[PATCH] Fix 32bit statfs on NFS

From: Olaf Kirch <okir@suse.de>

The attached patch fixes a problem with the 32bit statfs call on NFS file
systems.  Some NFS servers return a value of -1 for the f_files and f_ffree.
The current code would think this is a 64bit value that cannot be converted
to 32bits.  Consequently, the system call would always fail.

The patch adds two special if() to detect a value of -1 for f_files and
f_ffree.

fs/open.c

@@ -57,10 +57,19 @@ static int vfs_statfs_native(struct super_block *sb, struct statfs *buf)
 		memcpy(buf, &st, sizeof(st));
 	else {
 		if (sizeof buf->f_blocks == 4) {
-			if ((st.f_blocks | st.f_bfree |
-			     st.f_bavail | st.f_files | st.f_ffree) &
+			if ((st.f_blocks | st.f_bfree | st.f_bavail) &
 			    0xffffffff00000000ULL)
 				return -EOVERFLOW;
+			/*
+			 * f_files and f_ffree may be -1; it's okay to stuff
+			 * that into 32 bits
+			 */
+			if (st.f_files != 0xffffffffffffffffULL &&
+			    (st.f_files & 0xffffffff00000000ULL))
+				return -EOVERFLOW;
+			if (st.f_ffree != 0xffffffffffffffffULL &&
+			    (st.f_ffree & 0xffffffff00000000ULL))
+				return -EOVERFLOW;
 		}
 
 		buf->f_type = st.f_type;