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authorOliver O'Halloran2016-07-26 15:22:17 -0700
committerLinus Torvalds2016-07-26 16:19:19 -0700
commit90cae1fe1c3540f791d5b8e025985fa5e699b2bb (patch)
treed1d8fc1dcc765e4264378ec94d42de9bb47ada9c
parent48406ef897f48d1a189d73f8c8cd2ece0dc19e5e (diff)
mm/init: fix zone boundary creation
As a part of memory initialisation the architecture passes an array to free_area_init_nodes() which specifies the max PFN of each memory zone. This array is not necessarily monotonic (due to unused zones) so this array is parsed to build monotonic lists of the min and max PFN for each zone. ZONE_MOVABLE is special cased here as its limits are managed by the mm subsystem rather than the architecture. Unfortunately, this special casing is broken when ZONE_MOVABLE is the not the last zone in the zone list. The core of the issue is: if (i == ZONE_MOVABLE) continue; arch_zone_lowest_possible_pfn[i] = arch_zone_highest_possible_pfn[i-1]; As ZONE_MOVABLE is skipped the lowest_possible_pfn of the next zone will be set to zero. This patch fixes this bug by adding explicitly tracking where the next zone should start rather than relying on the contents arch_zone_highest_possible_pfn[]. Thie is low priority. To get bitten by this you need to enable a zone that appears after ZONE_MOVABLE in the zone_type enum. As far as I can tell this means running a kernel with ZONE_DEVICE or ZONE_CMA enabled, so I can't see this affecting too many people. I only noticed this because I've been fiddling with ZONE_DEVICE on powerpc and 4.6 broke my test kernel. This bug, in conjunction with the changes in Taku Izumi's kernelcore=mirror patch (d91749c1dda71) and powerpc being the odd architecture which initialises max_zone_pfn[] to ~0ul instead of 0 caused all of system memory to be placed into ZONE_DEVICE at boot, followed a panic since device memory cannot be used for kernel allocations. I've already submitted a patch to fix the powerpc specific bits, but I figured this should be fixed too. Link: http://lkml.kernel.org/r/1462435033-15601-1-git-send-email-oohall@gmail.com Signed-off-by: Oliver O'Halloran <oohall@gmail.com> Cc: Anton Blanchard <anton@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8b3e1341b754..8129922a1504 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6467,15 +6467,18 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)
sizeof(arch_zone_lowest_possible_pfn));
memset(arch_zone_highest_possible_pfn, 0,
sizeof(arch_zone_highest_possible_pfn));
- arch_zone_lowest_possible_pfn[0] = find_min_pfn_with_active_regions();
- arch_zone_highest_possible_pfn[0] = max_zone_pfn[0];
- for (i = 1; i < MAX_NR_ZONES; i++) {
+
+ start_pfn = find_min_pfn_with_active_regions();
+
+ for (i = 0; i < MAX_NR_ZONES; i++) {
if (i == ZONE_MOVABLE)
continue;
- arch_zone_lowest_possible_pfn[i] =
- arch_zone_highest_possible_pfn[i-1];
- arch_zone_highest_possible_pfn[i] =
- max(max_zone_pfn[i], arch_zone_lowest_possible_pfn[i]);
+
+ end_pfn = max(max_zone_pfn[i], start_pfn);
+ arch_zone_lowest_possible_pfn[i] = start_pfn;
+ arch_zone_highest_possible_pfn[i] = end_pfn;
+
+ start_pfn = end_pfn;
}
arch_zone_lowest_possible_pfn[ZONE_MOVABLE] = 0;
arch_zone_highest_possible_pfn[ZONE_MOVABLE] = 0;