Commit ec56b1f1 authored Jun 04, 2015 by Dave Chinner Committed by Dave Chinner Jun 04, 2015

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>

parent 5ebe6afa

fs/xfs/xfs_file.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -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 = {