do_mremap() untangling, part 2

Take the MREMAP_FIXED into a separate helper, simplify the living
hell out of conditions in both cases.

Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 72 insertions, 48 deletions

diff --git a/mm/mremap.c b/mm/mremap.c
index 67761361c46..5f346178f16 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -313,6 +313,59 @@ Eagain:
         return ERR_PTR(-EAGAIN);
 }
 
+static unsigned long mremap_to(unsigned long addr,
+        unsigned long old_len, unsigned long new_addr,
+        unsigned long new_len)
+{
+        struct mm_struct *mm = current->mm;
+        struct vm_area_struct *vma;
+        unsigned long ret = -EINVAL;
+        unsigned long charged = 0;
+
+        if (new_addr & ~PAGE_MASK)
+                goto out;
+
+        if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
+                goto out;
+
+        /* Check if the location we're moving into overlaps the
+         * old location at all, and fail if it does.
+         */
+        if ((new_addr <= addr) && (new_addr+new_len) > addr)
+                goto out;
+
+        if ((addr <= new_addr) && (addr+old_len) > new_addr)
+                goto out;
+
+        ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+        if (ret)
+                goto out;
+
+        ret = do_munmap(mm, new_addr, new_len);
+        if (ret)
+                goto out;
+
+        if (old_len >= new_len) {
+                ret = do_munmap(mm, addr+new_len, old_len - new_len);
+                if (ret && old_len != new_len)
+                        goto out;
+                old_len = new_len;
+        }
+
+        vma = vma_to_resize(addr, old_len, new_len, &charged);
+        if (IS_ERR(vma)) {
+                ret = PTR_ERR(vma);
+                goto out;
+        }
+
+        ret = move_vma(vma, addr, old_len, new_len, new_addr);
+        if (ret & ~PAGE_MASK)
+                vm_unacct_memory(charged);
+
+out:
+        return ret;
+}
+
 /*
  * Expand (or shrink) an existing mapping, potentially moving it at the
  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
@@ -346,32 +399,10 @@ unsigned long do_mremap(unsigned long addr,
         if (!new_len)
                 goto out;
 
-        /* new_addr is only valid if MREMAP_FIXED is specified */
         if (flags & MREMAP_FIXED) {
-                if (new_addr & ~PAGE_MASK)
-                        goto out;
-                if (!(flags & MREMAP_MAYMOVE))
-                        goto out;
-
-                if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
-                        goto out;
-
-                /* Check if the location we're moving into overlaps the
-                 * old location at all, and fail if it does.
-                 */
-                if ((new_addr <= addr) && (new_addr+new_len) > addr)
-                        goto out;
-
-                if ((addr <= new_addr) && (addr+old_len) > new_addr)
-                        goto out;
-
-                ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
-                if (ret)
-                        goto out;
-
-                ret = do_munmap(mm, new_addr, new_len);
-                if (ret)
-                        goto out;
+                if (flags & MREMAP_MAYMOVE)
+                        ret = mremap_to(addr, old_len, new_addr, new_len);
+                goto out;
         }
 
         /*
@@ -384,13 +415,11 @@ unsigned long do_mremap(unsigned long addr,
                 if (ret && old_len != new_len)
                         goto out;
                 ret = addr;
-                if (!(flags & MREMAP_FIXED) || (new_addr == addr))
-                        goto out;
-                old_len = new_len;
+                goto out;
         }
 
         /*
-         * Ok, we need to grow..  or relocate.
+         * Ok, we need to grow..
          */
         vma = vma_to_resize(addr, old_len, new_len, &charged);
         if (IS_ERR(vma)) {
@@ -399,11 +428,8 @@ unsigned long do_mremap(unsigned long addr,
         }
 
         /* old_len exactly to the end of the area..
-         * And we're not relocating the area.
          */
-        if (old_len == vma->vm_end - addr &&
-            !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
-            (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
+        if (old_len == vma->vm_end - addr) {
                 unsigned long max_addr = TASK_SIZE;
                 if (vma->vm_next)
                         max_addr = vma->vm_next->vm_start;
@@ -432,22 +458,20 @@ unsigned long do_mremap(unsigned long addr,
          */
         ret = -ENOMEM;
         if (flags & MREMAP_MAYMOVE) {
-                if (!(flags & MREMAP_FIXED)) {
-                        unsigned long map_flags = 0;
-                        if (vma->vm_flags & VM_MAYSHARE)
-                                map_flags |= MAP_SHARED;
-
-                        new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
-                                                vma->vm_pgoff, map_flags);
-                        if (new_addr & ~PAGE_MASK) {
-                                ret = new_addr;
-                                goto out;
-                        }
-
-                        ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
-                        if (ret)
-                                goto out;
+                unsigned long map_flags = 0;
+                if (vma->vm_flags & VM_MAYSHARE)
+                        map_flags |= MAP_SHARED;
+
+                new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
+                                        vma->vm_pgoff, map_flags);
+                if (new_addr & ~PAGE_MASK) {
+                        ret = new_addr;
+                        goto out;
                 }
+
+                ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+                if (ret)
+                        goto out;
                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
         }
 out: