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memblock: Reimplement memblock_add_region()
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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>
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Tejun Heo authored and H. Peter Anvin committed Jul 14, 2011
1 parent ed7b56a commit 784656f
Showing 1 changed file with 110 additions and 85 deletions.
195 changes: 110 additions & 85 deletions mm/memblock.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
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