From 49731baa41df404c2c3f44555869ab387363af43 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 14 Jan 2011 18:43:57 +0100 Subject: block: restore multiple bd_link_disk_holder() support Commit e09b457b (block: simplify holder symlink handling) incorrectly assumed that there is only one link at maximum. dm may use multiple links and expects block layer to track reference count for each link, which is different from and unrelated to the exclusive device holder identified by @holder when the device is opened. Remove the single holder assumption and automatic removal of the link and revive the per-link reference count tracking. The code essentially behaves the same as before commit e09b457b sans the unnecessary kobject reference count dancing. While at it, note that this facility should not be used by anyone else than the current ones. Sysfs symlinks shouldn't be abused like this and the whole thing doesn't belong in the block layer at all. Signed-off-by: Tejun Heo Reported-by: Milan Broz Cc: Jun'ichi Nomura Cc: Neil Brown Cc: linux-raid@vger.kernel.org Cc: Kay Sievers Signed-off-by: Jens Axboe --- fs/block_dev.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 75 insertions(+), 18 deletions(-) (limited to 'fs/block_dev.c') diff --git a/fs/block_dev.c b/fs/block_dev.c index fe3f59c14a02..333a7bb4cb9c 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -432,6 +432,9 @@ static void init_once(void *foo) mutex_init(&bdev->bd_mutex); INIT_LIST_HEAD(&bdev->bd_inodes); INIT_LIST_HEAD(&bdev->bd_list); +#ifdef CONFIG_SYSFS + INIT_LIST_HEAD(&bdev->bd_holder_disks); +#endif inode_init_once(&ei->vfs_inode); /* Initialize mutex for freeze. */ mutex_init(&bdev->bd_fsfreeze_mutex); @@ -779,6 +782,23 @@ static struct block_device *bd_start_claiming(struct block_device *bdev, } #ifdef CONFIG_SYSFS +struct bd_holder_disk { + struct list_head list; + struct gendisk *disk; + int refcnt; +}; + +static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev, + struct gendisk *disk) +{ + struct bd_holder_disk *holder; + + list_for_each_entry(holder, &bdev->bd_holder_disks, list) + if (holder->disk == disk) + return holder; + return NULL; +} + static int add_symlink(struct kobject *from, struct kobject *to) { return sysfs_create_link(from, to, kobject_name(to)); @@ -794,6 +814,8 @@ static void del_symlink(struct kobject *from, struct kobject *to) * @bdev: the claimed slave bdev * @disk: the holding disk * + * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. + * * This functions creates the following sysfs symlinks. * * - from "slaves" directory of the holder @disk to the claimed @bdev @@ -817,47 +839,83 @@ static void del_symlink(struct kobject *from, struct kobject *to) */ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) { + struct bd_holder_disk *holder; int ret = 0; mutex_lock(&bdev->bd_mutex); - WARN_ON_ONCE(!bdev->bd_holder || bdev->bd_holder_disk); + WARN_ON_ONCE(!bdev->bd_holder); /* FIXME: remove the following once add_disk() handles errors */ if (WARN_ON(!disk->slave_dir || !bdev->bd_part->holder_dir)) goto out_unlock; - ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj); - if (ret) + holder = bd_find_holder_disk(bdev, disk); + if (holder) { + holder->refcnt++; goto out_unlock; + } - ret = add_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj); - if (ret) { - del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj); + holder = kzalloc(sizeof(*holder), GFP_KERNEL); + if (!holder) { + ret = -ENOMEM; goto out_unlock; } - bdev->bd_holder_disk = disk; + INIT_LIST_HEAD(&holder->list); + holder->disk = disk; + holder->refcnt = 1; + + ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj); + if (ret) + goto out_free; + + ret = add_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj); + if (ret) + goto out_del; + + list_add(&holder->list, &bdev->bd_holder_disks); + goto out_unlock; + +out_del: + del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj); +out_free: + kfree(holder); out_unlock: mutex_unlock(&bdev->bd_mutex); return ret; } EXPORT_SYMBOL_GPL(bd_link_disk_holder); -static void bd_unlink_disk_holder(struct block_device *bdev) +/** + * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder() + * @bdev: the calimed slave bdev + * @disk: the holding disk + * + * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. + * + * CONTEXT: + * Might sleep. + */ +void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) { - struct gendisk *disk = bdev->bd_holder_disk; + struct bd_holder_disk *holder; - bdev->bd_holder_disk = NULL; - if (!disk) - return; + mutex_lock(&bdev->bd_mutex); - del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj); - del_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj); + holder = bd_find_holder_disk(bdev, disk); + + if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { + del_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj); + del_symlink(bdev->bd_part->holder_dir, + &disk_to_dev(disk)->kobj); + list_del_init(&holder->list); + kfree(holder); + } + + mutex_unlock(&bdev->bd_mutex); } -#else -static inline void bd_unlink_disk_holder(struct block_device *bdev) -{ } +EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); #endif /** @@ -1380,7 +1438,6 @@ int blkdev_put(struct block_device *bdev, fmode_t mode) * unblock evpoll if it was a write holder. */ if (bdev_free) { - bd_unlink_disk_holder(bdev); if (bdev->bd_write_holder) { disk_unblock_events(bdev->bd_disk); bdev->bd_write_holder = false; -- cgit v1.2.3