mm/mmap: check on file instead of the rb_root_cached of its address_space

In __vma_adjust(), we do the check on *root* to decide whether to adjust
the address_space.  It seems to be more meaningful to do the check on
*file* itself.  This means we are adjusting some data because it is a file
backed vma.

Since we seem to assume the address_space is valid if it is a file backed
vma, let's just replace *root* with *file* here.

Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200913133631.37781-2-richard.weiyang@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 295197b75cb0dbed35434782b17624d41736dad5..19cd69524837d8492f428b9cf8062f3ccffb508b 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -823,7 +823,7 @@ again:
                        anon_vma_interval_tree_pre_update_vma(next);
        }
 
-       if (root) {
+       if (file) {
                flush_dcache_mmap_lock(mapping);
                vma_interval_tree_remove(vma, root);
                if (adjust_next)
@@ -844,7 +844,7 @@ again:
                next->vm_pgoff += adjust_next >> PAGE_SHIFT;
        }
 
-       if (root) {
+       if (file) {
                if (adjust_next)
                        vma_interval_tree_insert(next, root);
                vma_interval_tree_insert(vma, root);
@@ -896,7 +896,7 @@ again:
                anon_vma_unlock_write(anon_vma);
        }
 
-       if (root) {
+       if (file) {
                i_mmap_unlock_write(mapping);
                uprobe_mmap(vma);