内存管理之memblock管理之移除块

此函数是整个memblock中分配和释放内存的核心函数，主要是对region操作。详细实现如下：

static int __init_memblock memblock_remove_range(struct memblock_type *type,  phys_addr_t base, phys_addr_t size){int start_rgn, end_rgn;int i, ret;//先确定移除的逻辑块所在的region，这步就是隔离isolate操作。ret = memblock_isolate_range(type, base, size, &start_rgn, &end_rgn);if (ret)return ret;//把整个region从指定类型中移除。for (i = end_rgn - 1; i >= start_rgn; i--)memblock_remove_region(type, i);return 0;}

/** * memblock_isolate_range - isolate given range into disjoint memblocks

把给出的范围内的逻辑块从以所在的块中脱离出来，这样会增加一个新的region。

 * @type: memblock type to isolate range for * @base: base of range to isolate * @size: size of range to isolate * @start_rgn: out parameter for the start of isolated region * @end_rgn: out parameter for the end of isolated region * * Walk @type and ensure that regions don't cross the boundaries defined by * [@base,@base+@size).  Crossing regions are split at the boundaries, * which may create at most two more regions.  The index of the first * region inside the range is returned in *@start_rgn and end in *@end_rgn. * * RETURNS: * 0 on success, -errno on failure. */

    region[min, max]

pre -->  memory：  min<--------------|----------------|-------------------->max

示例：            0x1000----------0x5000-----------0x8000---------------0xc0000

base:0x5000, size:0x3000,

region1[min, 0x5000]        region2[0x8000, max] 

now -->  memory： min<----------->        hole     <------------------->max

0x1000--------0x5000             0x8000-------------0xc0000

static int memblock_isolate_range(struct memblock_type *type,phys_addr_t base, phys_addr_t size,int *start_rgn, int *end_rgn){phys_addr_t end = base + memblock_cap_size(base, &size);int idx;struct memblock_region *rgn;*start_rgn = *end_rgn = 0;if (!size)return 0;/* we'll create at most two more regions 太多region，目前最大支持128个*/while (type->cnt + 2 > type->max)if (memblock_double_array(type, base, size) < 0)return -ENOMEM;//依次对每个region确定大小和覆盖范围。

for_each_memblock_type(type, rgn) {phys_addr_t rbase = rgn->base;phys_addr_t rend = rbase + rgn->size;if (rbase >= end)break;if (rend <= base)continue;if (rbase < base) {/* * @rgn intersects from below.  Split and continue * to process the next region - the new top half. */rgn->base = base;rgn->size -= base - rbase;type->total_size -= base - rbase;插入新的region

memblock_insert_region(type, idx, rbase, base - rbase,       memblock_get_region_node(rgn),       rgn->flags);} else if (rend > end) {/* * @rgn intersects from above.  Split and redo the * current region - the new bottom half. */rgn->base = end;rgn->size -= end - rbase;type->total_size -= end - rbase;

另外一种插入方式

memblock_insert_region(type, idx--, rbase, end - rbase,       memblock_get_region_node(rgn),       rgn->flags);} else {/* @rgn is fully contained, record it */if (!*end_rgn)*start_rgn = idx;*end_rgn = idx + 1;}}return 0;}

static void memblock_remove_region(struct memblock_type *type, unsigned long r){type->total_size -= type->regions[r].size;更新大小

memmove(&type->regions[r], &type->regions[r + 1],(type->cnt - (r + 1)) * sizeof(type->regions[r]));type->cnt--;

更新总的region大小/* Special case for empty arrays */if (type->cnt == 0) {WARN_ON(type->total_size != 0);type->cnt = 1;type->regions[0].base = 0;type->regions[0].size = 0;type->regions[0].flags = 0;memblock_set_region_node(&type->regions[0], MAX_NUMNODES);}}