memblock: Reimplement memblock_add_region()

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>
Link: http://lkml.kernel.org/r/1310462166-31469-3-git-send-email-tj@kernel.org
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 110 insertions, 85 deletions

diff --git a/mm/memblock.c b/mm/memblock.c
index bd3a3a9591d4..992aa1807473 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,