On Wed, Jan 21, 2009 at 06:42:39PM -0500, J. Bruce Fields wrote: > On Wed, Jan 21, 2009 at 11:34:50AM -0500, Jeff Layton wrote: > > dlm_posix_get fills out the relevant fields in the file_lock before > > returning when there is a lock conflict, but doesn't clean out any of > > the other fields in the file_lock. > > > > When nfsd does a NFSv4 lockt call, it sets the fl_lmops to > > nfsd_posix_mng_ops before calling the lower fs. When the lock comes back > > after testing a lock on GFS2, it still has that field set. This confuses > > nfsd into thinking that the file_lock is a nfsd4 lock. > > I think of the lock system as supporting two types of objects, both > stored in "struct lock"'s: > > - Heavyweight locks: these have callbacks set and the filesystem > or lock manager could in theory have some private data > associated with them, so it's important that the appropriate > callbacks be called when they're released or copied. These > are what are actually passed to posix_lock_file() and kept on > the inode lock lists. > - Lightweight locks: just start, end, pid, flags, and type, with > everything zeroed out and/or ignored. > > I don't see any reason why the lock passed into dlm_posix_get() needs to > be a heavyweight lock. In any case, if it were, then dlm_posix_get() > would need to release the passed-in-lock before initializing the new one > that it's returning. It seems the nfs code is mixing those two types up a bit. Regardless, the rationale I see in Jeff's dlm patch is to make the two different locking paths equivalent: Without cfs/dlm, nfsd4_lockt -> nfsd_test_lock -> vfs_test_lock -> posix_test_lock With cfs/dlm, nfsd4_lockt -> nfsd_test_lock -> vfs_test_lock -> (cfs) -> dlm_posix_get When there's a conflict, dlm_posix_get() and posix_test_lock() should do the same/equivalent things to the fl they are given. posix_test_lock() does __locks_copy_lock() on the fl and then sets the pid. dlm_posix_get() isn't using __locks_copy_lock() because it doesn't have a conflicting file_lock to copy from. Jeff's patch does nearly the same thing using locks_init_lock() plus the existing assignments. But, I think the best solution may be for dlm_posix_get() to set up a new lightweight file_lock with the values we need, and then call __locks_copy_lock() with it, just like posix_test_lock(). Dave -- 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
