kern/44661: msdosfs rename has sprung a vnode leek

[pooka%iki.fi@localhost]

>Number:         44661
>Category:       kern
>Synopsis:       msdosfs rename has sprung a vnode leek
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Mar 01 20:15:01 +0000 2011
>Originator:     Antti Kantee
>Release:        
>Organization:
>Environment:
>Description:
tests/fs/vfs/t_vnops:msdosfs_rename_dir now fails with EBUSY.
It seems the msdosfs rename code has developed a vnode leak.

The test used to pass, but was disabled because it failed
with "out of stack space" in some environments.  I retested
it today and re-enabled it because it now fails
even without the new subtest I committed today.

(the "Check failed" below looks like another unrelated bug)
>How-To-Repeat:
run msdosfs_rename_dir from tests/fs/vfs/t_vnops:

src/tests/fs/vfs> ./t_vnops msdosfs_rename_dir
*** Check failed: t_vnops.c:296: sb.st_nlink != 3

==== dumping mountpoint at ``/mnt'' ====

vnodecovered = 0xbb695620 syncer = 0x0 data = 0xbb6b1160
fs_bshift 12 dev_bshift = 9
flag = 0x1000<MNT_LOCAL>
iflag = 0x80<IMNT_HAS_TRANS>
refcnt = 3 unmounting @ 0xbb771024 updating @ 0xbb771900
statvfs cache:
        bsize = 4096
        frsize = 4096
        iosize = 4096
        blocks = 1239
        bfree = 1239
        bavail = 1239
        bresvd = 0
        files = 512
        ffree = 0
        favail = 0
        fresvd = 0
        f_fsidx = { 0xc500, 0x764f }
        owner = 0
        namemax = 255
        flag = 0x0
        syncwrites = 30
        asyncwrites = 4
        syncreads = 132
        asyncreads = 0
        fstypename = msdos
        mntonname = /mnt
        mntfromname = /dev/device0.msdosfs
locked vnodes =
all vnodes = 0xbb695218, 0xbb69541c

== dumping vnodes ==

VM OBJECT at 0xbb695218, refs 1
VNODE flags 0x0
mp 0xbb771000 numoutput 0 size 0x1000 writesize 0x1000
data 0xbb6c5d90 writecount 0 holdcnt 0
tag VT_MSDOSFS(4) type VDIR(2) mount 0xbb771000 typedata 0x0
v_lock 0xbb6952b8
clean bufs:
dirty bufs:
VM OBJECT at 0xbb69541c, refs 1
VNODE flags 0x1<ROOT>
mp 0xbb771000 numoutput 0 size 0x4000 writesize 0x4000
data 0xbb6c5d14 writecount 0 holdcnt 0
tag VT_MSDOSFS(4) type VDIR(2) mount 0xbb771000 typedata 0x0
v_lock 0xbb6954bc
clean bufs:
dirty bufs:

==== done ====

failed: unmount failed: Device busy
>Fix: