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 AC35B1922D6; Thu, 29 Aug 2024 11:45:34 +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=1724931934; cv=none; b=VMy3UmjnFAJ8AYACM5dqYAU1jRcx/Q9anmXvLNSuDB8LIti1BBr7ub9wf66QjMyoVdgrMXkzzgUcrcszYji/akE5oa2vdnvbZZsLF5vYd01GjiJTqcNOA+dqfeufQXzeQYg73nsF7T1LEv8GG/s7+GprI3Y+YdQoXmyieN6Ps6I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724931934; c=relaxed/simple; bh=Fzpp5lWGYq6D2U6mpbSKGfb8KD6P7B2eTFch/Jw6mhM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=RcC1KGv186VHUcot3ZbgGQwZ1gUgdySdXFDpQm20cn5umP+YN/P6QArl3IpYmPP90dKRpE+z1SfqDbdDMciBaazvBtBE+1vYi+sDeFwQF7t53O8cgBl5/JHiwpku/qhozcYU4jYRUDfT3ZtuYbeMNWSxFoYAH6K3ZvnPpaubZQw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uiHpW42Q; 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="uiHpW42Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F748C4CEC1; Thu, 29 Aug 2024 11:45:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724931934; bh=Fzpp5lWGYq6D2U6mpbSKGfb8KD6P7B2eTFch/Jw6mhM=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=uiHpW42QJcll2suZJGMOVyp+OfHfsg6ee8MKLRFRR1ip5CLCZJTmw7uRCQKPTJcC5 jxLfCZBzlvr/6qBhwW2oNzY2yu0b5u3gDrA8RmNV1+Rxhu5B5QsbSxYj7/WsRcRhnS e3vOFzpmouXEXa4eiVxxupOD/B6/Kme90TLdODiIV98yodWy/KpJJGWa31ZVIz0RfX qchfSygMPCWlBvmHvRiXV4mgGiJdsybDCW1pMHw4n0Vfoyg1K0xnHgF5VV5bujWhfb InZyYAc9N53G0xKVvXqlFEjl6ljQhPlON0s1399gRzJSdcMiYwUSH5kMwbH7KEqhFX 0H3MJgRGGKqEg== Message-ID: <15fc35fb6ba9550da47bba04deb9e28b8c702bb2.camel@kernel.org> Subject: Re: [RFC PATCH 2/7] NFSD: Limit the number of concurrent async COPY operations From: Jeff Layton To: cel@kernel.org, linux-nfs@vger.kernel.org Cc: Olga Kornievskaia , Dai Ngo , Chuck Lever , stable@vger.kernel.org Date: Thu, 29 Aug 2024 07:45:32 -0400 In-Reply-To: <20240828174001.322745-11-cel@kernel.org> References: <20240828174001.322745-9-cel@kernel.org> <20240828174001.322745-11-cel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV 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Wed, 2024-08-28 at 13:40 -0400, cel@kernel.org wrote: > From: Chuck Lever >=20 > Nothing appears to limit the number of concurrent async COPY > operations that clients can start. In addition, AFAICT each async > COPY can copy an unlimited number of 4MB chunks, so can run for a > long time. Thus IMO async COPY can become a DoS vector. >=20 > Add a restriction mechanism that bounds the number of concurrent > background COPY operations. Start simple and try to be fair -- this > patch implements a per-namespace limit. >=20 > An async COPY request that occurs while this limit is exceeded gets > NFS4ERR_DELAY. The requesting client can choose to send the request > again after a delay or fall back to a traditional read/write style > copy. >=20 > If there is need to make the mechanism more sophisticated, we can > visit that in future patches. >=20 > Cc: stable@vger.kernel.org > Signed-off-by: Chuck Lever > --- > fs/nfsd/netns.h | 1 + > fs/nfsd/nfs4proc.c | 12 ++++++++++-- > fs/nfsd/nfs4state.c | 1 + > fs/nfsd/xdr4.h | 1 + > 4 files changed, 13 insertions(+), 2 deletions(-) >=20 > diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h > index 14ec15656320..5cae26917436 100644 > --- a/fs/nfsd/netns.h > +++ b/fs/nfsd/netns.h > @@ -148,6 +148,7 @@ struct nfsd_net { > u32 s2s_cp_cl_id; > struct idr s2s_cp_stateids; > spinlock_t s2s_cp_lock; > + atomic_t pending_async_copies; > =20 > /* > * Version information > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > index 60c526adc27c..27f7eceb3b00 100644 > --- a/fs/nfsd/nfs4proc.c > +++ b/fs/nfsd/nfs4proc.c > @@ -1279,6 +1279,7 @@ static void nfs4_put_copy(struct nfsd4_copy *copy) > { > if (!refcount_dec_and_test(©->refcount)) > return; > + atomic_dec(©->cp_nn->pending_async_copies); > kfree(copy->cp_src); > kfree(copy); > } > @@ -1833,10 +1834,17 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_c= ompound_state *cstate, > memcpy(©->fh, &cstate->current_fh.fh_handle, > sizeof(struct knfsd_fh)); > if (nfsd4_copy_is_async(copy)) { > - status =3D nfserrno(-ENOMEM); > + /* Arbitrary cap on number of pending async copy operations */ > + int nrthreads =3D atomic_read(&rqstp->rq_pool->sp_nrthreads); > + > async_copy =3D kzalloc(sizeof(struct nfsd4_copy), GFP_KERNEL); > if (!async_copy) > goto out_err; > + async_copy->cp_nn =3D nn; > + if (atomic_inc_return(&nn->pending_async_copies) > nrthreads) { > + atomic_dec(&nn->pending_async_copies); > + goto out_err; > + } > INIT_LIST_HEAD(&async_copy->copies); > refcount_set(&async_copy->refcount, 1); > async_copy->cp_src =3D kmalloc(sizeof(*async_copy->cp_src), GFP_KERNEL= ); > @@ -1876,7 +1884,7 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_com= pound_state *cstate, > } > if (async_copy) > cleanup_async_copy(async_copy); > - status =3D nfserrno(-ENOMEM); > + status =3D nfserr_jukebox; ENOMEM gets translated to nfserr_jukebox anyway, so this doesn't change anything (good). > goto out; > } > =20 > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index a20c2c9d7d45..aaebc60cc77c 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -8554,6 +8554,7 @@ static int nfs4_state_create_net(struct net *net) > spin_lock_init(&nn->client_lock); > spin_lock_init(&nn->s2s_cp_lock); > idr_init(&nn->s2s_cp_stateids); > + atomic_set(&nn->pending_async_copies, 0); > =20 > spin_lock_init(&nn->blocked_locks_lock); > INIT_LIST_HEAD(&nn->blocked_locks_lru); > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h > index fbdd42cde1fa..2a21a7662e03 100644 > --- a/fs/nfsd/xdr4.h > +++ b/fs/nfsd/xdr4.h > @@ -713,6 +713,7 @@ struct nfsd4_copy { > struct nfsd4_ssc_umount_item *ss_nsui; > struct nfs_fh c_fh; > nfs4_stateid stateid; > + struct nfsd_net *cp_nn; > }; > =20 > static inline void nfsd4_copy_set_sync(struct nfsd4_copy *copy, bool syn= c) A per-ns limit sounds like a reasonable place to start. Reviewed-by: Jeff Layton