[RFC PATCH 1/3] CMA: generalize CMA reserved area management functionality

diff --git a/include/linux/cma.h b/include/linux/cma.h
new file mode 100644
index 0000000..60ba06f
--- /dev/null
+++ b/include/linux/cma.h

@@ -0,0 +1,28 @@
+/*
+ * Contiguous Memory Allocator
+ *
+ * Copyright LG Electronics Inc., 2014
+ * Written by:
+ *	Joonsoo Kim <iamjoonsoo.kim@lge.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License or (at your optional) any later version of the license.
+ *

+ */
+
+#ifndef __CMA_H__
+#define __CMA_H__
+
+struct cma;
+
+extern struct page *cma_alloc(struct cma *cma, unsigned long count,
+				unsigned long align);
+extern bool cma_release(struct cma *cma, struct page *pages,
+				unsigned long count);
+extern int __init cma_declare_contiguous(phys_addr_t size, phys_addr_t base,
+				phys_addr_t limit, phys_addr_t alignment,
+				unsigned long bitmap_shift, bool fixed,
+				struct cma **res_cma);
+#endif

diff --git a/mm/cma.c b/mm/cma.c
new file mode 100644
index 0000000..0dae88d
--- /dev/null
+++ b/mm/cma.c

@@ -0,0 +1,329 @@

+static int __init cma_activate_area(struct cma *cma)
+{
+	int max_bitmapno = cma_bitmap_max_no(cma);
+	int bitmap_size = BITS_TO_LONGS(max_bitmapno) * sizeof(long);
+	unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
+	unsigned i = cma->count >> pageblock_order;
+	struct zone *zone;
+
+	pr_debug("%s()\n", __func__);
+	if (!cma->count)
+		return 0;

+
+	cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
+	if (!cma->bitmap)
+		return -ENOMEM;
+
+	WARN_ON_ONCE(!pfn_valid(pfn));
+	zone = page_zone(pfn_to_page(pfn));
+
+	do {
+		unsigned j;
+
+		base_pfn = pfn;
+		for (j = pageblock_nr_pages; j; --j, pfn++) {
+			WARN_ON_ONCE(!pfn_valid(pfn));
+			/*
+			 * alloc_contig_range requires the pfn range
+			 * specified to be in the same zone. Make this
+			 * simple by forcing the entire CMA resv range
+			 * to be in the same zone.
+			 */
+			if (page_zone(pfn_to_page(pfn)) != zone)
+				goto err;
+		}
+		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
+	} while (--i);
+
+	mutex_init(&cma->lock);
+	return 0;
+
+err:
+	kfree(cma->bitmap);
+	return -EINVAL;
+}

+static int __init cma_init_reserved_areas(void)
+{
+	int i;
+
+	for (i = 0; i < cma_area_count; i++) {
+		int ret = cma_activate_area(&cma_areas[i]);
+
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}

+int __init cma_declare_contiguous(phys_addr_t size, phys_addr_t base,
+				phys_addr_t limit, phys_addr_t alignment,
+				unsigned long bitmap_shift, bool fixed,
+				struct cma **res_cma)
+{
+	struct cma *cma = &cma_areas[cma_area_count];

+	int ret = 0;
+
+	pr_debug("%s(size %lx, base %08lx, limit %08lx, alignment %08lx)\n",
+			__func__, (unsigned long)size, (unsigned long)base,
+			(unsigned long)limit, (unsigned long)alignment);
+
+	/* Sanity checks */
+	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
+		pr_err("Not enough slots for CMA reserved regions!\n");
+		return -ENOSPC;
+	}
+
+	if (!size)
+		return -EINVAL;
+
+	/*
+	 * Sanitise input arguments.
+	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
+	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
+	 * and CMA property will be broken.
+	 */
+	alignment >>= PAGE_SHIFT;
+	alignment = PAGE_SIZE << max3(MAX_ORDER - 1, pageblock_order,
+						(int)alignment);
+	base = ALIGN(base, alignment);
+	size = ALIGN(size, alignment);
+	limit &= ~(alignment - 1);
+	/* size should be aligned with bitmap_shift */
+	BUG_ON(!IS_ALIGNED(size >> PAGE_SHIFT, 1 << cma->bitmap_shift));

+
+	/* Reserve memory */
+	if (base && fixed) {
+		if (memblock_is_region_reserved(base, size) ||
+		    memblock_reserve(base, size) < 0) {
+			ret = -EBUSY;
+			goto err;
+		}
+	} else {
+		phys_addr_t addr = memblock_alloc_range(size, alignment, base,
+							limit);
+		if (!addr) {
+			ret = -ENOMEM;
+			goto err;
+		} else {
+			base = addr;
+		}
+	}
+
+	/*
+	 * Each reserved area must be initialised later, when more kernel
+	 * subsystems (like slab allocator) are available.
+	 */
+	cma->base_pfn = PFN_DOWN(base);
+	cma->count = size >> PAGE_SHIFT;
+	cma->bitmap_shift = bitmap_shift;
+	*res_cma = cma;
+	cma_area_count++;
+
+	pr_info("CMA: reserved %ld MiB at %08lx\n", (unsigned long)size / SZ_1M,
+		(unsigned long)base);

+
+	return 0;
+
+err:
+	pr_err("CMA: failed to reserve %ld MiB\n", (unsigned long)size / SZ_1M);
+	return ret;
+}