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 0CDCF1B78E1; Thu, 29 Aug 2024 17:48:31 +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=1724953712; cv=none; b=fZv+3xcxMoHpC0/tcOLT5riIZlmVSG0mbb1NIhf9/hkDyE1va4ixOBjmK75OipWL/TKpxusDqMjL5nGxcRyVaptlNASRsXp20KlScHH/v456kTIqXoyZtqiBP4PVtsGH81vH5lAYGn2CvsB0D/W6WLZ7171znIeJeI3JeFPOcLY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724953712; c=relaxed/simple; bh=Yus5cdWabaGj3Jv5j4m1SNdVxjf4SrMfLG6VNeAqazU=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=WVnG9s1jyuOFXjW0/C399HQBYttN46Xq69rS5gcai6kJs6ut61Td5LmD+DYO9ISmZOh/kDDJC/m77XDseZSOOVAfqvu8wkl1aoT2xYLRnCpInMQbh0Q67brS0sxxL+li2JBOC644WPLKqlM2GORhGxjNWypGdwQalQtPohlZh8M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=duqW8i4C; 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="duqW8i4C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA66DC4CEC1; Thu, 29 Aug 2024 17:48:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724953711; bh=Yus5cdWabaGj3Jv5j4m1SNdVxjf4SrMfLG6VNeAqazU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=duqW8i4CM5SqlDheevzZefhu6AEQtj15Zk2UNoSfiThjmDysrOjGlNhy/2qfmxv4C zTqUtBWSjWlfJCKkMJn+5Y62Vdrrw4SQ8PVF1X5zvRht8QCARPzL4+jhaBqJJRtl8Q +4Z4E2i2CjNjcOX9FrspwXvxyrBj9a0WNl6aTisIxQgEOpV6F/QVFF80woK5I89Qf7 AxrzScxkr7FxCBd1BA+6F5iK8mDjvFzpXTnh9iXqtSgk6rQg/31+Y7XGtpx05Bllls bknD9azYWMMRZztNGdyfuQig45ld/iwcwlsmM7mlaeNCyEfEhgVod1TJMW7Ax5cIQK sS6HMNPCm/nDQ== Message-ID: <95776943752608072e60f185e98f35a97175eecd.camel@kernel.org> Subject: Re: [PATCH v14 15/25] nfs_common: introduce nfs_localio_ctx struct and interfaces From: Jeff Layton To: Mike Snitzer Cc: linux-nfs@vger.kernel.org, Chuck Lever , Anna Schumaker , Trond Myklebust , NeilBrown , linux-fsdevel@vger.kernel.org Date: Thu, 29 Aug 2024 13:48:29 -0400 In-Reply-To: References: <20240829010424.83693-1-snitzer@kernel.org> <20240829010424.83693-16-snitzer@kernel.org> <43d5ce3b7b374ed2ac7595932e2109e14ffd13e7.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV 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Thu, 2024-08-29 at 12:52 -0400, Mike Snitzer wrote: > On Thu, Aug 29, 2024 at 12:40:27PM -0400, Jeff Layton wrote: > > On Wed, 2024-08-28 at 21:04 -0400, Mike Snitzer wrote: > > > Introduce struct nfs_localio_ctx and the interfaces > > > nfs_localio_ctx_alloc() and nfs_localio_ctx_free(). The next commit > > > will introduce nfsd_open_local_fh() which returns a nfs_localio_ctx > > > structure. > > >=20 > > > Also, expose localio's required NFSD symbols to NFS client: > > > - Cache nfsd_open_local_fh symbol and other required NFSD symbols in = a > > > globally accessible 'nfs_to' nfs_to_nfsd_t struct. Add interfaces > > > get_nfs_to_nfsd_symbols() and put_nfs_to_nfsd_symbols() to allow > > > each NFS client to take a reference on NFSD symbols. > > >=20 > > > - Apologies for the DEFINE_NFS_TO_NFSD_SYMBOL macro that makes > > > defining get_##NFSD_SYMBOL() and put_##NFSD_SYMBOL() functions far > > > simpler (and avoids cut-n-paste bugs, which is what motivated the > > > development and use of a macro for this). But as C macros go it is = a > > > very simple one and there are many like it all over the kernel. > > >=20 > > > - Given the unique nature of NFS LOCALIO being an optional feature > > > that when used requires NFS share access to NFSD memory: a unique > > > bridging of NFSD resources to NFS (via nfs_common) is needed. But > > > that bridge must be dynamic, hence the use of symbol_request() and > > > symbol_put(). Proposed ideas to accomolish the same without using > > > symbol_{request,put} would be far more tedious to implement and > > > very likely no easier to review. Anyway: sorry NeilBrown... > > >=20 > > > - Despite the use of indirect function calls, caching these nfsd > > > symbols for use by the client offers a ~10% performance win > > > (compared to always doing get+call+put) for high IOPS workloads. > > >=20 > > > - Introduce nfsd_file_file() wrapper that provides access to > > > nfsd_file's backing file. Keeps nfsd_file structure opaque to NFS > > > client (as suggested by Jeff Layton). > > >=20 > > > - The addition of nfsd_file_get, nfsd_file_put and nfsd_file_file > > > symbols prepares for the NFS client to use nfsd_file for localio. > > >=20 > > > Suggested-by: Trond Myklebust # nfs= _to > > > Suggested-by: Jeff Layton # nfsd_file_file > > > Signed-off-by: Mike Snitzer > > > --- > > > fs/nfs_common/nfslocalio.c | 159 +++++++++++++++++++++++++++++++++++= ++ > > > fs/nfsd/filecache.c | 25 ++++++ > > > fs/nfsd/filecache.h | 1 + > > > fs/nfsd/nfssvc.c | 5 ++ > > > include/linux/nfslocalio.h | 38 +++++++++ > > > 5 files changed, 228 insertions(+) > > >=20 > > > diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c > > > index 1a35a4a6dbe0..cc30fdb0cb46 100644 > > > --- a/fs/nfs_common/nfslocalio.c > > > +++ b/fs/nfs_common/nfslocalio.c > > > @@ -72,3 +72,162 @@ bool nfs_uuid_is_local(const uuid_t *uuid, struct= net *net, struct auth_domain * > > > return is_local; > > > } > > > EXPORT_SYMBOL_GPL(nfs_uuid_is_local); > > > + > > > +/* > > > + * The nfs localio code needs to call into nfsd using various symbol= s (below), > > > + * but cannot be statically linked, because that will make the nfs m= odule > > > + * depend on the nfsd module. > > > + * > > > + * Instead, do dynamic linking to the nfsd module (via nfs_common mo= dule). The > > > + * nfs_common module will only hold a reference on nfsd when localio= is in use. > > > + * This allows some sanity checking, like giving up on localio if nf= sd isn't loaded. > > > + */ > > > +static DEFINE_SPINLOCK(nfs_to_nfsd_lock); > > > +nfs_to_nfsd_t nfs_to; > > > +EXPORT_SYMBOL_GPL(nfs_to); > > > + > > > +/* Macro to define nfs_to get and put methods, avoids copy-n-paste b= ugs */ > > > +#define DEFINE_NFS_TO_NFSD_SYMBOL(NFSD_SYMBOL) \ > > > +static nfs_to_##NFSD_SYMBOL##_t get_##NFSD_SYMBOL(void) \ > > > +{ \ > > > + return symbol_request(NFSD_SYMBOL); \ > > > +} \ > > > +static void put_##NFSD_SYMBOL(void) \ > > > +{ \ > > > + symbol_put(NFSD_SYMBOL); \ > > > + nfs_to.NFSD_SYMBOL =3D NULL; \ > > > +} > > > + > > > +/* The nfs localio code needs to call into nfsd to map filehandle ->= struct nfsd_file */ > > > +extern struct nfs_localio_ctx * > > > +nfsd_open_local_fh(struct net *, struct auth_domain *, struct rpc_cl= nt *, > > > + const struct cred *, const struct nfs_fh *, const fmode_t); > > > +DEFINE_NFS_TO_NFSD_SYMBOL(nfsd_open_local_fh); > > > + > > > +/* The nfs localio code needs to call into nfsd to acquire the nfsd_= file */ > > > +extern struct nfsd_file *nfsd_file_get(struct nfsd_file *nf); > > > +DEFINE_NFS_TO_NFSD_SYMBOL(nfsd_file_get); > > > + > > > +/* The nfs localio code needs to call into nfsd to release the nfsd_= file */ > > > +extern void nfsd_file_put(struct nfsd_file *nf); > > > +DEFINE_NFS_TO_NFSD_SYMBOL(nfsd_file_put); > > > + > > > +/* The nfs localio code needs to call into nfsd to access the nf->nf= _file */ > > > +extern struct file * nfsd_file_file(struct nfsd_file *nf); > > > +DEFINE_NFS_TO_NFSD_SYMBOL(nfsd_file_file); > > > + > > > +/* The nfs localio code needs to call into nfsd to release nn->nfsd_= serv */ > > > +extern void nfsd_serv_put(struct nfsd_net *nn); > > > +DEFINE_NFS_TO_NFSD_SYMBOL(nfsd_serv_put); > > > +#undef DEFINE_NFS_TO_NFSD_SYMBOL > > > + > >=20 > > I have the same concerns as Neil did with this patch in v13. An ops > > structure that nfsd registers with nfs_common and that has pointers to > > all of these functions would be a lot cleaner. I think it'll end up > > being less code too. > >=20 > > In fact, for that I'd probably break my usual guideline of not > > introducing new interfaces without callers, and just do a separate > > patch that adds the ops structure and sets up the handling of the > > pointer to it in nfs_common. >=20 > OK, as much as it pains me to set aside proven code that I put a > decent amount of time to honing: I'll humor you guys and try to make > an ops structure workable. (we can always fall back to my approach if > I/we come up short). >=20 > I'm just concerned about the optional use aspect. There is the pain > point of how does NFS client come to _know_ NFSD loaded? Using > symbol_request() deals with that nicely. >=20 Have a pointer to a struct nfsd_localio_ops or something in the nfs_common module. That's initially set to NULL. Then, have a static structure of that type in nfsd.ko, and have its __init routine set the pointer in nfs_common to point to the right structure. The __exit routine will later set it to NULL. > I really don't want all calls in NFS client (or nfs_common) to have to > first check if nfs_common's 'nfs_to' ops structure is NULL or not. Neil seems to think that's not necessary: "If nfs/localio holds an auth_domain, then it implicitly holds a reference to the nfsd module and the functions cannot disappear." That'll need to be clearly documented though as it's a subtle thing to rely on for this. --=20 Jeff Layton