mm: Move may_expand_vm() check in mmap_region()

The may_expand_vm() check requires the count of the pages within the
munmap range.  Since this is needed for accounting and obtained later,
the reodering of ma_expand_vm() to later in the call stack, after the
vma munmap struct (vms) is initialised and the gather stage is
potentially run, will allow for a single loop over the vmas.  The gather
sage does not commit any work and so everything can be undone in the
case of a failure.

The MAP_FIXED page count is available after the vms_gather_munmap_vmas()
call, so use it instead of looping over the vmas twice.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

diff --git a/mm/mmap.c b/mm/mmap.c
index 51ab0bdb856c412e5e0cc7d8e361d73bda9a361a..5937607f6949682e9248e58b6264fa911edbce2f 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1376,17 +1376,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
        pgoff_t vm_pgoff;
        int error = -ENOMEM;
        VMA_ITERATOR(vmi, mm, addr);
-       unsigned long nr_pages, nr_accounted;
-
-       nr_pages = count_vma_pages_range(mm, addr, end, &nr_accounted);
-
-       /*
-        * Check against address space limit.
-        * MAP_FIXED may remove pages of mappings that intersects with requested
-        * mapping. Account for the pages it would unmap.
-        */
-       if (!may_expand_vm(mm, vm_flags, pglen - nr_pages))
-               return -ENOMEM;
 
        /* Find the first overlapping VMA */
        vma = vma_find(&vmi, end);
@@ -1409,6 +1398,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
                        vma_iter_next_range(&vmi);
        }
 
+       /* Check against address space limit. */
+       if (!may_expand_vm(mm, vm_flags, pglen - vms.nr_pages))
+               goto abort_munmap;
+
        /*
         * Private writable mapping: check memory availability
         */

diff --git a/mm/vma.c b/mm/vma.c
index 70c3f25e8026db8e20cd19bc469c3aeb92e91a80..32a642bee7829e5f227f1f54a6fd71336513ca1d 100644 (file)
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -1645,27 +1645,6 @@ bool vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
        return vma_fs_can_writeback(vma);
 }
 
-unsigned long count_vma_pages_range(struct mm_struct *mm,
-               unsigned long addr, unsigned long end,
-               unsigned long *nr_accounted)
-{
-       VMA_ITERATOR(vmi, mm, addr);
-       struct vm_area_struct *vma;
-       unsigned long nr_pages = 0;
-
-       *nr_accounted = 0;
-       for_each_vma_range(vmi, vma, end) {
-               unsigned long vm_start = max(addr, vma->vm_start);
-               unsigned long vm_end = min(end, vma->vm_end);
-
-               nr_pages += PHYS_PFN(vm_end - vm_start);
-               if (vma->vm_flags & VM_ACCOUNT)
-                       *nr_accounted += PHYS_PFN(vm_end - vm_start);
-       }
-
-       return nr_pages;
-}
-
 static DEFINE_MUTEX(mm_all_locks_mutex);
 
 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)

diff --git a/mm/vma.h b/mm/vma.h
index 45d5e1f7b0f4f89064a475f45556aaa1d7c19f30..81543e6016e0f8acf1174e29e4e9781a7964bc84 100644 (file)
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -317,9 +317,6 @@ bool vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot);
 
 int mm_take_all_locks(struct mm_struct *mm);
 void mm_drop_all_locks(struct mm_struct *mm);
-unsigned long count_vma_pages_range(struct mm_struct *mm,
-                                   unsigned long addr, unsigned long end,
-                                   unsigned long *nr_accounted);
 
 static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma)
 {