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 0D0D426FDBF; Sat, 13 Dec 2025 21:55:57 +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=1765662958; cv=none; b=hU754Urd3unR8OsDAptjzXt04JHwNHmhv6JKsFmEXNcSZoEzvrn8Z+Z8yf89/nVL4FmK/bAzmnRYPpxPWVWqhyCOfN5DMmjwQShb+Tkwj6nGp90PJISrIvzm+pqS8aFNVlTFeF3LOgCTmrMnJs/tRP8p6hJm0Ecb1HkwJ+3825M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765662958; c=relaxed/simple; bh=2xXDN5GQtvuUy7mVsijHOan3JazOdGgX6Y1+ikFCXH4=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Bt4w5mNmNn1v04bY4eb99B18Nwm1HTJj8EJzFgzX4rY9xXg8aystowrY/IMaSgprssLAAasMncUKoZMsRvyrKUuqWXcyg1i0GyPRNhO0ciJyNo/E+OClvXunNfmfYhbZh7txOSbDfY5dRVON8YUUPzny0VDjaxPwKpA/lzIZxxA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cU8QHQLL; 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="cU8QHQLL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D4AAC4CEF7; Sat, 13 Dec 2025 21:55:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765662957; bh=2xXDN5GQtvuUy7mVsijHOan3JazOdGgX6Y1+ikFCXH4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=cU8QHQLLGZ8wh8sPIw7E0u+YqjPxa8+96Arv2e1uCfBzT/AxAw0IZjhxpygAEIc5Y lChQ5emIns0cyJwpTc8OunmNFMUA4EOYQmyW2Gfvylq5vQaQUfzsd7CGRXVBwThZ0l KjjOkcIfO/J5+nPMbDvqx63ywqHY4LGfi/PWiNW99s6vvatsKYyrUpmud/GV2ePQEz kZ6VKWe/Y5H+gujGTaIzc4Q+tUWROJTF4Kjls7hwSJ4YgxUY0BXgljcvK+fsi0k3/0 fRqXj5n0juF3kZCfm5xol1kiFP3xNH0adm7NARaI4B78obpz127hh8kPqv60GrhTmT nKyFvi3fFaHhw== Message-ID: Subject: Re: [PATCH RFC 1/6] sunrpc: split svc_set_num_threads() into two functions From: Jeff Layton To: Chuck Lever , Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , Trond Myklebust , Anna Schumaker Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Sun, 14 Dec 2025 06:55:53 +0900 In-Reply-To: <587f5358-fdb2-4834-b50e-6d48c9b43214@app.fastmail.com> References: <20251213-nfsd-dynathread-v1-0-de755e59cbc4@kernel.org> <20251213-nfsd-dynathread-v1-1-de755e59cbc4@kernel.org> <587f5358-fdb2-4834-b50e-6d48c9b43214@app.fastmail.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv 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linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sat, 2025-12-13 at 14:29 -0500, Chuck Lever wrote: >=20 > On Fri, Dec 12, 2025, at 5:39 PM, Jeff Layton wrote: > > svc_set_num_threads() will set the number of running threads for a give= n > > pool. If the pool argument is set to NULL however, it will distribute > > the threads among all of the pools evenly. > >=20 > > These divergent codepaths complicate the move to dynamic threading. > > Simplify the API by splitting these two cases into different helpers: > >=20 > > Add a new svc_set_pool_threads() function that sets the number of > > threads in a single, given pool. Modify svc_set_num_threads() to > > distribute the threads evenly between all of the pools and then call > > svc_set_pool_threads() for each. > >=20 > > Signed-off-by: Jeff Layton > > --- > > fs/lockd/svc.c | 4 ++-- > > fs/nfs/callback.c | 8 +++---- > > fs/nfsd/nfssvc.c | 21 ++++++++---------- > > include/linux/sunrpc/svc.h | 3 ++- > > net/sunrpc/svc.c | 54 +++++++++++++++++++++++++++++++++++++-= -------- > > 5 files changed, 61 insertions(+), 29 deletions(-) > >=20 > > diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c > > index=20 > > d68afa196535a8785bab2931c2b14f03a1174ef9..fbf132b4e08d11a91784c21ee0209= fd7c149fd9d=20 > > 100644 > > --- a/fs/lockd/svc.c > > +++ b/fs/lockd/svc.c > > @@ -340,7 +340,7 @@ static int lockd_get(void) > > return -ENOMEM; > > } > >=20 > > - error =3D svc_set_num_threads(serv, NULL, 1); > > + error =3D svc_set_num_threads(serv, 1); > > if (error < 0) { > > svc_destroy(&serv); > > return error; > > @@ -368,7 +368,7 @@ static void lockd_put(void) > > unregister_inet6addr_notifier(&lockd_inet6addr_notifier); > > #endif > >=20 > > - svc_set_num_threads(nlmsvc_serv, NULL, 0); > > + svc_set_num_threads(nlmsvc_serv, 0); > > timer_delete_sync(&nlmsvc_retry); > > svc_destroy(&nlmsvc_serv); > > dprintk("lockd_down: service destroyed\n"); > > diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c > > index=20 > > c8b837006bb27277ab34fe516f1b63992fee9b7f..44b35b7f8dc022f1d8c069eaf2f7d= 334c93f77fc=20 > > 100644 > > --- a/fs/nfs/callback.c > > +++ b/fs/nfs/callback.c > > @@ -119,9 +119,9 @@ static int nfs_callback_start_svc(int minorversion,= =20 > > struct rpc_xprt *xprt, > > if (serv->sv_nrthreads =3D=3D nrservs) > > return 0; > >=20 > > - ret =3D svc_set_num_threads(serv, NULL, nrservs); > > + ret =3D svc_set_num_threads(serv, nrservs); > > if (ret) { > > - svc_set_num_threads(serv, NULL, 0); > > + svc_set_num_threads(serv, 0); > > return ret; > > } > > dprintk("nfs_callback_up: service started\n"); > > @@ -242,7 +242,7 @@ int nfs_callback_up(u32 minorversion, struct=20 > > rpc_xprt *xprt) > > cb_info->users++; > > err_net: > > if (!cb_info->users) { > > - svc_set_num_threads(cb_info->serv, NULL, 0); > > + svc_set_num_threads(cb_info->serv, 0); > > svc_destroy(&cb_info->serv); > > } > > err_create: > > @@ -268,7 +268,7 @@ void nfs_callback_down(int minorversion, struct net= =20 > > *net) > > nfs_callback_down_net(minorversion, serv, net); > > cb_info->users--; > > if (cb_info->users =3D=3D 0) { > > - svc_set_num_threads(serv, NULL, 0); > > + svc_set_num_threads(serv, 0); > > dprintk("nfs_callback_down: service destroyed\n"); > > svc_destroy(&cb_info->serv); > > } > > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c > > index=20 > > 93f7435cafd2362d9ddb28815277c824067cb370..aafec8ff588b85b0e26d40b76ef00= 953dc6472b4=20 > > 100644 > > --- a/fs/nfsd/nfssvc.c > > +++ b/fs/nfsd/nfssvc.c > > @@ -594,7 +594,7 @@ void nfsd_shutdown_threads(struct net *net) > > } > >=20 > > /* Kill outstanding nfsd threads */ > > - svc_set_num_threads(serv, NULL, 0); > > + svc_set_num_threads(serv, 0); > > nfsd_destroy_serv(net); > > mutex_unlock(&nfsd_mutex); > > } > > @@ -702,12 +702,9 @@ int nfsd_set_nrthreads(int n, int *nthreads,=20 > > struct net *net) > > if (nn->nfsd_serv =3D=3D NULL || n <=3D 0) > > return 0; > >=20 > > - /* > > - * Special case: When n =3D=3D 1, pass in NULL for the pool, so that = the > > - * change is distributed equally among them. > > - */ > > + /* Special case: When n =3D=3D 1, distribute threads equally among po= ols. */ > > if (n =3D=3D 1) > > - return svc_set_num_threads(nn->nfsd_serv, NULL, nthreads[0]); > > + return svc_set_num_threads(nn->nfsd_serv, nthreads[0]); > >=20 > > if (n > nn->nfsd_serv->sv_nrpools) > > n =3D nn->nfsd_serv->sv_nrpools; > > @@ -733,18 +730,18 @@ int nfsd_set_nrthreads(int n, int *nthreads,=20 > > struct net *net) > >=20 > > /* apply the new numbers */ > > for (i =3D 0; i < n; i++) { > > - err =3D svc_set_num_threads(nn->nfsd_serv, > > - &nn->nfsd_serv->sv_pools[i], > > - nthreads[i]); > > + err =3D svc_set_pool_threads(nn->nfsd_serv, > > + &nn->nfsd_serv->sv_pools[i], > > + nthreads[i]); > > if (err) > > goto out; > > } > >=20 > > /* Anything undefined in array is considered to be 0 */ > > for (i =3D n; i < nn->nfsd_serv->sv_nrpools; ++i) { > > - err =3D svc_set_num_threads(nn->nfsd_serv, > > - &nn->nfsd_serv->sv_pools[i], > > - 0); > > + err =3D svc_set_pool_threads(nn->nfsd_serv, > > + &nn->nfsd_serv->sv_pools[i], > > + 0); > > if (err) > > goto out; > > } > > diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h > > index=20 > > 5506d20857c318774cd223272d4b0022cc19ffb8..dd5fbbf8b3d39df6c17a7624edf34= 4557fffd32c=20 > > 100644 > > --- a/include/linux/sunrpc/svc.h > > +++ b/include/linux/sunrpc/svc.h > > @@ -446,7 +446,8 @@ struct svc_serv * svc_create_pooled(struct=20 > > svc_program *prog, > > struct svc_stat *stats, > > unsigned int bufsize, > > int (*threadfn)(void *data)); > > -int svc_set_num_threads(struct svc_serv *, struct svc_pool *, int)= ; > > +int svc_set_pool_threads(struct svc_serv *, struct svc_pool *,=20 > > int); > > +int svc_set_num_threads(struct svc_serv *, int); > > int svc_pool_stats_open(struct svc_info *si, struct file *file); > > void svc_process(struct svc_rqst *rqstp); > > void svc_process_bc(struct rpc_rqst *req, struct svc_rqst *rqstp); > > diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c > > index=20 > > 4704dce7284eccc9e2bc64cf22947666facfa86a..3fe5a7f8e57e3fa3837265ec06884= b357d5373ff=20 > > 100644 > > --- a/net/sunrpc/svc.c > > +++ b/net/sunrpc/svc.c > > @@ -856,15 +856,12 @@ svc_stop_kthreads(struct svc_serv *serv, struct= =20 > > svc_pool *pool, int nrservs) > > } > >=20 > > /** > > - * svc_set_num_threads - adjust number of threads per RPC service > > + * svc_set_pool_threads - adjust number of threads per pool > > * @serv: RPC service to adjust > > - * @pool: Specific pool from which to choose threads, or NULL > > + * @pool: Specific pool from which to choose threads > > * @nrservs: New number of threads for @serv (0 or less means kill all= =20 > > threads) > > * > > - * Create or destroy threads to make the number of threads for @serv= =20 > > the > > - * given number. If @pool is non-NULL, change only threads in that=20 > > pool; > > - * otherwise, round-robin between all pools for @serv. @serv's > > - * sv_nrthreads is adjusted for each thread created or destroyed. > > + * Create or destroy threads in @pool to bring it to @nrservs. > > * > > * Caller must ensure mutual exclusion between this and server startup= =20 > > or > > * shutdown. > > @@ -873,12 +870,12 @@ svc_stop_kthreads(struct svc_serv *serv, struct= =20 > > svc_pool *pool, int nrservs) > > * starting a thread. > > */ > > int > > -svc_set_num_threads(struct svc_serv *serv, struct svc_pool *pool, int= =20 > > nrservs) > > +svc_set_pool_threads(struct svc_serv *serv, struct svc_pool *pool, int= =20 > > nrservs) > > { > > if (!pool) > > - nrservs -=3D serv->sv_nrthreads; > > - else > > - nrservs -=3D pool->sp_nrthreads; > > + return -EINVAL; > > + > > + nrservs -=3D pool->sp_nrthreads; > >=20 > > if (nrservs > 0) > > return svc_start_kthreads(serv, pool, nrservs); > > @@ -886,6 +883,43 @@ svc_set_num_threads(struct svc_serv *serv, struct= =20 > > svc_pool *pool, int nrservs) > > return svc_stop_kthreads(serv, pool, nrservs); > > return 0; > > } > > +EXPORT_SYMBOL_GPL(svc_set_pool_threads); > > + > > +/** > > + * svc_set_num_threads - adjust number of threads in serv > > + * @serv: RPC service to adjust > > + * @nrservs: New number of threads for @serv (0 or less means kill all= =20 > > threads) > > + * > > + * Create or destroy threads in @serv to bring it to @nrservs. If ther= e > > + * are multiple pools then the new threads or victims will be=20 > > distributed > > + * evenly among them. > > + * > > + * Caller must ensure mutual exclusion between this and server startup= =20 > > or > > + * shutdown. > > + * > > + * Returns zero on success or a negative errno if an error occurred= =20 > > while > > + * starting a thread. > > + */ > > +int > > +svc_set_num_threads(struct svc_serv *serv, int nrservs) > > +{ > > + int base =3D nrservs / serv->sv_nrpools; > > + int remain =3D nrservs % serv->sv_nrpools; > > + int i, err; > > + > > + for (i =3D 0; i < serv->sv_nrpools; ++i) { >=20 > If sv_nrpools happens to be zero, then the loop doesn't > execute at all, and err is left containing stack garbage. > Is sv_nrpools guaranteed to be non-zero? If not then err > needs to be initialized before the loop runs. I see that > nfsd_set_nrthreads() in fs/nfsd/nfssvc.c has "int err =3D 0" > for a similar loop pattern. >=20 sv_nrpools should always be non-zero. There are many places in the rpc layer that depend on having at least one pool. From __svc_create: serv->sv_nrpools =3D npools; serv->sv_pools =3D kcalloc(serv->sv_nrpools, sizeof(struct svc_pool), GFP_KERNEL); if (!serv->sv_pools) { kfree(serv); return NULL; } I think kcalloc returns NULL if you pass it 0 for "n", so creation should fail if that happens. None of the in-tree callers ever pass in 0 for the npools, but maybe that's worth an explicit check in __svc_create(). I can add one. >=20 > > + int threads =3D base; > > + > > + if (remain) { > > + ++threads; > > + --remain; > > + } > > + err =3D svc_set_pool_threads(serv, &serv->sv_pools[i], threads); > > + if (err) > > + break; > > + } > > + return err; > > +} > > EXPORT_SYMBOL_GPL(svc_set_num_threads); > >=20 > > /** > >=20 > > --=20 > > 2.52.0 --=20 Jeff Layton