Don't lock guardpage if the stack is growing up

Linux kernel excludes guard page when performing mlock on a VMA with
down-growing stack. However, some architectures have up-growing stack
and locking the guard page should be excluded in this case too.

This patch fixes lvm2 on PA-RISC (and possibly other architectures with
up-growing stack). lvm2 calculates number of used pages when locking and
when unlocking and reports an internal error if the numbers mismatch.

[ Patch changed fairly extensively to also fix /proc/<pid>/maps for the
  grows-up case, and to move things around a bit to clean it all up and
  share the infrstructure with the /proc bits.

  Tested on ia64 that has both grow-up and grow-down segments  - Linus ]

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Tested-by: Tony Luck <tony.luck@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 2e7addfd9803..318d8654989b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -214,7 +214,7 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
         int flags = vma->vm_flags;
         unsigned long ino = 0;
         unsigned long long pgoff = 0;
-        unsigned long start;
+        unsigned long start, end;
         dev_t dev = 0;
         int len;
 
@@ -227,13 +227,15 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
 
         /* We don't show the stack guard page in /proc/maps */
         start = vma->vm_start;
-        if (vma->vm_flags & VM_GROWSDOWN)
-                if (!vma_stack_continue(vma->vm_prev, vma->vm_start))
-                        start += PAGE_SIZE;
+        if (stack_guard_page_start(vma, start))
+                start += PAGE_SIZE;
+        end = vma->vm_end;
+        if (stack_guard_page_end(vma, end))
+                end -= PAGE_SIZE;
 
         seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
                         start,
-                        vma->vm_end,
+                        end,
                         flags & VM_READ ? 'r' : '-',
                         flags & VM_WRITE ? 'w' : '-',
                         flags & VM_EXEC ? 'x' : '-',