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/genhd.c | 210 +++++++--------------------------------------------------- 1 file changed, 24 insertions(+), 186 deletions(-) (limited to 'block/genhd.c') 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"; -- cgit v1.2.3