Re: sync(1) not really syncing??

[Antti Kantee <pooka%cs.hut.fi@localhost>]

On Thu Sep 11 2008 at 14:18:45 +0200, Jonathan Schleifer wrote:
> Am 11.09.2008 um 14:15 schrieb Ephaeton%gmx.net@localhost:
> 
> >Yeah I mean having sync(2) block until it's "really" done. Which
> >could stall the system for quite a bit with big / many buffers around.
> 
> That would be a DoS as a user could write big files and then sync to  
> stall the whole system. It may block sync(1), but *NEVER* the system  
> as a whole.

Please, actually study the kernel code before making incorrect claims.
There is no such possibility for a large file DoS in NetBSD since files
are flushed as they are written (this, however, may be argued to be
suboptimal ...).

Also, sync does not necessarily even start to sync all buffers.  Unmount,
however, does, and it also waits for buffers to be synced.  Even so,
it is implemented in the file system and some file systems may have bugs.