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Commit 1ca69c4b authored by NeilBrown's avatar NeilBrown
Browse files

md: avoid taking the mutex on some ioctls. 



Some ioctls don't need to take the mutex and doing so can cause
a delay as it is held during super-block update.
So move those ioctls out of the mutex and rely on rcu locking
to ensure we don't access stale data.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 4ed8731d

drivers/md/md.c

+62 −23
Original line number Diff line number Diff line
@@ -674,6 +674,17 @@ static struct md_rdev * find_rdev_nr(struct mddev *mddev, int nr) 
	return NULL;

}



static struct md_rdev *find_rdev_nr_rcu(struct mddev *mddev, int nr)

{

	struct md_rdev *rdev;



	rdev_for_each_rcu(rdev, mddev)

		if (rdev->desc_nr == nr)

			return rdev;



	return NULL;

}



static struct md_rdev *find_rdev(struct mddev *mddev, dev_t dev)

{

	struct md_rdev *rdev;
@@ -685,6 +696,17 @@ static struct md_rdev * find_rdev(struct mddev * mddev, dev_t dev) 
	return NULL;

}



static struct md_rdev *find_rdev_rcu(struct mddev *mddev, dev_t dev)

{

	struct md_rdev *rdev;



	rdev_for_each_rcu(rdev, mddev)

		if (rdev->bdev->bd_dev == dev)

			return rdev;



	return NULL;

}



static struct md_personality *find_pers(int level, char *clevel)

{

	struct md_personality *pers;
@@ -5510,7 +5532,8 @@ static int get_array_info(struct mddev * mddev, void __user * arg) 
	struct md_rdev *rdev;



	nr = working = insync = failed = spare = 0;

	rdev_for_each(rdev, mddev) {

	rcu_read_lock();

	rdev_for_each_rcu(rdev, mddev) {

		nr++;

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

			failed++;
@@ -5522,6 +5545,7 @@ static int get_array_info(struct mddev * mddev, void __user * arg) 
				spare++;

		}

	}

	rcu_read_unlock();



	info.major_version = mddev->major_version;

	info.minor_version = mddev->minor_version;
@@ -5605,7 +5629,8 @@ static int get_disk_info(struct mddev * mddev, void __user * arg) 
	if (copy_from_user(&info, arg, sizeof(info)))

		return -EFAULT;



	rdev = find_rdev_nr(mddev, info.number);

	rcu_read_lock();

	rdev = find_rdev_nr_rcu(mddev, info.number);

	if (rdev) {

		info.major = MAJOR(rdev->bdev->bd_dev);

		info.minor = MINOR(rdev->bdev->bd_dev);
@@ -5624,6 +5649,7 @@ static int get_disk_info(struct mddev * mddev, void __user * arg) 
		info.raid_disk = -1;

		info.state = (1<<MD_DISK_REMOVED);

	}

	rcu_read_unlock();



	if (copy_to_user(arg, &info, sizeof(info)))

		return -EFAULT;
@@ -6232,18 +6258,22 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info) 
static int set_disk_faulty(struct mddev *mddev, dev_t dev)

{

	struct md_rdev *rdev;

	int err = 0;



	if (mddev->pers == NULL)

		return -ENODEV;



	rdev = find_rdev(mddev, dev);

	rcu_read_lock();

	rdev = find_rdev_rcu(mddev, dev);

	if (!rdev)

		return -ENODEV;



		err =  -ENODEV;

	else {

		md_error(mddev, rdev);

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

		return -EBUSY;

	return 0;

			err = -EBUSY;

	}

	rcu_read_unlock();

	return err;

}



/*
@@ -6315,6 +6345,27 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode, 
		goto abort;

	}



	/* Some actions do not requires the mutex */

	switch (cmd) {

	case GET_ARRAY_INFO:

		if (!mddev->raid_disks && !mddev->external)

			err = -ENODEV;

		else

			err = get_array_info(mddev, argp);

		goto abort;



	case GET_DISK_INFO:

		if (!mddev->raid_disks && !mddev->external)

			err = -ENODEV;

		else

			err = get_disk_info(mddev, argp);

		goto abort;



	case SET_DISK_FAULTY:

		err = set_disk_faulty(mddev, new_decode_dev(arg));

		goto abort;

	}



	err = mddev_lock(mddev);

	if (err) {

		printk(KERN_INFO
@@ -6387,18 +6438,10 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode, 
	 */

	switch (cmd)

	{

		case GET_ARRAY_INFO:

			err = get_array_info(mddev, argp);

			goto done_unlock;



		case GET_BITMAP_FILE:

			err = get_bitmap_file(mddev, argp);

			goto done_unlock;



		case GET_DISK_INFO:

			err = get_disk_info(mddev, argp);

			goto done_unlock;



		case RESTART_ARRAY_RW:

			err = restart_array(mddev);

			goto done_unlock;
@@ -6480,10 +6523,6 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode, 
			err = hot_add_disk(mddev, new_decode_dev(arg));

			goto done_unlock;



		case SET_DISK_FAULTY:

			err = set_disk_faulty(mddev, new_decode_dev(arg));

			goto done_unlock;



		case RUN_ARRAY:

			err = do_md_run(mddev);

			goto done_unlock;