Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:45854 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754473AbdJIP6G (ORCPT ); Mon, 9 Oct 2017 11:58:06 -0400 Date: Mon, 9 Oct 2017 11:58:05 -0400 From: "J. Bruce Fields" To: Olga Kornievskaia Cc: Olga Kornievskaia , linux-nfs Subject: Re: [PATCH v4 08/10] NFSD handle OFFLOAD_CANCEL op Message-ID: <20171009155804.GA1586@parsley.fieldses.org> References: <20170928172945.50780-1-kolga@netapp.com> <20170928172945.50780-9-kolga@netapp.com> <20170928183846.GG10182@parsley.fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, Oct 09, 2017 at 10:53:13AM -0400, Olga Kornievskaia wrote: > On Thu, Sep 28, 2017 at 2:38 PM, J. Bruce Fields wrote: > > On Thu, Sep 28, 2017 at 01:29:43PM -0400, Olga Kornievskaia wrote: > >> Upon receiving OFFLOAD_CANCEL search the list of copy stateids, > >> if found mark it cancelled. If copy has more interations to > >> call vfs_copy_file_range, it'll stop it. Server won't be sending > >> CB_OFFLOAD to the client since it received a cancel. > >> > >> Signed-off-by: Olga Kornievskaia > >> --- > >> fs/nfsd/nfs4proc.c | 26 ++++++++++++++++++++++++-- > >> fs/nfsd/nfs4state.c | 16 ++++++++++++++++ > >> fs/nfsd/state.h | 4 ++++ > >> 3 files changed, 44 insertions(+), 2 deletions(-) > >> > >> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > >> index 3cddebb..f4f3d93 100644 > >> --- a/fs/nfsd/nfs4proc.c > >> +++ b/fs/nfsd/nfs4proc.c > >> @@ -1139,6 +1139,7 @@ static int _nfsd_copy_file_range(struct nfsd4_copy *copy) > >> size_t bytes_to_copy; > >> u64 src_pos = copy->cp_src_pos; > >> u64 dst_pos = copy->cp_dst_pos; > >> + bool cancelled = false; > >> > >> do { > >> bytes_to_copy = min_t(u64, bytes_total, MAX_RW_COUNT); > >> @@ -1150,7 +1151,12 @@ static int _nfsd_copy_file_range(struct nfsd4_copy *copy) > >> copy->cp_res.wr_bytes_written += bytes_copied; > >> src_pos += bytes_copied; > >> dst_pos += bytes_copied; > >> - } while (bytes_total > 0 && !copy->cp_synchronous); > >> + if (!copy->cp_synchronous) { > >> + spin_lock(©->cps->cp_lock); > >> + cancelled = copy->cps->cp_cancelled; > >> + spin_unlock(©->cps->cp_lock); > >> + } > >> + } while (bytes_total > 0 && !copy->cp_synchronous && !cancelled); > >> return bytes_copied; > > > > I'd rather we sent a signal, and then we won't need this > > logic--vfs_copy_range() will just return EINTR or something. > > Hi Bruce, > > Now that I've implemented using the kthread instead of the workqueue, > I don't see that it can provide any better guarantee than the work > queue. vfs_copy_range() is not interrupted in the middle and returning > the EINTR. The function that runs the kthread, it has to at some point > call signalled()/kthread_should_stop() function to see if it was > signaled and use it to 'stop working instead of continuing on'. > > If I were to remove the loop and check (if signaled() || > kthread_should_stop()) before and after calling the > vfs_copy_file_range(), the copy will either not start if the > OFFLOAD_CANCEL was received before copy started or the whole copy > would happen. > > Even with the loop, I'd be checking after every call for > vfs_copy_file_range() just like it was in the current version with the > workqueue. > > Please advise if you still want the kthread-based implementation or > keep the workqueue. That's interesting. To me that sounds like a bug somewhere under vfs_copy_file_range(). splice_direct_to_actor() can do long-running copies, so it should be interruptible, shouldn't it? --b. > > > That will help us get rid of the 4MB-at-a-time loop. And will mean we > > don't need to wait for the next 4MB copy to finish before stopping the > > loop. Normally I wouldn't expect that to take too long, but it might. > > And a situation where a cancel is sent is a situation where we're > > probably more likely to have some problem slowing down the copy. > > > > Also: don't we want OFFLOAD_CANCEL to wait until the cancel has actually > > taken effect before returning? > > > > I can't see any language in the spec to that affect, but it would seem > > surprising to me if I got back a succesful response to OFFLOAD_CANCEL > > and then noticed that the target file was still changing. > > > > --b. > > > >> } > >> > >> @@ -1198,6 +1204,10 @@ static void nfsd4_do_async_copy(struct work_struct *work) > >> struct nfsd4_copy *cb_copy; > >> > >> copy->nfserr = nfsd4_do_copy(copy, 0); > >> + > >> + if (copy->cps->cp_cancelled) > >> + goto out; > >> + > >> cb_copy = kzalloc(sizeof(struct nfsd4_copy), GFP_KERNEL); > >> if (!cb_copy) > >> goto out; > >> @@ -1269,7 +1279,19 @@ static void nfsd4_do_async_copy(struct work_struct *work) > >> struct nfsd4_compound_state *cstate, > >> union nfsd4_op_u *u) > >> { > >> - return 0; > >> + struct nfsd4_offload_status *os = &u->offload_status; > >> + struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id); > >> + __be32 status; > >> + struct nfs4_cp_state *state = NULL; > >> + > >> + status = find_cp_state(nn, &os->stateid, &state); > >> + if (state) { > >> + spin_lock(&state->cp_lock); > >> + state->cp_cancelled = true; > >> + spin_unlock(&state->cp_lock); > >> + } > >> + > >> + return status; > >> } > >> > >> static __be32 > >> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > >> index be59baf..97ab3f8 100644 > >> --- a/fs/nfsd/nfs4state.c > >> +++ b/fs/nfsd/nfs4state.c > >> @@ -752,6 +752,22 @@ static void nfs4_free_deleg(struct nfs4_stid *stid) > >> atomic_long_dec(&num_delegations); > >> } > >> > >> +__be32 find_cp_state(struct nfsd_net *nn, stateid_t *st, > >> + struct nfs4_cp_state **cps) > >> +{ > >> + struct nfs4_cp_state *state = NULL; > >> + > >> + if (st->si_opaque.so_clid.cl_id != nn->s2s_cp_cl_id) > >> + return nfserr_bad_stateid; > >> + spin_lock(&nn->s2s_cp_lock); > >> + state = idr_find(&nn->s2s_cp_stateids, st->si_opaque.so_id); > >> + spin_unlock(&nn->s2s_cp_lock); > >> + if (!state) > >> + return nfserr_bad_stateid; > >> + *cps = state; > >> + return 0; > >> +} > >> + > >> /* > >> * When we recall a delegation, we should be careful not to hand it > >> * out again straight away. > >> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > >> index 8724955..7a070d5 100644 > >> --- a/fs/nfsd/state.h > >> +++ b/fs/nfsd/state.h > >> @@ -111,6 +111,8 @@ struct nfs4_cp_state { > >> stateid_t cp_stateid; > >> struct list_head cp_list; /* per parent nfs4_stid */ > >> struct nfs4_stid *cp_p_stid; /* pointer to parent */ > >> + bool cp_cancelled; /* copy cancelled */ > >> + spinlock_t cp_lock; > >> }; > >> > >> /* > >> @@ -647,6 +649,8 @@ extern struct nfs4_client_reclaim *nfs4_client_to_reclaim(const char *name, > >> extern bool nfs4_has_reclaimed_state(const char *name, struct nfsd_net *nn); > >> extern int nfsd4_create_copy_queue(void); > >> extern void nfsd4_destroy_copy_queue(void); > >> +extern __be32 find_cp_state(struct nfsd_net *nn, stateid_t *st, > >> + struct nfs4_cp_state **cps); > >> > >> struct nfs4_file *find_file(struct knfsd_fh *fh); > >> void put_nfs4_file(struct nfs4_file *fi); > >> -- > >> 1.8.3.1 > >> > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html