mm: remove free_area_cache use in powerpc architecture

As all other architectures have been converted to use vm_unmapped_area(),
we are about to retire the free_area_cache.

This change simply removes the use of that cache in
slice_get_unmapped_area(), which will most certainly have a
performance cost. Next one will convert that function to use the
vm_unmapped_area() infrastructure and regain the performance.

Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 20 insertions, 90 deletions

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 1a6de0a7d8eb..5dc52d803ed8 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -742,7 +742,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
         struct hstate *hstate = hstate_file(file);
         int mmu_psize = shift_to_mmu_psize(huge_page_shift(hstate));
 
-        return slice_get_unmapped_area(addr, len, flags, mmu_psize, 1, 0);
+        return slice_get_unmapped_area(addr, len, flags, mmu_psize, 1);
 }
 #endif
 
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index cf9dada734b6..999a74f25ebe 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -240,23 +240,15 @@ static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psiz
 static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
                                               unsigned long len,
                                               struct slice_mask available,
-                                              int psize, int use_cache)
+                                              int psize)
 {
         struct vm_area_struct *vma;
-        unsigned long start_addr, addr;
+        unsigned long addr;
         struct slice_mask mask;
         int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
 
-        if (use_cache) {
-                if (len <= mm->cached_hole_size) {
-                        start_addr = addr = TASK_UNMAPPED_BASE;
-                        mm->cached_hole_size = 0;
-                } else
-                        start_addr = addr = mm->free_area_cache;
-        } else
-                start_addr = addr = TASK_UNMAPPED_BASE;
+        addr = TASK_UNMAPPED_BASE;
 
-full_search:
         for (;;) {
                 addr = _ALIGN_UP(addr, 1ul << pshift);
                 if ((TASK_SIZE - len) < addr)
@@ -272,63 +264,24 @@ full_search:
                                 addr = _ALIGN_UP(addr + 1,  1ul << SLICE_HIGH_SHIFT);
                         continue;
                 }
-                if (!vma || addr + len <= vma->vm_start) {
-                        /*
-                         * Remember the place where we stopped the search:
-                         */
-                        if (use_cache)
-                                mm->free_area_cache = addr + len;
+                if (!vma || addr + len <= vma->vm_start)
                         return addr;
-                }
-                if (use_cache && (addr + mm->cached_hole_size) < vma->vm_start)
-                        mm->cached_hole_size = vma->vm_start - addr;
                 addr = vma->vm_end;
         }
 
-        /* Make sure we didn't miss any holes */
-        if (use_cache && start_addr != TASK_UNMAPPED_BASE) {
-                start_addr = addr = TASK_UNMAPPED_BASE;
-                mm->cached_hole_size = 0;
-                goto full_search;
-        }
         return -ENOMEM;
 }
 
 static unsigned long slice_find_area_topdown(struct mm_struct *mm,
                                              unsigned long len,
                                              struct slice_mask available,
-                                             int psize, int use_cache)
+                                             int psize)
 {
         struct vm_area_struct *vma;
         unsigned long addr;
         struct slice_mask mask;
         int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
 
-        /* check if free_area_cache is useful for us */
-        if (use_cache) {
-                if (len <= mm->cached_hole_size) {
-                        mm->cached_hole_size = 0;
-                        mm->free_area_cache = mm->mmap_base;
-                }
-
-                /* either no address requested or can't fit in requested
-                 * address hole
-                 */
-                addr = mm->free_area_cache;
-
-                /* make sure it can fit in the remaining address space */
-                if (addr > len) {
-                        addr = _ALIGN_DOWN(addr - len, 1ul << pshift);
-                        mask = slice_range_to_mask(addr, len);
-                        if (slice_check_fit(mask, available) &&
-                            slice_area_is_free(mm, addr, len))
-                                        /* remember the address as a hint for
-                                         * next time
-                                         */
-                                        return (mm->free_area_cache = addr);
-                }
-        }
-
         addr = mm->mmap_base;
         while (addr > len) {
                 /* Go down by chunk size */
@@ -352,16 +305,8 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm,
                  * return with success:
                  */
                 vma = find_vma(mm, addr);
-                if (!vma || (addr + len) <= vma->vm_start) {
-                        /* remember the address as a hint for next time */
-                        if (use_cache)
-                                mm->free_area_cache = addr;
+                if (!vma || (addr + len) <= vma->vm_start)
                         return addr;
-                }
-
-                /* remember the largest hole we saw so far */
-                if (use_cache && (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;
@@ -373,28 +318,18 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm,
          * can happen with large stack limits and large mmap()
          * allocations.
          */
-        addr = slice_find_area_bottomup(mm, len, available, psize, 0);
-
-        /*
-         * Restore the topdown base:
-         */
-        if (use_cache) {
-                mm->free_area_cache = mm->mmap_base;
-                mm->cached_hole_size = ~0UL;
-        }
-
-        return addr;
+        return slice_find_area_bottomup(mm, len, available, psize);
 }
 
 
 static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
                                      struct slice_mask mask, int psize,
-                                     int topdown, int use_cache)
+                                     int topdown)
 {
         if (topdown)
-                return slice_find_area_topdown(mm, len, mask, psize, use_cache);
+                return slice_find_area_topdown(mm, len, mask, psize);
         else
-                return slice_find_area_bottomup(mm, len, mask, psize, use_cache);
+                return slice_find_area_bottomup(mm, len, mask, psize);
 }
 
 #define or_mask(dst, src)       do {                    \
@@ -415,7 +350,7 @@ static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
 
 unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
                                       unsigned long flags, unsigned int psize,
-                                      int topdown, int use_cache)
+                                      int topdown)
 {
         struct slice_mask mask = {0, 0};
         struct slice_mask good_mask;
@@ -430,8 +365,8 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
         BUG_ON(mm->task_size == 0);
 
         slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
-        slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d, use_cache=%d\n",
-                  addr, len, flags, topdown, use_cache);
+        slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d\n",
+                  addr, len, flags, topdown);
 
         if (len > mm->task_size)
                 return -ENOMEM;
@@ -503,8 +438,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
                 /* Now let's see if we can find something in the existing
                  * slices for that size
                  */
-                newaddr = slice_find_area(mm, len, good_mask, psize, topdown,
-                                          use_cache);
+                newaddr = slice_find_area(mm, len, good_mask, psize, topdown);
                 if (newaddr != -ENOMEM) {
                         /* Found within the good mask, we don't have to setup,
                          * we thus return directly
@@ -536,8 +470,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
          * anywhere in the good area.
          */
         if (addr) {
-                addr = slice_find_area(mm, len, good_mask, psize, topdown,
-                                       use_cache);
+                addr = slice_find_area(mm, len, good_mask, psize, topdown);
                 if (addr != -ENOMEM) {
                         slice_dbg(" found area at 0x%lx\n", addr);
                         return addr;
@@ -547,15 +480,14 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
         /* Now let's see if we can find something in the existing slices
          * for that size plus free slices
          */
-        addr = slice_find_area(mm, len, potential_mask, psize, topdown,
-                               use_cache);
+        addr = slice_find_area(mm, len, potential_mask, psize, topdown);
 
 #ifdef CONFIG_PPC_64K_PAGES
         if (addr == -ENOMEM && psize == MMU_PAGE_64K) {
                 /* retry the search with 4k-page slices included */
                 or_mask(potential_mask, compat_mask);
                 addr = slice_find_area(mm, len, potential_mask, psize,
-                                       topdown, use_cache);
+                                       topdown);
         }
 #endif
 
@@ -586,8 +518,7 @@ unsigned long arch_get_unmapped_area(struct file *filp,
                                      unsigned long flags)
 {
         return slice_get_unmapped_area(addr, len, flags,
-                                       current->mm->context.user_psize,
-                                       0, 1);
+                                       current->mm->context.user_psize, 0);
 }
 
 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
@@ -597,8 +528,7 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
                                              const unsigned long flags)
 {
         return slice_get_unmapped_area(addr0, len, flags,
-                                       current->mm->context.user_psize,
-                                       1, 1);
+                                       current->mm->context.user_psize, 1);
 }
 
 unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)