diff options
| -rw-r--r-- | fs/block_dev.c | 297 | ||||
| -rw-r--r-- | include/linux/fs.h | 10 |
2 files changed, 307 insertions, 0 deletions
diff --git a/fs/block_dev.c b/fs/block_dev.c index 5983d42df01..3f36df7e037 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -266,6 +266,9 @@ static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags) mutex_init(&bdev->bd_mount_mutex); INIT_LIST_HEAD(&bdev->bd_inodes); INIT_LIST_HEAD(&bdev->bd_list); +#ifdef CONFIG_SYSFS + INIT_LIST_HEAD(&bdev->bd_holder_list); +#endif inode_init_once(&ei->vfs_inode); } } @@ -490,6 +493,300 @@ void bd_release(struct block_device *bdev) EXPORT_SYMBOL(bd_release); +#ifdef CONFIG_SYSFS +/* + * Functions for bd_claim_by_kobject / bd_release_from_kobject + * + * If a kobject is passed to bd_claim_by_kobject() + * and the kobject has a parent directory, + * following symlinks are created: + * o from the kobject to the claimed bdev + * o from "holders" directory of the bdev to the parent of the kobject + * bd_release_from_kobject() removes these symlinks. + * + * Example: + * If /dev/dm-0 maps to /dev/sda, kobject corresponding to + * /sys/block/dm-0/slaves is passed to bd_claim_by_kobject(), then: + * /sys/block/dm-0/slaves/sda --> /sys/block/sda + * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0 + */ + +static struct kobject *bdev_get_kobj(struct block_device *bdev) +{ + if (bdev->bd_contains != bdev) + return kobject_get(&bdev->bd_part->kobj); + else + return kobject_get(&bdev->bd_disk->kobj); +} + +static struct kobject *bdev_get_holder(struct block_device *bdev) +{ + if (bdev->bd_contains != bdev) + return kobject_get(bdev->bd_part->holder_dir); + else + return kobject_get(bdev->bd_disk->holder_dir); +} + +static void add_symlink(struct kobject *from, struct kobject *to) +{ + if (!from || !to) + return; + sysfs_create_link(from, to, kobject_name(to)); +} + +static void del_symlink(struct kobject *from, struct kobject *to) +{ + if (!from || !to) + return; + sysfs_remove_link(from, kobject_name(to)); +} + +/* + * 'struct bd_holder' contains pointers to kobjects symlinked by + * bd_claim_by_kobject. + * It's connected to bd_holder_list which is protected by bdev->bd_sem. + */ +struct bd_holder { + struct list_head list; /* chain of holders of the bdev */ + int count; /* references from the holder */ + struct kobject *sdir; /* holder object, e.g. "/block/dm-0/slaves" */ + struct kobject *hdev; /* e.g. "/block/dm-0" */ + struct kobject *hdir; /* e.g. "/block/sda/holders" */ + struct kobject *sdev; /* e.g. "/block/sda" */ +}; + +/* + * Get references of related kobjects at once. + * Returns 1 on success. 0 on failure. + * + * Should call bd_holder_release_dirs() after successful use. + */ +static int bd_holder_grab_dirs(struct block_device *bdev, + struct bd_holder *bo) +{ + if (!bdev || !bo) + return 0; + + bo->sdir = kobject_get(bo->sdir); + if (!bo->sdir) + return 0; + + bo->hdev = kobject_get(bo->sdir->parent); + if (!bo->hdev) + goto fail_put_sdir; + + bo->sdev = bdev_get_kobj(bdev); + if (!bo->sdev) + goto fail_put_hdev; + + bo->hdir = bdev_get_holder(bdev); + if (!bo->hdir) + goto fail_put_sdev; + + return 1; + +fail_put_sdev: + kobject_put(bo->sdev); +fail_put_hdev: + kobject_put(bo->hdev); +fail_put_sdir: + kobject_put(bo->sdir); + + return 0; +} + +/* Put references of related kobjects at once. */ +static void bd_holder_release_dirs(struct bd_holder *bo) +{ + kobject_put(bo->hdir); + kobject_put(bo->sdev); + kobject_put(bo->hdev); + kobject_put(bo->sdir); +} + +static struct bd_holder *alloc_bd_holder(struct kobject *kobj) +{ + struct bd_holder *bo; + + bo = kzalloc(sizeof(*bo), GFP_KERNEL); + if (!bo) + return NULL; + + bo->count = 1; + bo->sdir = kobj; + + return bo; +} + +static void free_bd_holder(struct bd_holder *bo) +{ + kfree(bo); +} + +/** + * add_bd_holder - create sysfs symlinks for bd_claim() relationship + * + * @bdev: block device to be bd_claimed + * @bo: preallocated and initialized by alloc_bd_holder() + * + * If there is no matching entry with @bo in @bdev->bd_holder_list, + * add @bo to the list, create symlinks. + * + * Returns 1 if @bo was added to the list. + * Returns 0 if @bo wasn't used by any reason and should be freed. + */ +static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo) +{ + struct bd_holder *tmp; + + if (!bo) + return 0; + + list_for_each_entry(tmp, &bdev->bd_holder_list, list) { + if (tmp->sdir == bo->sdir) { + tmp->count++; + return 0; + } + } + + if (!bd_holder_grab_dirs(bdev, bo)) + return 0; + + add_symlink(bo->sdir, bo->sdev); + add_symlink(bo->hdir, bo->hdev); + list_add_tail(&bo->list, &bdev->bd_holder_list); + return 1; +} + +/** + * del_bd_holder - delete sysfs symlinks for bd_claim() relationship + * + * @bdev: block device to be bd_claimed + * @kobj: holder's kobject + * + * If there is matching entry with @kobj in @bdev->bd_holder_list + * and no other bd_claim() from the same kobject, + * remove the struct bd_holder from the list, delete symlinks for it. + * + * Returns a pointer to the struct bd_holder when it's removed from the list + * and ready to be freed. + * Returns NULL if matching claim isn't found or there is other bd_claim() + * by the same kobject. + */ +static struct bd_holder *del_bd_holder(struct block_device *bdev, + struct kobject *kobj) +{ + struct bd_holder *bo; + + list_for_each_entry(bo, &bdev->bd_holder_list, list) { + if (bo->sdir == kobj) { + bo->count--; + BUG_ON(bo->count < 0); + if (!bo->count) { + list_del(&bo->list); + del_symlink(bo->sdir, bo->sdev); + del_symlink(bo->hdir, bo->hdev); + bd_holder_release_dirs(bo); + return bo; + } + break; + } + } + + return NULL; +} + +/** + * bd_claim_by_kobject - bd_claim() with additional kobject signature + * + * @bdev: block device to be claimed + * @holder: holder's signature + * @kobj: holder's kobject + * + * Do bd_claim() and if it succeeds, create sysfs symlinks between + * the bdev and the holder's kobject. + * Use bd_release_from_kobject() when relesing the claimed bdev. + * + * Returns 0 on success. (same as bd_claim()) + * Returns errno on failure. + */ +static int bd_claim_by_kobject(struct block_device *bdev, void *holder, + struct kobject *kobj) +{ + int res; + struct bd_holder *bo; + + if (!kobj) + return -EINVAL; + + bo = alloc_bd_holder(kobj); + if (!bo) + return -ENOMEM; + + down(&bdev->bd_sem); + res = bd_claim(bdev, holder); + if (res || !add_bd_holder(bdev, bo)) + free_bd_holder(bo); + up(&bdev->bd_sem); + + return res; +} + +/** + * bd_release_from_kobject - bd_release() with additional kobject signature + * + * @bdev: block device to be released + * @kobj: holder's kobject + * + * Do bd_release() and remove sysfs symlinks created by bd_claim_by_kobject(). + */ +static void bd_release_from_kobject(struct block_device *bdev, + struct kobject *kobj) +{ + struct bd_holder *bo; + + if (!kobj) + return; + + down(&bdev->bd_sem); + bd_release(bdev); + if ((bo = del_bd_holder(bdev, kobj))) + free_bd_holder(bo); + up(&bdev->bd_sem); +} + +/** + * bd_claim_by_disk - wrapper function for bd_claim_by_kobject() + * + * @bdev: block device to be claimed + * @holder: holder's signature + * @disk: holder's gendisk + * + * Call bd_claim_by_kobject() with getting @disk->slave_dir. + */ +int bd_claim_by_disk(struct block_device *bdev, void *holder, + struct gendisk *disk) +{ + return bd_claim_by_kobject(bdev, holder, kobject_get(disk->slave_dir)); +} +EXPORT_SYMBOL_GPL(bd_claim_by_disk); + +/** + * bd_release_from_disk - wrapper function for bd_release_from_kobject() + * + * @bdev: block device to be claimed + * @disk: holder's gendisk + * + * Call bd_release_from_kobject() and put @disk->slave_dir. + */ +void bd_release_from_disk(struct block_device *bdev, struct gendisk *disk) +{ + bd_release_from_kobject(bdev, disk->slave_dir); + kobject_put(disk->slave_dir); +} +EXPORT_SYMBOL_GPL(bd_release_from_disk); +#endif + /* * Tries to open block device by device number. Use it ONLY if you * really do not have anything better - i.e. when you are behind a diff --git a/include/linux/fs.h b/include/linux/fs.h index 9d967494695..680d913350e 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -410,6 +410,9 @@ struct block_device { struct list_head bd_inodes; void * bd_holder; int bd_holders; +#ifdef CONFIG_SYSFS + struct list_head bd_holder_list; +#endif struct block_device * bd_contains; unsigned bd_block_size; struct hd_struct * bd_part; @@ -1399,6 +1402,13 @@ extern int blkdev_get(struct block_device *, mode_t, unsigned); extern int blkdev_put(struct block_device *); extern int bd_claim(struct block_device *, void *); extern void bd_release(struct block_device *); +#ifdef CONFIG_SYSFS +extern int bd_claim_by_disk(struct block_device *, void *, struct gendisk *); +extern void bd_release_from_disk(struct block_device *, struct gendisk *); +#else +#define bd_claim_by_disk(bdev, holder, disk) bd_claim(bdev, holder) +#define bd_release_from_disk(bdev, disk) bd_release(bdev) +#endif /* fs/char_dev.c */ extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *); |