msm: Allow lowmem to be non contiguous and mixed

Currently on 32 bit systems, virtual space above
PAGE_OFFSET is reserved for direct mapped lowmem
and part of virtual address space is reserved for
vmalloc. We want to optimize such as to have as
much direct mapped memory as possible since there is
penalty for mapping/unmapping highmem. Now, we may
have an image that is expected to have a lifetime of
the entire system and is reserved in physical region
that would be part of direct mapped lowmem. The
physical memory which is thus reserved is never used
by Linux. This means that even though the system is
not actually accessing the  virtual memory
corresponding to the reserved physical memory, we
are still losing that portion of direct mapped lowmem
space.

So by allowing lowmem to be non contiguous we can
give this unused virtual address space of reserved
region back for use in vmalloc.

Change-Id: I980b3dfafac71884dcdcb8cd2e4a6363cde5746a
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5cb30464691c..5e0abc97d992 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1144,6 +1144,33 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t pro
 EXPORT_SYMBOL(vm_map_ram);
 
 static struct vm_struct *vmlist __initdata;
+
+/**
+ * vm_area_check_early - check if vmap area is already mapped
+ * @vm: vm_struct to be checked
+ *
+ * This function is used to check if the vmap area has been
+ * mapped already. @vm->addr, @vm->size and @vm->flags should
+ * contain proper values.
+ *
+ */
+int __init vm_area_check_early(struct vm_struct *vm)
+{
+	struct vm_struct *tmp, **p;
+
+	BUG_ON(vmap_initialized);
+	for (p = &vmlist; (tmp = *p) != NULL; p = &tmp->next) {
+		if (tmp->addr >= vm->addr) {
+			if (tmp->addr < vm->addr + vm->size)
+				return 1;
+		} else {
+			if (tmp->addr + tmp->size > vm->addr)
+				return 1;
+		}
+	}
+	return 0;
+}
+
 /**
  * vm_area_add_early - add vmap area early during boot
  * @vm: vm_struct to add