xfs: mmap lock needs to be inside freeze protection

Lock ordering for the new mmap lock needs to be:

mmap_sem
  sb_start_pagefault
    i_mmap_lock
      page lock
        <fault processsing>

Right now xfs_vm_page_mkwrite gets this the wrong way around,
While technically it cannot deadlock due to the current freeze
ordering, it's still a landmine that might explode if we change
anything in future. Hence we need to nest the locks correctly.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 8121e75352ee..0b4e79fd8d05 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1487,15 +1487,20 @@ xfs_filemap_page_mkwrite(
         struct vm_fault         *vmf)
 {
         struct xfs_inode        *ip = XFS_I(vma->vm_file->f_mapping->host);
-        int                     error;
+        int                     ret;
 
         trace_xfs_filemap_page_mkwrite(ip);
 
+        sb_start_pagefault(VFS_I(ip)->i_sb);
+        file_update_time(vma->vm_file);
         xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
-        error = block_page_mkwrite(vma, vmf, xfs_get_blocks);
+
+        ret = __block_page_mkwrite(vma, vmf, xfs_get_blocks);
+
         xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
+        sb_end_pagefault(VFS_I(ip)->i_sb);
 
-        return error;
+        return block_page_mkwrite_return(ret);
 }
 
 const struct file_operations xfs_file_operations = {