On Tue, Dec 2, 2008 at 2:20 PM, Steve French <smfrench@xxxxxxxxx> wrote: > On Tue, Dec 2, 2008 at 2:06 PM, Jamie Lokier <jamie@xxxxxxxxxxxxx> wrote: >> Andreas Dilger wrote: >> >>> I can't see any reason for O_DENYREAD or O_DENYWRITE that can't be met >>> with existing file locking to maintain coherency if that is really needed. > > I don't see how O_DENYREAD or more importantly, O_DENYWRITE can help. A typo in my earlier post ... I meant ... I don't think (just) posix locking (without also using O_DENYREAD) can be sufficient. > If client A (Linux/Wine) does an open O_DENYWRITE, and we don't send > the O_DENYWRITE on open, Samba (or Windows or NetApp or random NAS > appliance etc.) > will allow the open even if another Windows client is writing to the > file. The Linux/Wine > subsystem could try to do a posix byte range lock from byte 0 to end > of file and that > would get mapped by the cifs client to a mandatory lock, but it > doesn't help the case > where another Windows client already has the file open for write, and you expect > the open from your client to fail in that case. > >> Is there any reason why Wine cannot take an advisory lock _every_ time >> it opens a file? That would give Windows apps the behaviour they >> expect, including across the network, without DOSing unix apps. >> >>> As for O_DENYDELETE - wouldn't that be irrelevant if the WINE code keeps >>> an open file reference? The data would still be accessible until WINE >>> exits, and it wouldn't be a DOS. >> >> Windows apps do expect a file can't disappear while it's open. This >> is one way to detect if an app is running, and this particular >> behaviour goes back to the oldest versions of Windows. >> >> Inside a single WINE instance or on a single host, your suggestion >> works, but what about Windows apps on different hosts over a network share? >> >> The bit I find interesting is that other CIFS clients are said to >> implement these flags. If that means real unixes, maybe they've >> worked out a sensible way to handle them? > > I thought that MacOS uses these flags (not just Windows, and of course > older clients too OS/2, DOS etc.). > > > -- > Thanks, > > Steve > -- Thanks, Steve -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
