Windows 10 (1803 and higher) support and use SMB_FILE_NORMALIZED_NAME_INFORMATION calls over the network. As a fallback (in case the server don't support it) the client traverses all path components, which is very expensive. Implementing SMB_FILE_NORMALIZED_NAME_INFORMATION is very cheap for us as the open already went through unix_convert() and we have the information the client is asking for.
Created attachment 15115 [details] git-am fix for 4.10.next, 4.9.next Cherry-picked from master.
Pushed to autobuild-v4-{10,9}-test.
(In reply to Karolin Seeger from comment #2) Pushed to both branches. Closing out bug report. Thanks!