[PATCH v4 03/27] mm/cma: introduce cma_intersects function

[Frank van der Linden <fvdl@google.com>]

Now that CMA areas can have multiple physical ranges,
code can't assume a CMA struct represents a base_pfn
plus a size, as returned from cma_get_base.

Most cases are ok though, since they all explicitly
refer to CMA areas that were created using existing
interfaces (cma_declare_contiguous_nid or
cma_init_reserved_mem), which guarantees they have just
one physical range.

An exception is the s390 code, which walks all CMA
ranges to see if they intersect with a range of memory
that is about to be hotremoved. So, in the future,
it might run in to multi-range areas. To keep this check
working, define a cma_intersects function. This just checks
if a physaddr range intersects any of the ranges.
Use it in the s390 check.

Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Frank van der Linden <fvdl@google.com>
---
 arch/s390/mm/init.c | 13 +++++--------
 include/linux/cma.h |  1 +
 mm/cma.c            | 21 +++++++++++++++++++++
 3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index f2298f7a3f21..d88cb1c13f7d 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -239,16 +239,13 @@ struct s390_cma_mem_data {
 static int s390_cma_check_range(struct cma *cma, void *data)
 {
 	struct s390_cma_mem_data *mem_data;
-	unsigned long start, end;
 
 	mem_data = data;
-	start = cma_get_base(cma);
-	end = start + cma_get_size(cma);
-	if (end < mem_data->start)
-		return 0;
-	if (start >= mem_data->end)
-		return 0;
-	return -EBUSY;
+
+	if (cma_intersects(cma, mem_data->start, mem_data->end))
+		return -EBUSY;
+
+	return 0;
 }
 
 static int s390_cma_mem_notifier(struct notifier_block *nb,
diff --git a/include/linux/cma.h b/include/linux/cma.h
index 863427c27dc2..03d85c100dcc 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -53,6 +53,7 @@ extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned
 extern bool cma_release(struct cma *cma, const struct page *pages, unsigned long count);
 
 extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
+extern bool cma_intersects(struct cma *cma, unsigned long start, unsigned long end);
 
 extern void cma_reserve_pages_on_error(struct cma *cma);
 
diff --git a/mm/cma.c b/mm/cma.c
index 6ac9173d3a7d..c7116a5819c5 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -978,3 +978,24 @@ int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data)
 
 	return 0;
 }
+
+bool cma_intersects(struct cma *cma, unsigned long start, unsigned long end)
+{
+	int r;
+	struct cma_memrange *cmr;
+	unsigned long rstart, rend;
+
+	for (r = 0; r < cma->nranges; r++) {
+		cmr = &cma->ranges[r];
+
+		rstart = PFN_PHYS(cmr->base_pfn);
+		rend = PFN_PHYS(cmr->base_pfn + cmr->count);
+		if (end < rstart)
+			continue;
+		if (start >= rend)
+			continue;
+		return true;
+	}
+
+	return false;
+}
-- 
2.48.1.601.g30ceb7b040-goog