From: Dave Chinner <dchinner@redhat.com>
Date: Wed, 3 Jun 2015 23:18:18 +0000 (+1000)
Subject: xfs: mmap lock needs to be inside freeze protection
X-Git-Tag: firefly_0821_release~176^2~1521^2~4^2~7
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=ec56b1f1fdc69599963574ce94cc5693d535dd64;p=firefly-linux-kernel-4.4.55.git

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>
---

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 = {