CIFS: Fix wsize usage in writepages

If a server change maximum buffer size for write (wsize) requests
on reconnect we can fail on repeating with a big size buffer on
-EAGAIN error in writepages. Fix this by checking wsize all the
time before repeating request in writepages.
Reviewed-by: NShirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: NPavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: NSteve French <smfrench@gmail.com>

fs/cifs/file.c

@@ -2009,19 +2009,17 @@ wdata_send_pages(struct cifs_writedata *wdata, unsigned int nr_pages,
 			(loff_t)PAGE_CACHE_SIZE);
 	wdata->bytes = ((nr_pages - 1) * PAGE_CACHE_SIZE) + wdata->tailsz;
 
-	do {
 	if (wdata->cfile != NULL)
 		cifsFileInfo_put(wdata->cfile);
 	wdata->cfile = find_writable_file(CIFS_I(mapping->host), false);
 	if (!wdata->cfile) {
 		cifs_dbg(VFS, "No writable handles for inode\n");
 		rc = -EBADF;
-			break;
-		}
+	} else {
 		wdata->pid = wdata->cfile->pid;
 		server = tlink_tcon(wdata->cfile->tlink)->ses->server;
 		rc = server->ops->async_writev(wdata, cifs_writedata_release);
-	} while (wbc->sync_mode == WB_SYNC_ALL && rc == -EAGAIN);
+	}
 
 	for (i = 0; i < nr_pages; ++i)
 		unlock_page(wdata->pages[i]);
@@ -2058,7 +2056,7 @@ static int cifs_writepages(struct address_space *mapping,
 retry:
 	while (!done && index <= end) {
 		unsigned int i, nr_pages, found_pages;
-		pgoff_t next = 0, tofind;
+		pgoff_t next = 0, tofind, saved_index = index;
 
 		tofind = min((cifs_sb->wsize / PAGE_CACHE_SIZE) - 1,
 				end - index) + 1;
@@ -2102,6 +2100,11 @@ static int cifs_writepages(struct address_space *mapping,
 		}
 		kref_put(&wdata->refcount, cifs_writedata_release);
 
+		if (wbc->sync_mode == WB_SYNC_ALL && rc == -EAGAIN) {
+			index = saved_index;
+			continue;
+		}
+
 		wbc->nr_to_write -= nr_pages;
 		if (wbc->nr_to_write <= 0)
 			done = true;