Re: [PATCH 00/14] Swap-over-NBD without deadlocking v5

On Thu, Jul 07, 2011 at 08:58:31AM -0400, Christoph Hellwig wrote:

On Thu, Jul 07, 2011 at 10:47:37AM +0100, Mel Gorman wrote:

quoted

Additional complexity is required for swap-over-NFS but affects the
core kernel far less than this series. I do not have a series prepared
but from what's in a distro kernel, supporting NFS requires extending
address_space_operations for swapfile activation/deactivation with
some minor helpers and the bulk of the remaining complexity within
NFS itself.

The biggest addition for swap over NFS is to add proper support for
a filesystem interface to do I/O on random kernel pages instead of
the current nasty bmap hack the swapfile code is using. Splitting
that work from all the required VM infrastructure should make life
easier for everyone involved and allows merging it independeny as
both bits have other uses case as well.

The swap-over-nfs patches allows this possibility. There is a swapon
interface added that could be used by the filesystem to ensure the
underlying blocks are allocated and a swap_out/swap_in interface that
takes a struct file, struct page and writeback_control. This would
be an alternative to bmap being used to record the blocks backing
each extent.

Any objection to the swap-over-NBD stuff going ahead to get part of the
complexity out of the way?

-- 
Mel Gorman
SUSE Labs

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