mm: Change munmap splitting order and move_vma()

Splitting can be more efficient when the order is not of concern.
Change do_vmi_align_munmap() to reduce walking of the tree during split
operations.

move_vma() must also be altered to remove the dependency of keeping the
original VMA as the active part of the split.  Transition to using vma
iterator to look up the prev and/or next vma after munmap.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>

diff --git a/mm/mmap.c b/mm/mmap.c
index be9ba141cb6f8904e2dc093a26077441a82611ae..0e0bca66addb69cce08b4ede3c0c40e2d89a86ac 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2387,21 +2387,9 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
        for_each_vma_range(*vmi, next, end) {
                /* Does it split the end? */
                if (next->vm_end > end) {
-                       struct vm_area_struct *split;
-
-                       error = __split_vma(vmi, next, end, 1);
+                       error = __split_vma(vmi, next, end, 0);
                        if (error)
                                goto end_split_failed;
-
-                       split = vma_prev(vmi);
-                       error = munmap_sidetree(split, &mas_detach);
-                       if (error)
-                               goto munmap_sidetree_failed;
-
-                       count++;
-                       if (vma == next)
-                               vma = split;
-                       break;
                }
                error = munmap_sidetree(next, &mas_detach);
                if (error)
@@ -2414,9 +2402,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 #endif
        }
 
-       if (!next)
-               next = vma_next(vmi);
-
+       next = vma_next(vmi);
        if (unlikely(uf)) {
                /*
                 * If userfaultfd_unmap_prep returns an error the vmas

diff --git a/mm/mremap.c b/mm/mremap.c
index cbafea7fe89548ca9b43be54a4442890cf2611f9..00b39f0121bcee807a5ed68ca9e0ce3931d7d352 100644 (file)
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -580,11 +580,12 @@ static unsigned long move_vma(struct vm_area_struct *vma,
        unsigned long vm_flags = vma->vm_flags;
        unsigned long new_pgoff;
        unsigned long moved_len;
-       unsigned long excess = 0;
+       unsigned long account_start = 0;
+       unsigned long account_end = 0;
        unsigned long hiwater_vm;
-       int split = 0;
        int err = 0;
        bool need_rmap_locks;
+       VMA_ITERATOR(vmi, mm, old_addr);
 
        /*
         * We'd prefer to avoid failure later on in do_munmap:
@@ -662,10 +663,10 @@ static unsigned long move_vma(struct vm_area_struct *vma,
        /* Conceal VM_ACCOUNT so old reservation is not undone */
        if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) {
                vma->vm_flags &= ~VM_ACCOUNT;
-               excess = vma->vm_end - vma->vm_start - old_len;
-               if (old_addr > vma->vm_start &&
-                   old_addr + old_len < vma->vm_end)
-                       split = 1;
+               if (vma->vm_start < old_addr)
+                       account_start = vma->vm_start;
+               if (vma->vm_end > old_addr + old_len)
+                       account_end = vma->vm_end;
        }
 
        /*
@@ -700,11 +701,11 @@ static unsigned long move_vma(struct vm_area_struct *vma,
                return new_addr;
        }
 
-       if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
+       if (do_vmi_munmap(&vmi, mm, old_addr, old_len, uf_unmap, false) < 0) {
                /* OOM: unable to split vma, just get accounts right */
                if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
                        vm_acct_memory(old_len >> PAGE_SHIFT);
-               excess = 0;
+               account_start = account_end = 0;
        }
 
        if (vm_flags & VM_LOCKED) {
@@ -715,10 +716,14 @@ static unsigned long move_vma(struct vm_area_struct *vma,
        mm->hiwater_vm = hiwater_vm;
 
        /* Restore VM_ACCOUNT if one or two pieces of vma left */
-       if (excess) {
+       if (account_start) {
+               vma = vma_prev(&vmi);
+               vma->vm_flags |= VM_ACCOUNT;
+       }
+
+       if (account_end) {
+               vma = vma_next(&vmi);
                vma->vm_flags |= VM_ACCOUNT;
-               if (split)
-                       find_vma(mm, vma->vm_end)->vm_flags |= VM_ACCOUNT;
        }
 
        return new_addr;