[PATCH 25/45] block: simplify bdev/disk lookup in blkdev_get

Christoph Hellwig
2020-11-28T22:12:02Z

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: Christoph Hellwig <hch@lst.de>
---
block/blk-cgroup.c | 42 ++++----
block/blk-iocost.c | 36 +++----
block/blk.h | 2 +-
block/genhd.c | 210 +++++--------------------------------
block/partitions/core.c | 29 ++---
fs/block_dev.c | 177 +++++++++++++++++--------------
include/linux/blk-cgroup.h | 4 +-
include/linux/blkdev.h | 6 ++
include/linux/genhd.h | 7 +-
9 files changed, 194 insertions(+), 319 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 54fbe1e80cc41a..19650eb42b9f00 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -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 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
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);

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index bbe86d1199dc5b..8e20fe4bddecf7 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -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;
}

diff --git a/block/blk.h b/block/blk.h
index dfab98465db9a5..c4839abcfa27eb 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -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);
}

diff --git a/block/genhd.c b/block/genhd.c
index f46e89226fdf91..bf8fa82f135f4e 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -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");
@@ -916,16 +864,6 @@ 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";
diff --git a/block/partitions/core.c b/block/partitions/core.c
index a02e224115943d..696bd9ff63c64a 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -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);

+ err = -ENOMEM;
p->dkstats = alloc_percpu(struct disk_stats);
- if (!p->dkstats) {
- err = -ENOMEM;
+ 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:
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 6d6e4d50834cd0..b350ed3af83bad 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -863,31 +863,46 @@ void __init bdev_cache_init(void)
blockdev_superblock = bd_mnt->mnt_sb; /* For writeback */
}

-static struct block_device *bdget(dev_t dev)
+struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
{
struct block_device *bdev;
struct inode *inode;

- inode = iget_locked(blockdev_superblock, dev);
+ inode = new_inode(blockdev_superblock);
if (!inode)
return NULL;
+ inode->i_mode = S_IFBLK;
+ inode->i_rdev = 0;
+ inode->i_data.a_ops = &def_blk_aops;
+ mapping_set_gfp_mask(&inode->i_data, GFP_USER);
+
+ bdev = I_BDEV(inode);
+ spin_lock_init(&bdev->bd_size_lock);
+ bdev->bd_disk = disk;
+ bdev->bd_partno = partno;
+ bdev->bd_contains = NULL;
+ bdev->bd_super = NULL;
+ bdev->bd_inode = inode;
+ bdev->bd_part_count = 0;
+ return bdev;
+}

- bdev = &BDEV_I(inode)->bdev;
+void bdev_add(struct block_device *bdev, dev_t dev)
+{
+ bdev->bd_dev = dev;
+ bdev->bd_inode->i_rdev = dev;
+ bdev->bd_inode->i_ino = dev;
+ insert_inode_hash(bdev->bd_inode);
+}

- if (inode->i_state & I_NEW) {
- spin_lock_init(&bdev->bd_size_lock);
- bdev->bd_contains = NULL;
- bdev->bd_super = NULL;
- bdev->bd_inode = inode;
- bdev->bd_part_count = 0;
- bdev->bd_dev = dev;
- inode->i_mode = S_IFBLK;
- inode->i_rdev = dev;
- inode->i_data.a_ops = &def_blk_aops;
- mapping_set_gfp_mask(&inode->i_data, GFP_USER);
- unlock_new_inode(inode);
- }
- return bdev;
+static struct block_device *bdget(dev_t dev)
+{
+ struct inode *inode;
+
+ inode = ilookup(blockdev_superblock, dev);
+ if (!inode)
+ return NULL;
+ return &BDEV_I(inode)->bdev;
}

/**
@@ -1004,27 +1019,6 @@ int bd_prepare_to_claim(struct block_device *bdev, struct block_device *whole,
}
EXPORT_SYMBOL_GPL(bd_prepare_to_claim); /* only for the loop driver */

-static struct gendisk *bdev_get_gendisk(struct block_device *bdev, int *partno)
-{
- struct gendisk *disk = get_gendisk(bdev->bd_dev, partno);
-
- if (!disk)
- return NULL;
- /*
- * Now that we hold gendisk reference we make sure bdev we looked up is
- * not stale. If it is, it means device got removed and created before
- * we looked up gendisk and we fail open in such case. Associating
- * unhashed bdev with newly created gendisk could lead to two bdevs
- * (and thus two independent caches) being associated with one device
- * which is bad.
- */
- if (inode_unhashed(bdev->bd_inode)) {
- put_disk_and_module(disk);
- return NULL;
- }
- return disk;
-}
-
static void bd_clear_claiming(struct block_device *whole, void *holder)
{
lockdep_assert_held(&bdev_lock);
@@ -1347,19 +1341,17 @@ EXPORT_SYMBOL_GPL(bdev_disk_changed);
* mutex_lock(part->bd_mutex)
* mutex_lock_nested(whole->bd_mutex, 1)
*/
-static int __blkdev_get(struct block_device *bdev, struct gendisk *disk,
- int partno, fmode_t mode)
+static int __blkdev_get(struct block_device *bdev, fmode_t mode)
{
+ struct gendisk *disk = bdev->bd_disk;
int ret;

if (!bdev->bd_openers) {
- bdev->bd_disk = disk;
bdev->bd_contains = bdev;
- bdev->bd_partno = partno;

- if (!partno) {
+ if (!bdev->bd_partno) {
ret = -ENXIO;
- bdev->bd_part = disk_get_part(disk, partno);
+ bdev->bd_part = disk_get_part(disk, 0);
if (!bdev->bd_part)
goto out_clear;

@@ -1388,7 +1380,7 @@ static int __blkdev_get(struct block_device *bdev, struct gendisk *disk,
struct block_device *whole = bdget_disk(disk, 0);

mutex_lock_nested(&whole->bd_mutex, 1);
- ret = __blkdev_get(whole, disk, 0, mode);
+ ret = __blkdev_get(whole, mode);
if (ret) {
mutex_unlock(&whole->bd_mutex);
bdput(whole);
@@ -1398,7 +1390,7 @@ static int __blkdev_get(struct block_device *bdev, struct gendisk *disk,
mutex_unlock(&whole->bd_mutex);

bdev->bd_contains = whole;
- bdev->bd_part = disk_get_part(disk, partno);
+ bdev->bd_part = disk_get_part(disk, bdev->bd_partno);
if (!(disk->flags & GENHD_FL_UP) ||
!bdev->bd_part || !bdev->bd_part->nr_sects) {
__blkdev_put(whole, mode, 1);
@@ -1430,12 +1422,53 @@ static int __blkdev_get(struct block_device *bdev, struct gendisk *disk,

out_clear:
disk_put_part(bdev->bd_part);
- bdev->bd_disk = NULL;
bdev->bd_part = NULL;
bdev->bd_contains = NULL;
return ret;
}

+struct block_device *blkdev_get_no_open(dev_t dev)
+{
+ struct block_device *bdev;
+ struct gendisk *disk;
+
+ down_read(&bdev_lookup_sem);
+ bdev = bdget(dev);
+ if (!bdev) {
+ up_read(&bdev_lookup_sem);
+ blk_request_module(dev);
+ down_read(&bdev_lookup_sem);
+
+ bdev = bdget(dev);
+ if (!bdev)
+ goto unlock;
+ }
+
+ disk = bdev->bd_disk;
+ if (!kobject_get_unless_zero(&disk_to_dev(disk)->kobj))
+ goto bdput;
+ if ((disk->flags & (GENHD_FL_UP | GENHD_FL_HIDDEN)) != GENHD_FL_UP)
+ goto put_disk;
+ if (!try_module_get(bdev->bd_disk->fops->owner))
+ goto put_disk;
+ up_read(&bdev_lookup_sem);
+ return bdev;
+put_disk:
+ put_disk(disk);
+bdput:
+ bdput(bdev);
+unlock:
+ up_read(&bdev_lookup_sem);
+ return NULL;
+}
+
+void blkdev_put_no_open(struct block_device *bdev)
+{
+ module_put(bdev->bd_disk->fops->owner);
+ put_disk(bdev->bd_disk);
+ bdput(bdev);
+}
+
/**
* blkdev_get_by_dev - open a block device by device number
* @dev: device number of block device to open
@@ -1463,7 +1496,6 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
bool unblock_events = true;
struct block_device *bdev;
struct gendisk *disk;
- int partno;
int ret;

ret = devcgroup_check_permission(DEVCG_DEV_BLOCK,
@@ -1473,18 +1505,14 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
if (ret)
return ERR_PTR(ret);

- bdev = bdget(dev);
- if (!bdev)
- return ERR_PTR(-ENOMEM);
-
/*
* If we lost a race with 'disk' being deleted, try again. See md.c.
*/
retry:
- ret = -ENXIO;
- disk = bdev_get_gendisk(bdev, &partno);
- if (!disk)
- goto bdput;
+ bdev = blkdev_get_no_open(dev);
+ if (!bdev)
+ return ERR_PTR(-ENXIO);
+ disk = bdev->bd_disk;

if (mode & FMODE_EXCL) {
WARN_ON_ONCE(!holder);
@@ -1492,7 +1520,7 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
ret = -ENOMEM;
claiming = bdget_disk(disk, 0);
if (!claiming)
- goto put_disk;
+ goto put_blkdev;
ret = bd_prepare_to_claim(bdev, claiming, holder);
if (ret)
goto put_claiming;
@@ -1501,12 +1529,10 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
disk_block_events(disk);

mutex_lock(&bdev->bd_mutex);
- ret =__blkdev_get(bdev, disk, partno, mode);
- if (!(mode & FMODE_EXCL)) {
- ; /* nothing to do here */
- } else if (ret) {
- bd_abort_claiming(bdev, claiming, holder);
- } else {
+ ret =__blkdev_get(bdev, mode);
+ if (ret)
+ goto abort_claiming;
+ if (mode & FMODE_EXCL) {
bd_finish_claiming(bdev, claiming, holder);

/*
@@ -1526,21 +1552,23 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)

if (unblock_events)
disk_unblock_events(disk);
+ if (mode & FMODE_EXCL)
+ bdput(claiming);
+ return bdev;

+abort_claiming:
+ if (mode & FMODE_EXCL)
+ bd_abort_claiming(bdev, claiming, holder);
+ mutex_unlock(&bdev->bd_mutex);
+ disk_unblock_events(disk);
put_claiming:
if (mode & FMODE_EXCL)
bdput(claiming);
-put_disk:
- if (ret)
- put_disk_and_module(disk);
+put_blkdev:
+ blkdev_put_no_open(bdev);
if (ret == -ERESTARTSYS)
goto retry;
-bdput:
- if (ret) {
- bdput(bdev);
- return ERR_PTR(ret);
- }
- return bdev;
+ return ERR_PTR(ret);
}
EXPORT_SYMBOL(blkdev_get_by_dev);

@@ -1641,7 +1669,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)

disk_put_part(bdev->bd_part);
bdev->bd_part = NULL;
- bdev->bd_disk = NULL;
if (bdev_is_partition(bdev))
victim = bdev->bd_contains;
bdev->bd_contains = NULL;
@@ -1699,12 +1726,10 @@ void blkdev_put(struct block_device *bdev, fmode_t mode)
* from userland - e.g. eject(1).
*/
disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);
-
mutex_unlock(&bdev->bd_mutex);

__blkdev_put(bdev, mode, 0);
- bdput(bdev);
- put_disk_and_module(disk);
+ blkdev_put_no_open(bdev);
}
EXPORT_SYMBOL(blkdev_put);

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index c8fc9792ac776d..b9f3c246c3c908 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -197,12 +197,12 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);

struct blkg_conf_ctx {
- struct gendisk *disk;
+ struct block_device *bdev;
struct blkcg_gq *blkg;
char *body;
};

-struct gendisk *blkcg_conf_get_disk(char **inputp);
+struct block_device *blkcg_conf_open_bdev(char **inputp);
int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
char *input, struct blkg_conf_ctx *ctx);
void blkg_conf_finish(struct blkg_conf_ctx *ctx);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index bdd7339bcda462..5d48b92f5e4348 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1994,6 +1994,12 @@ void bd_abort_claiming(struct block_device *bdev, struct block_device *whole,
void *holder);
void blkdev_put(struct block_device *bdev, fmode_t mode);

+/* just for blk-cgroup, don't use elsewhere */
+struct block_device *blkdev_get_no_open(dev_t dev);
+void blkdev_put_no_open(struct block_device *bdev);
+
+struct block_device *bdev_alloc(struct gendisk *disk, u8 partno);
+void bdev_add(struct block_device *bdev, dev_t dev);
struct block_device *I_BDEV(struct inode *inode);
struct block_device *bdget_part(struct hd_struct *part);
struct block_device *bdgrab(struct block_device *bdev);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index ca5e356084c353..42a51653c7303e 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -65,6 +65,7 @@ struct hd_struct {
struct disk_stats __percpu *dkstats;
struct percpu_ref ref;

+ struct block_device *bdev;
struct device __dev;
struct kobject *holder_dir;
int policy, partno;
@@ -193,7 +194,6 @@ struct gendisk {
int flags;
unsigned long state;
#define GD_NEED_PART_SCAN 0
- struct rw_semaphore lookup_sem;
struct kobject *slave_dir;

struct timer_rand_state *random;
@@ -300,7 +300,6 @@ static inline void add_disk_no_queue_reg(struct gendisk *disk)
}

extern void del_gendisk(struct gendisk *gp);
-extern struct gendisk *get_gendisk(dev_t dev, int *partno);
extern struct block_device *bdget_disk(struct gendisk *disk, int partno);

extern void set_disk_ro(struct gendisk *disk, int flag);
@@ -338,7 +337,6 @@ int blk_drop_partitions(struct block_device *bdev);

extern struct gendisk *__alloc_disk_node(int minors, int node_id);
extern void put_disk(struct gendisk *disk);
-extern void put_disk_and_module(struct gendisk *disk);

#define alloc_disk_node(minors, node_id) \
({ \
@@ -388,7 +386,10 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev,
}
#endif /* CONFIG_SYSFS */

+extern struct rw_semaphore bdev_lookup_sem;
+
dev_t blk_lookup_devt(const char *name, int partno);
+void blk_request_module(dev_t devt);
#ifdef CONFIG_BLOCK
void printk_all_partitions(void);
#else /* CONFIG_BLOCK */
--
2.29.2