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authorChristoph Hellwig <hch@lst.de>2020-11-26 09:23:26 +0100
committerJens Axboe <axboe@kernel.dk>2020-12-01 14:53:39 -0700
commit22ae8ce8b89241c94ac00c237752c0ffa37ba5ae (patch)
treeaf6d4dfd72e76789c25c64cd1765f037d91f6b72 /block
parent4e7b5671c6a883d94b5428e1a9c141bbd56cb2a6 (diff)
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>
Diffstat (limited to 'block')
-rw-r--r--block/blk-cgroup.c42
-rw-r--r--block/blk-iocost.c36
-rw-r--r--block/blk.h2
-rw-r--r--block/genhd.c210
-rw-r--r--block/partitions/core.c29
5 files changed, 81 insertions, 238 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c68bdf58c9a6..ad02289a4f7f 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 @@ 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);
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index bbe86d1199dc..8e20fe4bddec 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 dfab98465db9..c4839abcfa27 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 f46e89226fdf..bf8fa82f135f 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 a02e22411594..696bd9ff63c6 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: