On Fri, March 11, 2011 12:55, Arnd Bergmann wrote: > On Friday 11 March 2011, Indan Zupancic wrote: >> > http://marc.info/?l=linux-fsdevel&m=127970513829285&w=2 >> >> The patch there seems much more reasonable than introducing a whole >> new systemcall just for 20 lines of kernel code. New system calls are >> added too easily nowadays. > > The only problem with adding new system calls is that we are stuck > with the interface until the end of time, so we must be sure not > to get it wrong. The same thing is true for any other interface > such as ioctl or extensions to existing system calls. People usually > get away with adding new ioctls more easily because it is less > obvious when they are added. Agreed. I'm not sure this feature is important enough to add. I can't really think of a regular use case where this would be useful, generally it's transparent on which mount files are. Add symlinks, and you give users a lot of rope. Any user has to make sure that all the files they want to sync are on the same file system. About the arguments against sync(2): > - On machines with many mounts, it is not at all uncommon for some of > them to hang (e.g. unresponsive NFS server). sync(2) will get stuck on > those and may never get to the one you do care about (e.g., /). It would be better to fix NFS, or mount it with the fsc option (assuming a sync will write to the local cache instead of hanging forever then). > - Some applications write lots of data to the file system and then > want to make sure it is flushed to disk. Calling fsync(2) on each > file introduces unnecessary ordering constraints that result in a large > amount of sub-optimal writeback/flush/commit behavior by the file > system. You can use sync_file_range() on those files to schedule the writes and then do the fsync(2) as usual (both on files and dirs). If there still is a good reason to implement this, please don't add it as a new system call, but add it to sync_file_range(), as that seems the best place for odd file synchronisation operations. Greetings, Indan -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
