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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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2020-11-26 09:23:26 +01:00 committed by Jens Axboe
parent 4e7b5671c6
commit 22ae8ce8b8
9 changed files with 195 additions and 320 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
block/blk-cgroup.c
View File

@ -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);

36
block/blk-iocost.c
View File

@ -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;
}

2
block/blk.h
View File

@ -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);
}

212
block/genhd.c
View File

@ -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.dkstats = alloc_percpu(struct disk_stats);
if (!disk->part0.dkstats)
disk->part0.bdev = bdev_alloc(disk, 0);
if (!disk->part0.bdev)
goto out_free_disk;
init_rwsem(&disk->lookup_sem);
disk->part0.dkstats = alloc_percpu(struct disk_stats);
if (!disk->part0.dkstats)
goto out_bdput;
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";

29
block/partitions/core.c
View File

@ -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:

177
fs/block_dev.c
View File

@ -863,33 +863,48 @@ 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 = &BDEV_I(inode)->bdev;
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);
}
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;
}
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);
}
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;
}
/**
* bdgrab -- Grab a reference to an already referenced block device
* @bdev: Block device to grab a reference to.
@ -1004,27 +1019,6 @@ retry:
}
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 @@ retry:
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 @@ retry:
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 @@ retry:
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);

4
include/linux/blk-cgroup.h
View File

@ -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);

6
include/linux/blkdev.h
View File

@ -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);

7
include/linux/genhd.h
View File

@ -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 */