kern/39277: wapbl+nullfs crash

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>Number:         39277
>Category:       kern
>Synopsis:       wapbl+nullfs crash
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Aug 03 12:50:00 +0000 2008
>Originator:     Alan Barrett
>Release:        NetBSD 4.99.71
>Organization:
Not much
>Environment:
System: NetBSD 4.99.71
Architecture: i386
Machine: i386
>Description:
        The system crashed while attempting to edit a file in a nullfs
        file system where the lower layer was ffs with wapbl logging.

>How-To-Repeat:
        boot a wapbl-enabled kernel.

        mount all file systems without logging.  This includes "/" as a
        plain ffs file system, "/xetc" as nullfs backed by the root file
        system, and several others.

        enable logging on all ffs file systems, via "mount -u -o log ${dir}"

        attempt to edit a file on a nullfs file system backed by ffs:

        $ sudo vi /xetc/rc

        panic: kernel diagnostic assertion "!(bp->b_oflags & BO_DELWRI)"
        failed, file .../vfs_wapbl.c line 898
        [...]
        db{0}> bt
        breakpoint ...
        panic ...
        __kernassert ...
        wapbl_add_buf ...
        bdwrite ...
        ffs_alloccg ...
        ffs_hashalloc ...
        ffs_alloc ...
        ffs_balloc_ufs1 ...
        ffs_balloc ...
        ufs_gop_alloc ...
        ufs_balloc_range ...
        ffs_write ...
        layer_bypass ...
        VOP_WRITE ...
        vn_write ...
        dofilewrite ...
        sys_pwrite ...
        syscall ...
>Fix:
        Unknown