svn commit: r285384 - head/sys/kern

[Edward Tomasz Napierała]

On 0711T1121, Konstantin Belousov wrote:
> Author: kib
> Date: Sat Jul 11 11:21:56 2015
> New Revision: 285384
> URL: https://svnweb.freebsd.org/changeset/base/285384
> 
> Log:
>   Do not allow creation of the dirty buffers for the dead buffer
>   objects, i.e. for buffer objects which vnode was reclaimed.  Buffer
>   cache cannot write such buffers.  Return the error and discard the
>   buffer immediately on write attempt.
>   
>   BO_DIRTY now always set during vnode reclamation, since it is used not
>   only for the INVARIANTS checks.  Do allow placement of the clean
>   buffers on dead bufobj list, otherwise filesystems cannot use bufcache
>   at all after the devvp reclaim.

Note that it also fixes the "dead bo" panic that happens eg after
yanking a mounted flash drive.