From 77f33c03739697d01c2e730e4c2610424059ceaf Mon Sep 17 00:00:00 2001 From: Josh Durgin Date: Mon, 30 Sep 2013 17:09:54 -0700 Subject: rbd: move calls that may sleep out of spin lock range get_user() and set_disk_ro() may allocate memory, leading to a potential deadlock if theye are called while a spin lock is held. Move the acquisition and release of rbd_dev->lock from rbd_ioctl() into rbd_ioctl_set_ro(), so it can occur between get_user() and set_disk_ro(). Signed-off-by: Josh Durgin Reviewed-by: Alex Elder --- drivers/block/rbd.c | 29 ++++++++++++++++++----------- 1 file changed, 18 insertions(+), 11 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 1c88fba98c8..6423f6e3b07 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -561,9 +561,12 @@ static void rbd_release(struct gendisk *disk, fmode_t mode) static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg) { + int ret = 0; int val; bool ro; + bool ro_changed = false; + /* get_user() may sleep, so call it before taking rbd_dev->lock */ if (get_user(val, (int __user *)(arg))) return -EFAULT; @@ -572,12 +575,25 @@ static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg) if (rbd_dev->spec->snap_id != CEPH_NOSNAP && !ro) return -EROFS; + spin_lock_irq(&rbd_dev->lock); + /* prevent others open this device */ + if (rbd_dev->open_count > 1) { + ret = -EBUSY; + goto out; + } + if (rbd_dev->mapping.read_only != ro) { rbd_dev->mapping.read_only = ro; - set_disk_ro(rbd_dev->disk, ro ? 1 : 0); + ro_changed = true; } - return 0; +out: + spin_unlock_irq(&rbd_dev->lock); + /* set_disk_ro() may sleep, so call it after releasing rbd_dev->lock */ + if (ret == 0 && ro_changed) + set_disk_ro(rbd_dev->disk, ro ? 1 : 0); + + return ret; } static int rbd_ioctl(struct block_device *bdev, fmode_t mode, @@ -586,13 +602,6 @@ static int rbd_ioctl(struct block_device *bdev, fmode_t mode, struct rbd_device *rbd_dev = bdev->bd_disk->private_data; int ret = 0; - spin_lock_irq(&rbd_dev->lock); - /* prevent others open this device */ - if (rbd_dev->open_count > 1) { - ret = -EBUSY; - goto out; - } - switch (cmd) { case BLKROSET: ret = rbd_ioctl_set_ro(rbd_dev, arg); @@ -601,8 +610,6 @@ static int rbd_ioctl(struct block_device *bdev, fmode_t mode, ret = -ENOTTY; } -out: - spin_unlock_irq(&rbd_dev->lock); return ret; } -- cgit v1.2.3-70-g09d2