From 22ae8ce8b89241c94ac00c237752c0ffa37ba5ae Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 26 Nov 2020 09:23:26 +0100 Subject: 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 Reviewed-by: Jan Kara Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe --- block/blk-cgroup.c | 42 +++++----- block/blk-iocost.c | 36 ++++----- block/blk.h | 2 +- block/genhd.c | 210 ++++++------------------------------------------ block/partitions/core.c | 29 ++++--- 5 files changed, 81 insertions(+), 238 deletions(-) (limited to 'block') 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: -- cgit v1.2.3