From: Steve French <stfrench@microsoft.com>
Date: Tue, 8 Oct 2019 00:27:14 -0500
Subject: [PATCH] smb3: Fix regression in time handling
Git-commit: d4cfbf04b2aafcb657eb8ea0835e5cf51d371448
References: bsc#1144333
Patch-mainline: v5.4-rc3

Fixes: cb7a69e60590 ("cifs: Initialize filesystem timestamp ranges")

Only very old servers (e.g. OS/2 and DOS) did not support
DCE TIME (100 nanosecond granularity).  Fix the checks used
to set minimum and maximum times.

Fixes xfstest generic/258 (on 5.4-rc1 and later)

CC: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/cifsfs.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -159,8 +159,19 @@ cifs_read_super(struct super_block *sb)
 	else
 		sb->s_maxbytes = MAX_NON_LFS;
 
-	/* BB FIXME fix time_gran to be larger for LANMAN sessions */
-	sb->s_time_gran = 100;
+	/* Some very old servers like DOS and OS/2 used 2 second granularity */
+	if ((tcon->ses->server->vals->protocol_id == SMB10_PROT_ID) &&
+	    ((tcon->ses->capabilities &
+	      tcon->ses->server->vals->cap_nt_find) == 0) &&
+	    !tcon->unix_ext) {
+		sb->s_time_gran = 1000000000; /* 1 second is max allowed gran */
+	} else {
+		/*
+		 * Almost every server, including all SMB2+, uses DCE TIME
+		 * ie 100 nanosecond units, since 1601.  See MS-DTYP and MS-FSCC
+		 */
+		sb->s_time_gran = 100;
+	}
 
 	sb->s_magic = CIFS_MAGIC_NUMBER;
 	sb->s_op = &cifs_super_ops;