On Sun, Aug 15, 2010 at 05:06:58PM +0200, Florian Weimer wrote: > It seems that it might be useful to have a locally shared, globally > exclusive file lock. "Local" is defined as "when the file is mapped > shared, memory accesses follow the architecture memory model across > threads and processes, and shared POSIX mutexes work". This could be > used to make the new WAL code in SQLite 3.7 more foolproof, but there > are other applications which would benefit as well. This sounds like you're trying to fix a problem with NFS. I think there are network filesystems which practice mmap coherency. We could define a sideband protocol for NFS that would allow NFS to act the same way. > It seems to me that this would not need changes to network file > systems because you can implement it by acquring a traditional > fcntl()-style exclusive lock on the network side, without creating a > corresponding local lock. fcntl locks are advisory ... I think you actually want leases / oplocks. More than that, you probably want range oplocks rather than file scope oplocks. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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
