From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C9F061AA1E6; Mon, 11 Nov 2024 18:27:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731349661; cv=none; b=XlSnmM0quaN6KSWciYcWbphszi4BYM/d6CuVEeEl33kYYjYSR1bh0V4z5n2nJcwGS9OM3ZR/eatWdhoJoREj0Aoylx/fAxAHFgBYaiBjwco6LqN6QfxIykf1FKihXZFrYPJaIdY4vhqN+cSy2J4c3SvBLpzTjs6ebr+FosIMK28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731349661; c=relaxed/simple; bh=Fu/nUhJ9Zcv34OFI0EADTB3J2CuN567rAgcM3/bq3+E=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=BwqVvtngb6C3Q/VtrHSVIF1NQytrAreNREyvC4nJxm0wgQftufgfEblxr0ngZJSWfnYDdoPccnVUpVTAnP94F/GotKkXVJg/UnYBr1/O7ysYKzzgDqTG63yirYMIYB90h32xEfM2GDOFynCJB5B9Bqqel8fNNXvSZ5gt8Lp/wT8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FaJWfIza; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FaJWfIza" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A06E4C4CECF; Mon, 11 Nov 2024 18:27:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1731349661; bh=Fu/nUhJ9Zcv34OFI0EADTB3J2CuN567rAgcM3/bq3+E=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=FaJWfIzaVlMuLvyfzCaYxwo0+KwgHVaPwnnjapyPgTQuM2s+gYSpxZLxxLLhBcyfi e1Q7jOPjmJgR8BF5t0luGdsHFw+Wl2a44CaXI6kbNYY8VdM2T3JhlB+u5RmopelNMt nO4FgRwDtCMcs8EiTyhaKclN4sKRK+SpiA7WF+cwAv52LJsTCP+I6ba01B/2oSdOSR VZm7vb+f5eKG3J2yEm/MCP5EjgX8J3toWrSsQnNWEmPom50pOiev+xqxBL8ZFAoNS1 tU/v4XWzdxeT6/2TpNFac84Zz7CiIpsWXH9QuhYiyFMmvF76bJDJe4hhf0tAeY7Zz7 MJStAlzbeC52A== Message-ID: <14e6f6af974c5c17884c418560f385d051d7bdf7.camel@kernel.org> Subject: Re: [PATCH v4] nfsd: allow for up to 32 callback session slots From: Jeff Layton To: Olga Kornievskaia Cc: Chuck Lever , Neil Brown , Dai Ngo , Tom Talpey , Olga Kornievskaia , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 11 Nov 2024 13:27:39 -0500 In-Reply-To: <3c60acaa79ec27ed1ecb8fdc42a2cb75c75c0a25.camel@kernel.org> References: <20241105-bcwide-v4-1-48f52ee0fb0c@kernel.org> <59e803abae0b7441c1440ebd4657e573b1c02dd2.camel@kernel.org> <83b950633c5b7f6949939a4d51581196b5757c07.camel@kernel.org> <3c60acaa79ec27ed1ecb8fdc42a2cb75c75c0a25.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw 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Evolution 3.52.4 (3.52.4-2.fc40) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-11-11 at 13:17 -0500, Jeff Layton wrote: > On Mon, 2024-11-11 at 12:56 -0500, Olga Kornievskaia wrote: > > On Mon, Nov 11, 2024 at 12:40=E2=80=AFPM Jeff Layton wrote: > > >=20 > > > On Mon, 2024-11-11 at 12:17 -0500, Olga Kornievskaia wrote: > > > > On Mon, Nov 11, 2024 at 9:56=E2=80=AFAM Chuck Lever wrote: > > > > >=20 > > > > > On Mon, Nov 11, 2024 at 08:22:07AM -0500, Jeff Layton wrote: > > > > > > On Sun, 2024-11-10 at 21:19 -0500, Olga Kornievskaia wrote: > > > > > > > On Sat, Nov 9, 2024 at 2:26=E2=80=AFPM Jeff Layton wrote: > > > > > > > >=20 > > > > > > > > On Sat, 2024-11-09 at 13:50 -0500, Olga Kornievskaia wrote: > > > > > > > > > On Tue, Nov 5, 2024 at 7:31=E2=80=AFPM Jeff Layton wrote: > > > > > > > > > >=20 > > > > > > > > > > nfsd currently only uses a single slot in the callback = channel, which is > > > > > > > > > > proving to be a bottleneck in some cases. Widen the cal= lback channel to > > > > > > > > > > a max of 32 slots (subject to the client's target_maxre= qs value). > > > > > > > > > >=20 > > > > > > > > > > Change the cb_holds_slot boolean to an integer that tra= cks the current > > > > > > > > > > slot number (with -1 meaning "unassigned"). Move the c= allback slot > > > > > > > > > > tracking info into the session. Add a new u32 that acts= as a bitmap to > > > > > > > > > > track which slots are in use, and a u32 to track the la= test callback > > > > > > > > > > target_slotid that the client reports. To protect the n= ew fields, add > > > > > > > > > > a new per-session spinlock (the se_lock). Fix nfsd41_cb= _get_slot to always > > > > > > > > > > search for the lowest slotid (using ffs()). > > > > > > > > > >=20 > > > > > > > > > > Finally, convert the session->se_cb_seq_nr field into a= n array of > > > > > > > > > > counters and add the necessary handling to ensure that = the seqids get > > > > > > > > > > reset at the appropriate times. > > > > > > > > > >=20 > > > > > > > > > > Signed-off-by: Jeff Layton > > > > > > > > > > Signed-off-by: Chuck Lever > > > > > > > > > > --- > > > > > > > > > > v3 has a bug that Olga hit in testing. This version sho= uld fix the wait > > > > > > > > > > when the slot table is full. Olga, if you're able to te= st this one, it > > > > > > > > > > would be much appreciated. > > > > > > > > > > --- > > > > > > > > > > Changes in v4: > > > > > > > > > > - Fix the wait for a slot in nfsd41_cb_get_slot() > > > > > > > > > > - Link to v3: https://lore.kernel.org/r/20241030-bcwide= -v3-0-c2df49a26c45@kernel.org > > > > > > > > > >=20 > > > > > > > > > > Changes in v3: > > > > > > > > > > - add patch to convert se_flags to single se_dead bool > > > > > > > > > > - fix off-by-one bug in handling of NFSD_BC_SLOT_TABLE_= MAX > > > > > > > > > > - don't reject target highest slot value of 0 > > > > > > > > > > - Link to v2: https://lore.kernel.org/r/20241029-bcwide= -v2-1-e9010b6ef55d@kernel.org > > > > > > > > > >=20 > > > > > > > > > > Changes in v2: > > > > > > > > > > - take cl_lock when fetching fields from session to be = encoded > > > > > > > > > > - use fls() instead of bespoke highest_unset_index() > > > > > > > > > > - rename variables in several functions with more descr= iptive names > > > > > > > > > > - clamp limit of for loop in update_cb_slot_table() > > > > > > > > > > - re-add missing rpc_wake_up_queued_task() call > > > > > > > > > > - fix slotid check in decode_cb_sequence4resok() > > > > > > > > > > - add new per-session spinlock > > > > > > > > > > --- > > > > > > > > > > fs/nfsd/nfs4callback.c | 113 +++++++++++++++++++++++++= +++++++++++------------- > > > > > > > > > > fs/nfsd/nfs4state.c | 11 +++-- > > > > > > > > > > fs/nfsd/state.h | 15 ++++--- > > > > > > > > > > fs/nfsd/trace.h | 2 +- > > > > > > > > > > 4 files changed, 101 insertions(+), 40 deletions(-) > > > > > > > > > >=20 > > > > > > > > > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callb= ack.c > > > > > > > > > > index e38fa834b3d91333acf1425eb14c644e5d5f2601..47a6783= 33907eaa92db305dada503704c34c15b2 100644 > > > > > > > > > > --- a/fs/nfsd/nfs4callback.c > > > > > > > > > > +++ b/fs/nfsd/nfs4callback.c > > > > > > > > > > @@ -406,6 +406,19 @@ encode_cb_getattr4args(struct xdr_= stream *xdr, struct nfs4_cb_compound_hdr *hdr, > > > > > > > > > > hdr->nops++; > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > +static u32 highest_slotid(struct nfsd4_session *ses) > > > > > > > > > > +{ > > > > > > > > > > + u32 idx; > > > > > > > > > > + > > > > > > > > > > + spin_lock(&ses->se_lock); > > > > > > > > > > + idx =3D fls(~ses->se_cb_slot_avail); > > > > > > > > > > + if (idx > 0) > > > > > > > > > > + --idx; > > > > > > > > > > + idx =3D max(idx, ses->se_cb_highest_slot); > > > > > > > > > > + spin_unlock(&ses->se_lock); > > > > > > > > > > + return idx; > > > > > > > > > > +} > > > > > > > > > > + > > > > > > > > > > /* > > > > > > > > > > * CB_SEQUENCE4args > > > > > > > > > > * > > > > > > > > > > @@ -432,15 +445,35 @@ static void encode_cb_sequence4ar= gs(struct xdr_stream *xdr, > > > > > > > > > > encode_sessionid4(xdr, session); > > > > > > > > > >=20 > > > > > > > > > > p =3D xdr_reserve_space(xdr, 4 + 4 + 4 + 4 + 4)= ; > > > > > > > > > > - *p++ =3D cpu_to_be32(session->se_cb_seq_nr); = /* csa_sequenceid */ > > > > > > > > > > - *p++ =3D xdr_zero; /* cs= a_slotid */ > > > > > > > > > > - *p++ =3D xdr_zero; /* cs= a_highest_slotid */ > > > > > > > > > > + *p++ =3D cpu_to_be32(session->se_cb_seq_nr[cb->= cb_held_slot]); /* csa_sequenceid */ > > > > > > > > > > + *p++ =3D cpu_to_be32(cb->cb_held_slot); = /* csa_slotid */ > > > > > > > > > > + *p++ =3D cpu_to_be32(highest_slotid(session)); = /* csa_highest_slotid */ > > > > > > > > > > *p++ =3D xdr_zero; /* cs= a_cachethis */ > > > > > > > > > > xdr_encode_empty_array(p); /* csa_= referring_call_lists */ > > > > > > > > > >=20 > > > > > > > > > > hdr->nops++; > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > +static void update_cb_slot_table(struct nfsd4_session = *ses, u32 target) > > > > > > > > > > +{ > > > > > > > > > > + /* No need to do anything if nothing changed */ > > > > > > > > > > + if (likely(target =3D=3D READ_ONCE(ses->se_cb_h= ighest_slot))) > > > > > > > > > > + return; > > > > > > > > > > + > > > > > > > > > > + spin_lock(&ses->se_lock); > > > > > > > > > > + if (target > ses->se_cb_highest_slot) { > > > > > > > > > > + int i; > > > > > > > > > > + > > > > > > > > > > + target =3D min(target, NFSD_BC_SLOT_TAB= LE_MAX); > > > > > > > > > > + > > > > > > > > > > + /* Growing the slot table. Reset any ne= w sequences to 1 */ > > > > > > > > > > + for (i =3D ses->se_cb_highest_slot + 1;= i <=3D target; ++i) > > > > > > > > > > + ses->se_cb_seq_nr[i] =3D 1; > > > > > > > > > > + } > > > > > > > > > > + ses->se_cb_highest_slot =3D target; > > > > > > > > > > + spin_unlock(&ses->se_lock); > > > > > > > > > > +} > > > > > > > > > > + > > > > > > > > > > /* > > > > > > > > > > * CB_SEQUENCE4resok > > > > > > > > > > * > > > > > > > > > > @@ -468,7 +501,7 @@ static int decode_cb_sequence4resok= (struct xdr_stream *xdr, > > > > > > > > > > struct nfsd4_session *session =3D cb->cb_clp->c= l_cb_session; > > > > > > > > > > int status =3D -ESERVERFAULT; > > > > > > > > > > __be32 *p; > > > > > > > > > > - u32 dummy; > > > > > > > > > > + u32 seqid, slotid, target; > > > > > > > > > >=20 > > > > > > > > > > /* > > > > > > > > > > * If the server returns different values for s= essionID, slotID or > > > > > > > > > > @@ -484,21 +517,22 @@ static int decode_cb_sequence4res= ok(struct xdr_stream *xdr, > > > > > > > > > > } > > > > > > > > > > p +=3D XDR_QUADLEN(NFS4_MAX_SESSIONID_LEN); > > > > > > > > > >=20 > > > > > > > > > > - dummy =3D be32_to_cpup(p++); > > > > > > > > > > - if (dummy !=3D session->se_cb_seq_nr) { > > > > > > > > > > + seqid =3D be32_to_cpup(p++); > > > > > > > > > > + if (seqid !=3D session->se_cb_seq_nr[cb->cb_hel= d_slot]) { > > > > > > > > > > dprintk("NFS: %s Invalid sequence numbe= r\n", __func__); > > > > > > > > > > goto out; > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > - dummy =3D be32_to_cpup(p++); > > > > > > > > > > - if (dummy !=3D 0) { > > > > > > > > > > + slotid =3D be32_to_cpup(p++); > > > > > > > > > > + if (slotid !=3D cb->cb_held_slot) { > > > > > > > > > > dprintk("NFS: %s Invalid slotid\n", __f= unc__); > > > > > > > > > > goto out; > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > - /* > > > > > > > > > > - * FIXME: process highest slotid and target hig= hest slotid > > > > > > > > > > - */ > > > > > > > > > > + p++; // ignore current highest slot value > > > > > > > > > > + > > > > > > > > > > + target =3D be32_to_cpup(p++); > > > > > > > > > > + update_cb_slot_table(session, target); > > > > > > > > > > status =3D 0; > > > > > > > > > > out: > > > > > > > > > > cb->cb_seq_status =3D status; > > > > > > > > > > @@ -1203,6 +1237,22 @@ void nfsd4_change_callback(struc= t nfs4_client *clp, struct nfs4_cb_conn *conn) > > > > > > > > > > spin_unlock(&clp->cl_lock); > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > +static int grab_slot(struct nfsd4_session *ses) > > > > > > > > > > +{ > > > > > > > > > > + int idx; > > > > > > > > > > + > > > > > > > > > > + spin_lock(&ses->se_lock); > > > > > > > > > > + idx =3D ffs(ses->se_cb_slot_avail) - 1; > > > > > > > > > > + if (idx < 0 || idx > ses->se_cb_highest_slot) { > > > > > > > > > > + spin_unlock(&ses->se_lock); > > > > > > > > > > + return -1; > > > > > > > > > > + } > > > > > > > > > > + /* clear the bit for the slot */ > > > > > > > > > > + ses->se_cb_slot_avail &=3D ~BIT(idx); > > > > > > > > > > + spin_unlock(&ses->se_lock); > > > > > > > > > > + return idx; > > > > > > > > > > +} > > > > > > > > > > + > > > > > > > > > > /* > > > > > > > > > > * There's currently a single callback channel slot. > > > > > > > > > > * If the slot is available, then mark it busy. Other= wise, set the > > > > > > > > > > @@ -1211,28 +1261,32 @@ void nfsd4_change_callback(stru= ct nfs4_client *clp, struct nfs4_cb_conn *conn) > > > > > > > > > > static bool nfsd41_cb_get_slot(struct nfsd4_callback *= cb, struct rpc_task *task) > > > > > > > > > > { > > > > > > > > > > struct nfs4_client *clp =3D cb->cb_clp; > > > > > > > > > > + struct nfsd4_session *ses =3D clp->cl_cb_sessio= n; > > > > > > > > > >=20 > > > > > > > > > > - if (!cb->cb_holds_slot && > > > > > > > > > > - test_and_set_bit(0, &clp->cl_cb_slot_busy) = !=3D 0) { > > > > > > > > > > + if (cb->cb_held_slot >=3D 0) > > > > > > > > > > + return true; > > > > > > > > > > + cb->cb_held_slot =3D grab_slot(ses); > > > > > > > > > > + if (cb->cb_held_slot < 0) { > > > > > > > > > > rpc_sleep_on(&clp->cl_cb_waitq, task, N= ULL); > > > > > > > > > > /* Race breaker */ > > > > > > > > > > - if (test_and_set_bit(0, &clp->cl_cb_slo= t_busy) !=3D 0) { > > > > > > > > > > - dprintk("%s slot is busy\n", __= func__); > > > > > > > > > > + cb->cb_held_slot =3D grab_slot(ses); > > > > > > > > > > + if (cb->cb_held_slot < 0) > > > > > > > > > > return false; > > > > > > > > > > - } > > > > > > > > > > rpc_wake_up_queued_task(&clp->cl_cb_wai= tq, task); > > > > > > > > > > } > > > > > > > > > > - cb->cb_holds_slot =3D true; > > > > > > > > > > return true; > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > static void nfsd41_cb_release_slot(struct nfsd4_callba= ck *cb) > > > > > > > > > > { > > > > > > > > > > struct nfs4_client *clp =3D cb->cb_clp; > > > > > > > > > > + struct nfsd4_session *ses =3D clp->cl_cb_sessio= n; > > > > > > > > > >=20 > > > > > > > > > > - if (cb->cb_holds_slot) { > > > > > > > > > > - cb->cb_holds_slot =3D false; > > > > > > > > > > - clear_bit(0, &clp->cl_cb_slot_busy); > > > > > > > > > > + if (cb->cb_held_slot >=3D 0) { > > > > > > > > > > + spin_lock(&ses->se_lock); > > > > > > > > > > + ses->se_cb_slot_avail |=3D BIT(cb->cb_h= eld_slot); > > > > > > > > > > + spin_unlock(&ses->se_lock); > > > > > > > > > > + cb->cb_held_slot =3D -1; > > > > > > > > > > rpc_wake_up_next(&clp->cl_cb_waitq); > > > > > > > > > > } > > > > > > > > > > } > > > > > > > > > > @@ -1249,8 +1303,8 @@ static void nfsd41_destroy_cb(str= uct nfsd4_callback *cb) > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > /* > > > > > > > > > > - * TODO: cb_sequence should support referring call lis= ts, cachethis, multiple > > > > > > > > > > - * slots, and mark callback channel down on communicat= ion errors. > > > > > > > > > > + * TODO: cb_sequence should support referring call lis= ts, cachethis, > > > > > > > > > > + * and mark callback channel down on communication err= ors. > > > > > > > > > > */ > > > > > > > > > > static void nfsd4_cb_prepare(struct rpc_task *task, vo= id *calldata) > > > > > > > > > > { > > > > > > > > > > @@ -1292,7 +1346,7 @@ static bool nfsd4_cb_sequence_don= e(struct rpc_task *task, struct nfsd4_callback > > > > > > > > > > return true; > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > - if (!cb->cb_holds_slot) > > > > > > > > > > + if (cb->cb_held_slot < 0) > > > > > > > > > > goto need_restart; > > > > > > > > > >=20 > > > > > > > > > > /* This is the operation status code for CB_SEQ= UENCE */ > > > > > > > > > > @@ -1306,10 +1360,10 @@ static bool nfsd4_cb_sequence_d= one(struct rpc_task *task, struct nfsd4_callback > > > > > > > > > > * If CB_SEQUENCE returns an error, the= n the state of the slot > > > > > > > > > > * (sequence ID, cached reply) MUST NOT= change. > > > > > > > > > > */ > > > > > > > > > > - ++session->se_cb_seq_nr; > > > > > > > > > > + ++session->se_cb_seq_nr[cb->cb_held_slo= t]; > > > > > > > > > > break; > > > > > > > > > > case -ESERVERFAULT: > > > > > > > > > > - ++session->se_cb_seq_nr; > > > > > > > > > > + ++session->se_cb_seq_nr[cb->cb_held_slo= t]; > > > > > > > > > > nfsd4_mark_cb_fault(cb->cb_clp); > > > > > > > > > > ret =3D false; > > > > > > > > > > break; > > > > > > > > > > @@ -1335,17 +1389,16 @@ static bool nfsd4_cb_sequence_d= one(struct rpc_task *task, struct nfsd4_callback > > > > > > > > > > case -NFS4ERR_BADSLOT: > > > > > > > > > > goto retry_nowait; > > > > > > > > > > case -NFS4ERR_SEQ_MISORDERED: > > > > > > > > > > - if (session->se_cb_seq_nr !=3D 1) { > > > > > > > > > > - session->se_cb_seq_nr =3D 1; > > > > > > > > > > + if (session->se_cb_seq_nr[cb->cb_held_s= lot] !=3D 1) { > > > > > > > > > > + session->se_cb_seq_nr[cb->cb_he= ld_slot] =3D 1; > > > > > > > > > > goto retry_nowait; > > > > > > > > > > } > > > > > > > > > > break; > > > > > > > > > > default: > > > > > > > > > > nfsd4_mark_cb_fault(cb->cb_clp); > > > > > > > > > > } > > > > > > > > > > - nfsd41_cb_release_slot(cb); > > > > > > > > > > - > > > > > > > > > > trace_nfsd_cb_free_slot(task, cb); > > > > > > > > > > + nfsd41_cb_release_slot(cb); > > > > > > > > > >=20 > > > > > > > > > > if (RPC_SIGNALLED(task)) > > > > > > > > > > goto need_restart; > > > > > > > > > > @@ -1565,7 +1618,7 @@ void nfsd4_init_cb(struct nfsd4_c= allback *cb, struct nfs4_client *clp, > > > > > > > > > > INIT_WORK(&cb->cb_work, nfsd4_run_cb_work); > > > > > > > > > > cb->cb_status =3D 0; > > > > > > > > > > cb->cb_need_restart =3D false; > > > > > > > > > > - cb->cb_holds_slot =3D false; > > > > > > > > > > + cb->cb_held_slot =3D -1; > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > /** > > > > > > > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > > > > > > > > > index baf7994131fe1b0a4715174ba943fd2a9882aa12..75557e7= cc9265517f51952563beaa4cfe8adcc3f 100644 > > > > > > > > > > --- a/fs/nfsd/nfs4state.c > > > > > > > > > > +++ b/fs/nfsd/nfs4state.c > > > > > > > > > > @@ -2002,6 +2002,9 @@ static struct nfsd4_session *allo= c_session(struct nfsd4_channel_attrs *fattrs, > > > > > > > > > > } > > > > > > > > > >=20 > > > > > > > > > > memcpy(&new->se_fchannel, fattrs, sizeof(struct= nfsd4_channel_attrs)); > > > > > > > > > > + new->se_cb_slot_avail =3D ~0U; > > > > > > > > > > + new->se_cb_highest_slot =3D battrs->maxreqs - 1= ; > > > > > > > > > > + spin_lock_init(&new->se_lock); > > > > > > > > > > return new; > > > > > > > > > > out_free: > > > > > > > > > > while (i--) > > > > > > > > > > @@ -2132,11 +2135,14 @@ static void init_session(struct= svc_rqst *rqstp, struct nfsd4_session *new, stru > > > > > > > > > >=20 > > > > > > > > > > INIT_LIST_HEAD(&new->se_conns); > > > > > > > > > >=20 > > > > > > > > > > - new->se_cb_seq_nr =3D 1; > > > > > > > > > > + atomic_set(&new->se_ref, 0); > > > > > > > > > > new->se_dead =3D false; > > > > > > > > > > new->se_cb_prog =3D cses->callback_prog; > > > > > > > > > > new->se_cb_sec =3D cses->cb_sec; > > > > > > > > > > - atomic_set(&new->se_ref, 0); > > > > > > > > > > + > > > > > > > > > > + for (idx =3D 0; idx < NFSD_BC_SLOT_TABLE_MAX; += +idx) > > > > > > > > > > + new->se_cb_seq_nr[idx] =3D 1; > > > > > > > > > > + > > > > > > > > > > idx =3D hash_sessionid(&new->se_sessionid); > > > > > > > > > > list_add(&new->se_hash, &nn->sessionid_hashtbl[= idx]); > > > > > > > > > > spin_lock(&clp->cl_lock); > > > > > > > > > > @@ -3159,7 +3165,6 @@ static struct nfs4_client *create= _client(struct xdr_netobj name, > > > > > > > > > > kref_init(&clp->cl_nfsdfs.cl_ref); > > > > > > > > > > nfsd4_init_cb(&clp->cl_cb_null, clp, NULL, NFSP= ROC4_CLNT_CB_NULL); > > > > > > > > > > clp->cl_time =3D ktime_get_boottime_seconds(); > > > > > > > > > > - clear_bit(0, &clp->cl_cb_slot_busy); > > > > > > > > > > copy_verf(clp, verf); > > > > > > > > > > memcpy(&clp->cl_addr, sa, sizeof(struct sockadd= r_storage)); > > > > > > > > > > clp->cl_cb_session =3D NULL; > > > > > > > > > > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > > > > > > > > > > index d22e4f2c9039324a0953a9e15a3c255fb8ee1a44..848d023= cb308f0b69916c4ee34b09075708f0de3 100644 > > > > > > > > > > --- a/fs/nfsd/state.h > > > > > > > > > > +++ b/fs/nfsd/state.h > > > > > > > > > > @@ -71,8 +71,8 @@ struct nfsd4_callback { > > > > > > > > > > struct work_struct cb_work; > > > > > > > > > > int cb_seq_status; > > > > > > > > > > int cb_status; > > > > > > > > > > + int cb_held_slot; > > > > > > > > > > bool cb_need_restart; > > > > > > > > > > - bool cb_holds_slot; > > > > > > > > > > }; > > > > > > > > > >=20 > > > > > > > > > > struct nfsd4_callback_ops { > > > > > > > > > > @@ -307,6 +307,9 @@ struct nfsd4_conn { > > > > > > > > > > unsigned char cn_flags; > > > > > > > > > > }; > > > > > > > > > >=20 > > > > > > > > > > +/* Highest slot index that nfsd implements in NFSv4.1+= backchannel */ > > > > > > > > > > +#define NFSD_BC_SLOT_TABLE_MAX (sizeof(u32) * 8 - 1) > > > > > > > > >=20 > > > > > > > > > Are there some values that are known not to work? I was e= xperimenting > > > > > > > > > with values and set it to 2 and 4 and the kernel oopsed. = I understand > > > > > > > > > it's not a configurable value but it would still be good = to know the > > > > > > > > > expectations... > > > > > > > > >=20 > > > > > > > > > [ 198.625021] Unable to handle kernel paging request at = virtual > > > > > > > > > address dfff800020000000 > > > > > > > > > [ 198.625870] KASAN: probably user-memory-access in rang= e > > > > > > > > > [0x0000000100000000-0x0000000100000007] > > > > > > > > > [ 198.626444] Mem abort info: > > > > > > > > > [ 198.626630] ESR =3D 0x0000000096000005 > > > > > > > > > [ 198.626882] EC =3D 0x25: DABT (current EL), IL =3D 3= 2 bits > > > > > > > > > [ 198.627234] SET =3D 0, FnV =3D 0 > > > > > > > > > [ 198.627441] EA =3D 0, S1PTW =3D 0 > > > > > > > > > [ 198.627627] FSC =3D 0x05: level 1 translation fault > > > > > > > > > [ 198.627859] Data abort info: > > > > > > > > > [ 198.628000] ISV =3D 0, ISS =3D 0x00000005, ISS2 =3D = 0x00000000 > > > > > > > > > [ 198.628272] CM =3D 0, WnR =3D 0, TnD =3D 0, TagAcces= s =3D 0 > > > > > > > > > [ 198.628619] GCS =3D 0, Overlay =3D 0, DirtyBit =3D 0= , Xs =3D 0 > > > > > > > > > [ 198.628967] [dfff800020000000] address between user an= d kernel address ranges > > > > > > > > > [ 198.629438] Internal error: Oops: 0000000096000005 [#1= ] SMP > > > > > > > > > [ 198.629806] Modules linked in: rpcsec_gss_krb5 nfsv4 d= ns_resolver > > > > > > > > > nfs netfs nfnetlink_queue nfnetlink_log nfnetlink bluetoo= th cfg80211 > > > > > > > > > rpcrdma rdma_cm iw_cm ib_cm ib_core nfsd auth_rpcgss nfs_= acl lockd > > > > > > > > > grace isofs uinput snd_seq_dummy snd_hrtimer vsock_loopba= ck > > > > > > > > > vmw_vsock_virtio_transport_common qrtr rfkill vmw_vsock_v= mci_transport > > > > > > > > > vsock sunrpc vfat fat snd_hda_codec_generic snd_hda_intel > > > > > > > > > snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd= _seq uvcvideo > > > > > > > > > videobuf2_vmalloc snd_seq_device videobuf2_memops uvc vid= eobuf2_v4l2 > > > > > > > > > videodev snd_pcm videobuf2_common mc snd_timer snd vmw_vm= ci soundcore > > > > > > > > > xfs libcrc32c vmwgfx drm_ttm_helper ttm nvme drm_kms_help= er > > > > > > > > > crct10dif_ce nvme_core ghash_ce sha2_ce sha256_arm64 sha1= _ce drm > > > > > > > > > nvme_auth sr_mod cdrom e1000e sg fuse > > > > > > > > > [ 198.633799] CPU: 5 UID: 0 PID: 6081 Comm: nfsd Kdump: = loaded Not > > > > > > > > > tainted 6.12.0-rc6+ #47 > > > > > > > > > [ 198.634345] Hardware name: VMware, Inc. VMware20,1/VBS= A, BIOS > > > > > > > > > VMW201.00V.21805430.BA64.2305221830 05/22/2023 > > > > > > > > > [ 198.635014] pstate: 11400005 (nzcV daif +PAN -UAO -TCO= +DIT -SSBS BTYPE=3D--) > > > > > > > > > [ 198.635492] pc : nfsd4_sequence+0x5a0/0x1f60 [nfsd] > > > > > > > > > [ 198.635798] lr : nfsd4_sequence+0x340/0x1f60 [nfsd] > > > > > > > > > [ 198.636065] sp : ffff8000884977e0 > > > > > > > > > [ 198.636234] x29: ffff800088497910 x28: ffff0000b1b3928= 0 x27: ffff0000ab508128 > > > > > > > > > [ 198.636624] x26: ffff0000b1b39298 x25: ffff0000b1b3929= 0 x24: ffff0000a65e1c64 > > > > > > > > > [ 198.637049] x23: 1fffe000212e6804 x22: ffff00010973402= 4 x21: 1ffff00011092f16 > > > > > > > > > [ 198.637472] x20: ffff00010aed8000 x19: ffff00010973400= 0 x18: 1fffe0002de20c8b > > > > > > > > > [ 198.637883] x17: 0100000000000000 x16: 1ffff0000fcef23= 4 x15: 1fffe000212e600f > > > > > > > > > [ 198.638286] x14: ffff80007e779000 x13: ffff80007e7791a= 0 x12: 0000000000000000 > > > > > > > > > [ 198.638697] x11: ffff0000a65e1c38 x10: ffff00010aedaca= 0 x9 : 1fffe000215db594 > > > > > > > > > [ 198.639110] x8 : 1fffe00014cbc387 x7 : ffff0000a65e1c0= 3 x6 : ffff0000a65e1c00 > > > > > > > > > [ 198.639541] x5 : ffff0000a65e1c00 x4 : 000000002000000= 0 x3 : 0000000100000001 > > > > > > > > > [ 198.639962] x2 : ffff000109730060 x1 : 000000000000000= 3 x0 : dfff800000000000 > > > > > > > > > [ 198.640332] Call trace: > > > > > > > > > [ 198.640460] nfsd4_sequence+0x5a0/0x1f60 [nfsd] > > > > > > > > > [ 198.640715] nfsd4_proc_compound+0xb94/0x23b0 [nfsd] > > > > > > > > > [ 198.640997] nfsd_dispatch+0x22c/0x718 [nfsd] > > > > > > > > > [ 198.641260] svc_process_common+0x8e8/0x1968 [sunrpc] > > > > > > > > > [ 198.641566] svc_process+0x3d4/0x7e0 [sunrpc] > > > > > > > > > [ 198.641827] svc_handle_xprt+0x828/0xe10 [sunrpc] > > > > > > > > > [ 198.642108] svc_recv+0x2cc/0x6a8 [sunrpc] > > > > > > > > > [ 198.642346] nfsd+0x270/0x400 [nfsd] > > > > > > > > > [ 198.642562] kthread+0x288/0x310 > > > > > > > > > [ 198.642745] ret_from_fork+0x10/0x20 > > > > > > > > > [ 198.642937] Code: f2fbffe0 f9003be4 f94007e2 52800061 = (38e06880) > > > > > > > > > [ 198.643267] SMP: stopping secondary CPUs > > > > > > > > >=20 > > > > > > > > >=20 > > > > > > > > >=20 > > > > > > > >=20 > > > > > > > >=20 > > > > > > > > Good catch. I think the problem here is that we don't curre= ntly cap the > > > > > > > > initial value of se_cb_highest_slot at NFSD_BC_SLOT_TABLE_M= AX. Does > > > > > > > > this patch prevent the panic? > > > > > > > >=20 > > > > > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > > > > > > > index 3afe56ab9e0a..839be4ba765a 100644 > > > > > > > > --- a/fs/nfsd/nfs4state.c > > > > > > > > +++ b/fs/nfsd/nfs4state.c > > > > > > > > @@ -2011,7 +2011,7 @@ static struct nfsd4_session *alloc_se= ssion(struct nfsd4_channel_attrs *fattrs, > > > > > > > >=20 > > > > > > > > memcpy(&new->se_fchannel, fattrs, sizeof(struct nfs= d4_channel_attrs)); > > > > > > > > new->se_cb_slot_avail =3D ~0U; > > > > > > > > - new->se_cb_highest_slot =3D battrs->maxreqs - 1; > > > > > > > > + new->se_cb_highest_slot =3D min(battrs->maxreqs - 1= , NFSD_BC_SLOT_TABLE_MAX); > > > > > > > > spin_lock_init(&new->se_lock); > > > > > > > > return new; > > > > > > > > out_free: > > > > > > >=20 > > > > > > > It does help. I thought that the CREATE_SESSION reply for the > > > > > > > backchannel would be guided by the NFSD_BC_SLOT_TABLE_MAX val= ue but > > > > > > > instead it seems like it's not. But yes I can see that the hi= ghest > > > > > > > slot used by the server is capped by the NFSD_BC_SLOT_TABLE_M= AX value. > > > > > >=20 > > > > > > Thanks for testing it, Olga. > > > > > >=20 > > > > > > Chuck, would you be OK with folding the above delta into 9ab4c4= 077de9, > > > > > > or would you rather I resend the patch? > > > > >=20 > > > > > I've folded the above one-liner into the applied patch. > > > > >=20 > > > > > I agree with Tom, I think there's probably a (surprising) > > > > > explanation lurking for not seeing the expected performance > > > > > improvement. I can delay sending the NFSD v6.13 merge window pull > > > > > request for a bit to see if you can get it teased out. > > > >=20 > > > > I would like to raise a couple of issues: > > > > (1) I believe the server should be reporting back an accurate value > > > > for the backchannel session table size. I think if the > > > > NFSD_BC_SLOT_TABLE_MAX was way lower than the client's value then t= he > > > > client would be wasting resources for its bc session table? > > >=20 > > > Yes, but those resources are 32-bit integer per wasted slot. The Linu= x > > > client allows for up to 16 slots, so we're wasting 64 bytes per sessi= on > > > with this scheme with the Linux client. I didn't think it was worth > > > doing a separate allocation for that. > > >=20 > > > We could make NFSD_BC_SLOT_TABLE_MAX smaller though. Maybe we should > > > match the client's size and make it 15? > > >=20 > > > > ->back_channel->maxreqs gets decoded in nfsd4_decode_create_session= () > > > > and is never adjusted for the reply to be based on the > > > > NFSD_BC_SLOT_TABLE_MAX. The problem is currently invisible because > > > > linux client's bc slot table size is 16 and nfsd's is higher. > > > >=20 > > >=20 > > > I'm not sure I understand the problem here. We don't care about most = of > > > the backchannel attributes. maxreqs is the only one that matters, and > > > track that in se_cb_highest_slot. > >=20 > > Client sends a create_session with cba_back_chan_attrs with max_reqs > > of 16 -- stating that the client can handle 16 slots in it's slot > > table. Server currently doesn't do anything about reflecting back to > > the client its session slot table. It blindly returns what the client > > sent. Say NFSD_BC_SLOT_TABLE_MAX was 4. Server would never use more > > than 4 slots and yet the client would have to create a reply cache > > table for 16 slots. Isn't that poor sportsmanship on behalf of the > > linux server? > >=20 > >=20 >=20 > Thanks, that does sound like a bug. I think we can fix that with > another one-liner.=C2=A0 When we allocate the new session, update the > back_channel attrs in the request with the correct maxreqs. Thoughts? >=20 > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index 15438826ed5b..c35d8fc2f693 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -3885,6 +3885,7 @@ nfsd4_create_session(struct svc_rqst *rqstp, > new =3D alloc_session(&cr_ses->fore_channel, &cr_ses->back_channel); > if (!new) > goto out_release_drc_mem; > + cr_ses->back_channel.maxreqs =3D new->se_cb_highest_slot; > conn =3D alloc_conn_from_crses(rqstp, cr_ses); > if (!conn) > goto out_free_session; Actually, I think this is better, since we're already modifying things in this section of the code. Also the earlier patch was off-by-one: ------------------------8<---------------------- [PATCH] SQUASH: report the correct number of backchannel slots to client Signed-off-by: Jeff Layton --- fs/nfsd/nfs4state.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 15438826ed5b..cfc2190ffce5 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -3955,6 +3955,8 @@ nfsd4_create_session(struct svc_rqst *rqstp, cr_ses->flags &=3D ~SESSION4_PERSIST; /* Upshifting from TCP to RDMA is not supported */ cr_ses->flags &=3D ~SESSION4_RDMA; + /* Report the correct number of backchannel slots */ + cr_ses->back_channel.maxreqs =3D new->se_cb_highest_slot + 1; =20 init_session(rqstp, new, conf, cr_ses); nfsd4_get_session_locked(new); --=20 2.47.0