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Subject[PATCH] cma: make number of CMA areas dynamic, remove CONFIG_CMA_AREAS
Date
The number of distinct CMA areas is limited by the constant
CONFIG_CMA_AREAS. In most environments, this was set to a default
value of 7. Not too long ago, support was added to allocate hugetlb
gigantic pages from CMA. More recent changes to make dma_alloc_coherent
NUMA-aware on arm64 added more potential users of CMA areas. Along
with the dma_alloc_coherent changes, the default value of CMA_AREAS
was bumped up to 19 if NUMA is enabled.

It seems that the number of CMA users is likely to grow. Instead of
using a static array for cma areas, use a simple linked list. These
areas are used before normal memory allocators, so use the memblock
allocator.

Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
rfc->v1
- Made minor changes suggested by Song Bao Hua (Barry Song)
- Removed check for late calls to cma_init_reserved_mem that was part
of RFC.
- Added ACK from Roman Gushchin
- Still in need of arm testing

arch/arm/mm/dma-mapping.c | 28 ++++++++++++-------
arch/mips/configs/cu1000-neo_defconfig | 1 -
arch/mips/configs/cu1830-neo_defconfig | 1 -
include/linux/cma.h | 12 ---------
mm/Kconfig | 12 ---------
mm/cma.c | 37 +++++++++++---------------
mm/cma.h | 4 +--
mm/cma_debug.c | 6 ++---
8 files changed, 39 insertions(+), 62 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 8a8949174b1c..764286637a0b 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -383,25 +383,33 @@ postcore_initcall(atomic_pool_init);
struct dma_contig_early_reserve {
phys_addr_t base;
unsigned long size;
+ struct list_head areas;
};

-static struct dma_contig_early_reserve dma_mmu_remap[MAX_CMA_AREAS] __initdata;
-
-static int dma_mmu_remap_num __initdata;
+static __initdata LIST_HEAD(dma_mmu_remap_areas);

void __init dma_contiguous_early_fixup(phys_addr_t base, unsigned long size)
{
- dma_mmu_remap[dma_mmu_remap_num].base = base;
- dma_mmu_remap[dma_mmu_remap_num].size = size;
- dma_mmu_remap_num++;
+ struct dma_contig_early_reserve *d;
+
+ d = memblock_alloc(sizeof(*d), sizeof(void *));
+ if (!d) {
+ pr_err("Unable to allocate dma_contig_early_reserve struct!\n");
+ return;
+ }
+
+ d->base = base;
+ d->size = size;
+ list_add_tail(&d->areas, &dma_mmu_remap_areas);
}

void __init dma_contiguous_remap(void)
{
- int i;
- for (i = 0; i < dma_mmu_remap_num; i++) {
- phys_addr_t start = dma_mmu_remap[i].base;
- phys_addr_t end = start + dma_mmu_remap[i].size;
+ struct dma_contig_early_reserve *d;
+
+ list_for_each_entry(d, &dma_mmu_remap_areas, areas) {
+ phys_addr_t start = d->base;
+ phys_addr_t end = start + d->size;
struct map_desc map;
unsigned long addr;

diff --git a/arch/mips/configs/cu1000-neo_defconfig b/arch/mips/configs/cu1000-neo_defconfig
index e924c817f73d..b86f3fd420f2 100644
--- a/arch/mips/configs/cu1000-neo_defconfig
+++ b/arch/mips/configs/cu1000-neo_defconfig
@@ -31,7 +31,6 @@ CONFIG_HZ_100=y
# CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS is not set
# CONFIG_COMPACTION is not set
CONFIG_CMA=y
-CONFIG_CMA_AREAS=7
CONFIG_NET=y
CONFIG_PACKET=y
CONFIG_UNIX=y
diff --git a/arch/mips/configs/cu1830-neo_defconfig b/arch/mips/configs/cu1830-neo_defconfig
index cbfb62900273..98a31334fc57 100644
--- a/arch/mips/configs/cu1830-neo_defconfig
+++ b/arch/mips/configs/cu1830-neo_defconfig
@@ -31,7 +31,6 @@ CONFIG_HZ_100=y
# CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS is not set
# CONFIG_COMPACTION is not set
CONFIG_CMA=y
-CONFIG_CMA_AREAS=7
CONFIG_NET=y
CONFIG_PACKET=y
CONFIG_UNIX=y
diff --git a/include/linux/cma.h b/include/linux/cma.h
index 217999c8a762..ea9a3dab0c20 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -6,18 +6,6 @@
#include <linux/types.h>
#include <linux/numa.h>

-/*
- * There is always at least global CMA area and a few optional
- * areas configured in kernel .config.
- */
-#ifdef CONFIG_CMA_AREAS
-#define MAX_CMA_AREAS (1 + CONFIG_CMA_AREAS)
-
-#else
-#define MAX_CMA_AREAS (0)
-
-#endif
-
#define CMA_MAX_NAME 64

struct cma;
diff --git a/mm/Kconfig b/mm/Kconfig
index 7d56281ff41e..a52345093f4d 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -513,18 +513,6 @@ config CMA_DEBUGFS
help
Turns on the DebugFS interface for CMA.

-config CMA_AREAS
- int "Maximum count of the CMA areas"
- depends on CMA
- default 19 if NUMA
- default 7
- help
- CMA allows to create CMA areas for particular purpose, mainly,
- used as device private area. This parameter sets the maximum
- number of CMA area in the system.
-
- If unsure, leave the default value "7" in UMA and "19" in NUMA.
-
config MEM_SOFT_DIRTY
bool "Track memory changes"
depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
diff --git a/mm/cma.c b/mm/cma.c
index 7f415d7cda9f..f3a983acf70e 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -36,8 +36,9 @@

#include "cma.h"

-struct cma cma_areas[MAX_CMA_AREAS];
-unsigned cma_area_count;
+/* modify here */
+LIST_HEAD(cma_areas);
+static unsigned int cma_area_count;
static DEFINE_MUTEX(cma_mutex);

phys_addr_t cma_get_base(const struct cma *cma)
@@ -143,10 +144,10 @@ static void __init cma_activate_area(struct cma *cma)

static int __init cma_init_reserved_areas(void)
{
- int i;
+ struct cma *c;

- for (i = 0; i < cma_area_count; i++)
- cma_activate_area(&cma_areas[i]);
+ list_for_each_entry(c, &cma_areas, areas)
+ cma_activate_area(c);

return 0;
}
@@ -172,12 +173,6 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
struct cma *cma;
phys_addr_t alignment;

- /* Sanity checks */
- if (cma_area_count == ARRAY_SIZE(cma_areas)) {
- pr_err("Not enough slots for CMA reserved regions!\n");
- return -ENOSPC;
- }
-
if (!size || !memblock_is_region_reserved(base, size))
return -EINVAL;

@@ -192,12 +187,17 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
if (ALIGN(base, alignment) != base || ALIGN(size, alignment) != size)
return -EINVAL;

+ cma = memblock_alloc(sizeof(*cma), sizeof(long));
+ if (!cma) {
+ pr_err("Unable to allocate CMA descriptor!\n");
+ return -ENOSPC;
+ }
+ list_add_tail(&cma->areas, &cma_areas);
+
/*
* Each reserved area must be initialised later, when more kernel
* subsystems (like slab allocator) are available.
*/
- cma = &cma_areas[cma_area_count];
-
if (name)
snprintf(cma->name, CMA_MAX_NAME, name);
else
@@ -253,11 +253,6 @@ int __init cma_declare_contiguous_nid(phys_addr_t base,
pr_debug("%s(size %pa, base %pa, limit %pa alignment %pa)\n",
__func__, &size, &base, &limit, &alignment);

- if (cma_area_count == ARRAY_SIZE(cma_areas)) {
- pr_err("Not enough slots for CMA reserved regions!\n");
- return -ENOSPC;
- }
-
if (!size)
return -EINVAL;

@@ -530,10 +525,10 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)

int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data)
{
- int i;
+ struct cma *c;

- for (i = 0; i < cma_area_count; i++) {
- int ret = it(&cma_areas[i], data);
+ list_for_each_entry(c, &cma_areas, areas) {
+ int ret = it(c, data);

if (ret)
return ret;
diff --git a/mm/cma.h b/mm/cma.h
index 42ae082cb067..fed800b63819 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -15,11 +15,11 @@ struct cma {
spinlock_t mem_head_lock;
struct debugfs_u32_array dfs_bitmap;
#endif
+ struct list_head areas;
char name[CMA_MAX_NAME];
};

-extern struct cma cma_areas[MAX_CMA_AREAS];
-extern unsigned cma_area_count;
+extern struct list_head cma_areas;

static inline unsigned long cma_bitmap_maxno(struct cma *cma)
{
diff --git a/mm/cma_debug.c b/mm/cma_debug.c
index d5bf8aa34fdc..c39695d50224 100644
--- a/mm/cma_debug.c
+++ b/mm/cma_debug.c
@@ -188,12 +188,12 @@ static void cma_debugfs_add_one(struct cma *cma, struct dentry *root_dentry)
static int __init cma_debugfs_init(void)
{
struct dentry *cma_debugfs_root;
- int i;
+ struct cma *c;

cma_debugfs_root = debugfs_create_dir("cma", NULL);

- for (i = 0; i < cma_area_count; i++)
- cma_debugfs_add_one(&cma_areas[i], cma_debugfs_root);
+ list_for_each_entry(c, &cma_areas, areas)
+ cma_debugfs_add_one(c, cma_debugfs_root);

return 0;
}
--
2.25.4
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