CIFS: Use multicredits for SMB 2.1/3 writes

If we negotiate SMB 2.1 and higher version of the protocol and
a server supports large write buffer size, we need to consume 1
credit per 65536 bytes. So, we need to know how many credits
we have and obtain the required number of them before constructing
a writedata structure in writepages and iovec write.

Reviewed-by: Shirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/file.c

@@ -1670,8 +1670,8 @@ cifs_write(struct cifsFileInfo *open_file, __u32 pid, const char *write_data,
 					break;
 			}
 
-			len = min((size_t)cifs_sb->wsize,
-				  write_size - total_written);
+			len = min(server->ops->wp_retry_size(dentry->d_inode),
+				  (unsigned int)write_size - total_written);
 			/* iov[0] is reserved for smb header */
 			iov[1].iov_base = (char *)write_data + total_written;
 			iov[1].iov_len = len;
@@ -2031,6 +2031,7 @@ static int cifs_writepages(struct address_space *mapping,
 			   struct writeback_control *wbc)
 {
 	struct cifs_sb_info *cifs_sb = CIFS_SB(mapping->host->i_sb);
+	struct TCP_Server_Info *server;
 	bool done = false, scanned = false, range_whole = false;
 	pgoff_t end, index;
 	struct cifs_writedata *wdata;
@@ -2053,23 +2054,30 @@ static int cifs_writepages(struct address_space *mapping,
 			range_whole = true;
 		scanned = true;
 	}
+	server = cifs_sb_master_tcon(cifs_sb)->ses->server;
 retry:
 	while (!done && index <= end) {
-		unsigned int i, nr_pages, found_pages;
+		unsigned int i, nr_pages, found_pages, wsize, credits;
 		pgoff_t next = 0, tofind, saved_index = index;
 
-		tofind = min((cifs_sb->wsize / PAGE_CACHE_SIZE) - 1,
-				end - index) + 1;
+		rc = server->ops->wait_mtu_credits(server, cifs_sb->wsize,
+						   &wsize, &credits);
+		if (rc)
+			break;
+
+		tofind = min((wsize / PAGE_CACHE_SIZE) - 1, end - index) + 1;
 
 		wdata = wdata_alloc_and_fillpages(tofind, mapping, end, &index,
 						  &found_pages);
 		if (!wdata) {
 			rc = -ENOMEM;
+			add_credits_and_wake_if(server, credits, 0);
 			break;
 		}
 
 		if (found_pages == 0) {
 			kref_put(&wdata->refcount, cifs_writedata_release);
+			add_credits_and_wake_if(server, credits, 0);
 			break;
 		}
 
@@ -2079,13 +2087,17 @@ retry:
 		/* nothing to write? */
 		if (nr_pages == 0) {
 			kref_put(&wdata->refcount, cifs_writedata_release);
+			add_credits_and_wake_if(server, credits, 0);
 			continue;
 		}
 
+		wdata->credits = credits;
+
 		rc = wdata_send_pages(wdata, nr_pages, mapping, wbc);
 
 		/* send failure -- clean up the mess */
 		if (rc != 0) {
+			add_credits_and_wake_if(server, wdata->credits, 0);
 			for (i = 0; i < nr_pages; ++i) {
 				if (rc == -EAGAIN)
 					redirty_page_for_writepage(wbc,
@@ -2466,17 +2478,26 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 	memcpy(&saved_from, from, sizeof(struct iov_iter));
 
 	do {
-		nr_pages = get_numpages(cifs_sb->wsize, len, &cur_len);
+		unsigned int wsize, credits;
+
+		rc = server->ops->wait_mtu_credits(server, cifs_sb->wsize,
+						   &wsize, &credits);
+		if (rc)
+			break;
+
+		nr_pages = get_numpages(wsize, len, &cur_len);
 		wdata = cifs_writedata_alloc(nr_pages,
 					     cifs_uncached_writev_complete);
 		if (!wdata) {
 			rc = -ENOMEM;
+			add_credits_and_wake_if(server, credits, 0);
 			break;
 		}
 
 		rc = cifs_write_allocate_pages(wdata->pages, nr_pages);
 		if (rc) {
 			kfree(wdata);
+			add_credits_and_wake_if(server, credits, 0);
 			break;
 		}
 
@@ -2486,6 +2507,7 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 			for (i = 0; i < nr_pages; i++)
 				put_page(wdata->pages[i]);
 			kfree(wdata);
+			add_credits_and_wake_if(server, credits, 0);
 			break;
 		}
 
@@ -2504,12 +2526,14 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 		wdata->bytes = cur_len;
 		wdata->pagesz = PAGE_SIZE;
 		wdata->tailsz = cur_len - ((nr_pages - 1) * PAGE_SIZE);
+		wdata->credits = credits;
 
 		if (!wdata->cfile->invalidHandle ||
 		    !cifs_reopen_file(wdata->cfile, false))
 			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,
 				 cifs_uncached_writedata_release);
 			if (rc == -EAGAIN) {