On 16.01.2022 15:44, Vasily Averin wrote: > On 03.01.2022 22:53, J. Bruce Fields wrote: >> On Wed, Dec 29, 2021 at 11:24:43AM +0300, Vasily Averin wrote: >>> nfsd and lockd use F_SETLK cmd with the FL_SLEEP flag set to request >>> asynchronous processing of blocking locks. >>> >>> Currently nfs4 use locks_lock_inode_wait() function which is blocked >>> for such requests. To handle them correctly FL_SLEEP flag should be >>> temporarily reset before executing the locks_lock_inode_wait() function. >>> >>> Additionally block flag is forced to set, to translate blocking lock to >>> remote nfs server, expecting it supports async processing of the blocking >>> locks too. >> >> But this on its own isn't enough for the client to support asynchronous >> blocking locks, right? Don't we also need the logic that calls knfsd's >> lm_notify when it gets a CB_NOTIFY_LOCK from the server? > > No, I think this should be enough. > We are here a nfs client, > we can get F_SETLK with FL_SLEEP from nfsd only (i.e. in re-export case) > we need to avoid blocking if lock is already taken, > so we need to call locks_lock_inode_wait without FL_SLEEP, > then we submit _sleeping_ request to NFS server (i.e. set )data->arg.block = 1) > and waiting for reply from server. > > Here we rely that server will NOT block on such request too, so our reply wel not be blocked too. Now I think this assumption is wrong. We cannot guarantee that NFS server will process our sleeping request asynchronously. yes, new version of knfsd will do it. however there are a lot of other NFS servers, that can process this request synchronously and wait till locked fail will be unlocked. All we can do here is just drop FL_SLEEP and handle incoming async request (F_SETLK with FL_SLEEP) like a regular non-blocking F_SETLK. Thank you, Vasily Averin > Under "block" I mean that handler can sleep or process request for a very long time > but it will NOT BE BLOCKED if lock is taken already, it WILL NOT WAIT when lock will be released, > it just return some error in this case. > > I think it is correct. > Do you think I am wrong or maybe I missed something? > > Thank you, > Vasily Averin > > However I noticed now that past is incorrect, > temporally dropped FL_SLEEP should be restored back in _nfs4_proc_setlk before _nfs4_do_setlk() call. > I'll fix it in next version of this patch-set. > >>> https://bugzilla.kernel.org/show_bug.cgi?id=215383 >>> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> >>> --- >>> fs/nfs/nfs4proc.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c >>> index ee3bc79f6ca3..9b1380c4223c 100644 >>> --- a/fs/nfs/nfs4proc.c >>> +++ b/fs/nfs/nfs4proc.c >>> @@ -7094,7 +7094,7 @@ static int _nfs4_do_setlk(struct nfs4_state *state, int cmd, struct file_lock *f >>> recovery_type == NFS_LOCK_NEW ? GFP_KERNEL : GFP_NOFS); >>> if (data == NULL) >>> return -ENOMEM; >>> - if (IS_SETLKW(cmd)) >>> + if (IS_SETLKW(cmd) || (fl->fl_flags & FL_SLEEP)) >>> data->arg.block = 1; >>> nfs4_init_sequence(&data->arg.seq_args, &data->res.seq_res, 1, >>> recovery_type > NFS_LOCK_NEW); >>> @@ -7200,6 +7200,9 @@ static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock >>> int status; >>> >>> request->fl_flags |= FL_ACCESS; >>> + if (((fl_flags & FL_SLEEP_POSIX) == FL_SLEEP_POSIX) && IS_SETLK(cmd)) >>> + request->fl_flags &= ~FL_SLEEP; >>> + >>> status = locks_lock_inode_wait(state->inode, request); >>> if (status < 0) >>> goto out; >>> -- >>> 2.25.1 >
