xfs: mmap lock needs to be inside freeze protection

Orabug: 22913653

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>
(cherry picked from commit ec56b1f1fdc69599963574ce94cc5693d535dd64)
Signed-off-by: Dan Duval <dan.duval@oracle.com>

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5c65dfced8ba7b7db39b380684adfdb67c2062d9..037012d5169cb0b1f2a9fc9341eeb6b65286c505 100644 (file)
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1490,15 +1490,20 @@ 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 = {