On Sat, 2008-06-21 at 20:05 +0100, Phil Endecott wrote: > Dear Experts, > > I have a program which uses an mmap()ed read-mostly data file. When > not using NFS, each instance of the program can use inotify to detect > when other instances have made changes to the data file. Since inotify > doesn't work with NFS, I have now implemented a scheme using network > broadcasts to announce changes. At present it works like this: > > All instances of the program mmap(MAP_SHARED) the data file. > > One instance stores some new data at the end of the file and calls > msync(MS_SYNC) on the affected pages. It then "atomically commits" the > new data by write()ing a new header at the start of the file with an > "end of data" field advanced to include the new data. It then calls > fdatasync(). Then it transmits a broadcast packet. > > The other instance(s) of the program receive the broadcast packet and > read() the header at the start of the file. My hope was that they > would see the new value, but they don't; they continue to see the old value. open(O_DIRECT) is your friend. Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
