Squashfs: Use vmalloc rather than kmalloc for zlib workspace

Bugzilla bug 31422 reports occasional "page allocation failure. order:4"
at Squashfs mount time.  Fix this by making zlib workspace allocation
use vmalloc rather than kmalloc.
Reported-by: Mehmet Giritli <mehmet@giritli.eu>
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

fs/squashfs/zlib_wrapper.c

@@ -26,6 +26,7 @@
 #include <linux/buffer_head.h>
 #include <linux/slab.h>
 #include <linux/zlib.h>
+#include <linux/vmalloc.h>
 
 #include "squashfs_fs.h"
 #include "squashfs_fs_sb.h"
@@ -37,8 +38,7 @@ static void *zlib_init(struct squashfs_sb_info *dummy, void *buff, int len)
 	z_stream *stream = kmalloc(sizeof(z_stream), GFP_KERNEL);
 	if (stream == NULL)
 		goto failed;
-	stream->workspace = kmalloc(zlib_inflate_workspacesize(),
-		GFP_KERNEL);
+	stream->workspace = vmalloc(zlib_inflate_workspacesize());
 	if (stream->workspace == NULL)
 		goto failed;
 
@@ -56,7 +56,7 @@ static void zlib_free(void *strm)
 	z_stream *stream = strm;
 
 	if (stream)
-		kfree(stream->workspace);
+		vfree(stream->workspace);
 	kfree(stream);
 }