On Tue 26-01-16 18:17:01, Vlastimil Babka wrote: > >>>- GFP_NOFS is another one which would be good to discuss. Its primary > >>> use is to prevent from reclaim recursion back into FS. This makes > >>> such an allocation context weaker and historically we haven't > >>> triggered OOM killer and rather hopelessly retry the request and > >>> rely on somebody else to make a progress for us. There are two issues > >>> here. > >>> First we shouldn't retry endlessly and rather fail the allocation and > >>> allow the FS to handle the error. As per my experiments most FS cope > >>> with that quite reasonably. Btrfs unfortunately handles many of those > >>> failures by BUG_ON which is really unfortunate. > >> > >>Are there any new datapoints on how to deal with failing allocations? > >>IIRC the conclusion last time was that some filesystems simply can't > >>support this without a reservation system - which I don't believe > >>anybody is working on. Does it make sense to rehash this when nothing > >>really changed since last time? > > > >There have been patches posted during the year to fortify those places > >which cannot cope with allocation failures for ext[34] and testing > >has shown that ext* resp. xfs are quite ready to see NOFS allocation > >failures. > > Hmm from last year I remember Dave Chinner saying there really are some > places that can't handle failure, period? That's why all the discussions > about reservations, and I would be surprised if all such places were gone > today? Which of course doesn't mean that there couldn't be different NOFS > places that can handle failures, which however don't happen in current > implementation. Well, but we have GFP_NOFAIL (or equivalent of thereof opencoded) in there. So yes, there are GFP_NOFAIL | GFP_NOFS allocations and allocator must deal with it somehow. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
