[PATCH v3 1/3] vmalloc: Choose a better start address in vm_area_register_early()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

There are some fixed locations in the vmalloc area be reserved
in ARM(see iotable_init()) and ARM64(see map_kernel()), but for
pcpu_page_first_chunk(), it calls vm_area_register_early() and
choose VMALLOC_START as the start address of vmap area which
could be conflicted with above address, then could trigger a
BUG_ON in vm_area_add_early().

Let's choose the end of existing address range in vmlist as the
start address instead of VMALLOC_START to avoid the BUG_ON.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 mm/vmalloc.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d5cd52805149..1e8fe08725b8 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2238,11 +2238,17 @@ void __init vm_area_add_early(struct vm_struct *vm)
  */
 void __init vm_area_register_early(struct vm_struct *vm, size_t align)
 {
-	static size_t vm_init_off __initdata;
-	unsigned long addr;
-
-	addr = ALIGN(VMALLOC_START + vm_init_off, align);
-	vm_init_off = PFN_ALIGN(addr + vm->size) - VMALLOC_START;
+	struct vm_struct *head = vmlist, *curr, *next;
+	unsigned long addr = ALIGN(VMALLOC_START, align);
+
+	while (head != NULL) {
+		next = head->next;
+		curr = head;
+		head = next;
+		addr = ALIGN((unsigned long)curr->addr + curr->size, align);
+		if (next && (unsigned long)next->addr - addr > vm->size)
+			break;
+	}
 
 	vm->addr = (void *)addr;
 
-- 
2.26.2