct md_rdev, and use it to
replace. We modify md_sync_acct() and md_sync_acct_bio()
to fit for this change as well. md_sync_acct_bio() need
access to the rdev, so we set bio->bi_bdev to rdev before
calling it, and reset bio->bi_bdev to bdev in this function.

Please make that two patches, one for moving sync_io and one for
fixing the undefined behaviour.

ok.

quoted

quoted

Signed-off-by: Li Jinlin <redacted>
---
  drivers/md/md.c       |  6 +++---
  drivers/md/md.h       | 13 +++++++++----
  drivers/md/raid1.c    |  4 ++--
  drivers/md/raid10.c   | 24 ++++++++++++------------
  drivers/md/raid5.c    |  4 ++--
  include/linux/genhd.h |  1 -
  6 files changed, 28 insertions(+), 24 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5111ed966947..f1b71a92801e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c

@@ -8429,14 +8429,14 @@ static int is_mddev_idle(struct mddev *mddev, int init)
  {
  	struct md_rdev *rdev;
  	int idle;
-	int curr_events;
+	s64 curr_events;
  
  	idle = 1;
  	rcu_read_lock();
  	rdev_for_each_rcu(rdev, mddev) {
  		struct gendisk *disk = rdev->bdev->bd_disk;
-		curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
-			      atomic_read(&disk->sync_io);
+		curr_events = (s64)part_stat_read_accum(disk->part0, sectors) -
+			      atomic64_read(&rdev->sync_io);

So you are replacing a 'signed integer' (ie 32bit) calculation with a 
'signed 64-bit integer' calculation.
IE you just shifted the overflow from INT_MAX to LONG_MAX, without 
actually fixing it, or?

Yes, for the disk with 512-byte sector sizes, the data size of INT_MAX
sectors is 1T. LONG_MAX is enough to use until the server restarts,
and overflow will not occur anymore.

quoted

quoted

  		/* sync IO will cause sync_io to increase before the disk_stats
  		 * as sync_io is counted when a request starts, and
  		 * disk_stats is counted when it completes.

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 53ea7a6961de..584e357e0940 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h

@@ -50,7 +50,7 @@ struct md_rdev {
  
  	sector_t sectors;		/* Device size (in 512bytes sectors) */
  	struct mddev *mddev;		/* RAID array if running */
-	int last_events;		/* IO event timestamp */
+	s64 last_events;		/* IO event timestamp */
  
  	/*
  	 * If meta_bdev is non-NULL, it means that a separate device is

@@ -138,6 +138,8 @@ struct md_rdev {
  		unsigned int size;	/* Size in sectors of the PPL space */
  		sector_t sector;	/* First sector of the PPL space */
  	} ppl;
+
+	atomic64_t sync_io;		/* counter of sync IO (unit sectors) */
  };
  enum flag_bits {
  	Faulty,			/* device is known to have a fault */

@@ -549,14 +551,17 @@ static inline int mddev_trylock(struct mddev *mddev)
  }
  extern void mddev_unlock(struct mddev *mddev);
  
-static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
+static inline void md_sync_acct(struct md_rdev *rdev, unsigned long nr_sectors)
  {
-	atomic_add(nr_sectors, &bdev->bd_disk->sync_io);
+	atomic64_add(nr_sectors, &rdev->sync_io);
  }
  
  static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
  {
-	md_sync_acct(bio->bi_bdev, nr_sectors);
+	struct md_rdev *rdev = (void *)bio->bi_bdev;

That look weird. bio->bi_bdev should be a 'struct gendisk', not a MD 
internal data structure.

You mean a "struct block_device". right ? :)

Here is a difficult point for moving sync_io. We need a good way
to slove it or not move sync_io.

quoted

quoted

+
+	bio_set_dev(bio, rdev->bdev);
+	md_sync_acct(rdev, nr_sectors);
  }
  
  struct md_personality

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 7dc8026cf6ee..74c42dabe57c 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c

@@ -2232,7 +2232,7 @@ static void sync_request_write(struct mddev *mddev, struct r1bio *r1_bio)
  
  		wbio->bi_end_io = end_sync_write;
  		atomic_inc(&r1_bio->remaining);
-		md_sync_acct(conf->mirrors[i].rdev->bdev, bio_sectors(wbio));
+		md_sync_acct(conf->mirrors[i].rdev, bio_sectors(wbio));
  
  		submit_bio_noacct(wbio);
  	}

@@ -2791,7 +2791,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
  		if (rdev && bio->bi_end_io) {
  			atomic_inc(&rdev->nr_pending);
  			bio->bi_iter.bi_sector = sector_nr + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
  			if (test_bit(FailFast, &rdev->flags))
  				bio->bi_opf |= MD_FAILFAST;
  		}

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index dde98f65bd04..fc1e6c0996de 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c

@@ -2407,7 +2407,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  
  		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
  		atomic_inc(&r10_bio->remaining);
-		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(tbio));
+		md_sync_acct(conf->mirrors[d].rdev, bio_sectors(tbio));
  
  		if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
  			tbio->bi_opf |= MD_FAILFAST;

@@ -2430,7 +2430,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  			bio_copy_data(tbio, fbio);
  		d = r10_bio->devs[i].devnum;
  		atomic_inc(&r10_bio->remaining);
-		md_sync_acct(conf->mirrors[d].replacement->bdev,
+		md_sync_acct(conf->mirrors[d].replacement,
  			     bio_sectors(tbio));
  		submit_bio_noacct(tbio);
  	}

@@ -2562,12 +2562,12 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  		wbio2 = NULL;
  	if (wbio->bi_end_io) {
  		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
-		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
+		md_sync_acct(conf->mirrors[d].rdev, bio_sectors(wbio));
  		submit_bio_noacct(wbio);
  	}
  	if (wbio2) {
  		atomic_inc(&conf->mirrors[d].replacement->nr_pending);
-		md_sync_acct(conf->mirrors[d].replacement->bdev,
+		md_sync_acct(conf->mirrors[d].replacement,
  			     bio_sectors(wbio2));
  		submit_bio_noacct(wbio2);
  	}

@@ -3486,7 +3486,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  				from_addr = r10_bio->devs[j].addr;
  				bio->bi_iter.bi_sector = from_addr +
  					rdev->data_offset;
-				bio_set_dev(bio, rdev->bdev);
+				bio->bi_bdev = (void *)rdev;
  				atomic_inc(&rdev->nr_pending);
  				/* and we write to 'i' (if not in_sync) */
  

@@ -3508,7 +3508,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  					bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
  					bio->bi_iter.bi_sector = to_addr
  						+ mrdev->data_offset;
-					bio_set_dev(bio, mrdev->bdev);
+					bio->bi_bdev = (void *)mrdev;
  					atomic_inc(&r10_bio->remaining);
  				} else
  					r10_bio->devs[1].bio->bi_end_io = NULL;

@@ -3529,7 +3529,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  				bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
  				bio->bi_iter.bi_sector = to_addr +
  					mreplace->data_offset;
-				bio_set_dev(bio, mreplace->bdev);
+				bio->bi_bdev = (void *)mreplace;
  				atomic_inc(&r10_bio->remaining);
  				break;
  			}

@@ -3684,7 +3684,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  			if (test_bit(FailFast, &rdev->flags))
  				bio->bi_opf |= MD_FAILFAST;
  			bio->bi_iter.bi_sector = sector + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
  			count++;
  
  			rdev = rcu_dereference(conf->mirrors[d].replacement);

@@ -3706,7 +3706,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
  			if (test_bit(FailFast, &rdev->flags))
  				bio->bi_opf |= MD_FAILFAST;
  			bio->bi_iter.bi_sector = sector + rdev->data_offset;
-			bio_set_dev(bio, rdev->bdev);
+			bio->bi_bdev = (void *)rdev;
  			count++;
  			rcu_read_unlock();
  		}

@@ -4865,7 +4865,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
  
  	read_bio = bio_alloc_bioset(GFP_KERNEL, RESYNC_PAGES, &mddev->bio_set);
  
-	bio_set_dev(read_bio, rdev->bdev);
+	read_bio->bi_bdev = (void *)rdev;
  	read_bio->bi_iter.bi_sector = (r10_bio->devs[r10_bio->read_slot].addr
  			       + rdev->data_offset);
  	read_bio->bi_private = r10_bio;

@@ -4921,7 +4921,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
  		if (!rdev2 || test_bit(Faulty, &rdev2->flags))
  			continue;
  
-		bio_set_dev(b, rdev2->bdev);
+		b->bi_bdev = (void *)rdev2;
  		b->bi_iter.bi_sector = r10_bio->devs[s/2].addr +
  			rdev2->new_data_offset;
  		b->bi_end_io = end_reshape_write;

@@ -5016,7 +5016,7 @@ static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio)
  		}
  		atomic_inc(&rdev->nr_pending);
  		rcu_read_unlock();
-		md_sync_acct_bio(b, r10_bio->sectors);
+		md_sync_acct(rdev, r10_bio->sectors);
  		atomic_inc(&r10_bio->remaining);
  		b->bi_next = NULL;
  		submit_bio_noacct(b);

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9c1a5877cf9f..b932282ff50a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c

@@ -1167,7 +1167,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
  		if (rdev) {
  			if (s->syncing || s->expanding || s->expanded
  			    || s->replacing)
-				md_sync_acct(rdev->bdev, RAID5_STRIPE_SECTORS(conf));
+				md_sync_acct(rdev, RAID5_STRIPE_SECTORS(conf));
  
  			set_bit(STRIPE_IO_STARTED, &sh->state);
  

@@ -1234,7 +1234,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
  		if (rrdev) {
  			if (s->syncing || s->expanding || s->expanded
  			    || s->replacing)
-				md_sync_acct(rrdev->bdev, RAID5_STRIPE_SECTORS(conf));
+				md_sync_acct(rrdev, RAID5_STRIPE_SECTORS(conf));
  
  			set_bit(STRIPE_IO_STARTED, &sh->state);
  

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 74c410263113..6b84444111e4 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h

@@ -150,7 +150,6 @@ struct gendisk {
  	struct list_head slave_bdevs;
  #endif
  	struct timer_rand_state *random;
-	atomic_t sync_io;		/* RAID */
  	struct disk_events *ev;
  #ifdef  CONFIG_BLK_DEV_INTEGRITY
  	struct kobject integrity_kobj;

Cheers,

Hannes