From b11a7b94100cba5ec926a181894c2897a22651b9 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 17 Mar 2016 14:19:41 -0700 Subject: [PATCH] mm: exclude ZONE_DEVICE from GFP_ZONE_TABLE ZONE_DEVICE (merged in 4.3) and ZONE_CMA (proposed) are examples of new mm zones that are bumping up against the current maximum limit of 4 zones, i.e. 2 bits in page->flags for the GFP_ZONE_TABLE. The GFP_ZONE_TABLE poses an interesting constraint since include/linux/gfp.h gets included by the 32-bit portion of a 64-bit build. We need to be careful to only build the table for zones that have a corresponding gfp_t flag. GFP_ZONES_SHIFT is introduced for this purpose. This patch does not attempt to solve the problem of adding a new zone that also has a corresponding GFP_ flag. Vlastimil points out that ZONE_DEVICE, by depending on x86_64 and SPARSEMEM_VMEMMAP implies that SECTIONS_WIDTH is zero. In other words even though ZONE_DEVICE does not fit in GFP_ZONE_TABLE it is free to consume another bit in page->flags (expand ZONES_WIDTH) with room to spare. Link: https://bugzilla.kernel.org/show_bug.cgi?id=110931 Fixes: 033fbae988fc ("mm: ZONE_DEVICE for "device memory"") Signed-off-by: Dan Williams Reported-by: Mark Reported-by: Vlastimil Babka Cc: Mel Gorman Cc: Rik van Riel Cc: Joonsoo Kim Cc: Dave Hansen Cc: Sudip Mukherjee Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/gfp.h | 33 +++++++++++++++++++------------ include/linux/page-flags-layout.h | 2 ++ mm/Kconfig | 2 -- 3 files changed, 22 insertions(+), 15 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 11d56c6e7ef2..570383a41853 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -331,22 +331,29 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags) * 0xe => BAD (MOVABLE+DMA32+HIGHMEM) * 0xf => BAD (MOVABLE+DMA32+HIGHMEM+DMA) * - * ZONES_SHIFT must be <= 2 on 32 bit platforms. + * GFP_ZONES_SHIFT must be <= 2 on 32 bit platforms. */ -#if 16 * ZONES_SHIFT > BITS_PER_LONG -#error ZONES_SHIFT too large to create GFP_ZONE_TABLE integer +#if defined(CONFIG_ZONE_DEVICE) && (MAX_NR_ZONES-1) <= 4 +/* ZONE_DEVICE is not a valid GFP zone specifier */ +#define GFP_ZONES_SHIFT 2 +#else +#define GFP_ZONES_SHIFT ZONES_SHIFT +#endif + +#if 16 * GFP_ZONES_SHIFT > BITS_PER_LONG +#error GFP_ZONES_SHIFT too large to create GFP_ZONE_TABLE integer #endif #define GFP_ZONE_TABLE ( \ - (ZONE_NORMAL << 0 * ZONES_SHIFT) \ - | (OPT_ZONE_DMA << ___GFP_DMA * ZONES_SHIFT) \ - | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * ZONES_SHIFT) \ - | (OPT_ZONE_DMA32 << ___GFP_DMA32 * ZONES_SHIFT) \ - | (ZONE_NORMAL << ___GFP_MOVABLE * ZONES_SHIFT) \ - | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * ZONES_SHIFT) \ - | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * ZONES_SHIFT) \ - | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * ZONES_SHIFT) \ + (ZONE_NORMAL << 0 * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_DMA << ___GFP_DMA * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_HIGHMEM << ___GFP_HIGHMEM * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_DMA32 << ___GFP_DMA32 * GFP_ZONES_SHIFT) \ + | (ZONE_NORMAL << ___GFP_MOVABLE * GFP_ZONES_SHIFT) \ + | (OPT_ZONE_DMA << (___GFP_MOVABLE | ___GFP_DMA) * GFP_ZONES_SHIFT) \ + | (ZONE_MOVABLE << (___GFP_MOVABLE | ___GFP_HIGHMEM) * GFP_ZONES_SHIFT)\ + | (OPT_ZONE_DMA32 << (___GFP_MOVABLE | ___GFP_DMA32) * GFP_ZONES_SHIFT)\ ) /* @@ -371,8 +378,8 @@ static inline enum zone_type gfp_zone(gfp_t flags) enum zone_type z; int bit = (__force int) (flags & GFP_ZONEMASK); - z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) & - ((1 << ZONES_SHIFT) - 1); + z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & + ((1 << GFP_ZONES_SHIFT) - 1); VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); return z; } diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h index da523661500a..77b078c103b2 100644 --- a/include/linux/page-flags-layout.h +++ b/include/linux/page-flags-layout.h @@ -17,6 +17,8 @@ #define ZONES_SHIFT 1 #elif MAX_NR_ZONES <= 4 #define ZONES_SHIFT 2 +#elif MAX_NR_ZONES <= 8 +#define ZONES_SHIFT 3 #else #error ZONES_SHIFT -- too many zones configured adjust calculation #endif diff --git a/mm/Kconfig b/mm/Kconfig index c07776503708..520dae6e6ed0 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -651,8 +651,6 @@ config IDLE_PAGE_TRACKING config ZONE_DEVICE bool "Device memory (pmem, etc...) hotplug support" if EXPERT - default !ZONE_DMA - depends on !ZONE_DMA depends on MEMORY_HOTPLUG depends on MEMORY_HOTREMOVE depends on X86_64 #arch_add_memory() comprehends device memory -- 2.20.1