Re: [PATCH 12/14] vmscan: Do not writeback pages in direct reclaim

[Johannes Weiner]

On Tue, Jul 06, 2010 at 04:25:39PM +0100, Mel Gorman wrote:
> On Tue, Jul 06, 2010 at 08:24:57PM +0900, Minchan Kim wrote:
> > but it is still problem in case of swap file.
> > That's because swapout on swapfile cause file system writepage which
> > makes kernel stack overflow.
> 
> I don't *think* this is a problem unless I missed where writing out to
> swap enters teh filesystem code. I'll double check.

It bypasses the fs.  On swapon, the blocks are resolved
(mm/swapfile.c::setup_swap_extents) and then the writeout path uses
bios directly (mm/page_io.c::swap_writepage).

(GFP_NOFS still includes __GFP_IO, so allows swapping)

	Hannes
--
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/