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Subject[PATCH 02/13] memblock: Reimplement memblock_add_region()
Date
memblock_add_region() carefully checked for merge and overlap
conditions while adding a new region, which is complicated and makes
it difficult to allow arbitrary overlaps or add more merge conditions
(e.g. node ID).

This re-implements memblock_add_region() such that insertion is done
in two steps - all non-overlapping portions of new area are inserted
as separate regions first and then memblock_merge_regions() scan and
merge all neighbouring compatible regions.

This makes addition logic simpler and more versatile and enables
adding node information to memblock.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
mm/memblock.c | 197 ++++++++++++++++++++++++++++++++-------------------------
1 files changed, 111 insertions(+), 86 deletions(-)
diff --git a/mm/memblock.c b/mm/memblock.c
index bd3a3a9..992aa18 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -251,117 +251,142 @@ static int __init_memblock memblock_double_array(struct memblock_type *type)
return 0;
}

-static long __init_memblock memblock_add_region(struct memblock_type *type,
- phys_addr_t base, phys_addr_t size)
+/**
+ * memblock_merge_regions - merge neighboring compatible regions
+ * @type: memblock type to scan
+ *
+ * Scan @type and merge neighboring compatible regions.
+ */
+static void __init_memblock memblock_merge_regions(struct memblock_type *type)
{
- phys_addr_t end = base + size;
- int i, slot = -1;
+ int i = 0;

- /* First try and coalesce this MEMBLOCK with others */
- for (i = 0; i < type->cnt; i++) {
- struct memblock_region *rgn = &type->regions[i];
- phys_addr_t rend = rgn->base + rgn->size;
+ /* cnt never goes below 1 */
+ while (i < type->cnt - 1) {
+ struct memblock_region *this = &type->regions[i];
+ struct memblock_region *next = &type->regions[i + 1];

- /* Exit if there's no possible hits */
- if (rgn->base > end || rgn->size == 0)
- break;
-
- /* Check if we are fully enclosed within an existing
- * block
- */
- if (rgn->base <= base && rend >= end)
- return 0;
+ if (this->base + this->size != next->base) {
+ BUG_ON(this->base + this->size > next->base);
+ i++;
+ continue;
+ }

- /* Check if we overlap or are adjacent with the bottom
- * of a block.
- */
- if (base < rgn->base && end >= rgn->base) {
- /* We extend the bottom of the block down to our
- * base
- */
- rgn->base = base;
- rgn->size = rend - base;
+ this->size += next->size;
+ memmove(next, next + 1, (type->cnt - (i + 1)) * sizeof(*next));
+ type->cnt--;
+ }
+}

- /* Return if we have nothing else to allocate
- * (fully coalesced)
- */
- if (rend >= end)
- return 0;
+/**
+ * memblock_insert_region - insert new memblock region
+ * @type: memblock type to insert into
+ * @idx: index for the insertion point
+ * @base: base address of the new region
+ * @size: size of the new region
+ *
+ * Insert new memblock region [@base,@base+@size) into @type at @idx.
+ * @type must already have extra room to accomodate the new region.
+ */
+static void __init_memblock memblock_insert_region(struct memblock_type *type,
+ int idx, phys_addr_t base,
+ phys_addr_t size)
+{
+ struct memblock_region *rgn = &type->regions[idx];

- /* We continue processing from the end of the
- * coalesced block.
- */
- base = rend;
- size = end - base;
- }
+ BUG_ON(type->cnt >= type->max);
+ memmove(rgn + 1, rgn, (type->cnt - idx) * sizeof(*rgn));
+ rgn->base = base;
+ rgn->size = size;
+ type->cnt++;
+}

- /* Now check if we overlap or are adjacent with the
- * top of a block
- */
- if (base <= rend && end >= rend) {
- /* We adjust our base down to enclose the
- * original block and destroy it. It will be
- * part of our new allocation. Since we've
- * freed an entry, we know we won't fail
- * to allocate one later, so we won't risk
- * losing the original block allocation.
- */
- size += (base - rgn->base);
- base = rgn->base;
- memblock_remove_region(type, i--);
- }
- }
+/**
+ * memblock_add_region - add new memblock region
+ * @type: memblock type to add new region into
+ * @base: base address of the new region
+ * @size: size of the new region
+ *
+ * Add new memblock region [@base,@base+@size) into @type. The new region
+ * is allowed to overlap with existing ones - overlaps don't affect already
+ * existing regions. @type is guaranteed to be minimal (all neighbouring
+ * compatible regions are merged) after the addition.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static long __init_memblock memblock_add_region(struct memblock_type *type,
+ phys_addr_t base, phys_addr_t size)
+{
+ bool insert = false;
+ phys_addr_t obase = base, end = base + size;
+ int i, nr_new;

- /* If the array is empty, special case, replace the fake
- * filler region and return
- */
- if ((type->cnt == 1) && (type->regions[0].size == 0)) {
+ /* special case for empty array */
+ if (type->regions[0].size == 0) {
+ WARN_ON(type->cnt != 1);
type->regions[0].base = base;
type->regions[0].size = size;
return 0;
}
-
- /* If we are out of space, we fail. It's too late to resize the array
- * but then this shouldn't have happened in the first place.
+repeat:
+ /*
+ * The following is executed twice. Once with %false @insert and
+ * then with %true. The first counts the number of regions needed
+ * to accomodate the new area. The second actually inserts them.
*/
- if (WARN_ON(type->cnt >= type->max))
- return -1;
+ base = obase;
+ nr_new = 0;
+
+ for (i = 0; i < type->cnt; i++) {
+ struct memblock_region *rgn = &type->regions[i];
+ phys_addr_t rbase = rgn->base;
+ phys_addr_t rend = rbase + rgn->size;

- /* Couldn't coalesce the MEMBLOCK, so add it to the sorted table. */
- for (i = type->cnt - 1; i >= 0; i--) {
- if (base < type->regions[i].base) {
- type->regions[i+1].base = type->regions[i].base;
- type->regions[i+1].size = type->regions[i].size;
- } else {
- type->regions[i+1].base = base;
- type->regions[i+1].size = size;
- slot = i + 1;
+ if (rbase >= end)
break;
+ if (rend <= base)
+ continue;
+ /*
+ * @rgn overlaps. If it separates the lower part of new
+ * area, insert that portion.
+ */
+ if (rbase > base) {
+ nr_new++;
+ if (insert)
+ memblock_insert_region(type, i++, base,
+ rbase - base);
}
+ /* area below @rend is dealt with, forget about it */
+ base = min(rend, end);
}
- if (base < type->regions[0].base) {
- type->regions[0].base = base;
- type->regions[0].size = size;
- slot = 0;
+
+ /* insert the remaining portion */
+ if (base < end) {
+ nr_new++;
+ if (insert)
+ memblock_insert_region(type, i, base, end - base);
}
- type->cnt++;

- /* The array is full ? Try to resize it. If that fails, we undo
- * our allocation and return an error
+ /*
+ * If this was the first round, resize array and repeat for actual
+ * insertions; otherwise, merge and return.
*/
- if (type->cnt == type->max && memblock_double_array(type)) {
- BUG_ON(slot < 0);
- memblock_remove_region(type, slot);
- return -1;
+ if (!insert) {
+ while (type->cnt + nr_new > type->max)
+ if (memblock_double_array(type) < 0)
+ return -ENOMEM;
+ insert = true;
+ goto repeat;
+ } else {
+ memblock_merge_regions(type);
+ return 0;
}
-
- return 0;
}

long __init_memblock memblock_add(phys_addr_t base, phys_addr_t size)
{
return memblock_add_region(&memblock.memory, base, size);
-
}

static long __init_memblock __memblock_remove(struct memblock_type *type,
--
1.7.6


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