[PATCH v4 1/6] resources: ensure alignment callback doesn't allocate below available start

[Bjorn Helgaas <bjorn.helgaas@hp.com>]

The alignment callback returns a proposed location, which may have been
adjusted to avoid ISA aliases or for other architecture-specific reasons.
We already had a check ("tmp.start < tmp.end") to make sure the callback
doesn't return a location above the available area.

This patch adds a check to make sure the callback doesn't return something
*below* the available area, as may happen if the callback tries to allocate
top-down.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
---

 kernel/resource.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)


diff --git a/kernel/resource.c b/kernel/resource.c
index 7b36976..ace2269 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -371,6 +371,7 @@ static int find_resource(struct resource *root, struct resource *new,
 {
 	struct resource *this = root->child;
 	struct resource tmp = *new;
+	resource_size_t start;
 
 	tmp.start = root->start;
 	/*
@@ -391,8 +392,13 @@ static int find_resource(struct resource *root, struct resource *new,
 		if (tmp.end > max)
 			tmp.end = max;
 		tmp.start = ALIGN(tmp.start, align);
-		if (alignf)
-			tmp.start = alignf(alignf_data, &tmp, size, align);
+		if (alignf) {
+			start = alignf(alignf_data, &tmp, size, align);
+			if (tmp.start <= start && start <= tmp.end)
+				tmp.start = start;
+			else
+				tmp.start = tmp.end;
+		}
 		if (tmp.start < tmp.end && tmp.end - tmp.start >= size - 1) {
 			new->start = tmp.start;
 			new->end = tmp.start + size - 1;