GFS2: use __vmalloc GFP_NOFS for fs-related allocations.

leaf_dealloc uses vzalloc as a fallback to kzalloc(GFP_NOFS), so
it clearly does not want any shrinker activity within the fs itself.
convert vzalloc into __vmalloc(GFP_NOFS|__GFP_ZERO) to better achieve
this goal.
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/dir.c

@@ -1896,7 +1896,8 @@ static int leaf_dealloc(struct gfs2_inode *dip, u32 index, u32 len,
 
 	ht = kzalloc(size, GFP_NOFS | __GFP_NOWARN);
 	if (ht == NULL)
-		ht = vzalloc(size);
+		ht = __vmalloc(size, GFP_NOFS | __GFP_NOWARN | __GFP_ZERO,
+			       PAGE_KERNEL);
 	if (!ht)
 		return -ENOMEM;