kern/40331: msdosfs issues

[kefren%ngnetworks.ro@localhost]

>Number:         40331
>Category:       kern
>Synopsis:       panic while accessing msdosfs
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 06 08:50:01 +0000 2009
>Originator:     Mihai Chelaru
>Release:        NetBSD 5.99.5
>Organization:
        
>Environment:
        
        
System: NetBSD kefren64.netbsd.ro 5.99.5 NetBSD 5.99.5 (Home) #3: Wed Dec 31 
10:25:20 EET 2008 
root%kefren64.netbsd.ro@localhost:/disk2/work/src/sys/arch/amd64/compile/obj/Home
 amd64
Architecture: x86_64
Machine: amd64
>Description:
        
        I observed that when I write a file on a compact flash I end up with
        zero sized files after remount (or when I move the stick to another
        computer). This looked fixed when I mount the filesystem synchronously
        (-o sync). This said, I tried the same strategy on an msdos filesystem
        I have locally on a partition, and I wrote some files there. After a 
        while I got a panic that is mostly reproductible now. I just have to
        mount the FS (no matter if I use -o sync or not) and try to walk to
        directory where I wrote those files. Here is the panic (handwritten):

        uvm_fault(0xffff800052d6c478, 0x0, 2) -> e
        fatal page fault in supervisor mode
        trap type 6 code 3 rip ffffffff804bd796 cs 8 rflags 10286 cr2  7 cpl 0 
rsp ffff800052f65730
        kernel: page fault trap, code=0
        Stopped in pid 646.1 (smbd) at netbsd: pool_get+390:   movq %rax,8(%rdx)

        pool_get() at netbsd:pool_get+390
        allocbuf+137
        getblk+243
        bio_doread+36
        bread+34
        msdos_lookup+661
        VOP_LOOKUP+62
        lookup+826
        namei+368
        do_sys_stat+68
        sys___stat30+45
        syscall+182
>How-To-Repeat:
        
>Fix:
        

>Unformatted: