mm: search from free_area_cache for the bigger size

If the required size is bigger than cached_hole_size it is better to
search from free_area_cache - it is easier to get a free region,
specifically for the 64 bit process whose address space is large enough

Do it just as hugetlb_get_unmapped_area_topdown() in arch/x86/mm/hugetlbpage.c

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 15 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 4f31764d838f..9e0c0de2e7e3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1442,7 +1442,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 {
         struct vm_area_struct *vma;
         struct mm_struct *mm = current->mm;
-        unsigned long addr = addr0;
+        unsigned long addr = addr0, start_addr;
 
         /* requested length too big for entire address space */
         if (len > TASK_SIZE)
@@ -1466,22 +1466,14 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
                 mm->free_area_cache = mm->mmap_base;
         }
 
+try_again:
         /* either no address requested or can't fit in requested address hole */
-        addr = mm->free_area_cache;
+        start_addr = addr = mm->free_area_cache;
 
-        /* make sure it can fit in the remaining address space */
-        if (addr > len) {
-                vma = find_vma(mm, addr-len);
-                if (!vma || addr <= vma->vm_start)
-                        /* remember the address as a hint for next time */
-                        return (mm->free_area_cache = addr-len);
-        }
-
-        if (mm->mmap_base < len)
-                goto bottomup;
-
-        addr = mm->mmap_base-len;
+        if (addr < len)
+                goto fail;
 
+        addr -= len;
         do {
                 /*
                  * Lookup failure means no vma is above this address,
@@ -1501,7 +1493,21 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
                 addr = vma->vm_start-len;
         } while (len < vma->vm_start);
 
-bottomup:
+fail:
+        /*
+         * if hint left us with no space for the requested
+         * mapping then try again:
+         *
+         * Note: this is different with the case of bottomup
+         * which does the fully line-search, but we use find_vma
+         * here that causes some holes skipped.
+         */
+        if (start_addr != mm->mmap_base) {
+                mm->free_area_cache = mm->mmap_base;
+                mm->cached_hole_size = 0;
+                goto try_again;
+        }
+
         /*
          * A failed mmap() very likely causes application failure,
          * so fall back to the bottom-up function here. This scenario