Commit 2d32777d authored by Yu Kuai's avatar Yu Kuai Committed by Song Liu
Browse files

md/raid1: remove rcu protection to access rdev from conf 



Because it's safe to accees rdev from conf:
 - If any spinlock is held, because synchronize_rcu() from
   md_kick_rdev_from_array() will prevent 'rdev' to be freed until
   spinlock is released;
 - If 'reconfig_lock' is held, because rdev can't be added or removed from
   array;
 - If there is normal IO inflight, because mddev_suspend() will prevent
   rdev to be added or removed from array;
 - If there is sync IO inflight, because 'MD_RECOVERY_RUNNING' is
   checked in remove_and_add_spares().

And these will cover all the scenarios in raid1.

Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231125081604.3939938-4-yukuai1@huaweicloud.com
parent a448af25

drivers/md/raid1.c

+23 −39
Original line number Diff line number Diff line
@@ -609,7 +609,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect 
	int choose_first;

	int choose_next_idle;



	rcu_read_lock();

	/*

	 * Check if we can balance. We can balance on the whole

	 * device if no resync is going on, or below the resync window.
@@ -642,7 +641,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect 
		unsigned int pending;

		bool nonrot;



		rdev = rcu_dereference(conf->mirrors[disk].rdev);

		rdev = conf->mirrors[disk].rdev;

		if (r1_bio->bios[disk] == IO_BLOCKED

		    || rdev == NULL

		    || test_bit(Faulty, &rdev->flags))
@@ -773,7 +772,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect 
	}



	if (best_disk >= 0) {

		rdev = rcu_dereference(conf->mirrors[best_disk].rdev);

		rdev = conf->mirrors[best_disk].rdev;

		if (!rdev)

			goto retry;

		atomic_inc(&rdev->nr_pending);
@@ -784,7 +783,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect 


		conf->mirrors[best_disk].next_seq_sect = this_sector + sectors;

	}

	rcu_read_unlock();

	*max_sectors = sectors;



	return best_disk;
@@ -1235,14 +1233,12 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio, 


	if (r1bio_existed) {

		/* Need to get the block device name carefully */

		struct md_rdev *rdev;

		rcu_read_lock();

		rdev = rcu_dereference(conf->mirrors[r1_bio->read_disk].rdev);

		struct md_rdev *rdev = conf->mirrors[r1_bio->read_disk].rdev;



		if (rdev)

			snprintf(b, sizeof(b), "%pg", rdev->bdev);

		else

			strcpy(b, "???");

		rcu_read_unlock();

	}



	/*
@@ -1396,10 +1392,9 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, 


	disks = conf->raid_disks * 2;

	blocked_rdev = NULL;

	rcu_read_lock();

	max_sectors = r1_bio->sectors;

	for (i = 0;  i < disks; i++) {

		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);

		struct md_rdev *rdev = conf->mirrors[i].rdev;



		/*

		 * The write-behind io is only attempted on drives marked as
@@ -1465,7 +1460,6 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, 
		}

		r1_bio->bios[i] = bio;

	}

	rcu_read_unlock();



	if (unlikely(blocked_rdev)) {

		/* Wait for this device to become unblocked */
@@ -1617,15 +1611,16 @@ static void raid1_status(struct seq_file *seq, struct mddev *mddev) 
	struct r1conf *conf = mddev->private;

	int i;



	lockdep_assert_held(&mddev->lock);



	seq_printf(seq, " [%d/%d] [", conf->raid_disks,

		   conf->raid_disks - mddev->degraded);

	rcu_read_lock();

	for (i = 0; i < conf->raid_disks; i++) {

		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);

		struct md_rdev *rdev = READ_ONCE(conf->mirrors[i].rdev);



		seq_printf(seq, "%s",

			   rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");

	}

	rcu_read_unlock();

	seq_printf(seq, "]");

}
@@ -1691,16 +1686,15 @@ static void print_conf(struct r1conf *conf) 
	pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,

		 conf->raid_disks);



	rcu_read_lock();

	lockdep_assert_held(&conf->mddev->reconfig_mutex);

	for (i = 0; i < conf->raid_disks; i++) {

		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);

		struct md_rdev *rdev = conf->mirrors[i].rdev;

		if (rdev)

			pr_debug(" disk %d, wo:%d, o:%d, dev:%pg\n",

				 i, !test_bit(In_sync, &rdev->flags),

				 !test_bit(Faulty, &rdev->flags),

				 rdev->bdev);

	}

	rcu_read_unlock();

}



static void close_sync(struct r1conf *conf)
@@ -1810,7 +1804,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev) 
			 */

			if (rdev->saved_raid_disk < 0)

				conf->fullsync = 1;

			rcu_assign_pointer(p->rdev, rdev);

			WRITE_ONCE(p->rdev, rdev);

			break;

		}

		if (test_bit(WantReplacement, &p->rdev->flags) &&
@@ -1826,7 +1820,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev) 
		rdev->raid_disk = repl_slot;

		err = 0;

		conf->fullsync = 1;

		rcu_assign_pointer(p[conf->raid_disks].rdev, rdev);

		WRITE_ONCE(p[conf->raid_disks].rdev, rdev);

	}



	print_conf(conf);
@@ -1862,7 +1856,7 @@ static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 
			err = -EBUSY;

			goto abort;

		}

		p->rdev = NULL;

		WRITE_ONCE(p->rdev, NULL);

		if (conf->mirrors[conf->raid_disks + number].rdev) {

			/* We just removed a device that is being replaced.

			 * Move down the replacement.  We drain all IO before
@@ -1883,7 +1877,7 @@ static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 
				goto abort;

			}

			clear_bit(Replacement, &repl->flags);

			p->rdev = repl;

			WRITE_ONCE(p->rdev, repl);

			conf->mirrors[conf->raid_disks + number].rdev = NULL;

			unfreeze_array(conf);

		}
@@ -2281,8 +2275,7 @@ static void fix_read_error(struct r1conf *conf, int read_disk, 
			sector_t first_bad;

			int bad_sectors;



			rcu_read_lock();

			rdev = rcu_dereference(conf->mirrors[d].rdev);

			rdev = conf->mirrors[d].rdev;

			if (rdev &&

			    (test_bit(In_sync, &rdev->flags) ||

			     (!test_bit(Faulty, &rdev->flags) &&
@@ -2290,15 +2283,14 @@ static void fix_read_error(struct r1conf *conf, int read_disk, 
			    is_badblock(rdev, sect, s,

					&first_bad, &bad_sectors) == 0) {

				atomic_inc(&rdev->nr_pending);

				rcu_read_unlock();

				if (sync_page_io(rdev, sect, s<<9,

					 conf->tmppage, REQ_OP_READ, false))

					success = 1;

				rdev_dec_pending(rdev, mddev);

				if (success)

					break;

			} else

				rcu_read_unlock();

			}



			d++;

			if (d == conf->raid_disks * 2)

				d = 0;
@@ -2317,29 +2309,24 @@ static void fix_read_error(struct r1conf *conf, int read_disk, 
			if (d==0)

				d = conf->raid_disks * 2;

			d--;

			rcu_read_lock();

			rdev = rcu_dereference(conf->mirrors[d].rdev);

			rdev = conf->mirrors[d].rdev;

			if (rdev &&

			    !test_bit(Faulty, &rdev->flags)) {

				atomic_inc(&rdev->nr_pending);

				rcu_read_unlock();

				r1_sync_page_io(rdev, sect, s,

						conf->tmppage, WRITE);

				rdev_dec_pending(rdev, mddev);

			} else

				rcu_read_unlock();

			}

		}

		d = start;

		while (d != read_disk) {

			if (d==0)

				d = conf->raid_disks * 2;

			d--;

			rcu_read_lock();

			rdev = rcu_dereference(conf->mirrors[d].rdev);

			rdev = conf->mirrors[d].rdev;

			if (rdev &&

			    !test_bit(Faulty, &rdev->flags)) {

				atomic_inc(&rdev->nr_pending);

				rcu_read_unlock();

				if (r1_sync_page_io(rdev, sect, s,

						    conf->tmppage, READ)) {

					atomic_add(s, &rdev->corrected_errors);
@@ -2350,8 +2337,7 @@ static void fix_read_error(struct r1conf *conf, int read_disk, 
						rdev->bdev);

				}

				rdev_dec_pending(rdev, mddev);

			} else

				rcu_read_unlock();

			}

		}

		sectors -= s;

		sect += s;
@@ -2732,7 +2718,6 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr, 


	r1_bio = raid1_alloc_init_r1buf(conf);



	rcu_read_lock();

	/*

	 * If we get a correctably read error during resync or recovery,

	 * we might want to read from a different device.  So we
@@ -2753,7 +2738,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr, 
		struct md_rdev *rdev;

		bio = r1_bio->bios[i];



		rdev = rcu_dereference(conf->mirrors[i].rdev);

		rdev = conf->mirrors[i].rdev;

		if (rdev == NULL ||

		    test_bit(Faulty, &rdev->flags)) {

			if (i < conf->raid_disks)
@@ -2811,7 +2796,6 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr, 
				bio->bi_opf |= MD_FAILFAST;

		}

	}

	rcu_read_unlock();

	if (disk < 0)

		disk = wonly;

	r1_bio->read_disk = disk;