On Mar 8 08:15, Jeffrey Altman via Cygwin wrote: > On 3/8/2024 7:52 AM, Thomas Wolff via Cygwin wrote: > > Am 08.03.2024 um 11:37 schrieb Corinna Vinschen via Cygwin: > > > Yesterday I stumbled over a certain NtCreateFile flag: > > > > > > FILE_OPEN_NO_RECALL (0x00400000) > > > > > > Instructs any filters that perform offline storage or > > > virtualization > > > to not recall the contents of the file as a result of this open. > > > > > > MS-CIFS described it like this: > > > > > > FILE_OPEN_NO_RECALL > > > 0x00400000 > > > > > > In a hierarchical storage management environment, this option > > > requests that the file SHOULD NOT be recalled from tertiary storage > > > such as tape. A file recall can take up to several minutes in a > > > hierarchical storage management environment. The clients can > > > specify > > > this option to avoid such delays. > > > > > > This sounds like we could simply add this flag to all NtOpenFile > > > used for path conversion or stat-like calls, without having to care > > > for any file attributes specificially. > > > > > > Does that make sense? > > Sounds good, without even studying the other details... > > I speculate some more handling would still be needed to avoid executable > > detection via magic tags. > > > Agreed. FILE_OPEN_NO_RECALL has been defined for at least a decade but was > not documented by Microsoft relatively recently.
Thanks for the feedback, guys. > Another suggestion would be to try opening the file with > FILE_READ_ATTRIBUTES instead of GENERIC_READ if the file data is not > required. See > > https://github.com/microsoft/BuildXL/commit/4fb8e7ce07d243ccd95de0d66da551538a794493 Cygwin uses the minimum of required permissions in NtCreateFile/ NtOpenFile calls anyway. I'm just running a test cygwin DLL locally with a lot of added FILE_OPEN_NO_RECALL bits and a couple of added attribute checks for being offline to allow skipping some code. I think I'll push this change in a bit so we get a test release out so people using OneDrive can test. Thanks, Corinna -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
