Re: [patch] sys_sync livelock fix

[Andrew Morton]

Alan Cox wrote:
> 
> > I don't see why it should be different for applications
> > that write data after sync has started.
> 
> The guarantee about data written _before_ the sync started is also being
> broken unless I misread the code

That would be very broken.

The theory is: newly dirtied buffers are added at the "new"
end of the LRU.  write_some_buffers() starts at the "old"
end of the LRU.

So if write_unlock_buffers writes out the "oldest"
nr_buffers_type[BUF_DIRTY] buffers, then it knows
that it has written out everything which was dirty
at the time it was called.

Or did I miss something?

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