Commit 85f5a4d6 authored Jan 08, 2019 by Ilya Dryomov

rbd: don't return 0 on unmap if RBD_DEV_FLAG_REMOVING is set



There is a window between when RBD_DEV_FLAG_REMOVING is set and when
the device is removed from rbd_dev_list.  During this window, we set
"already" and return 0.

Returning 0 from write(2) can confuse userspace tools because
0 indicates that nothing was written.  In particular, "rbd unmap"
will retry the write multiple times a second:

  10:28:05.463299 write(4, "0", 1)        = 0
  10:28:05.463509 write(4, "0", 1)        = 0
  10:28:05.463720 write(4, "0", 1)        = 0
  10:28:05.463942 write(4, "0", 1)        = 0
  10:28:05.464155 write(4, "0", 1)        = 0

Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Dongsheng Yang <dongsheng.yang@easystack.cn>

parent c64a2b05

drivers/block/rbd.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -5986,7 +5986,6 @@ static ssize_t do_rbd_remove(struct bus_type *bus,
		struct list_head *tmp;
		int dev_id;
		char opt_buf[6];
		bool already = false;
		bool force = false;
		int ret;

		@@ -6019,13 +6018,13 @@ static ssize_t do_rbd_remove(struct bus_type *bus,
		spin_lock_irq(&rbd_dev->lock);
		if (rbd_dev->open_count && !force)
		ret = -EBUSY;
		else
		already = test_and_set_bit(RBD_DEV_FLAG_REMOVING,
		&rbd_dev->flags);
		else if (test_and_set_bit(RBD_DEV_FLAG_REMOVING,
		&rbd_dev->flags))
		ret = -EINPROGRESS;
		spin_unlock_irq(&rbd_dev->lock);
		}
		spin_unlock(&rbd_dev_list_lock);
		if (ret < 0 \|\| already)
		if (ret)
		return ret;

		if (force) {