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[PATCH 06/16] mm: use vm_unmapped_area() on x86_64 architecture

To: Andrew Morton <akpm@linux-foundation.org>, Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org, Russell King <linux@arm.linux.org.uk>, Ralf Baechle <ralf@linux-mips.org>, Paul Mundt <lethal@linux-sh.org>, "David S. Miller" <davem@davemloft.net>, Chris Metcalf <cmetcalf@tilera.com>, x86@kernel.org, William Irwin <wli@holomorphy.com>
Subject: [PATCH 06/16] mm: use vm_unmapped_area() on x86_64 architecture
From: Michel Lespinasse <walken@google.com>
Date: Mon, 5 Nov 2012 14:47:03 -0800
Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org
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Update the x86_64 arch_get_unmapped_area[_topdown] functions to make
use of vm_unmapped_area() instead of implementing a brute force search.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>

---
 arch/x86/include/asm/elf.h   |    6 +-
 arch/x86/kernel/sys_x86_64.c |  151 ++++++++---------------------------------
 arch/x86/vdso/vma.c          |    2 +-
 3 files changed, 33 insertions(+), 126 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 5939f44fe0c0..9c999c1674fa 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -354,12 +354,10 @@ static inline int mmap_is_ia32(void)
        return 0;
 }
 
-/* The first two values are special, do not change. See align_addr() */
+/* Do not change the values. See get_align_mask() */
 enum align_flags {
        ALIGN_VA_32     = BIT(0),
        ALIGN_VA_64     = BIT(1),
-       ALIGN_VDSO      = BIT(2),
-       ALIGN_TOPDOWN   = BIT(3),
 };
 
 struct va_alignment {
@@ -368,5 +366,5 @@ struct va_alignment {
 } ____cacheline_aligned;
 
 extern struct va_alignment va_align;
-extern unsigned long align_addr(unsigned long, struct file *, enum 
align_flags);
+extern unsigned long align_vdso_addr(unsigned long);
 #endif /* _ASM_X86_ELF_H */
diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index b4d3c3927dd8..f00d006d60fd 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -21,37 +21,23 @@
 
 /*
  * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
- *
- * @flags denotes the allocation direction - bottomup or topdown -
- * or vDSO; see call sites below.
  */
-unsigned long align_addr(unsigned long addr, struct file *filp,
-                        enum align_flags flags)
+static unsigned long get_align_mask(void)
 {
-       unsigned long tmp_addr;
-
        /* handle 32- and 64-bit case with a single conditional */
        if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32())))
-               return addr;
+               return 0;
 
        if (!(current->flags & PF_RANDOMIZE))
-               return addr;
-
-       if (!((flags & ALIGN_VDSO) || filp))
-               return addr;
-
-       tmp_addr = addr;
-
-       /*
-        * We need an address which is <= than the original
-        * one only when in topdown direction.
-        */
-       if (!(flags & ALIGN_TOPDOWN))
-               tmp_addr += va_align.mask;
+               return 0;
 
-       tmp_addr &= ~va_align.mask;
+       return va_align.mask;
+}
 
-       return tmp_addr;
+unsigned long align_vdso_addr(unsigned long addr)
+{
+       unsigned long align_mask = get_align_mask();
+       return (addr + align_mask) & ~align_mask;
 }
 
 static int __init control_va_addr_alignment(char *str)
@@ -126,7 +112,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long 
addr,
 {
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
-       unsigned long start_addr;
+       struct vm_unmapped_area_info info;
        unsigned long begin, end;
 
        if (flags & MAP_FIXED)
@@ -144,50 +130,16 @@ arch_get_unmapped_area(struct file *filp, unsigned long 
addr,
                    (!vma || addr + len <= vma->vm_start))
                        return addr;
        }
-       if (((flags & MAP_32BIT) || test_thread_flag(TIF_ADDR32))
-           && len <= mm->cached_hole_size) {
-               mm->cached_hole_size = 0;
-               mm->free_area_cache = begin;
-       }
-       addr = mm->free_area_cache;
-       if (addr < begin)
-               addr = begin;
-       start_addr = addr;
-
-full_search:
-
-       addr = align_addr(addr, filp, 0);
-
-       for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
-               /* At this point:  (!vma || addr < vma->vm_end). */
-               if (end - len < addr) {
-                       /*
-                        * Start a new search - just in case we missed
-                        * some holes.
-                        */
-                       if (start_addr != begin) {
-                               start_addr = addr = begin;
-                               mm->cached_hole_size = 0;
-                               goto full_search;
-                       }
-                       return -ENOMEM;
-               }
-               if (!vma || addr + len <= vma->vm_start) {
-                       /*
-                        * Remember the place where we stopped the search:
-                        */
-                       mm->free_area_cache = addr + len;
-                       return addr;
-               }
-               if (addr + mm->cached_hole_size < vma->vm_start)
-                       mm->cached_hole_size = vma->vm_start - addr;
 
-               addr = vma->vm_end;
-               addr = align_addr(addr, filp, 0);
-       }
+       info.flags = 0;
+       info.length = len;
+       info.low_limit = begin;
+       info.high_limit = end;
+       info.align_mask = filp ? get_align_mask() : 0;
+       info.align_offset = 0;
+       return vm_unmapped_area(&info);
 }
 
-
 unsigned long
 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
                          const unsigned long len, const unsigned long pgoff,
@@ -195,7 +147,8 @@ 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, start_addr;
+       unsigned long addr = addr0;
+       struct vm_unmapped_area_info info;
 
        /* requested length too big for entire address space */
        if (len > TASK_SIZE)
@@ -217,51 +170,16 @@ arch_get_unmapped_area_topdown(struct file *filp, const 
unsigned long addr0,
                        return addr;
        }
 
-       /* check if free_area_cache is useful for us */
-       if (len <= mm->cached_hole_size) {
-               mm->cached_hole_size = 0;
-               mm->free_area_cache = mm->mmap_base;
-       }
-
-try_again:
-       /* either no address requested or can't fit in requested address hole */
-       start_addr = addr = mm->free_area_cache;
-
-       if (addr < len)
-               goto fail;
-
-       addr -= len;
-       do {
-               addr = align_addr(addr, filp, ALIGN_TOPDOWN);
-
-               /*
-                * Lookup failure means no vma is above this address,
-                * else if new region fits below vma->vm_start,
-                * return with success:
-                */
-               vma = find_vma(mm, addr);
-               if (!vma || addr+len <= vma->vm_start)
-                       /* remember the address as a hint for next time */
-                       return mm->free_area_cache = addr;
-
-               /* remember the largest hole we saw so far */
-               if (addr + mm->cached_hole_size < vma->vm_start)
-                       mm->cached_hole_size = vma->vm_start - addr;
-
-               /* try just below the current vma->vm_start */
-               addr = vma->vm_start-len;
-       } while (len < vma->vm_start);
-
-fail:
-       /*
-        * if hint left us with no space for the requested
-        * mapping then try again:
-        */
-       if (start_addr != mm->mmap_base) {
-               mm->free_area_cache = mm->mmap_base;
-               mm->cached_hole_size = 0;
-               goto try_again;
-       }
+       info.flags = VM_UNMAPPED_AREA_TOPDOWN;
+       info.length = len;
+       info.low_limit = PAGE_SIZE;
+       info.high_limit = mm->mmap_base;
+       info.align_mask = filp ? get_align_mask() : 0;
+       info.align_offset = 0;
+       addr = vm_unmapped_area(&info);
+       if (!(addr & ~PAGE_MASK))
+               return addr;
+       VM_BUG_ON(addr != -ENOMEM);
 
 bottomup:
        /*
@@ -270,14 +188,5 @@ bottomup:
         * can happen with large stack limits and large mmap()
         * allocations.
         */
-       mm->cached_hole_size = ~0UL;
-       mm->free_area_cache = TASK_UNMAPPED_BASE;
-       addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
-       /*
-        * Restore the topdown base:
-        */
-       mm->free_area_cache = mm->mmap_base;
-       mm->cached_hole_size = ~0UL;
-
-       return addr;
+       return arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 }
diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
index 00aaf047b39f..431e87544411 100644
--- a/arch/x86/vdso/vma.c
+++ b/arch/x86/vdso/vma.c
@@ -141,7 +141,7 @@ static unsigned long vdso_addr(unsigned long start, 
unsigned len)
         * unaligned here as a result of stack start randomization.
         */
        addr = PAGE_ALIGN(addr);
-       addr = align_addr(addr, NULL, ALIGN_VDSO);
+       addr = align_vdso_addr(addr);
 
        return addr;
 }
-- 
1.7.7.3

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