This patch introduces a new "guarantee" property for shared-dma-pool.
With this property, admin can create specific memory pool as
GCMA-based CMA if they care about allocation success rate and latency.
The downside of GCMA is that it can host only clean file-backed pages
since it's using cleancache as its secondary user.

Signed-off-by: Minchan Kim <redacted>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 arch/powerpc/kernel/fadump.c |  2 +-
 include/linux/cma.h          |  2 +-
 kernel/dma/contiguous.c      | 11 ++++++++++-
 mm/cma.c                     | 33 ++++++++++++++++++++++++++-------
 mm/cma.h                     |  1 +
 mm/cma_sysfs.c               | 10 ++++++++++
 6 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 4b371c738213..4eb7be0cdcdb 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c

@@ -111,7 +111,7 @@ void __init fadump_cma_init(void)
 		return;
 	}
 
-	rc = cma_init_reserved_mem(base, size, 0, "fadump_cma", &fadump_cma);
+	rc = cma_init_reserved_mem(base, size, 0, "fadump_cma", &fadump_cma, false);
 	if (rc) {
 		pr_err("Failed to init cma area for firmware-assisted dump,%d\n", rc);
 		/*

diff --git a/include/linux/cma.h b/include/linux/cma.h
index 62d9c1cf6326..3207db979e94 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h

@@ -46,7 +46,7 @@ extern int __init cma_declare_contiguous_multi(phys_addr_t size,
 extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
 					unsigned int order_per_bit,
 					const char *name,
-					struct cma **res_cma);
+					struct cma **res_cma, bool gcma);
 extern struct page *cma_alloc(struct cma *cma, unsigned long count, unsigned int align,
 			      bool no_warn);
 extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned long count);

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 055da410ac71..a68b3123438c 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c

@@ -459,6 +459,7 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
 	unsigned long node = rmem->fdt_node;
 	bool default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
 	struct cma *cma;
+	bool gcma;
 	int err;
 
 	if (size_cmdline != -1 && default_cma) {

@@ -476,7 +477,15 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
 		return -EINVAL;
 	}
 
-	err = cma_init_reserved_mem(rmem->base, rmem->size, 0, rmem->name, &cma);
+	gcma = !!of_get_flat_dt_prop(node, "guarantee", NULL);