On Thu, 22 Jan 2009 12:05:43 -0600 David Teigland <teigland@xxxxxxxxxx> wrote: > 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(). > Why would we want to make another lock here? Is that just to make sure that if new fields are added later that we deal with them appropriately? -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
