CIFS: Adjust MTU credits before reopening a file

Currently we adjust MTU credits before sending an IO request
and after reopening a file. This approach doesn't allow the
reopen routine to use existing credits that are not needed
for IO. Reorder credit adjustment and reopening a file to
use credits available to the client more efficiently. Also
unwrap complex if statement into few pieces to improve
readability.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsglob.h

@@ -457,6 +457,10 @@ struct smb_version_operations {
 	/* get mtu credits */
 	int (*wait_mtu_credits)(struct TCP_Server_Info *, unsigned int,
 				unsigned int *, struct cifs_credits *);
+	/* adjust previously taken mtu credits to request size */
+	int (*adjust_credits)(struct TCP_Server_Info *server,
+			      struct cifs_credits *credits,
+			      const unsigned int payload_size);
 	/* check if we need to issue closedir */
 	bool (*dir_needs_close)(struct cifsFileInfo *);
 	long (*fallocate)(struct file *, struct cifs_tcon *, int, loff_t,
@@ -763,6 +767,14 @@ set_credits(struct TCP_Server_Info *server, const int val)
 	server->ops->set_credits(server, val);
 }
 
+static inline int
+adjust_credits(struct TCP_Server_Info *server, struct cifs_credits *credits,
+	       const unsigned int payload_size)
+{
+	return server->ops->adjust_credits ?
+		server->ops->adjust_credits(server, credits, payload_size) : 0;
+}
+
 static inline __le64
 get_next_mid64(struct TCP_Server_Info *server)
 {

fs/cifs/file.c

@@ -2076,11 +2076,11 @@ wdata_prepare_pages(struct cifs_writedata *wdata, unsigned int found_pages,
 }
 
 static int
-wdata_send_pages(struct cifs_writedata *wdata, unsigned int nr_pages,
-		 struct address_space *mapping, struct writeback_control *wbc)
+wdata_send_pages(struct TCP_Server_Info *server, struct cifs_writedata *wdata,
+		 unsigned int nr_pages, struct address_space *mapping,
+		 struct writeback_control *wbc)
 {
 	int rc = 0;
-	struct TCP_Server_Info *server;
 	unsigned int i;
 
 	wdata->sync_mode = wbc->sync_mode;
@@ -2092,6 +2092,10 @@ wdata_send_pages(struct cifs_writedata *wdata, unsigned int nr_pages,
 			(loff_t)PAGE_SIZE);
 	wdata->bytes = ((nr_pages - 1) * PAGE_SIZE) + wdata->tailsz;
 
+	rc = adjust_credits(server, &wdata->credits, wdata->bytes);
+	if (rc)
+		goto send_pages_out;
+
 	if (wdata->cfile != NULL)
 		cifsFileInfo_put(wdata->cfile);
 	wdata->cfile = find_writable_file(CIFS_I(mapping->host), false);
@@ -2100,10 +2104,10 @@ wdata_send_pages(struct cifs_writedata *wdata, unsigned int nr_pages,
 		rc = -EBADF;
 	} else {
 		wdata->pid = wdata->cfile->pid;
-		server = tlink_tcon(wdata->cfile->tlink)->ses->server;
 		rc = server->ops->async_writev(wdata, cifs_writedata_release);
 	}
 
+send_pages_out:
 	for (i = 0; i < nr_pages; ++i)
 		unlock_page(wdata->pages[i]);
 
@@ -2184,7 +2188,7 @@ static int cifs_writepages(struct address_space *mapping,
 
 		wdata->credits = credits_on_stack;
 
-		rc = wdata_send_pages(wdata, nr_pages, mapping, wbc);
+		rc = wdata_send_pages(server, wdata, nr_pages, mapping, wbc);
 
 		/* send failure -- clean up the mess */
 		if (rc != 0) {
@@ -2743,10 +2747,17 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 		wdata->ctx = ctx;
 		kref_get(&ctx->refcount);
 
-		if (!wdata->cfile->invalidHandle ||
-		    !(rc = cifs_reopen_file(wdata->cfile, false)))
+		rc = adjust_credits(server, &wdata->credits, wdata->bytes);
+
+		if (!rc) {
+			if (wdata->cfile->invalidHandle)
+				rc = cifs_reopen_file(wdata->cfile, false);
+
+			if (!rc)
 				rc = server->ops->async_writev(wdata,
 					cifs_uncached_writedata_release);
+		}
+
 		if (rc) {
 			add_credits_and_wake_if(server, &wdata->credits, 0);
 			kref_put(&wdata->refcount,
@@ -3423,9 +3434,16 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 		rdata->ctx = ctx;
 		kref_get(&ctx->refcount);
 
-		if (!rdata->cfile->invalidHandle ||
-		    !(rc = cifs_reopen_file(rdata->cfile, true)))
+		rc = adjust_credits(server, &rdata->credits, rdata->bytes);
+
+		if (!rc) {
+			if (rdata->cfile->invalidHandle)
+				rc = cifs_reopen_file(rdata->cfile, true);
+
+			if (!rc)
 				rc = server->ops->async_readv(rdata);
+		}
+
 		if (rc) {
 			add_credits_and_wake_if(server, &rdata->credits, 0);
 			kref_put(&rdata->refcount,
@@ -4163,9 +4181,16 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 			rdata->pages[rdata->nr_pages++] = page;
 		}
 
-		if (!rdata->cfile->invalidHandle ||
-		    !(rc = cifs_reopen_file(rdata->cfile, true)))
+		rc = adjust_credits(server, &rdata->credits, rdata->bytes);
+
+		if (!rc) {
+			if (rdata->cfile->invalidHandle)
+				rc = cifs_reopen_file(rdata->cfile, true);
+
+			if (!rc)
 				rc = server->ops->async_readv(rdata);
+		}
+
 		if (rc) {
 			add_credits_and_wake_if(server, &rdata->credits, 0);
 			for (i = 0; i < rdata->nr_pages; i++) {

fs/cifs/smb2ops.c

@@ -222,6 +222,38 @@ smb2_wait_mtu_credits(struct TCP_Server_Info *server, unsigned int size,
 	return rc;
 }
 
+static int
+smb2_adjust_credits(struct TCP_Server_Info *server,
+		    struct cifs_credits *credits,
+		    const unsigned int payload_size)
+{
+	int new_val = DIV_ROUND_UP(payload_size, SMB2_MAX_BUFFER_SIZE);
+
+	if (!credits->value || credits->value == new_val)
+		return 0;
+
+	if (credits->value < new_val) {
+		WARN_ONCE(1, "request has less credits (%d) than required (%d)",
+			  credits->value, new_val);
+		return -ENOTSUPP;
+	}
+
+	spin_lock(&server->req_lock);
+
+	if (server->reconnect_instance != credits->instance) {
+		spin_unlock(&server->req_lock);
+		cifs_dbg(VFS, "trying to return %d credits to old session\n",
+			 credits->value - new_val);
+		return -EAGAIN;
+	}
+
+	server->credits += credits->value - new_val;
+	spin_unlock(&server->req_lock);
+	wake_up(&server->request_q);
+	credits->value = new_val;
+	return 0;
+}
+
 static __u64
 smb2_get_next_mid(struct TCP_Server_Info *server)
 {
@@ -3678,6 +3710,7 @@ struct smb_version_operations smb21_operations = {
 	.get_credits_field = smb2_get_credits_field,
 	.get_credits = smb2_get_credits,
 	.wait_mtu_credits = smb2_wait_mtu_credits,
+	.adjust_credits = smb2_adjust_credits,
 	.get_next_mid = smb2_get_next_mid,
 	.revert_current_mid = smb2_revert_current_mid,
 	.read_data_offset = smb2_read_data_offset,
@@ -3775,6 +3808,7 @@ struct smb_version_operations smb30_operations = {
 	.get_credits_field = smb2_get_credits_field,
 	.get_credits = smb2_get_credits,
 	.wait_mtu_credits = smb2_wait_mtu_credits,
+	.adjust_credits = smb2_adjust_credits,
 	.get_next_mid = smb2_get_next_mid,
 	.revert_current_mid = smb2_revert_current_mid,
 	.read_data_offset = smb2_read_data_offset,
@@ -3881,6 +3915,7 @@ struct smb_version_operations smb311_operations = {
 	.get_credits_field = smb2_get_credits_field,
 	.get_credits = smb2_get_credits,
 	.wait_mtu_credits = smb2_wait_mtu_credits,
+	.adjust_credits = smb2_adjust_credits,
 	.get_next_mid = smb2_get_next_mid,
 	.revert_current_mid = smb2_revert_current_mid,
 	.read_data_offset = smb2_read_data_offset,

fs/cifs/smb2pdu.c

@@ -3322,21 +3322,11 @@ smb2_async_readv(struct cifs_readdata *rdata)
 						SMB2_MAX_BUFFER_SIZE));
 		shdr->CreditRequest =
 			cpu_to_le16(le16_to_cpu(shdr->CreditCharge) + 1);
-		spin_lock(&server->req_lock);
-		if (server->reconnect_instance == rdata->credits.instance)
-			server->credits += rdata->credits.value -
-						le16_to_cpu(shdr->CreditCharge);
-		else {
-			spin_unlock(&server->req_lock);
-			cifs_dbg(VFS, "trying to return %u credits to old session\n",
-				 rdata->credits.value
-				 - le16_to_cpu(shdr->CreditCharge));
-			rc = -EAGAIN;
+
+		rc = adjust_credits(server, &rdata->credits, rdata->bytes);
+		if (rc)
 			goto async_readv_out;
-		}
-		spin_unlock(&server->req_lock);
-		wake_up(&server->request_q);
-		rdata->credits.value = le16_to_cpu(shdr->CreditCharge);
+
 		flags |= CIFS_HAS_CREDITS;
 	}
 
@@ -3626,21 +3616,11 @@ smb2_async_writev(struct cifs_writedata *wdata,
 						    SMB2_MAX_BUFFER_SIZE));
 		shdr->CreditRequest =
 			cpu_to_le16(le16_to_cpu(shdr->CreditCharge) + 1);
-		spin_lock(&server->req_lock);
-		if (server->reconnect_instance == wdata->credits.instance)
-			server->credits += wdata->credits.value -
-						le16_to_cpu(shdr->CreditCharge);
-		else {
-			spin_unlock(&server->req_lock);
-			cifs_dbg(VFS, "trying to return %d credits to old session\n",
-				 wdata->credits.value
-				 - le16_to_cpu(shdr->CreditCharge));
-			rc = -EAGAIN;
+
+		rc = adjust_credits(server, &wdata->credits, wdata->bytes);
+		if (rc)
 			goto async_writev_out;
-		}
-		spin_unlock(&server->req_lock);
-		wake_up(&server->request_q);
-		wdata->credits.value = le16_to_cpu(shdr->CreditCharge);
+
 		flags |= CIFS_HAS_CREDITS;
 	}