[PATCH] mmap topdown fix for large stack limit, large allocation

The topdown changes in 2.6.12-rc1 can cause large allocations with large
stack limit to fail, despite there being space available.  The
mmap_base-len is only valid when len >= mmap_base.  However, nothing in
topdown allocator checks this.  It's only (now) caught at higher level,
which will cause allocation to simply fail.  The following change restores
the fallback to bottom-up path, which will allow large allocations with
large stack limit to potentially still succeed.

Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 9da23c1..da3fa90 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1267,6 +1267,9 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
                        return (mm->free_area_cache = addr-len);
        }
 
+       if (mm->mmap_base < len)
+               goto bottomup;
+
        addr = mm->mmap_base-len;
 
        do {
@@ -1288,6 +1291,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
                addr = vma->vm_start-len;
        } while (len < vma->vm_start);
 
+bottomup:
        /*
         * A failed mmap() very likely causes application failure,
         * so fall back to the bottom-up function here. This scenario