On Tue, Sep 13, 2011 at 11:49:14AM +0100, Alex Bligh wrote: > > > --On 13 September 2011 12:36:07 +0200 Wouter Verhelst <[email protected]> wrote: > > > I should probably make another release some time soon, there are quite a > > number of new features waiting; > > Not on your list: my FUA/FLUSH stuff is in, but I must admit to having > lost track of where the ioctl() discussion got to. As there is apparently > now agreement on the ioctl(), it would be really nice if we could either > keep the current one or replace it in this version with one Paul et > al are happy with. > > For instance, Paul's suggestion on setting 'rotational' using /proc > instead is definitely better than the way nbd-client does it at the > moment. > > > - Make NBD_CMD_TRIM cause nbd-server to call fallocate() with > > FALLOC_FL_PUNCH_HOLE. > > We need to be a bit careful on these. IIRC (someone please check!) > on Linux fallocate() is an extended call that supports various stuff, > whereas posix_fallocate() is the normal POSIX call, and that doesn't > support PUNCH_HOLE. On non-Linux systems, fallocate() is the normal > POSIX call.
Oh, sure. Any fallocate() call is going into #ifdef HAVE_FALLOC_PH, which checks for existence of the FALLOCATE_FL_PUNCH_HOLE flag. If that doesn't exist, then the current code will be executed. > Secondly (a) PUNCH_HOLE is not supported on all kernel versions, > and (b) it isn't necessarily supported on all filing systems and > (c) on some filing systems it is buggy. Well, I'm not sure I want to check whether the file system is buggy. Also, if you say "trim = false" (or just don't say "trim = true") in your configuration, then we don't announce understanding of NBD_CMD_TRIM, and we don't get to deal with the issue. > I /think/ we can just see if FALLOC_FL_PUNCH_HOLE is defined, > and if so, make the call, and ignore the error condition. That > way if compiled on box X and run on box Y it will still be OK. > However, I think we ought to have a config option to turn it off. Definitely. And it's already there :-) -- The volume of a pizza of thickness a and radius z can be described by the following formula: pi zz a ------------------------------------------------------------------------------ BlackBerry® DevCon Americas, Oct. 18-20, San Francisco, CA Learn about the latest advances in developing for the BlackBerry® mobile platform with sessions, labs & more. See new tools and technologies. Register for BlackBerry® DevCon today! http://p.sf.net/sfu/rim-devcon-copy1 _______________________________________________ Nbd-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/nbd-general
