Re: remove sparse check in vnd

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

hi,

> On Sat, Feb 05, 2011 at 10:07:13PM -0500, der Mouse wrote:
>  > Of course, still better would be to fix vnd, though I'm not sure what
>  > the right fix would be. 
> 
> What's the problem? My vague understanding was that you could get into
> deadlocks allocating blocks, but maybe I'm confusing it with something
> else.

i vaguely remember:

- vnd doesn't have code to allocate blocks.
  even the current use of VOP_BMAP is racy.  we don't have good VOPs for
  vnd's purpose.

- block allocation always involve page cache population at least for ffs.
  doing it in a pageout path is deadlock-prune.

YAMAMOTO Takashi

> 
> -- 
> David A. Holland
> dholland%netbsd.org@localhost