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

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commit 85f5a4d666 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ilya Dryomov 2019-01-08 19:47:38 +01:00 committed by Greg Kroah-Hartman
parent c7ca8e94db
commit 997255351a
1 changed files with 4 additions and 5 deletions
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9
drivers/block/rbd.c
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@ -5982,7 +5982,6 @@ 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;
@ -6015,13 +6014,13 @@ 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) {