5 files changed, 37 insertions, 16 deletions
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 65f78b7a9062..cd80594f14d0 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -75,6 +75,18 @@
 #define SMB_ECHO_INTERVAL_MAX 600
 #define SMB_ECHO_INTERVAL_DEFAULT 60
 
+/*
+ * Default number of credits to keep available for SMB3.
+ * This value is chosen somewhat arbitrarily. The Windows client
+ * defaults to 128 credits, the Windows server allows clients up to
+ * 512 credits (or 8K for later versions), and the NetApp server
+ * does not limit clients at all.  Choose a high enough default value
+ * such that the client shouldn't limit performance, but allow mount
+ * to override (until you approach 64K, where we limit credits to 65000
+ * to reduce possibility of seeing more server credit overflow bugs.
+ */
+#define SMB2_MAX_CREDITS_AVAILABLE 32000
+
 #include "cifspdu.h"
 
 #ifndef XATTR_DOS_ATTRIB
@@ -510,6 +522,7 @@ struct smb_vol {
 	struct sockaddr_storage srcaddr; /* allow binding to a local IP */
 	struct nls_table *local_nls;
 	unsigned int echo_interval; /* echo interval in secs */
+	unsigned int max_credits; /* smb3 max_credits 10 < credits < 60000 */
 };
 
 #define CIFS_MOUNT_MASK (CIFS_MOUNT_NO_PERM | CIFS_MOUNT_SET_UID | \
@@ -567,7 +580,8 @@ struct TCP_Server_Info {
 	bool noblocksnd;		/* use blocking sendmsg */
 	bool noautotune;		/* do not autotune send buf sizes */
 	bool tcp_nodelay;
-	int credits;  /* send no more requests at once */
+	unsigned int credits;  /* send no more requests at once */
+	unsigned int max_credits; /* can override large 32000 default at mnt */
 	unsigned int in_flight;  /* number of requests on the wire to server */
 	spinlock_t req_lock;  /* protect the two values above */
 	struct mutex srv_mutex;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 7b67179521cf..657369db76df 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -63,7 +63,6 @@ extern mempool_t *cifs_req_poolp;
 #define TLINK_IDLE_EXPIRE	(600 * HZ)
 
 enum {
-
 	/* Mount options that take no arguments */
 	Opt_user_xattr, Opt_nouser_xattr,
 	Opt_forceuid, Opt_noforceuid,
@@ -95,7 +94,7 @@ enum {
 	Opt_cruid, Opt_gid, Opt_file_mode,
 	Opt_dirmode, Opt_port,
 	Opt_rsize, Opt_wsize, Opt_actimeo,
-	Opt_echo_interval,
+	Opt_echo_interval, Opt_max_credits,
 
 	/* Mount options which take string value */
 	Opt_user, Opt_pass, Opt_ip,
@@ -190,6 +189,7 @@ static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_wsize, "wsize=%s" },
 	{ Opt_actimeo, "actimeo=%s" },
 	{ Opt_echo_interval, "echo_interval=%s" },
+	{ Opt_max_credits, "max_credits=%s" },
 
 	{ Opt_blank_user, "user=" },
 	{ Opt_blank_user, "username=" },
@@ -1586,6 +1586,15 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			}
 			vol->echo_interval = option;
 			break;
+		case Opt_max_credits:
+			if (get_option_ul(args, &option) || (option < 20) ||
+			    (option > 60000)) {
+				cifs_dbg(VFS, "%s: Invalid max_credits value\n",
+					 __func__);
+				goto cifs_parse_mount_err;
+			}
+			vol->max_credits = option;
+			break;
 
 		/* String Arguments */
 
@@ -3598,7 +3607,11 @@ try_mount_again:
 		bdi_destroy(&cifs_sb->bdi);
 		goto out;
 	}
-
+	if ((volume_info->max_credits < 20) ||
+	     (volume_info->max_credits > 60000))
+		server->max_credits = SMB2_MAX_CREDITS_AVAILABLE;
+	else
+		server->max_credits = volume_info->max_credits;
 	/* get a reference to a SMB session */
 	ses = cifs_get_smb_ses(server, volume_info);
 	if (IS_ERR(ses)) {
diff --git a/fs/cifs/smb2glob.h b/fs/cifs/smb2glob.h
index 238759c146ba..0ffa18094335 100644
--- a/fs/cifs/smb2glob.h
+++ b/fs/cifs/smb2glob.h
@@ -61,14 +61,4 @@
 /* Maximum buffer size value we can send with 1 credit */
 #define SMB2_MAX_BUFFER_SIZE 65536
 
-/*
- * Maximum number of credits to keep available.
- * This value is chosen somewhat arbitrarily. The Windows client
- * defaults to 128 credits, the Windows server allows clients up to
- * 512 credits, and the NetApp server does not limit clients at all.
- * Choose a high enough value such that the client shouldn't limit
- * performance.
- */
-#define SMB2_MAX_CREDITS_AVAILABLE 32000
-
 #endif	/* _SMB2_GLOB_H */
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 91e53df4e420..378260cd25a6 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -70,6 +70,10 @@ smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
 	spin_lock(&server->req_lock);
 	val = server->ops->get_credits_field(server, optype);
 	*val += add;
+	if (*val > 65000) {
+		*val = 65000; /* Don't get near 64K credits, avoid srv bugs */
+		printk_once(KERN_WARNING "server overflowed SMB3 credits\n");
+	}
 	server->in_flight--;
 	if (server->in_flight == 0 && (optype & CIFS_OP_MASK) != CIFS_NEG_OP)
 		rc = change_conf(server);
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 4d944c4c55a8..d6a045690266 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -105,11 +105,11 @@ smb2_hdr_assemble(struct smb2_hdr *hdr, __le16 smb2_cmd /* command */ ,
 
 		spin_lock(&server->req_lock);
 		/* Request up to 2 credits but don't go over the limit. */
-		if (server->credits >= SMB2_MAX_CREDITS_AVAILABLE)
+		if (server->credits >= server->max_credits)
 			hdr->CreditRequest = cpu_to_le16(0);
 		else
 			hdr->CreditRequest = cpu_to_le16(
-				min_t(int, SMB2_MAX_CREDITS_AVAILABLE -
+				min_t(int, server->max_credits -
 						server->credits, 2));
 		spin_unlock(&server->req_lock);
 	} else {