Commit 22ae8ce8 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: simplify bdev/disk lookup in blkdev_get 



To simplify block device lookup and a few other upcoming areas, make sure
that we always have a struct block_device available for each disk and
each partition, and only find existing block devices in bdget.  The only
downside of this is that each device and partition uses a little more
memory.  The upside will be that a lot of code can be simplified.

With that all we need to look up the block device is to lookup the inode
and do a few sanity checks on the gendisk, instead of the separate lookup
for the gendisk.  For blk-cgroup which wants to access a gendisk without
opening it, a new blkdev_{get,put}_no_open low-level interface is added
to replace the previous get_gendisk use.

Note that the change to look up block device directly instead of the two
step lookup using struct gendisk causes a subtile change in behavior:
accessing a non-existing partition on an existing block device can now
cause a call to request_module.  That call is harmless, and in practice
no recent system will access these nodes as they aren't created by udev
and static /dev/ setups are unusual.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4e7b5671

block/blk-cgroup.c

+21 −21
Original line number Diff line number Diff line
@@ -556,22 +556,22 @@ static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg, 
}



/**

 * blkg_conf_prep - parse and prepare for per-blkg config update

 * blkcg_conf_open_bdev - parse and open bdev for per-blkg config update

 * @inputp: input string pointer

 *

 * Parse the device node prefix part, MAJ:MIN, of per-blkg config update

 * from @input and get and return the matching gendisk.  *@inputp is

 * from @input and get and return the matching bdev.  *@inputp is

 * updated to point past the device node prefix.  Returns an ERR_PTR()

 * value on error.

 *

 * Use this function iff blkg_conf_prep() can't be used for some reason.

 */

struct gendisk *blkcg_conf_get_disk(char **inputp)

struct block_device *blkcg_conf_open_bdev(char **inputp)

{

	char *input = *inputp;

	unsigned int major, minor;

	struct gendisk *disk;

	int key_len, part;

	struct block_device *bdev;

	int key_len;



	if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)

		return ERR_PTR(-EINVAL);
@@ -581,16 +581,16 @@ struct gendisk *blkcg_conf_get_disk(char **inputp) 
		return ERR_PTR(-EINVAL);

	input = skip_spaces(input);



	disk = get_gendisk(MKDEV(major, minor), &part);

	if (!disk)

	bdev = blkdev_get_no_open(MKDEV(major, minor));

	if (!bdev)

		return ERR_PTR(-ENODEV);

	if (part) {

		put_disk_and_module(disk);

	if (bdev_is_partition(bdev)) {

		blkdev_put_no_open(bdev);

		return ERR_PTR(-ENODEV);

	}



	*inputp = input;

	return disk;

	return bdev;

}



/**
@@ -607,18 +607,18 @@ struct gendisk *blkcg_conf_get_disk(char **inputp) 
 */

int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,

		   char *input, struct blkg_conf_ctx *ctx)

	__acquires(rcu) __acquires(&disk->queue->queue_lock)

	__acquires(rcu) __acquires(&bdev->bd_disk->queue->queue_lock)

{

	struct gendisk *disk;

	struct block_device *bdev;

	struct request_queue *q;

	struct blkcg_gq *blkg;

	int ret;



	disk = blkcg_conf_get_disk(&input);

	if (IS_ERR(disk))

		return PTR_ERR(disk);

	bdev = blkcg_conf_open_bdev(&input);

	if (IS_ERR(bdev))

		return PTR_ERR(bdev);



	q = disk->queue;

	q = bdev->bd_disk->queue;



	rcu_read_lock();

	spin_lock_irq(&q->queue_lock);
@@ -689,7 +689,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 
			goto success;

	}

success:

	ctx->disk = disk;

	ctx->bdev = bdev;

	ctx->blkg = blkg;

	ctx->body = input;

	return 0;
@@ -700,7 +700,7 @@ fail_unlock: 
	spin_unlock_irq(&q->queue_lock);

	rcu_read_unlock();

fail:

	put_disk_and_module(disk);

	blkdev_put_no_open(bdev);

	/*

	 * If queue was bypassing, we should retry.  Do so after a

	 * short msleep().  It isn't strictly necessary but queue
@@ -723,11 +723,11 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep); 
 * with blkg_conf_prep().

 */

void blkg_conf_finish(struct blkg_conf_ctx *ctx)

	__releases(&ctx->disk->queue->queue_lock) __releases(rcu)

	__releases(&ctx->bdev->bd_disk->queue->queue_lock) __releases(rcu)

{

	spin_unlock_irq(&ctx->disk->queue->queue_lock);

	spin_unlock_irq(&ctx->bdev->bd_disk->queue->queue_lock);

	rcu_read_unlock();

	put_disk_and_module(ctx->disk);

	blkdev_put_no_open(ctx->bdev);

}

EXPORT_SYMBOL_GPL(blkg_conf_finish);

block/blk-iocost.c

+18 −18
Original line number Diff line number Diff line
@@ -3120,23 +3120,23 @@ static const match_table_t qos_tokens = { 
static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,

			     size_t nbytes, loff_t off)

{

	struct gendisk *disk;

	struct block_device *bdev;

	struct ioc *ioc;

	u32 qos[NR_QOS_PARAMS];

	bool enable, user;

	char *p;

	int ret;



	disk = blkcg_conf_get_disk(&input);

	if (IS_ERR(disk))

		return PTR_ERR(disk);

	bdev = blkcg_conf_open_bdev(&input);

	if (IS_ERR(bdev))

		return PTR_ERR(bdev);



	ioc = q_to_ioc(disk->queue);

	ioc = q_to_ioc(bdev->bd_disk->queue);

	if (!ioc) {

		ret = blk_iocost_init(disk->queue);

		ret = blk_iocost_init(bdev->bd_disk->queue);

		if (ret)

			goto err;

		ioc = q_to_ioc(disk->queue);

		ioc = q_to_ioc(bdev->bd_disk->queue);

	}



	spin_lock_irq(&ioc->lock);
@@ -3231,12 +3231,12 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, 
	ioc_refresh_params(ioc, true);

	spin_unlock_irq(&ioc->lock);



	put_disk_and_module(disk);

	blkdev_put_no_open(bdev);

	return nbytes;

einval:

	ret = -EINVAL;

err:

	put_disk_and_module(disk);

	blkdev_put_no_open(bdev);

	return ret;

}
@@ -3287,23 +3287,23 @@ static const match_table_t i_lcoef_tokens = { 
static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,

				    size_t nbytes, loff_t off)

{

	struct gendisk *disk;

	struct block_device *bdev;

	struct ioc *ioc;

	u64 u[NR_I_LCOEFS];

	bool user;

	char *p;

	int ret;



	disk = blkcg_conf_get_disk(&input);

	if (IS_ERR(disk))

		return PTR_ERR(disk);

	bdev = blkcg_conf_open_bdev(&input);

	if (IS_ERR(bdev))

		return PTR_ERR(bdev);



	ioc = q_to_ioc(disk->queue);

	ioc = q_to_ioc(bdev->bd_disk->queue);

	if (!ioc) {

		ret = blk_iocost_init(disk->queue);

		ret = blk_iocost_init(bdev->bd_disk->queue);

		if (ret)

			goto err;

		ioc = q_to_ioc(disk->queue);

		ioc = q_to_ioc(bdev->bd_disk->queue);

	}



	spin_lock_irq(&ioc->lock);
@@ -3356,13 +3356,13 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, 
	ioc_refresh_params(ioc, true);

	spin_unlock_irq(&ioc->lock);



	put_disk_and_module(disk);

	blkdev_put_no_open(bdev);

	return nbytes;



einval:

	ret = -EINVAL;

err:

	put_disk_and_module(disk);

	blkdev_put_no_open(bdev);

	return ret;

}

block/blk.h

+1 −1
Original line number Diff line number Diff line
@@ -352,7 +352,6 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector); 


int blk_alloc_devt(struct hd_struct *part, dev_t *devt);

void blk_free_devt(dev_t devt);

void blk_invalidate_devt(dev_t devt);

char *disk_name(struct gendisk *hd, int partno, char *buf);

#define ADDPART_FLAG_NONE	0

#define ADDPART_FLAG_RAID	1
@@ -384,6 +383,7 @@ static inline void hd_free_part(struct hd_struct *part) 
{

	free_percpu(part->dkstats);

	kfree(part->info);

	bdput(part->bdev);

	percpu_ref_exit(&part->ref);

}

block/genhd.c

+24 −186
Original line number Diff line number Diff line
@@ -27,17 +27,11 @@ 


static struct kobject *block_depr;



static DEFINE_XARRAY(bdev_map);

static DEFINE_MUTEX(bdev_map_lock);

DECLARE_RWSEM(bdev_lookup_sem);



/* for extended dynamic devt allocation, currently only one major is used */

#define NR_EXT_DEVT		(1 << MINORBITS)



/* For extended devt allocation.  ext_devt_lock prevents look up

 * results from going away underneath its user.

 */

static DEFINE_SPINLOCK(ext_devt_lock);

static DEFINE_IDR(ext_devt_idr);

static DEFINE_IDA(ext_devt_ida);



static void disk_check_events(struct disk_events *ev,

			      unsigned int *clearing_ptr);
@@ -580,14 +574,7 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt) 
		return 0;

	}



	/* allocate ext devt */

	idr_preload(GFP_KERNEL);



	spin_lock_bh(&ext_devt_lock);

	idx = idr_alloc(&ext_devt_idr, part, 0, NR_EXT_DEVT, GFP_NOWAIT);

	spin_unlock_bh(&ext_devt_lock);



	idr_preload_end();

	idx = ida_alloc_range(&ext_devt_ida, 0, NR_EXT_DEVT, GFP_KERNEL);

	if (idx < 0)

		return idx == -ENOSPC ? -EBUSY : idx;
@@ -606,26 +593,8 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt) 
 */

void blk_free_devt(dev_t devt)

{

	if (devt == MKDEV(0, 0))

		return;



	if (MAJOR(devt) == BLOCK_EXT_MAJOR) {

		spin_lock_bh(&ext_devt_lock);

		idr_remove(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));

		spin_unlock_bh(&ext_devt_lock);

	}

}



/*

 * We invalidate devt by assigning NULL pointer for devt in idr.

 */

void blk_invalidate_devt(dev_t devt)

{

	if (MAJOR(devt) == BLOCK_EXT_MAJOR) {

		spin_lock_bh(&ext_devt_lock);

		idr_replace(&ext_devt_idr, NULL, blk_mangle_minor(MINOR(devt)));

		spin_unlock_bh(&ext_devt_lock);

	}

	if (MAJOR(devt) == BLOCK_EXT_MAJOR)

		ida_free(&ext_devt_ida, blk_mangle_minor(MINOR(devt)));

}



static char *bdevt_str(dev_t devt, char *buf)
@@ -640,28 +609,6 @@ static char *bdevt_str(dev_t devt, char *buf) 
	return buf;

}



static void blk_register_region(struct gendisk *disk)

{

	int i;



	mutex_lock(&bdev_map_lock);

	for (i = 0; i < disk->minors; i++) {

		if (xa_insert(&bdev_map, disk_devt(disk) + i, disk, GFP_KERNEL))

			WARN_ON_ONCE(1);

	}

	mutex_unlock(&bdev_map_lock);

}



static void blk_unregister_region(struct gendisk *disk)

{

	int i;



	mutex_lock(&bdev_map_lock);

	for (i = 0; i < disk->minors; i++)

		xa_erase(&bdev_map, disk_devt(disk) + i);

	mutex_unlock(&bdev_map_lock);

}



static void disk_scan_partitions(struct gendisk *disk)

{

	struct block_device *bdev;
@@ -805,7 +752,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk, 
		ret = bdi_register(bdi, "%u:%u", MAJOR(devt), MINOR(devt));

		WARN_ON(ret);

		bdi_set_owner(bdi, dev);

		blk_register_region(disk);

		bdev_add(disk->part0.bdev, devt);

	}

	register_disk(parent, disk, groups);

	if (register_queue)
@@ -847,8 +794,8 @@ static void invalidate_partition(struct gendisk *disk, int partno) 
	__invalidate_device(bdev, true);



	/*

	 * Unhash the bdev inode for this device so that it gets evicted as soon

	 * as last inode reference is dropped.

	 * Unhash the bdev inode for this device so that it can't be looked

	 * up any more even if openers still hold references to it.

	 */

	remove_inode_hash(bdev->bd_inode);

	bdput(bdev);
@@ -890,7 +837,8 @@ void del_gendisk(struct gendisk *disk) 
	 * Block lookups of the disk until all bdevs are unhashed and the

	 * disk is marked as dead (GENHD_FL_UP cleared).

	 */

	down_write(&disk->lookup_sem);

	down_write(&bdev_lookup_sem);



	/* invalidate stuff */

	disk_part_iter_init(&piter, disk,

			     DISK_PITER_INCL_EMPTY | DISK_PITER_REVERSE);
@@ -903,7 +851,7 @@ void del_gendisk(struct gendisk *disk) 
	invalidate_partition(disk, 0);

	set_capacity(disk, 0);

	disk->flags &= ~GENHD_FL_UP;

	up_write(&disk->lookup_sem);

	up_write(&bdev_lookup_sem);



	if (!(disk->flags & GENHD_FL_HIDDEN)) {

		sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
@@ -917,16 +865,6 @@ void del_gendisk(struct gendisk *disk) 


	blk_unregister_queue(disk);



	if (!(disk->flags & GENHD_FL_HIDDEN))

		blk_unregister_region(disk);

	/*

	 * Remove gendisk pointer from idr so that it cannot be looked up

	 * while RCU period before freeing gendisk is running to prevent

	 * use-after-free issues. Note that the device number stays

	 * "in-use" until we really free the gendisk.

	 */

	blk_invalidate_devt(disk_devt(disk));



	kobject_put(disk->part0.holder_dir);

	kobject_put(disk->slave_dir);
@@ -964,7 +902,7 @@ static ssize_t disk_badblocks_store(struct device *dev, 
	return badblocks_store(disk->bb, page, len, 0);

}



static void request_gendisk_module(dev_t devt)

void blk_request_module(dev_t devt)

{

	unsigned int major = MAJOR(devt);

	struct blk_major_name **n;
@@ -984,84 +922,6 @@ static void request_gendisk_module(dev_t devt) 
		request_module("block-major-%d", MAJOR(devt));

}



static bool get_disk_and_module(struct gendisk *disk)

{

	struct module *owner;



	if (!disk->fops)

		return false;

	owner = disk->fops->owner;

	if (owner && !try_module_get(owner))

		return false;

	if (!kobject_get_unless_zero(&disk_to_dev(disk)->kobj)) {

		module_put(owner);

		return false;

	}

	return true;



}



/**

 * get_gendisk - get partitioning information for a given device

 * @devt: device to get partitioning information for

 * @partno: returned partition index

 *

 * This function gets the structure containing partitioning

 * information for the given device @devt.

 *

 * Context: can sleep

 */

struct gendisk *get_gendisk(dev_t devt, int *partno)

{

	struct gendisk *disk = NULL;



	might_sleep();



	if (MAJOR(devt) != BLOCK_EXT_MAJOR) {

		mutex_lock(&bdev_map_lock);

		disk = xa_load(&bdev_map, devt);

		if (!disk) {

			mutex_unlock(&bdev_map_lock);

			request_gendisk_module(devt);

			mutex_lock(&bdev_map_lock);

			disk = xa_load(&bdev_map, devt);

		}

		if (disk && !get_disk_and_module(disk))

			disk = NULL;

		if (disk)

			*partno = devt - disk_devt(disk);

		mutex_unlock(&bdev_map_lock);

	} else {

		struct hd_struct *part;



		spin_lock_bh(&ext_devt_lock);

		part = idr_find(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));

		if (part && get_disk_and_module(part_to_disk(part))) {

			*partno = part->partno;

			disk = part_to_disk(part);

		}

		spin_unlock_bh(&ext_devt_lock);

	}



	if (!disk)

		return NULL;



	/*

	 * Synchronize with del_gendisk() to not return disk that is being

	 * destroyed.

	 */

	down_read(&disk->lookup_sem);

	if (unlikely((disk->flags & GENHD_FL_HIDDEN) ||

		     !(disk->flags & GENHD_FL_UP))) {

		up_read(&disk->lookup_sem);

		put_disk_and_module(disk);

		disk = NULL;

	} else {

		up_read(&disk->lookup_sem);

	}

	return disk;

}



/**

 * bdget_disk - do bdget() by gendisk and partition number

 * @disk: gendisk of interest
@@ -1559,11 +1419,6 @@ int disk_expand_part_tbl(struct gendisk *disk, int partno) 
 *

 * This function releases all allocated resources of the gendisk.

 *

 * The struct gendisk refcount is incremented with get_gendisk() or

 * get_disk_and_module(), and its refcount is decremented with

 * put_disk_and_module() or put_disk(). Once the refcount reaches 0 this

 * function is called.

 *

 * Drivers which used __device_add_disk() have a gendisk with a request_queue

 * assigned. Since the request_queue sits on top of the gendisk for these

 * drivers we also call blk_put_queue() for them, and we expect the
@@ -1748,16 +1603,17 @@ struct gendisk *__alloc_disk_node(int minors, int node_id) 
	if (!disk)

		return NULL;



	disk->part0.bdev = bdev_alloc(disk, 0);

	if (!disk->part0.bdev)

		goto out_free_disk;



	disk->part0.dkstats = alloc_percpu(struct disk_stats);

	if (!disk->part0.dkstats)

		goto out_free_disk;

		goto out_bdput;



	init_rwsem(&disk->lookup_sem);

	disk->node_id = node_id;

	if (disk_expand_part_tbl(disk, 0)) {

		free_percpu(disk->part0.dkstats);

		goto out_free_disk;

	}

	if (disk_expand_part_tbl(disk, 0))

		goto out_free_bdstats;



	ptbl = rcu_dereference_protected(disk->part_tbl, 1);

	rcu_assign_pointer(ptbl->part[0], &disk->part0);
@@ -1773,7 +1629,7 @@ struct gendisk *__alloc_disk_node(int minors, int node_id) 
	 */

	hd_sects_seq_init(&disk->part0);

	if (hd_ref_init(&disk->part0))

		goto out_free_part0;

		goto out_free_bdstats;



	disk->minors = minors;

	rand_initialize_disk(disk);
@@ -1782,8 +1638,10 @@ struct gendisk *__alloc_disk_node(int minors, int node_id) 
	device_initialize(disk_to_dev(disk));

	return disk;



out_free_part0:

	hd_free_part(&disk->part0);

out_free_bdstats:

	free_percpu(disk->part0.dkstats);

out_bdput:

	bdput(disk->part0.bdev);

out_free_disk:

	kfree(disk);

	return NULL;
@@ -1807,26 +1665,6 @@ void put_disk(struct gendisk *disk) 
}

EXPORT_SYMBOL(put_disk);



/**

 * put_disk_and_module - decrements the module and gendisk refcount

 * @disk: the struct gendisk to decrement the refcount for

 *

 * This is a counterpart of get_disk_and_module() and thus also of

 * get_gendisk().

 *

 * Context: Any context, but the last reference must not be dropped from

 *          atomic context.

 */

void put_disk_and_module(struct gendisk *disk)

{

	if (disk) {

		struct module *owner = disk->fops->owner;



		put_disk(disk);

		module_put(owner);

	}

}



static void set_disk_ro_uevent(struct gendisk *gd, int ro)

{

	char event[] = "DISK_RO=1";

block/partitions/core.c

+17 −12
Original line number Diff line number Diff line
@@ -340,12 +340,11 @@ void delete_partition(struct hd_struct *part) 
	device_del(part_to_dev(part));



	/*

	 * Remove gendisk pointer from idr so that it cannot be looked up

	 * while RCU period before freeing gendisk is running to prevent

	 * use-after-free issues. Note that the device number stays

	 * "in-use" until we really free the gendisk.

	 * Remove the block device from the inode hash, so that it cannot be

	 * looked up any more even when openers still hold references.

	 */

	blk_invalidate_devt(part_devt(part));

	remove_inode_hash(part->bdev->bd_inode);



	percpu_ref_kill(&part->ref);

}
@@ -368,6 +367,7 @@ static struct hd_struct *add_partition(struct gendisk *disk, int partno, 
	dev_t devt = MKDEV(0, 0);

	struct device *ddev = disk_to_dev(disk);

	struct device *pdev;

	struct block_device *bdev;

	struct disk_part_tbl *ptbl;

	const char *dname;

	int err;
@@ -402,11 +402,15 @@ static struct hd_struct *add_partition(struct gendisk *disk, int partno, 
	if (!p)

		return ERR_PTR(-EBUSY);



	p->dkstats = alloc_percpu(struct disk_stats);

	if (!p->dkstats) {

	err = -ENOMEM;

	p->dkstats = alloc_percpu(struct disk_stats);

	if (!p->dkstats)

		goto out_free;

	}



	bdev = bdev_alloc(disk, partno);

	if (!bdev)

		goto out_free_stats;

	p->bdev = bdev;



	hd_sects_seq_init(p);

	pdev = part_to_dev(p);
@@ -420,10 +424,8 @@ static struct hd_struct *add_partition(struct gendisk *disk, int partno, 
		struct partition_meta_info *pinfo;



		pinfo = kzalloc_node(sizeof(*pinfo), GFP_KERNEL, disk->node_id);

		if (!pinfo) {

			err = -ENOMEM;

			goto out_free_stats;

		}

		if (!pinfo)

			goto out_bdput;

		memcpy(pinfo, info, sizeof(*info));

		p->info = pinfo;

	}
@@ -470,6 +472,7 @@ static struct hd_struct *add_partition(struct gendisk *disk, int partno, 
	}



	/* everything is up and running, commence */

	bdev_add(bdev, devt);

	rcu_assign_pointer(ptbl->part[partno], p);



	/* suppress uevent if the disk suppresses it */
@@ -479,6 +482,8 @@ static struct hd_struct *add_partition(struct gendisk *disk, int partno, 


out_free_info:

	kfree(p->info);

out_bdput:

	bdput(bdev);

out_free_stats:

	free_percpu(p->dkstats);

out_free:

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