From patchwork Wed Jun 19 20:40:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Snitzer X-Patchwork-Id: 13704526 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 529E215A87F for ; Wed, 19 Jun 2024 20:40:54 +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=1718829654; cv=none; b=Knkyz3nTxGC2ID4KLY+X2Pe1IlV/Wnth9BFAu5u4zUojflHoUyqSGIi0rYSD/4nbeTMH7I+EH/5xuUv5H6V7o27BFnQZ0uUGPNDgDaGEo5+ywOfuY1kkhdb4XNa51SFJ+Xt/vdr/8yGE44V4bPfJA2t026b64EdAVIdulkMAq10= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718829654; c=relaxed/simple; bh=rL0rLxv2RAEagEikL1b7BA6JXAiXjIiCcnBxv0q+Tjw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AiADc+z15SkNoEYTGzoLKvVwkVbdK+UZYh0PoWHvUfeeERANNW9vLvXXSO5EVPEJ8W2KnvOcuQ3CXv/67X0Qxs0RnA8SBtliF7zGHRHb0C5THt5slLf7bfWPwgd/RObT2vSmQT7vD/ZNyTW1dbzYuKcUsx/tII8p+9F42AL96ps= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qzA65okb; 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="qzA65okb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05DD1C2BBFC; Wed, 19 Jun 2024 20:40:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1718829654; bh=rL0rLxv2RAEagEikL1b7BA6JXAiXjIiCcnBxv0q+Tjw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qzA65okbaucKf30wk7gCw4HdDJ5hRsWqY3qBbAbxDff2bIluGzp738mN4jjDyQ58D nfQXT+R0slOIBB8hHe5awwEceS12ePo/pygRfvPUCkBVx9lSGJgIzM6j96GxwpvlYR l+kP25Av8VibQoSTzDSpiLW3QEfIrJWC7/0qeKjGn1SZ2P5/IgLtY+bVscW8XHmCuG cNYNpD9dges5+A5eaTy/QsT0NaoJJqw0PH5ElzF/0Ir6LhsL6LGQEQcSQvAiXsFRDr dXCKwahR6VS8Qy1IWfKSY5CiWVdcaA9y9JaPJ7CsSrzTIPKcjBBIKDTicLI3Egk0Za HxGpGXuFjEL4A== From: Mike Snitzer To: linux-nfs@vger.kernel.org Cc: Jeff Layton , Chuck Lever , Trond Myklebust , NeilBrown , snitzer@hammerspace.com Subject: [PATCH v6 15/18] nfsd: use SRCU to dereference nn->nfsd_serv Date: Wed, 19 Jun 2024 16:40:29 -0400 Message-ID: <20240619204032.93740-16-snitzer@kernel.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240619204032.93740-1-snitzer@kernel.org> References: <20240619204032.93740-1-snitzer@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Introduce nfsd_serv_get, nfsd_serv_put and nfsd_serv_sync and update the nfsd code to prevent nfsd_destroy_serv from destroying nn->nfsd_serv until all nfsd code is done with it (particularly the localio code that doesn't run in the context of nfsd's svc threads, nor does it take the nfsd_mutex). Commit 83d5e5b0af90 ("dm: optimize use SRCU and RCU") provided a familiar well-worn pattern for how implement. Suggested-by: NeilBrown Signed-off-by: Mike Snitzer --- fs/nfsd/filecache.c | 13 ++++++++--- fs/nfsd/netns.h | 14 ++++++++++-- fs/nfsd/nfs4state.c | 25 ++++++++++++++------- fs/nfsd/nfsctl.c | 7 ++++-- fs/nfsd/nfssvc.c | 54 ++++++++++++++++++++++++++++++++++++--------- 5 files changed, 88 insertions(+), 25 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 99631fa56662..474b3a3af3fb 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -413,12 +413,15 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose) struct nfsd_file *nf = list_first_entry(dispose, struct nfsd_file, nf_lru); struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id); + int srcu_idx; + struct svc_serv *serv = nfsd_serv_get(nn, &srcu_idx); struct nfsd_fcache_disposal *l = nn->fcache_disposal; spin_lock(&l->lock); list_move_tail(&nf->nf_lru, &l->freeme); spin_unlock(&l->lock); - svc_wake_up(nn->nfsd_serv); + svc_wake_up(serv); + nfsd_serv_put(nn, srcu_idx); } } @@ -443,11 +446,15 @@ void nfsd_file_net_dispose(struct nfsd_net *nn) for (i = 0; i < 8 && !list_empty(&l->freeme); i++) list_move(l->freeme.next, &dispose); spin_unlock(&l->lock); - if (!list_empty(&l->freeme)) + if (!list_empty(&l->freeme)) { + int srcu_idx; + struct svc_serv *serv = nfsd_serv_get(nn, &srcu_idx); /* Wake up another thread to share the work * *before* doing any actual disposing. */ - svc_wake_up(nn->nfsd_serv); + svc_wake_up(serv); + nfsd_serv_put(nn, srcu_idx); + } nfsd_file_dispose_list(&dispose); } } diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h index 0c5a1d97e4ac..92d0d0883f17 100644 --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -139,8 +139,14 @@ struct nfsd_net { u32 clverifier_counter; struct svc_info nfsd_info; -#define nfsd_serv nfsd_info.serv - + /* + * The current 'nfsd_serv' at nfsd_info.serv. Using 'void' rather than + * 'struct svc_serv' to guard against new code dereferencing nfsd_serv + * without using proper synchronization. + * Use nfsd_serv_get() or take nfsd_mutex to dereference. + */ + void __rcu *nfsd_serv; + struct srcu_struct nfsd_serv_srcu; /* * clientid and stateid data for construction of net unique COPY @@ -225,6 +231,10 @@ struct nfsd_net { extern bool nfsd_support_version(int vers); extern void nfsd_netns_free_versions(struct nfsd_net *nn); +extern struct svc_serv *nfsd_serv_get(struct nfsd_net *nn, int *srcu_idx); +extern void nfsd_serv_put(struct nfsd_net *nn, int srcu_idx); +extern void nfsd_serv_sync(struct nfsd_net *nn); + extern unsigned int nfsd_net_id; void nfsd_copy_write_verifier(__be32 verf[2], struct nfsd_net *nn); diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index a20c2c9d7d45..8876810e569d 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1919,6 +1919,8 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca, struct nfsd_net *nn u32 num = ca->maxreqs; unsigned long avail, total_avail; unsigned int scale_factor; + int srcu_idx; + struct svc_serv *serv = nfsd_serv_get(nn, &srcu_idx); spin_lock(&nfsd_drc_lock); if (nfsd_drc_max_mem > nfsd_drc_mem_used) @@ -1940,7 +1942,7 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca, struct nfsd_net *nn * Give the client one slot even if that would require * over-allocation--it is better than failure. */ - scale_factor = max_t(unsigned int, 8, nn->nfsd_serv->sv_nrthreads); + scale_factor = max_t(unsigned int, 8, serv->sv_nrthreads); avail = clamp_t(unsigned long, avail, slotsize, total_avail/scale_factor); @@ -1949,6 +1951,8 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca, struct nfsd_net *nn nfsd_drc_mem_used += num * slotsize; spin_unlock(&nfsd_drc_lock); + nfsd_serv_put(nn, srcu_idx); + return num; } @@ -3702,12 +3706,16 @@ nfsd4_replay_create_session(struct nfsd4_create_session *cr_ses, static __be32 check_forechannel_attrs(struct nfsd4_channel_attrs *ca, struct nfsd_net *nn) { - u32 maxrpc = nn->nfsd_serv->sv_max_mesg; + int srcu_idx; + struct svc_serv *serv = nfsd_serv_get(nn, &srcu_idx); + u32 maxrpc = serv->sv_max_mesg; + __be32 status = nfs_ok; - if (ca->maxreq_sz < NFSD_MIN_REQ_HDR_SEQ_SZ) - return nfserr_toosmall; - if (ca->maxresp_sz < NFSD_MIN_RESP_HDR_SEQ_SZ) - return nfserr_toosmall; + if (ca->maxreq_sz < NFSD_MIN_REQ_HDR_SEQ_SZ || + ca->maxresp_sz < NFSD_MIN_RESP_HDR_SEQ_SZ) { + status = nfserr_toosmall; + goto out; + } ca->headerpadsz = 0; ca->maxreq_sz = min_t(u32, ca->maxreq_sz, maxrpc); ca->maxresp_sz = min_t(u32, ca->maxresp_sz, maxrpc); @@ -3726,8 +3734,9 @@ static __be32 check_forechannel_attrs(struct nfsd4_channel_attrs *ca, struct nfs * accounting is soft and provides no guarantees either way. */ ca->maxreqs = nfsd4_get_drc_mem(ca, nn); - - return nfs_ok; +out: + nfsd_serv_put(nn, srcu_idx); + return status; } /* diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index 1bddbbf7418e..2d4c29c25c6a 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1569,10 +1569,12 @@ int nfsd_nl_rpc_status_get_dumpit(struct sk_buff *skb, { struct nfsd_net *nn = net_generic(sock_net(skb->sk), nfsd_net_id); int i, ret, rqstp_index = 0; + int srcu_idx; + struct svc_serv *serv = nfsd_serv_get(nn, &srcu_idx); rcu_read_lock(); - for (i = 0; i < nn->nfsd_serv->sv_nrpools; i++) { + for (i = 0; i < serv->sv_nrpools; i++) { struct svc_rqst *rqstp; if (i < cb->args[0]) /* already consumed */ @@ -1580,7 +1582,7 @@ int nfsd_nl_rpc_status_get_dumpit(struct sk_buff *skb, rqstp_index = 0; list_for_each_entry_rcu(rqstp, - &nn->nfsd_serv->sv_pools[i].sp_all_threads, + &serv->sv_pools[i].sp_all_threads, rq_all) { struct nfsd_genl_rqstp genl_rqstp; unsigned int status_counter; @@ -1645,6 +1647,7 @@ int nfsd_nl_rpc_status_get_dumpit(struct sk_buff *skb, ret = skb->len; out: rcu_read_unlock(); + nfsd_serv_put(nn, srcu_idx); return ret; } diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c index bfc58001dd9a..42db1e6dcff7 100644 --- a/fs/nfsd/nfssvc.c +++ b/fs/nfsd/nfssvc.c @@ -300,6 +300,26 @@ int nfsd_minorversion(struct nfsd_net *nn, u32 minorversion, enum vers_op change return 0; } +struct svc_serv *nfsd_serv_get(struct nfsd_net *nn, int *srcu_idx) + __acquires(nn->nfsd_serv_srcu) +{ + *srcu_idx = srcu_read_lock(&nn->nfsd_serv_srcu); + + return srcu_dereference(nn->nfsd_serv, &nn->nfsd_serv_srcu); +} + +void nfsd_serv_put(struct nfsd_net *nn, int srcu_idx) + __releases(nn->nfsd_serv_srcu) +{ + srcu_read_unlock(&nn->nfsd_serv_srcu, srcu_idx); +} + +void nfsd_serv_sync(struct nfsd_net *nn) +{ + synchronize_srcu(&nn->nfsd_serv_srcu); + synchronize_rcu_expedited(); +} + /* * Maximum number of nfsd processes */ @@ -507,6 +527,7 @@ static void nfsd_shutdown_net(struct net *net) lockd_down(net); nn->lockd_up = false; } + cleanup_srcu_struct(&nn->nfsd_serv_srcu); #if IS_ENABLED(CONFIG_NFSD_LOCALIO) list_del_rcu(&nn->nfsd_uuid.list); #endif @@ -514,6 +535,7 @@ static void nfsd_shutdown_net(struct net *net) nfsd_shutdown_generic(); } +// FIXME: nfsd_serv_{get,put} should make it safe to eliminate nfsd_notifier_lock static DEFINE_SPINLOCK(nfsd_notifier_lock); static int nfsd_inetaddr_event(struct notifier_block *this, unsigned long event, void *ptr) @@ -523,20 +545,22 @@ static int nfsd_inetaddr_event(struct notifier_block *this, unsigned long event, struct net *net = dev_net(dev); struct nfsd_net *nn = net_generic(net, nfsd_net_id); struct sockaddr_in sin; + int srcu_idx; + struct svc_serv *serv = nfsd_serv_get(nn, &srcu_idx); - if (event != NETDEV_DOWN || !nn->nfsd_serv) + if (event != NETDEV_DOWN || !serv) goto out; spin_lock(&nfsd_notifier_lock); - if (nn->nfsd_serv) { + if (serv) { dprintk("nfsd_inetaddr_event: removed %pI4\n", &ifa->ifa_local); sin.sin_family = AF_INET; sin.sin_addr.s_addr = ifa->ifa_local; - svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin); + svc_age_temp_xprts_now(serv, (struct sockaddr *)&sin); } spin_unlock(&nfsd_notifier_lock); - out: + nfsd_serv_put(nn, srcu_idx); return NOTIFY_DONE; } @@ -553,22 +577,24 @@ static int nfsd_inet6addr_event(struct notifier_block *this, struct net *net = dev_net(dev); struct nfsd_net *nn = net_generic(net, nfsd_net_id); struct sockaddr_in6 sin6; + int srcu_idx; + struct svc_serv *serv = nfsd_serv_get(nn, &srcu_idx); - if (event != NETDEV_DOWN || !nn->nfsd_serv) + if (event != NETDEV_DOWN || !serv) goto out; spin_lock(&nfsd_notifier_lock); - if (nn->nfsd_serv) { + if (serv) { dprintk("nfsd_inet6addr_event: removed %pI6\n", &ifa->addr); sin6.sin6_family = AF_INET6; sin6.sin6_addr = ifa->addr; if (ipv6_addr_type(&sin6.sin6_addr) & IPV6_ADDR_LINKLOCAL) sin6.sin6_scope_id = ifa->idev->dev->ifindex; - svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin6); + svc_age_temp_xprts_now(serv, (struct sockaddr *)&sin6); } spin_unlock(&nfsd_notifier_lock); - out: + nfsd_serv_put(nn, srcu_idx); return NOTIFY_DONE; } @@ -589,9 +615,12 @@ void nfsd_destroy_serv(struct net *net) struct nfsd_net *nn = net_generic(net, nfsd_net_id); struct svc_serv *serv = nn->nfsd_serv; + lockdep_assert_held(&nfsd_mutex); + spin_lock(&nfsd_notifier_lock); - nn->nfsd_serv = NULL; + rcu_assign_pointer(nn->nfsd_serv, NULL); spin_unlock(&nfsd_notifier_lock); + nfsd_serv_sync(nn); /* check if the notifier still has clients */ if (atomic_dec_return(&nfsd_notifier_refcount) == 0) { @@ -711,6 +740,10 @@ int nfsd_create_serv(struct net *net) if (nn->nfsd_serv) return 0; + error = init_srcu_struct(&nn->nfsd_serv_srcu); + if (error) + return error; + if (nfsd_max_blksize == 0) nfsd_max_blksize = nfsd_get_default_max_blksize(); nfsd_reset_versions(nn); @@ -727,7 +760,8 @@ int nfsd_create_serv(struct net *net) } spin_lock(&nfsd_notifier_lock); nn->nfsd_info.mutex = &nfsd_mutex; - nn->nfsd_serv = serv; + nn->nfsd_info.serv = serv; + rcu_assign_pointer(nn->nfsd_serv, nn->nfsd_info.serv); spin_unlock(&nfsd_notifier_lock); set_max_drc();