On Fri, Jul 10, 2020 at 10:47:22AM +0200, Michal Privoznik wrote:
On 7/9/20 6:30 PM, Andrea Bolognani wrote:On Thu, 2020-07-09 at 13:44 +0200, Martin Kletzander wrote:On Thu, Jul 09, 2020 at 12:50:38PM +0200, Andrea Bolognani wrote:it seems to me that this change entirely flipped the semantics of the lock.Yep, you're right. When you have a lock that has boolean as a parameter I think the boolean should indicate whether the lock is writable, but maybe the proper and most readable solution would be virFileFlockShareable() and virFileFlockExclusive() to avoid any misconception in the future[2]. Given the fact that there are no (and most probably won't be) any other users of flock(2) and given the fact that resctrl is also pretty niche feature, I don't have any preference. Also I feel like after some time I'm a little bit rusty with C and the libvirt codebase (and most importantly the reasoning and decisions) has changed a bit, so I'll leave the decision on how to deal with that on someone else. I'm happy to provide the patches when clear decision is made.Either virFileFlockExclusive(fd) virFileFlockShared(fd) or virFileFlock(fd, VIR_FILE_FLOCK_EXCLUSIVE) virFileFlock(fd, VIR_FILE_FLOCK_SHARED) would work. I like the latter better because it's closer to the original flock(), which it ultimately acts as a very thin wrapper around of. I'm actually unclear why we'd have the last argument in the first place: personally I'd just use virFileFlock(fd, VIR_FILE_FLOCK_UNLOCK) and keep things as unambiguous as they can be. This is all bikeshedding, of course: what actually matters is making that lock exclusive once again :)Just realized that for exclusive (aka write) lock, the FD must be opened for writing (working on patches for the following report [1] and been experimenting a bit and that's what I'm seeing).
Good point, but luckily not related to flock(2).
1: https://www.redhat.com/archives/libvir-list/2020-July/msg00451.html Michal
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