mm/cma: provide option to opt out from exposing pages on activation failure

Patch series "powerpc/fadump: handle CMA activation failure appropriately", v3.

Commit 072355c1cf2d ("mm/cma: expose all pages to the buddy if
activation of an area fails") started exposing all pages to buddy
allocator on CMA activation failure.  But there can be CMA users that
want to handle the reserved memory differently on CMA allocation
failure.

Provide an option to opt out from exposing pages to buddy for such
cases.

Link: https://lkml.kernel.org/r/20220117075246.36072-1-hbathini@linux.ibm.com
Link: https://lkml.kernel.org/r/20220117075246.36072-2-hbathini@linux.ibm.com
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 10 insertions, 2 deletions

diff --git a/mm/cma.c b/mm/cma.c
index 5a2cd5851658..eaa4b5c920a2 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -131,8 +131,10 @@ not_in_zone:
 	bitmap_free(cma->bitmap);
 out_error:
 	/* Expose all pages to the buddy, they are useless for CMA. */
-	for (pfn = base_pfn; pfn < base_pfn + cma->count; pfn++)
-		free_reserved_page(pfn_to_page(pfn));
+	if (!cma->reserve_pages_on_error) {
+		for (pfn = base_pfn; pfn < base_pfn + cma->count; pfn++)
+			free_reserved_page(pfn_to_page(pfn));
+	}
 	totalcma_pages -= cma->count;
 	cma->count = 0;
 	pr_err("CMA area %s could not be activated\n", cma->name);
@@ -150,6 +152,11 @@ static int __init cma_init_reserved_areas(void)
 }
 core_initcall(cma_init_reserved_areas);
 
+void __init cma_reserve_pages_on_error(struct cma *cma)
+{
+	cma->reserve_pages_on_error = true;
+}
+
 /**
  * cma_init_reserved_mem() - create custom contiguous area from reserved memory
  * @base: Base address of the reserved area
diff --git a/mm/cma.h b/mm/cma.h
index 2c775877eae2..88a0595670b7 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -30,6 +30,7 @@ struct cma {
 	/* kobject requires dynamic object */
 	struct cma_kobject *cma_kobj;
 #endif
+	bool reserve_pages_on_error;
 };
 
 extern struct cma cma_areas[MAX_CMA_AREAS];