tree efeca197ae8a2421940006ace6c1b719b1811a0c
parent 3bb1a852ab6c9cdf211a2f4a2f502340c8c38eca
author Martin Bligh <mbligh@google.com> 1162057105 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> 1162060251 -0700

[PATCH] Use min of two prio settings in calculating distress for reclaim

If try_to_free_pages / balance_pgdat are called with a gfp_mask specifying
GFP_IO and/or GFP_FS, they will reclaim the requisite number of pages, and the
reset prev_priority to DEF_PRIORITY (or to some other high (ie: unurgent)
value).

However, another reclaimer without those gfp_mask flags set (say, GFP_NOIO)
may still be struggling to reclaim pages.  The concurrent overwrite of
zone->prev_priority will cause this GFP_NOIO thread to unexpectedly cease
deactivating mapped pages, thus causing reclaim difficulties.

Fix this is to key the distress calculation not off zone->prev_priority, but
also take into account the local caller's priority by using
min(zone->prev_priority, sc->priority)

Signed-off-by: Martin J. Bligh <mbligh@google.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>