mm: make expand_downwards() symmetrical with expand_upwards()

Currently we have expand_upwards exported while expand_downwards is
accessible only via expand_stack or expand_stack_downwards.

check_stack_guard_page is a nice example of the asymmetry.  It uses
expand_stack for VM_GROWSDOWN while expand_upwards is called for
VM_GROWSUP case.

Let's clean this up by exporting both functions and make those names
consistent.  Let's use expand_{upwards,downwards} because expanding
doesn't always involve stack manipulation (an example is
ia64_do_page_fault which uses expand_upwards for registers backing store
expansion).  expand_downwards has to be defined for both
CONFIG_STACK_GROWS{UP,DOWN} because get_arg_page calls the downwards
version in the early process initialization phase for growsup
configuration.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e173cd297d88..d2948af126ca 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1518,15 +1518,17 @@ unsigned long ra_submit(struct file_ra_state *ra,
                         struct address_space *mapping,
                         struct file *filp);
 
-/* Do stack extension */
+/* Generic expand stack which grows the stack according to GROWS{UP,DOWN} */
 extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
+
+/* CONFIG_STACK_GROWSUP still needs to to grow downwards at some places */
+extern int expand_downwards(struct vm_area_struct *vma,
+                unsigned long address);
 #if VM_GROWSUP
 extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);
 #else
   #define expand_upwards(vma, address) do { } while (0)
 #endif
-extern int expand_stack_downwards(struct vm_area_struct *vma,
-                                  unsigned long address);
 
 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
 extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr);