From 6946bd636364effce06ea46fe8f8cd6e2edb004e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Sun, 27 Aug 2006 01:23:31 -0700 Subject: [PATCH] [PATCH] lockdep: fix blkdev_open() warning On Wed, 2006-08-09 at 07:57 +0200, Rolf Eike Beer wrote: > ============================================= > [ INFO: possible recursive locking detected ] > --------------------------------------------- > parted/7929 is trying to acquire lock: > (&bdev->bd_mutex){--..}, at: [] __blkdev_put+0x1e/0x13c > > but task is already holding lock: > (&bdev->bd_mutex){--..}, at: [] do_open+0x72/0x3a8 > > other info that might help us debug this: > 1 lock held by parted/7929: > #0: (&bdev->bd_mutex){--..}, at: [] do_open+0x72/0x3a8 > stack backtrace: > [] show_trace_log_lvl+0x58/0x15b > [] show_trace+0xd/0x10 > [] dump_stack+0x17/0x1a > [] __lock_acquire+0x753/0x99c > [] lock_acquire+0x4a/0x6a > [] mutex_lock_nested+0xc8/0x20c > [] __blkdev_put+0x1e/0x13c > [] blkdev_put+0xa/0xc > [] do_open+0x336/0x3a8 > [] blkdev_open+0x1f/0x4c > [] __dentry_open+0xc7/0x1aa > [] nameidata_to_filp+0x1c/0x2e > [] do_filp_open+0x2e/0x35 > [] do_sys_open+0x38/0x68 > [] sys_open+0x16/0x18 > [] sysenter_past_esp+0x56/0x8d OK, I'm having a look here; its all new to me so bear with me. blkdev_open() calls do_open(bdev, ...,BD_MUTEX_NORMAL) and takes mutex_lock_nested(&bdev->bd_mutex, BD_MUTEX_NORMAL) then something fails, and we're thrown to: out_first: where if (bdev != bdev->bd_contains) blkdev_put(bdev->bd_contains) which is __blkdev_put(bdev->bd_contains, BD_MUTEX_NORMAL) which does mutex_lock_nested(&bdev->bd_contains->bd_mutex, BD_MUTEX_NORMAL) <--- lockdep trigger When going to out_first, dbev->bd_contains is either bdev or whole, and since we take the branch it must be whole. So it seems to me the following patch would be the right one: [akpm@osdl.org: compile fix] Signed-off-by: Peter Zijlstra Cc: Arjan van de Ven Acked-by: NeilBrown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/block_dev.c | 114 ++++++++++++++++++++++++------------------------- 1 file changed, 56 insertions(+), 58 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index 37534573960b..045f98854f14 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -884,6 +884,61 @@ void bd_set_size(struct block_device *bdev, loff_t size) } EXPORT_SYMBOL(bd_set_size); +static int __blkdev_put(struct block_device *bdev, unsigned int subclass) +{ + int ret = 0; + struct inode *bd_inode = bdev->bd_inode; + struct gendisk *disk = bdev->bd_disk; + + mutex_lock_nested(&bdev->bd_mutex, subclass); + lock_kernel(); + if (!--bdev->bd_openers) { + sync_blockdev(bdev); + kill_bdev(bdev); + } + if (bdev->bd_contains == bdev) { + if (disk->fops->release) + ret = disk->fops->release(bd_inode, NULL); + } else { + mutex_lock_nested(&bdev->bd_contains->bd_mutex, + subclass + 1); + bdev->bd_contains->bd_part_count--; + mutex_unlock(&bdev->bd_contains->bd_mutex); + } + if (!bdev->bd_openers) { + struct module *owner = disk->fops->owner; + + put_disk(disk); + module_put(owner); + + if (bdev->bd_contains != bdev) { + kobject_put(&bdev->bd_part->kobj); + bdev->bd_part = NULL; + } + bdev->bd_disk = NULL; + bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info; + if (bdev != bdev->bd_contains) + __blkdev_put(bdev->bd_contains, subclass + 1); + bdev->bd_contains = NULL; + } + unlock_kernel(); + mutex_unlock(&bdev->bd_mutex); + bdput(bdev); + return ret; +} + +int blkdev_put(struct block_device *bdev) +{ + return __blkdev_put(bdev, BD_MUTEX_NORMAL); +} +EXPORT_SYMBOL(blkdev_put); + +int blkdev_put_partition(struct block_device *bdev) +{ + return __blkdev_put(bdev, BD_MUTEX_PARTITION); +} +EXPORT_SYMBOL(blkdev_put_partition); + static int blkdev_get_whole(struct block_device *bdev, mode_t mode, unsigned flags); @@ -980,7 +1035,7 @@ out_first: bdev->bd_disk = NULL; bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info; if (bdev != bdev->bd_contains) - blkdev_put(bdev->bd_contains); + __blkdev_put(bdev->bd_contains, BD_MUTEX_WHOLE); bdev->bd_contains = NULL; put_disk(disk); module_put(owner); @@ -1079,63 +1134,6 @@ static int blkdev_open(struct inode * inode, struct file * filp) return res; } -static int __blkdev_put(struct block_device *bdev, unsigned int subclass) -{ - int ret = 0; - struct inode *bd_inode = bdev->bd_inode; - struct gendisk *disk = bdev->bd_disk; - - mutex_lock_nested(&bdev->bd_mutex, subclass); - lock_kernel(); - if (!--bdev->bd_openers) { - sync_blockdev(bdev); - kill_bdev(bdev); - } - if (bdev->bd_contains == bdev) { - if (disk->fops->release) - ret = disk->fops->release(bd_inode, NULL); - } else { - mutex_lock_nested(&bdev->bd_contains->bd_mutex, - subclass + 1); - bdev->bd_contains->bd_part_count--; - mutex_unlock(&bdev->bd_contains->bd_mutex); - } - if (!bdev->bd_openers) { - struct module *owner = disk->fops->owner; - - put_disk(disk); - module_put(owner); - - if (bdev->bd_contains != bdev) { - kobject_put(&bdev->bd_part->kobj); - bdev->bd_part = NULL; - } - bdev->bd_disk = NULL; - bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info; - if (bdev != bdev->bd_contains) - __blkdev_put(bdev->bd_contains, subclass + 1); - bdev->bd_contains = NULL; - } - unlock_kernel(); - mutex_unlock(&bdev->bd_mutex); - bdput(bdev); - return ret; -} - -int blkdev_put(struct block_device *bdev) -{ - return __blkdev_put(bdev, BD_MUTEX_NORMAL); -} - -EXPORT_SYMBOL(blkdev_put); - -int blkdev_put_partition(struct block_device *bdev) -{ - return __blkdev_put(bdev, BD_MUTEX_PARTITION); -} - -EXPORT_SYMBOL(blkdev_put_partition); - static int blkdev_close(struct inode * inode, struct file * filp) { struct block_device *bdev = I_BDEV(filp->f_mapping->host);