[linux-cifs-client] Re: best strategy for preventing unnecessary oplock breaks on doubly open files

[tridge at samba.org]

Jeremy,

 > What about adding a reaquire oplock call into the UNIX extentions ?

It might be better just to support the existing FSTCL ntiocl calls for
oplocks. These are supported by windows on local filesystems, but not
on remote filesystems. We can easily support them on remote
filesystems too. They are:

#define FSCTL_REQUEST_OPLOCK_LEVEL_1 (FSCTL_FILESYSTEM | (0<<2))
#define FSCTL_REQUEST_OPLOCK_LEVEL_2 (FSCTL_FILESYSTEM | (1<<2))
#define FSCTL_REQUEST_BATCH_OPLOCK   (FSCTL_FILESYSTEM | (2<<2))

w2k3 returns NT_STATUS_NOT_SUPPORTED on these, but at least their
existance on local filesystems means that the numbers are reserved,
and if windows ever does support this then its a pretty good bet they
will use these same opcodes.

Cheers, Tridge