Re: [PATCH] Use of getblk differs between locations

[Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>]

> > Is memory management ready for this? Can't deadlock like this happen?
> > - displaying dialog window needs memory, so it waits until memory will
> > be available
> > - system decides to write some write-back cached data in order to free
> > memory
> > - the write of these data waits until the dialog window is displayed,
> > user inserts the device and clicks 'OK'
>
> No, it's not, and deadlock is definitely possible. However, if we're at
> the point where memory is tight enough that it's an issue, the timer can
> expire and all the pending i/o is dropped just as it would be without
> the multipath code enabled.
>
> I'm not saying it's a solution ready for production, just a good
> starting point.

But discarding data sometimes on USB unplug is even worse than discarding 
data always --- users will by experimenting learn that linux doesn't 
discard write-cached data and reminds them to replug the device --- and 
one day, randomly, they lose their data because of some memory management 
condition...

Mikulas
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