Merge tag '5.0-rc1-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6

Pull cifs fixes from Steve French:
 "A set of cifs/smb3 fixes, 4 for stable, most from Pavel. His patches
  fix an important set of crediting (flow control) problems, and also
  two problems in cifs_writepages, ddressing some large i/o and also
  compounding issues"

* tag '5.0-rc1-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: update internal module version number
  CIFS: Fix error paths in writeback code
  CIFS: Move credit processing to mid callbacks for SMB3
  CIFS: Fix credits calculation for cancelled requests
  cifs: Fix potential OOB access of lock element array
  cifs: Limit memory used by lock request calls to a page
  cifs: move large array from stack to heap
  CIFS: Do not hide EINTR after sending network packets
  CIFS: Fix credit computation for compounded requests
  CIFS: Do not set credits to 1 if the server didn't grant anything
  CIFS: Fix adjustment of credits for MTU requests
  cifs: Fix a tiny potential memory leak
  cifs: Fix a debug message

10 files changed, 211 insertions, 65 deletions

diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 26776eddd85d..d1f9c2f3f575 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -150,5 +150,5 @@ extern long cifs_ioctl(struct file *filep, unsigned int cmd, unsigned long arg);
 extern const struct export_operations cifs_export_ops;
 #endif /* CONFIG_CIFS_NFSD_EXPORT */
 
-#define CIFS_VERSION   "2.15"
+#define CIFS_VERSION   "2.16"
 #endif				/* _CIFSFS_H */
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 01ded7038b19..94dbdbe5be34 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1438,6 +1438,7 @@ struct mid_q_entry {
 	int mid_state;	/* wish this were enum but can not pass to wait_event */
 	unsigned int mid_flags;
 	__le16 command;		/* smb command code */
+	unsigned int optype;	/* operation type */
 	bool large_buf:1;	/* if valid response, is pointer to large buf */
 	bool multiRsp:1;	/* multiple trans2 responses for one request  */
 	bool multiEnd:1;	/* both received */
@@ -1574,6 +1575,25 @@ static inline void free_dfs_info_array(struct dfs_info3_param *param,
 	kfree(param);
 }
 
+static inline bool is_interrupt_error(int error)
+{
+	switch (error) {
+	case -EINTR:
+	case -ERESTARTSYS:
+	case -ERESTARTNOHAND:
+	case -ERESTARTNOINTR:
+		return true;
+	}
+	return false;
+}
+
+static inline bool is_retryable_error(int error)
+{
+	if (is_interrupt_error(error) || error == -EAGAIN)
+		return true;
+	return false;
+}
+
 #define   MID_FREE 0
 #define   MID_REQUEST_ALLOCATED 1
 #define   MID_REQUEST_SUBMITTED 2
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index b1f49c1c543a..e18915415e13 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -128,24 +128,31 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
 	int rc;
 	struct dfs_cache_tgt_list tl;
 	struct dfs_cache_tgt_iterator *it = NULL;
-	char tree[MAX_TREE_SIZE + 1];
+	char *tree;
 	const char *tcp_host;
 	size_t tcp_host_len;
 	const char *dfs_host;
 	size_t dfs_host_len;
 
+	tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
+	if (!tree)
+		return -ENOMEM;
+
 	if (tcon->ipc) {
-		snprintf(tree, sizeof(tree), "\\\\%s\\IPC$",
+		snprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$",
 			 tcon->ses->server->hostname);
-		return CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
+		rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
+		goto out;
 	}
 
-	if (!tcon->dfs_path)
-		return CIFSTCon(0, tcon->ses, tcon->treeName, tcon, nlsc);
+	if (!tcon->dfs_path) {
+		rc = CIFSTCon(0, tcon->ses, tcon->treeName, tcon, nlsc);
+		goto out;
+	}
 
 	rc = dfs_cache_noreq_find(tcon->dfs_path + 1, NULL, &tl);
 	if (rc)
-		return rc;
+		goto out;
 
 	extract_unc_hostname(tcon->ses->server->hostname, &tcp_host,
 			     &tcp_host_len);
@@ -165,7 +172,7 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
 			continue;
 		}
 
-		snprintf(tree, sizeof(tree), "\\%s", tgt);
+		snprintf(tree, MAX_TREE_SIZE, "\\%s", tgt);
 
 		rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
 		if (!rc)
@@ -182,6 +189,8 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
 			rc = -ENOENT;
 	}
 	dfs_cache_free_tgts(&tl);
+out:
+	kfree(tree);
 	return rc;
 }
 #else
@@ -2114,7 +2123,7 @@ cifs_writev_requeue(struct cifs_writedata *wdata)
 
 		for (j = 0; j < nr_pages; j++) {
 			unlock_page(wdata2->pages[j]);
-			if (rc != 0 && rc != -EAGAIN) {
+			if (rc != 0 && !is_retryable_error(rc)) {
 				SetPageError(wdata2->pages[j]);
 				end_page_writeback(wdata2->pages[j]);
 				put_page(wdata2->pages[j]);
@@ -2123,7 +2132,7 @@ cifs_writev_requeue(struct cifs_writedata *wdata)
 
 		if (rc) {
 			kref_put(&wdata2->refcount, cifs_writedata_release);
-			if (rc == -EAGAIN)
+			if (is_retryable_error(rc))
 				continue;
 			break;
 		}
@@ -2132,7 +2141,8 @@ cifs_writev_requeue(struct cifs_writedata *wdata)
 		i += nr_pages;
 	} while (i < wdata->nr_pages);
 
-	mapping_set_error(inode->i_mapping, rc);
+	if (rc != 0 && !is_retryable_error(rc))
+		mapping_set_error(inode->i_mapping, rc);
 	kref_put(&wdata->refcount, cifs_writedata_release);
 }
 
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index f66529679ca2..683310f26171 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -433,9 +433,10 @@ static void reconn_inval_dfs_target(struct TCP_Server_Info *server,
 	kfree(server->hostname);
 
 	server->hostname = extract_hostname(name);
-	if (!server->hostname) {
-		cifs_dbg(FYI, "%s: failed to extract hostname from target: %d\n",
-			 __func__, -ENOMEM);
+	if (IS_ERR(server->hostname)) {
+		cifs_dbg(FYI,
+			 "%s: failed to extract hostname from target: %ld\n",
+			 __func__, PTR_ERR(server->hostname));
 	}
 }
 
diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index cd63c4a70875..09b7d0d4f6e4 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -776,6 +776,7 @@ static int get_tgt_list(const struct dfs_cache_entry *ce,
 		it->it_name = kstrndup(t->t_name, strlen(t->t_name),
 				       GFP_KERNEL);
 		if (!it->it_name) {
+			kfree(it);
 			rc = -ENOMEM;
 			goto err_free_it;
 		}
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e3e3a7550205..2c7689f3998d 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -733,7 +733,8 @@ reopen_success:
 
 	if (can_flush) {
 		rc = filemap_write_and_wait(inode->i_mapping);
-		mapping_set_error(inode->i_mapping, rc);
+		if (!is_interrupt_error(rc))
+			mapping_set_error(inode->i_mapping, rc);
 
 		if (tcon->unix_ext)
 			rc = cifs_get_inode_info_unix(&inode, full_path,
@@ -1132,14 +1133,18 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
 
 	/*
 	 * Accessing maxBuf is racy with cifs_reconnect - need to store value
-	 * and check it for zero before using.
+	 * and check it before using.
 	 */
 	max_buf = tcon->ses->server->maxBuf;
-	if (!max_buf) {
+	if (max_buf < (sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE))) {
 		free_xid(xid);
 		return -EINVAL;
 	}
 
+	BUILD_BUG_ON(sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE) >
+		     PAGE_SIZE);
+	max_buf = min_t(unsigned int, max_buf - sizeof(struct smb_hdr),
+			PAGE_SIZE);
 	max_num = (max_buf - sizeof(struct smb_hdr)) /
 						sizeof(LOCKING_ANDX_RANGE);
 	buf = kcalloc(max_num, sizeof(LOCKING_ANDX_RANGE), GFP_KERNEL);
@@ -1472,12 +1477,16 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
 
 	/*
 	 * Accessing maxBuf is racy with cifs_reconnect - need to store value
-	 * and check it for zero before using.
+	 * and check it before using.
 	 */
 	max_buf = tcon->ses->server->maxBuf;
-	if (!max_buf)
+	if (max_buf < (sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE)))
 		return -EINVAL;
 
+	BUILD_BUG_ON(sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE) >
+		     PAGE_SIZE);
+	max_buf = min_t(unsigned int, max_buf - sizeof(struct smb_hdr),
+			PAGE_SIZE);
 	max_num = (max_buf - sizeof(struct smb_hdr)) /
 						sizeof(LOCKING_ANDX_RANGE);
 	buf = kcalloc(max_num, sizeof(LOCKING_ANDX_RANGE), GFP_KERNEL);
@@ -2110,6 +2119,7 @@ static int cifs_writepages(struct address_space *mapping,
 	pgoff_t end, index;
 	struct cifs_writedata *wdata;
 	int rc = 0;
+	int saved_rc = 0;
 	unsigned int xid;
 
 	/*
@@ -2138,8 +2148,10 @@ retry:
 
 		rc = server->ops->wait_mtu_credits(server, cifs_sb->wsize,
 						   &wsize, &credits);
-		if (rc)
+		if (rc != 0) {
+			done = true;
 			break;
+		}
 
 		tofind = min((wsize / PAGE_SIZE) - 1, end - index) + 1;
 
@@ -2147,6 +2159,7 @@ retry:
 						  &found_pages);
 		if (!wdata) {
 			rc = -ENOMEM;
+			done = true;
 			add_credits_and_wake_if(server, credits, 0);
 			break;
 		}
@@ -2175,7 +2188,7 @@ retry:
 		if (rc != 0) {
 			add_credits_and_wake_if(server, wdata->credits, 0);
 			for (i = 0; i < nr_pages; ++i) {
-				if (rc == -EAGAIN)
+				if (is_retryable_error(rc))
 					redirty_page_for_writepage(wbc,
 							   wdata->pages[i]);
 				else
@@ -2183,7 +2196,7 @@ retry:
 				end_page_writeback(wdata->pages[i]);
 				put_page(wdata->pages[i]);
 			}
-			if (rc != -EAGAIN)
+			if (!is_retryable_error(rc))
 				mapping_set_error(mapping, rc);
 		}
 		kref_put(&wdata->refcount, cifs_writedata_release);
@@ -2193,6 +2206,15 @@ retry:
 			continue;
 		}
 
+		/* Return immediately if we received a signal during writing */
+		if (is_interrupt_error(rc)) {
+			done = true;
+			break;
+		}
+
+		if (rc != 0 && saved_rc == 0)
+			saved_rc = rc;
+
 		wbc->nr_to_write -= nr_pages;
 		if (wbc->nr_to_write <= 0)
 			done = true;
@@ -2210,6 +2232,9 @@ retry:
 		goto retry;
 	}
 
+	if (saved_rc != 0)
+		rc = saved_rc;
+
 	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
 		mapping->writeback_index = index;
 
@@ -2242,8 +2267,8 @@ cifs_writepage_locked(struct page *page, struct writeback_control *wbc)
 	set_page_writeback(page);
 retry_write:
 	rc = cifs_partialpagewrite(page, 0, PAGE_SIZE);
-	if (rc == -EAGAIN) {
-		if (wbc->sync_mode == WB_SYNC_ALL)
+	if (is_retryable_error(rc)) {
+		if (wbc->sync_mode == WB_SYNC_ALL && rc == -EAGAIN)
 			goto retry_write;
 		redirty_page_for_writepage(wbc, page);
 	} else if (rc != 0) {
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 13fb59aadebc..478003644916 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -2257,6 +2257,11 @@ cifs_setattr_unix(struct dentry *direntry, struct iattr *attrs)
 	 * the flush returns error?
 	 */
 	rc = filemap_write_and_wait(inode->i_mapping);
+	if (is_interrupt_error(rc)) {
+		rc = -ERESTARTSYS;
+		goto out;
+	}
+
 	mapping_set_error(inode->i_mapping, rc);
 	rc = 0;
 
@@ -2400,6 +2405,11 @@ cifs_setattr_nounix(struct dentry *direntry, struct iattr *attrs)
 	 * the flush returns error?
 	 */
 	rc = filemap_write_and_wait(inode->i_mapping);
+	if (is_interrupt_error(rc)) {
+		rc = -ERESTARTSYS;
+		goto cifs_setattr_exit;
+	}
+
 	mapping_set_error(inode->i_mapping, rc);
 	rc = 0;
 
diff --git a/fs/cifs/smb2file.c b/fs/cifs/smb2file.c
index 4ed10dd086e6..b204e84b87fb 100644
--- a/fs/cifs/smb2file.c
+++ b/fs/cifs/smb2file.c
@@ -122,12 +122,14 @@ smb2_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
 
 	/*
 	 * Accessing maxBuf is racy with cifs_reconnect - need to store value
-	 * and check it for zero before using.
+	 * and check it before using.
 	 */
 	max_buf = tcon->ses->server->maxBuf;
-	if (!max_buf)
+	if (max_buf < sizeof(struct smb2_lock_element))
 		return -EINVAL;
 
+	BUILD_BUG_ON(sizeof(struct smb2_lock_element) > PAGE_SIZE);
+	max_buf = min_t(unsigned int, max_buf, PAGE_SIZE);
 	max_num = max_buf / sizeof(struct smb2_lock_element);
 	buf = kcalloc(max_num, sizeof(struct smb2_lock_element), GFP_KERNEL);
 	if (!buf)
@@ -264,6 +266,8 @@ smb2_push_mandatory_locks(struct cifsFileInfo *cfile)
 		return -EINVAL;
 	}
 
+	BUILD_BUG_ON(sizeof(struct smb2_lock_element) > PAGE_SIZE);
+	max_buf = min_t(unsigned int, max_buf, PAGE_SIZE);
 	max_num = max_buf / sizeof(struct smb2_lock_element);
 	buf = kcalloc(max_num, sizeof(struct smb2_lock_element), GFP_KERNEL);
 	if (!buf) {
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index e57f6aa1d638..50811a7dc0e0 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -162,24 +162,31 @@ static int __smb2_reconnect(const struct nls_table *nlsc,
 	int rc;
 	struct dfs_cache_tgt_list tl;
 	struct dfs_cache_tgt_iterator *it = NULL;
-	char tree[MAX_TREE_SIZE + 1];
+	char *tree;
 	const char *tcp_host;
 	size_t tcp_host_len;
 	const char *dfs_host;
 	size_t dfs_host_len;
 
+	tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
+	if (!tree)
+		return -ENOMEM;
+
 	if (tcon->ipc) {
-		snprintf(tree, sizeof(tree), "\\\\%s\\IPC$",
+		snprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$",
 			 tcon->ses->server->hostname);
-		return SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
+		rc = SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
+		goto out;
 	}
 
-	if (!tcon->dfs_path)
-		return SMB2_tcon(0, tcon->ses, tcon->treeName, tcon, nlsc);
+	if (!tcon->dfs_path) {
+		rc = SMB2_tcon(0, tcon->ses, tcon->treeName, tcon, nlsc);
+		goto out;
+	}
 
 	rc = dfs_cache_noreq_find(tcon->dfs_path + 1, NULL, &tl);
 	if (rc)
-		return rc;
+		goto out;
 
 	extract_unc_hostname(tcon->ses->server->hostname, &tcp_host,
 			     &tcp_host_len);
@@ -199,7 +206,7 @@ static int __smb2_reconnect(const struct nls_table *nlsc,
 			continue;
 		}
 
-		snprintf(tree, sizeof(tree), "\\%s", tgt);
+		snprintf(tree, MAX_TREE_SIZE, "\\%s", tgt);
 
 		rc = SMB2_tcon(0, tcon->ses, tree, tcon, nlsc);
 		if (!rc)
@@ -216,6 +223,8 @@ static int __smb2_reconnect(const struct nls_table *nlsc,
 			rc = -ENOENT;
 	}
 	dfs_cache_free_tgts(&tl);
+out:
+	kfree(tree);
 	return rc;
 }
 #else
@@ -3278,12 +3287,14 @@ smb2_async_readv(struct cifs_readdata *rdata)
 	if (rdata->credits) {
 		shdr->CreditCharge = cpu_to_le16(DIV_ROUND_UP(rdata->bytes,
 						SMB2_MAX_BUFFER_SIZE));
-		shdr->CreditRequest = shdr->CreditCharge;
+		shdr->CreditRequest =
+			cpu_to_le16(le16_to_cpu(shdr->CreditCharge) + 1);
 		spin_lock(&server->req_lock);
 		server->credits += rdata->credits -
 						le16_to_cpu(shdr->CreditCharge);
 		spin_unlock(&server->req_lock);
 		wake_up(&server->request_q);
+		rdata->credits = le16_to_cpu(shdr->CreditCharge);
 		flags |= CIFS_HAS_CREDITS;
 	}
 
@@ -3555,12 +3566,14 @@ smb2_async_writev(struct cifs_writedata *wdata,
 	if (wdata->credits) {
 		shdr->CreditCharge = cpu_to_le16(DIV_ROUND_UP(wdata->bytes,
 						    SMB2_MAX_BUFFER_SIZE));
-		shdr->CreditRequest = shdr->CreditCharge;
+		shdr->CreditRequest =
+			cpu_to_le16(le16_to_cpu(shdr->CreditCharge) + 1);
 		spin_lock(&server->req_lock);
 		server->credits += wdata->credits -
 						le16_to_cpu(shdr->CreditCharge);
 		spin_unlock(&server->req_lock);
 		wake_up(&server->request_q);
+		wdata->credits = le16_to_cpu(shdr->CreditCharge);
 		flags |= CIFS_HAS_CREDITS;
 	}
 
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 5be7302853b6..202e0e84efdd 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -387,7 +387,7 @@ smbd_done:
 	if (rc < 0 && rc != -EINTR)
 		cifs_dbg(VFS, "Error %d sending data on socket to server\n",
 			 rc);
-	else
+	else if (rc > 0)
 		rc = 0;
 
 	return rc;
@@ -783,8 +783,34 @@ cifs_setup_request(struct cifs_ses *ses, struct smb_rqst *rqst)
 }
 
 static void
-cifs_noop_callback(struct mid_q_entry *mid)
+cifs_compound_callback(struct mid_q_entry *mid)
 {
+	struct TCP_Server_Info *server = mid->server;
+	unsigned int optype = mid->optype;
+	unsigned int credits_received = 0;
+
+	if (mid->mid_state == MID_RESPONSE_RECEIVED) {
+		if (mid->resp_buf)
+			credits_received = server->ops->get_credits(mid);
+		else
+			cifs_dbg(FYI, "Bad state for cancelled MID\n");
+	}
+
+	add_credits(server, credits_received, optype);
+}
+
+static void
+cifs_compound_last_callback(struct mid_q_entry *mid)
+{
+	cifs_compound_callback(mid);
+	cifs_wake_up_task(mid);
+}
+
+static void
+cifs_cancelled_callback(struct mid_q_entry *mid)
+{
+	cifs_compound_callback(mid);
+	DeleteMidQEntry(mid);
 }
 
 int
@@ -795,7 +821,8 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 	int i, j, rc = 0;
 	int timeout, optype;
 	struct mid_q_entry *midQ[MAX_COMPOUND];
-	unsigned int credits = 0;
+	bool cancelled_mid[MAX_COMPOUND] = {false};
+	unsigned int credits[MAX_COMPOUND] = {0};
 	char *buf;
 
 	timeout = flags & CIFS_TIMEOUT_MASK;
@@ -813,13 +840,31 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 		return -ENOENT;
 
 	/*
-	 * Ensure that we do not send more than 50 overlapping requests
-	 * to the same server. We may make this configurable later or
-	 * use ses->maxReq.
+	 * Ensure we obtain 1 credit per request in the compound chain.
+	 * It can be optimized further by waiting for all the credits
+	 * at once but this can wait long enough if we don't have enough
+	 * credits due to some heavy operations in progress or the server
+	 * not granting us much, so a fallback to the current approach is
+	 * needed anyway.
 	 */
-	rc = wait_for_free_request(ses->server, timeout, optype);
-	if (rc)
-		return rc;
+	for (i = 0; i < num_rqst; i++) {
+		rc = wait_for_free_request(ses->server, timeout, optype);
+		if (rc) {
+			/*
+			 * We haven't sent an SMB packet to the server yet but
+			 * we already obtained credits for i requests in the
+			 * compound chain - need to return those credits back
+			 * for future use. Note that we need to call add_credits
+			 * multiple times to match the way we obtained credits
+			 * in the first place and to account for in flight
+			 * requests correctly.
+			 */
+			for (j = 0; j < i; j++)
+				add_credits(ses->server, 1, optype);
+			return rc;
+		}
+		credits[i] = 1;
+	}
 
 	/*
 	 * Make sure that we sign in the same order that we send on this socket
@@ -835,18 +880,24 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 			for (j = 0; j < i; j++)
 				cifs_delete_mid(midQ[j]);
 			mutex_unlock(&ses->server->srv_mutex);
+
 			/* Update # of requests on wire to server */
-			add_credits(ses->server, 1, optype);
+			for (j = 0; j < num_rqst; j++)
+				add_credits(ses->server, credits[j], optype);
 			return PTR_ERR(midQ[i]);
 		}
 
 		midQ[i]->mid_state = MID_REQUEST_SUBMITTED;
+		midQ[i]->optype = optype;
 		/*
-		 * We don't invoke the callback compounds unless it is the last
-		 * request.
+		 * Invoke callback for every part of the compound chain
+		 * to calculate credits properly. Wake up this thread only when
+		 * the last element is received.
 		 */
 		if (i < num_rqst - 1)
-			midQ[i]->callback = cifs_noop_callback;
+			midQ[i]->callback = cifs_compound_callback;
+		else
+			midQ[i]->callback = cifs_compound_last_callback;
 	}
 	cifs_in_send_inc(ses->server);
 	rc = smb_send_rqst(ses->server, num_rqst, rqst, flags);
@@ -860,8 +911,20 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 
 	mutex_unlock(&ses->server->srv_mutex);
 
-	if (rc < 0)
+	if (rc < 0) {
+		/* Sending failed for some reason - return credits back */
+		for (i = 0; i < num_rqst; i++)
+			add_credits(ses->server, credits[i], optype);
 		goto out;
+	}
+
+	/*
+	 * At this point the request is passed to the network stack - we assume
+	 * that any credits taken from the server structure on the client have
+	 * been spent and we can't return them back. Once we receive responses
+	 * we will collect credits granted by the server in the mid callbacks
+	 * and add those credits to the server structure.
+	 */
 
 	/*
 	 * Compounding is never used during session establish.
@@ -875,36 +938,34 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 
 	for (i = 0; i < num_rqst; i++) {
 		rc = wait_for_response(ses->server, midQ[i]);
-		if (rc != 0) {
+		if (rc != 0)
+			break;
+	}
+	if (rc != 0) {
+		for (; i < num_rqst; i++) {
 			cifs_dbg(VFS, "Cancelling wait for mid %llu cmd: %d\n",
 				 midQ[i]->mid, le16_to_cpu(midQ[i]->command));
 			send_cancel(ses->server, &rqst[i], midQ[i]);
 			spin_lock(&GlobalMid_Lock);
 			if (midQ[i]->mid_state == MID_REQUEST_SUBMITTED) {
 				midQ[i]->mid_flags |= MID_WAIT_CANCELLED;
-				midQ[i]->callback = DeleteMidQEntry;
-				spin_unlock(&GlobalMid_Lock);
-				add_credits(ses->server, 1, optype);
-				return rc;
+				midQ[i]->callback = cifs_cancelled_callback;
+				cancelled_mid[i] = true;
+				credits[i] = 0;
 			}
 			spin_unlock(&GlobalMid_Lock);
 		}
 	}
 
-	for (i = 0; i < num_rqst; i++)
-		if (midQ[i]->resp_buf)
-			credits += ses->server->ops->get_credits(midQ[i]);
-	if (!credits)
-		credits = 1;
-
 	for (i = 0; i < num_rqst; i++) {
 		if (rc < 0)
 			goto out;
 
 		rc = cifs_sync_mid_result(midQ[i], ses->server);
 		if (rc != 0) {
-			add_credits(ses->server, credits, optype);
-			return rc;
+			/* mark this mid as cancelled to not free it below */
+			cancelled_mid[i] = true;
+			goto out;
 		}
 
 		if (!midQ[i]->resp_buf ||
@@ -951,9 +1012,10 @@ out:
 	 * This is prevented above by using a noop callback that will not
 	 * wake this thread except for the very last PDU.
 	 */
-	for (i = 0; i < num_rqst; i++)
-		cifs_delete_mid(midQ[i]);
-	add_credits(ses->server, credits, optype);
+	for (i = 0; i < num_rqst; i++) {
+		if (!cancelled_mid[i])
+			cifs_delete_mid(midQ[i]);
+	}
 
 	return rc;
 }