Re: kern/51129: Disconnecting USB SD card without umount causes file operations to hang

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR kern/51129; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/51129: Disconnecting USB SD card without umount causes file
 operations to hang
Date: Sat, 14 May 2016 18:05:40 +0000

 On Tue, May 10, 2016 at 07:20:00AM +0000, coypu%SDF.ORG@localhost wrote:
  >  Bonus:
  >  
  >  if you umount /new, you can now execute the following:
  >  mv /new /new/a/b
  >  
  >  whereas normally it would say device busy.
  >  
  >  if you run umount -f instead, this operation will also hang.
  >  
  >  normal umount is stuck in biowait
  >  umount -f is stuck in vcache
  >  mv after umount -f is stuck in vcache
 
 So, just to make sure I understand:
 
    mkdir /new         [so it's empty]
    attach device
    mount /dev/sd0a /new
    pull device
    umount /new &      [hangs in background]
    mv /new /new/a/b   [succeeds and *doesn't* hang?]
 
 and a/b is a subdirectory on the device? That is ... odd.
 
 and also
    mkdir /new         [so it's empty]
    attach device
    mount /dev/sd0a /new
    pull device
    umount -f /new     [hangs]
 
 ? (which is still a bug, but less surprising)
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost