[PATCH 06/11] memblock: Improve memblock to support allocation from lower address.

[Tang Chen]

This patch modifies the memblock_find_in_range_node() to support two
different allocation orders. After this patch, memblock will check
memblock.current_order, and decide in which order to allocate memory.

Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Reviewed-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
---
 mm/memblock.c |   90 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 75 insertions(+), 15 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 8f1e2d4..961d4a5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -85,6 +85,77 @@ static long __init_memblock memblock_overlaps_region(struct memblock_type *type,
 }
 
 /**
+ * __memblock_find_range - find free area utility
+ * @start: start of candidate range, can be %MEMBLOCK_ALLOC_ACCESSIBLE
+ * @end: end of candidate range, can be %MEMBLOCK_ALLOC_{ANYWHERE|ACCESSIBLE}
+ * @size: size of free area to find
+ * @align: alignment of free area to find
+ * @nid: nid of the free area to find, %MAX_NUMNODES for any node
+ *
+ * Utility called from memblock_find_in_range_node(), find free area from
+ * lower address to higher address.
+ *
+ * RETURNS:
+ * Found address on success, %0 on failure.
+ */
+phys_addr_t __init_memblock
+__memblock_find_range(phys_addr_t start, phys_addr_t end,
+		      phys_addr_t size, phys_addr_t align, int nid)
+{
+	phys_addr_t this_start, this_end, cand;
+	u64 i;
+
+	for_each_free_mem_range(i, nid, &this_start, &this_end, NULL) {
+		this_start = clamp(this_start, start, end);
+		this_end = clamp(this_end, start, end);
+
+		cand = round_up(this_start, align);
+		if (cand < this_end && this_end - cand >= size)
+			return cand;
+	}
+	return 0;
+}
+
+/**
+ * __memblock_find_range_rev - find free area utility, in reverse order
+ * @start: start of candidate range, can be %MEMBLOCK_ALLOC_ACCESSIBLE
+ * @end: end of candidate range, can be %MEMBLOCK_ALLOC_{ANYWHERE|ACCESSIBLE}
+ * @size: size of free area to find
+ * @align: alignment of free area to find
+ * @nid: nid of the free area to find, %MAX_NUMNODES for any node
+ *
+ * Utility called from memblock_find_in_range_node(), find free area from
+ * higher address to lower address.
+ *
+ * RETURNS:
+ * Found address on success, %0 on failure.
+ */
+phys_addr_t __init_memblock
+__memblock_find_range_rev(phys_addr_t start, phys_addr_t end,
+			  phys_addr_t size, phys_addr_t align, int nid)
+{
+	phys_addr_t this_start, this_end, cand;
+	u64 i;
+
+	for_each_free_mem_range_reverse(i, nid, &this_start, &this_end, NULL) {
+		this_start = clamp(this_start, start, end);
+		this_end = clamp(this_end, start, end);
+
+		/*
+		 * Just in case that (this_end - size) underflows and cause
+		 * (cand >= this_start) to be true incorrectly.
+		 */
+		if (this_end < size)
+			break;
+
+		cand = round_down(this_end - size, align);
+		if (cand >= this_start)
+			return cand;
+	}
+	return 0;
+}
+
+/**
  * memblock_find_in_range_node - find free area in given range and node
  * @start: start of candidate range, can be %MEMBLOCK_ALLOC_ACCESSIBLE
  * @end: end of candidate range, can be %MEMBLOCK_ALLOC_{ANYWHERE|ACCESSIBLE}
@@ -110,9 +181,6 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start,
 					phys_addr_t end, phys_addr_t size,
 					phys_addr_t align, int nid)
 {
-	phys_addr_t this_start, this_end, cand;
-	u64 i;
-
 	/* pump up @start and @end */
 	if (start == MEMBLOCK_ALLOC_ACCESSIBLE)
 		start = memblock.current_limit_low;
@@ -123,18 +191,10 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start,
 	start = max_t(phys_addr_t, start, PAGE_SIZE);
 	end = max(start, end);
 
-	for_each_free_mem_range_reverse(i, nid, &this_start, &this_end, NULL) {
-		this_start = clamp(this_start, start, end);
-		this_end = clamp(this_end, start, end);
-
-		if (this_end < size)
-			continue;
-
-		cand = round_down(this_end - size, align);
-		if (cand >= this_start)
-			return cand;
-	}
-	return 0;
+	if (memblock.current_order == MEMBLOCK_ORDER_DEFAULT)
+		return __memblock_find_range_rev(start, end, size, align, nid);
+	else
+		return __memblock_find_range(start, end, size, align, nid);
 }
 
 /**
-- 
1.7.1

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