From 5c6bd75d06db512515a3781aa97e42df2faf0815 Mon Sep 17 00:00:00 2001 From: Alasdair G Kergon Date: Mon, 26 Jun 2006 00:27:34 -0700 Subject: [PATCH] dm: prevent removal if open If you misuse the device-mapper interface (or there's a bug in your userspace tools) it's possible to end up with 'unlinked' mapped devices that cannot be removed until you reboot (along with uninterruptible processes). This patch prevents you from removing a device that is still open. It introduces dm_lock_for_deletion() which is called when a device is about to be removed to ensure that nothing has it open and nothing further can open it. It uses a private open_count for this which also lets us remove one of the problematic bdget_disk() calls elsewhere. Signed-off-by: Alasdair G Kergon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/dm.c | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) (limited to 'drivers/md/dm.c') diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 952c49c3b9aa..6982f86db6dc 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -64,12 +64,14 @@ union map_info *dm_get_mapinfo(struct bio *bio) #define DMF_SUSPENDED 1 #define DMF_FROZEN 2 #define DMF_FREEING 3 +#define DMF_DELETING 4 struct mapped_device { struct rw_semaphore io_lock; struct semaphore suspend_lock; rwlock_t map_lock; atomic_t holders; + atomic_t open_count; unsigned long flags; @@ -228,12 +230,14 @@ static int dm_blk_open(struct inode *inode, struct file *file) if (!md) goto out; - if (test_bit(DMF_FREEING, &md->flags)) { + if (test_bit(DMF_FREEING, &md->flags) || + test_bit(DMF_DELETING, &md->flags)) { md = NULL; goto out; } dm_get(md); + atomic_inc(&md->open_count); out: spin_unlock(&_minor_lock); @@ -246,10 +250,35 @@ static int dm_blk_close(struct inode *inode, struct file *file) struct mapped_device *md; md = inode->i_bdev->bd_disk->private_data; + atomic_dec(&md->open_count); dm_put(md); return 0; } +int dm_open_count(struct mapped_device *md) +{ + return atomic_read(&md->open_count); +} + +/* + * Guarantees nothing is using the device before it's deleted. + */ +int dm_lock_for_deletion(struct mapped_device *md) +{ + int r = 0; + + spin_lock(&_minor_lock); + + if (dm_open_count(md)) + r = -EBUSY; + else + set_bit(DMF_DELETING, &md->flags); + + spin_unlock(&_minor_lock); + + return r; +} + static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo) { struct mapped_device *md = bdev->bd_disk->private_data; @@ -867,6 +896,7 @@ static struct mapped_device *alloc_dev(int minor) init_MUTEX(&md->suspend_lock); rwlock_init(&md->map_lock); atomic_set(&md->holders, 1); + atomic_set(&md->open_count, 0); atomic_set(&md->event_nr, 0); md->queue = blk_alloc_queue(GFP_KERNEL); -- cgit v1.2.2