SMB3: Allow persistent handle timeout to be configurable on mount

Reconnecting after server or network failure can be improved
(to maintain availability and protect data integrity) by allowing
the client to choose the default persistent (or resilient)
handle timeout in some use cases.  Today we default to 0 which lets
the server pick the default timeout (usually 120 seconds) but this
can be problematic for some workloads.  Add the new mount parameter
to cifs.ko for SMB3 mounts "handletimeout" which enables the user
to override the default handle timeout for persistent (mount
option "persistenthandles") or resilient handles (mount option
"resilienthandles").  Maximum allowed is 16 minutes (960000 ms).
Units for the timeout are expressed in milliseconds. See
section 2.2.14.2.12 and 2.2.31.3 of the MS-SMB2 protocol
specification for more information.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
CC: Stable <stable@vger.kernel.org>

1 files changed, 29 insertions, 1 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a8e9738db691..4c0e44489f21 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -103,7 +103,7 @@ enum {
 	Opt_cruid, Opt_gid, Opt_file_mode,
 	Opt_dirmode, Opt_port,
 	Opt_blocksize, Opt_rsize, Opt_wsize, Opt_actimeo,
-	Opt_echo_interval, Opt_max_credits,
+	Opt_echo_interval, Opt_max_credits, Opt_handletimeout,
 	Opt_snapshot,
 
 	/* Mount options which take string value */
@@ -208,6 +208,7 @@ static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_rsize, "rsize=%s" },
 	{ Opt_wsize, "wsize=%s" },
 	{ Opt_actimeo, "actimeo=%s" },
+	{ Opt_handletimeout, "handletimeout=%s" },
 	{ Opt_echo_interval, "echo_interval=%s" },
 	{ Opt_max_credits, "max_credits=%s" },
 	{ Opt_snapshot, "snapshot=%s" },
@@ -1619,6 +1620,9 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 
 	vol->actimeo = CIFS_DEF_ACTIMEO;
 
+	/* Most clients set timeout to 0, allows server to use its default */
+	vol->handle_timeout = 0; /* See MS-SMB2 spec section 2.2.14.2.12 */
+
 	/* offer SMB2.1 and later (SMB3 etc). Secure and widely accepted */
 	vol->ops = &smb30_operations;
 	vol->vals = &smbdefault_values;
@@ -2017,6 +2021,18 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 				goto cifs_parse_mount_err;
 			}
 			break;
+		case Opt_handletimeout:
+			if (get_option_ul(args, &option)) {
+				cifs_dbg(VFS, "%s: Invalid handletimeout value\n",
+					 __func__);
+				goto cifs_parse_mount_err;
+			}
+			vol->handle_timeout = option;
+			if (vol->handle_timeout > SMB3_MAX_HANDLE_TIMEOUT) {
+				cifs_dbg(VFS, "Invalid handle cache timeout, longer than 16 minutes\n");
+				goto cifs_parse_mount_err;
+			}
+			break;
 		case Opt_echo_interval:
 			if (get_option_ul(args, &option)) {
 				cifs_dbg(VFS, "%s: Invalid echo interval value\n",
@@ -3183,6 +3199,8 @@ static int match_tcon(struct cifs_tcon *tcon, struct smb_vol *volume_info)
 		return 0;
 	if (tcon->snapshot_time != volume_info->snapshot_time)
 		return 0;
+	if (tcon->handle_timeout != volume_info->handle_timeout)
+		return 0;
 	return 1;
 }
 
@@ -3297,6 +3315,16 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
 			tcon->snapshot_time = volume_info->snapshot_time;
 	}
 
+	if (volume_info->handle_timeout) {
+		if (ses->server->vals->protocol_id == 0) {
+			cifs_dbg(VFS,
+			     "Use SMB2.1 or later for handle timeout option\n");
+			rc = -EOPNOTSUPP;
+			goto out_fail;
+		} else
+			tcon->handle_timeout = volume_info->handle_timeout;
+	}
+
 	tcon->ses = ses;
 	if (volume_info->password) {
 		tcon->password = kstrdup(volume_info->password, GFP_KERNEL);