Re: [PATCH] Deadlock during heavy write activity to userspace NFSserver on local NFS mount

[Nick Piggin]

Avi Kivity wrote:
> Nick Piggin wrote:

> > The solution is that PF_MEMALLOC tasks are allowed to access the reserve
> > pool. Dependencies don't matter to this system. It would be your job to
> > ensure all tasks that might need to allocate memory in order to free
> > memory have the flag set.
>
>
> In the general case that's not sufficient. What if the NFS server wrote 
> to ext3 via the VFS? We might have a ton of ext3 pagecache waiting for 
> kswapd to reclaim NFS memory, while kswapd is waiting on the NFS server 
> writing to ext3.

It is sufficient.

You didn't explain your example very well, but I'll assume it is the
following:

dirty NFS data -> NFS server on localhost -> ext3 filesystem.

So kswapd tries to reclaim some memory and writes out the dirty NFS
data. The NFS server then writes this data to ext3 (it can do this
because it is PF_MEMALLOC). The data gets written out, the NFS server
tells the client it is clean, kswapd continues.

Right?
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/