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: > > 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>