CIFS: Do not skip SMB2 message IDs on send failures

When we hit failures during constructing MIDs or sending PDUs
through the network, we end up not using message IDs assigned
to the packet. The next SMB packet will skip those message IDs
and continue with the next one. This behavior may lead to a server
not granting us credits until we use the skipped IDs. Fix this by
reverting the current ID to the original value if any errors occur
before we push the packet through the network stack.

This patch fixes the generic/310 test from the xfs-tests.

Cc: <stable@vger.kernel.org> # 4.19.x
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsglob.h

@@ -236,6 +236,8 @@ struct smb_version_operations {
 	int * (*get_credits_field)(struct TCP_Server_Info *, const int);
 	unsigned int (*get_credits)(struct mid_q_entry *);
 	__u64 (*get_next_mid)(struct TCP_Server_Info *);
+	void (*revert_current_mid)(struct TCP_Server_Info *server,
+				   const unsigned int val);
 	/* data offset from read response message */
 	unsigned int (*read_data_offset)(char *);
 	/*
@@ -771,6 +773,22 @@ get_next_mid(struct TCP_Server_Info *server)
 	return cpu_to_le16(mid);
 }
 
+static inline void
+revert_current_mid(struct TCP_Server_Info *server, const unsigned int val)
+{
+	if (server->ops->revert_current_mid)
+		server->ops->revert_current_mid(server, val);
+}
+
+static inline void
+revert_current_mid_from_hdr(struct TCP_Server_Info *server,
+			    const struct smb2_sync_hdr *shdr)
+{
+	unsigned int num = le16_to_cpu(shdr->CreditCharge);
+
+	return revert_current_mid(server, num > 0 ? num : 1);
+}
+
 static inline __u16
 get_mid(const struct smb_hdr *smb)
 {
@@ -1423,6 +1441,7 @@ struct mid_q_entry {
 	struct kref refcount;
 	struct TCP_Server_Info *server;	/* server corresponding to this mid */
 	__u64 mid;		/* multiplex id */
+	__u16 credits;		/* number of credits consumed by this mid */
 	__u32 pid;		/* process id */
 	__u32 sequence_number;  /* for CIFS signing */
 	unsigned long when_alloc;  /* when mid was created */

fs/cifs/smb2ops.c

@@ -219,6 +219,15 @@ smb2_get_next_mid(struct TCP_Server_Info *server)
 	return mid;
 }
 
+static void
+smb2_revert_current_mid(struct TCP_Server_Info *server, const unsigned int val)
+{
+	spin_lock(&GlobalMid_Lock);
+	if (server->CurrentMid >= val)
+		server->CurrentMid -= val;
+	spin_unlock(&GlobalMid_Lock);
+}
+
 static struct mid_q_entry *
 smb2_find_mid(struct TCP_Server_Info *server, char *buf)
 {
@@ -3560,6 +3569,7 @@ struct smb_version_operations smb20_operations = {
 	.get_credits = smb2_get_credits,
 	.wait_mtu_credits = cifs_wait_mtu_credits,
 	.get_next_mid = smb2_get_next_mid,
+	.revert_current_mid = smb2_revert_current_mid,
 	.read_data_offset = smb2_read_data_offset,
 	.read_data_length = smb2_read_data_length,
 	.map_error = map_smb2_to_linux_error,
@@ -3655,6 +3665,7 @@ struct smb_version_operations smb21_operations = {
 	.get_credits = smb2_get_credits,
 	.wait_mtu_credits = smb2_wait_mtu_credits,
 	.get_next_mid = smb2_get_next_mid,
+	.revert_current_mid = smb2_revert_current_mid,
 	.read_data_offset = smb2_read_data_offset,
 	.read_data_length = smb2_read_data_length,
 	.map_error = map_smb2_to_linux_error,
@@ -3751,6 +3762,7 @@ struct smb_version_operations smb30_operations = {
 	.get_credits = smb2_get_credits,
 	.wait_mtu_credits = smb2_wait_mtu_credits,
 	.get_next_mid = smb2_get_next_mid,
+	.revert_current_mid = smb2_revert_current_mid,
 	.read_data_offset = smb2_read_data_offset,
 	.read_data_length = smb2_read_data_length,
 	.map_error = map_smb2_to_linux_error,
@@ -3856,6 +3868,7 @@ struct smb_version_operations smb311_operations = {
 	.get_credits = smb2_get_credits,
 	.wait_mtu_credits = smb2_wait_mtu_credits,
 	.get_next_mid = smb2_get_next_mid,
+	.revert_current_mid = smb2_revert_current_mid,
 	.read_data_offset = smb2_read_data_offset,
 	.read_data_length = smb2_read_data_length,
 	.map_error = map_smb2_to_linux_error,

fs/cifs/smb2transport.c

@@ -576,6 +576,7 @@ smb2_mid_entry_alloc(const struct smb2_sync_hdr *shdr,
 		     struct TCP_Server_Info *server)
 {
 	struct mid_q_entry *temp;
+	unsigned int credits = le16_to_cpu(shdr->CreditCharge);
 
 	if (server == NULL) {
 		cifs_dbg(VFS, "Null TCP session in smb2_mid_entry_alloc\n");
@@ -586,6 +587,7 @@ smb2_mid_entry_alloc(const struct smb2_sync_hdr *shdr,
 	memset(temp, 0, sizeof(struct mid_q_entry));
 	kref_init(&temp->refcount);
 	temp->mid = le64_to_cpu(shdr->MessageId);
+	temp->credits = credits > 0 ? credits : 1;
 	temp->pid = current->pid;
 	temp->command = shdr->Command; /* Always LE */
 	temp->when_alloc = jiffies;
@@ -674,13 +676,18 @@ smb2_setup_request(struct cifs_ses *ses, struct smb_rqst *rqst)
 	smb2_seq_num_into_buf(ses->server, shdr);
 
 	rc = smb2_get_mid_entry(ses, shdr, &mid);
-	if (rc)
+	if (rc) {
+		revert_current_mid_from_hdr(ses->server, shdr);
 		return ERR_PTR(rc);
+	}
+
 	rc = smb2_sign_rqst(rqst, ses->server);
 	if (rc) {
+		revert_current_mid_from_hdr(ses->server, shdr);
 		cifs_delete_mid(mid);
 		return ERR_PTR(rc);
 	}
+
 	return mid;
 }
 
@@ -695,11 +702,14 @@ smb2_setup_async_request(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 	smb2_seq_num_into_buf(server, shdr);
 
 	mid = smb2_mid_entry_alloc(shdr, server);
-	if (mid == NULL)
+	if (mid == NULL) {
+		revert_current_mid_from_hdr(server, shdr);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	rc = smb2_sign_rqst(rqst, server);
 	if (rc) {
+		revert_current_mid_from_hdr(server, shdr);
 		DeleteMidQEntry(mid);
 		return ERR_PTR(rc);
 	}

fs/cifs/transport.c

@@ -647,6 +647,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
 	cifs_in_send_dec(server);
 
 	if (rc < 0) {
+		revert_current_mid(server, mid->credits);
 		server->sequence_number -= 2;
 		cifs_delete_mid(mid);
 	}
@@ -868,6 +869,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 	for (i = 0; i < num_rqst; i++) {
 		midQ[i] = ses->server->ops->setup_request(ses, &rqst[i]);
 		if (IS_ERR(midQ[i])) {
+			revert_current_mid(ses->server, i);
 			for (j = 0; j < i; j++)
 				cifs_delete_mid(midQ[j]);
 			mutex_unlock(&ses->server->srv_mutex);
@@ -897,8 +899,10 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 	for (i = 0; i < num_rqst; i++)
 		cifs_save_when_sent(midQ[i]);
 
-	if (rc < 0)
+	if (rc < 0) {
+		revert_current_mid(ses->server, num_rqst);
 		ses->server->sequence_number -= 2;
+	}
 
 	mutex_unlock(&ses->server->srv_mutex);