compiler: introduce __used and __maybe_unused

[powerpc.git] / mm / madvise.c

diff --git a/mm/madvise.c b/mm/madvise.c
index 4e19615..e75096b 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -11,6 +11,24 @@
 #include <linux/mempolicy.h>
 #include <linux/hugetlb.h>
 
+/*
+ * Any behaviour which results in changes to the vma->vm_flags needs to
+ * take mmap_sem for writing. Others, which simply traverse vmas, need
+ * to only take it for reading.
+ */
+static int madvise_need_mmap_write(int behavior)
+{
+       switch (behavior) {
+       case MADV_REMOVE:
+       case MADV_WILLNEED:
+       case MADV_DONTNEED:
+               return 0;
+       default:
+               /* be safe, default to 1. list exceptions explicitly */
+               return 1;
+       }
+}
+
 /*
  * We can potentially split a vm area into separate
  * areas, each area with its own behavior.
@@ -155,10 +173,14 @@ static long madvise_dontneed(struct vm_area_struct * vma,
  * Other filesystems return -ENOSYS.
  */
 static long madvise_remove(struct vm_area_struct *vma,
+                               struct vm_area_struct **prev,
                                unsigned long start, unsigned long end)
 {
        struct address_space *mapping;
-        loff_t offset, endoff;
+       loff_t offset, endoff;
+       int error;
+
+       *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 
        if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
                return -EINVAL;
@@ -177,7 +199,12 @@ static long madvise_remove(struct vm_area_struct *vma,
                        + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
        endoff = (loff_t)(end - vma->vm_start - 1)
                        + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
-       return  vmtruncate_range(mapping->host, offset, endoff);
+
+       /* vmtruncate_range needs to take i_mutex and i_alloc_sem */
+       up_read(&current->mm->mmap_sem);
+       error = vmtruncate_range(mapping->host, offset, endoff);
+       down_read(&current->mm->mmap_sem);
+       return error;
 }
 
 static long
@@ -199,7 +226,7 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
                error = madvise_behavior(vma, prev, start, end, behavior);
                break;
        case MADV_REMOVE:
-               error = madvise_remove(vma, start, end);
+               error = madvise_remove(vma, prev, start, end);
                break;
 
        case MADV_WILLNEED:
@@ -261,7 +288,10 @@ asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior)
        int error = -EINVAL;
        size_t len;
 
-       down_write(&current->mm->mmap_sem);
+       if (madvise_need_mmap_write(behavior))
+               down_write(&current->mm->mmap_sem);
+       else
+               down_read(&current->mm->mmap_sem);
 
        if (start & ~PAGE_MASK)
                goto out;
@@ -312,14 +342,21 @@ asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior)
                if (error)
                        goto out;
                start = tmp;
-               if (start < prev->vm_end)
+               if (prev && start < prev->vm_end)
                        start = prev->vm_end;
                error = unmapped_error;
                if (start >= end)
                        goto out;
-               vma = prev->vm_next;
+               if (prev)
+                       vma = prev->vm_next;
+               else    /* madvise_remove dropped mmap_sem */
+                       vma = find_vma(current->mm, start);
        }
 out:
-       up_write(&current->mm->mmap_sem);
+       if (madvise_need_mmap_write(behavior))
+               up_write(&current->mm->mmap_sem);
+       else
+               up_read(&current->mm->mmap_sem);
+
        return error;
 }