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 E32B8262FDD for ; Sun, 7 Sep 2025 11:35:26 +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=1757244927; cv=none; b=spL1YO8afNWlDrUGMu3jdr1i0+9hIZE/IbM6Z1NtZ8attE7338ZmLlQNN68Ul4VSgVnE4Zf+ULAGB6NpRLqMc19UOpfx5fb9TVkigeaZtGJTboXrom+9JCRNrnrneiQZIr0GOPZl+YkfTBaYlNVXYppD6jFvzH7C7C/vcg8RfWI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757244927; c=relaxed/simple; bh=T4mzpkm4yKCUHkhpwdtI6imATw3W3Ke7gzib/RSZdxk=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=QBdDZh7XHCVJ/CRz48xnJ0dJuHeIqmrO7JebMZU/gPSE5HQ5WD1cKY9ptqINpZXrsGiAj9quiwEdgePAzXH0f1gLd67TPaarjHB42wWeTTNj//jC1Vlr4WiiHUkBN2JKCS7v+VkQnDtwkYn30Wycnuu9hXHTaQr3XJuxYdyc+EQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=anaaaChA; 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="anaaaChA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5240C4CEF0; Sun, 7 Sep 2025 11:35:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757244926; bh=T4mzpkm4yKCUHkhpwdtI6imATw3W3Ke7gzib/RSZdxk=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=anaaaChAKBNCUNoqZZpUQU+CZeUFvxfxsORnPCyrANa/oWap0dxqoBpTUZySV0VdA 4L6OjRzu5cuLdQoIke9GnPj6/hN9KQF+sddXIpWzbutcL/rpqBCiema6K4tactVJfe VzdObYXmyQwslmcPFMuasPHl/4sT3gcygbIUfALg7Erv1Wi7K6WaSZKVpppOoXC6G2 9MyroB6V2lsJRcdnY0bA7chbWqask6mCS6PzHC6BvgKZ+OrjnbcUOdnx6k75OXDHBn HMOzkmRG1IJ4dy7mOwJKK2zQRvuIqJRS0blStoG1eRNgKqjt6x2ikdNzsrukDLtz6F T93R1t+iDg9CQ== Message-ID: <5b56612a687cacc836ec91d4b4f9408a30fa30c4.camel@kernel.org> Subject: Re: [PATCH v2] NFSD: Add io_cache_{read,write} controls to debugfs From: Jeff Layton To: Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Mike Snitzer Date: Sun, 07 Sep 2025 07:35:24 -0400 In-Reply-To: <20250906212511.9139-1-cel@kernel.org> References: <20250906212511.9139-1-cel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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2tAMJUvFTdDbfe3zKlPDTuVsyNsALBGclPLagJ5ZTP+Vp2irAN9uwBuacBOTtmOdz4ZN2tdvNgozz uxp4CHBDVzAslUi2idy+xpsp47DWPxYFIRP3M8QG/aNW052LaPc0cedYxp8+9eiVUNpxF4SiU4i9J DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sat, 2025-09-06 at 17:25 -0400, Chuck Lever wrote: > From: Mike Snitzer >=20 > Add 'io_cache_read' to NFSD's debugfs interface so that any data > read by NFSD will either be: > - cached using page cache (NFSD_IO_BUFFERED=3D0) > - cached but removed from the page cache upon completion > (NFSD_IO_DONTCACHE=3D1). >=20 > io_cache_read may be set by writing to: > /sys/kernel/debug/nfsd/io_cache_read >=20 > Add 'io_cache_write' to NFSD's debugfs interface so that any data > written by NFSD will either be: > - cached using page cache (NFSD_IO_BUFFERED=3D0) > - cached but removed from the page cache upon completion > (NFSD_IO_DONTCACHE=3D1). >=20 > io_cache_write may be set by writing to: > /sys/kernel/debug/nfsd/io_cache_write >=20 > The default value for both settings is NFSD_IO_BUFFERED, which is > NFSD's existing behavior for both read and write. Changes to these > settings take immediate effect for all exports and NFS versions. >=20 > Currently only xfs and ext4 implement RWF_DONTCACHE. For file > systems that do not implement RWF_DONTCACHE, NFSD use only buffered > I/O when the io_cache setting is NFSD_IO_DONTCACHE. >=20 > Signed-off-by: Mike Snitzer > Signed-off-by: Chuck Lever > --- > fs/nfsd/debugfs.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++ > fs/nfsd/nfsd.h | 9 +++++ > fs/nfsd/vfs.c | 21 +++++++++++ > 3 files changed, 123 insertions(+) >=20 > Changes since v1: > - Corrected patch author > - Break back to NFSD_IO_BUFFERED when exported file system does not > support RWF_DONTCACHE > - Smoke tested NFSD_IO_DONTCACHE with NFSv3,v4.0,v4.1 on xfs and > tmpfs >=20 > diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c > index 84b0c8b559dc..2b1bb716b608 100644 > --- a/fs/nfsd/debugfs.c > +++ b/fs/nfsd/debugfs.c > @@ -27,11 +27,98 @@ static int nfsd_dsr_get(void *data, u64 *val) > static int nfsd_dsr_set(void *data, u64 val) > { > nfsd_disable_splice_read =3D (val > 0) ? true : false; > + if (!nfsd_disable_splice_read) { > + /* > + * Must use buffered I/O if splice_read is enabled. > + */ > + nfsd_io_cache_read =3D NFSD_IO_BUFFERED; > + } > return 0; > } > =20 > DEFINE_DEBUGFS_ATTRIBUTE(nfsd_dsr_fops, nfsd_dsr_get, nfsd_dsr_set, "%ll= u\n"); > =20 > +/* > + * /sys/kernel/debug/nfsd/io_cache_read > + * > + * Contents: > + * %0: NFS READ will use buffered IO > + * %1: NFS READ will use dontcache (buffered IO w/ dropbehind) > + * > + * This setting takes immediate effect for all NFS versions, > + * all exports, and in all NFSD net namespaces. > + */ > + > +static int nfsd_io_cache_read_get(void *data, u64 *val) > +{ > + *val =3D nfsd_io_cache_read; > + return 0; > +} > + > +static int nfsd_io_cache_read_set(void *data, u64 val) > +{ > + int ret =3D 0; > + > + switch (val) { > + case NFSD_IO_BUFFERED: > + nfsd_io_cache_read =3D NFSD_IO_BUFFERED; > + break; > + case NFSD_IO_DONTCACHE: > + /* > + * Must disable splice_read when enabling > + * NFSD_IO_DONTCACHE. > + */ > + nfsd_disable_splice_read =3D true; > + nfsd_io_cache_read =3D val; > + break; > + default: > + ret =3D -EINVAL; > + break; > + } > + > + return ret; > +} > + > +DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_read_fops, nfsd_io_cache_read_get= , > + nfsd_io_cache_read_set, "%llu\n"); > + > +/* > + * /sys/kernel/debug/nfsd/io_cache_write > + * > + * Contents: > + * %0: NFS WRITE will use buffered IO > + * %1: NFS WRITE will use dontcache (buffered IO w/ dropbehind) > + * > + * This setting takes immediate effect for all NFS versions, > + * all exports, and in all NFSD net namespaces. > + */ > + > +static int nfsd_io_cache_write_get(void *data, u64 *val) > +{ > + *val =3D nfsd_io_cache_write; > + return 0; > +} > + > +static int nfsd_io_cache_write_set(void *data, u64 val) > +{ > + int ret =3D 0; > + > + switch (val) { > + case NFSD_IO_BUFFERED: > + case NFSD_IO_DONTCACHE: > + nfsd_io_cache_write =3D val; > + break; > + default: > + ret =3D -EINVAL; > + break; > + } > + > + return ret; > +} > + > +DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_write_fops, nfsd_io_cache_write_g= et, > + nfsd_io_cache_write_set, "%llu\n"); > + > void nfsd_debugfs_exit(void) > { > debugfs_remove_recursive(nfsd_top_dir); > @@ -44,4 +131,10 @@ void nfsd_debugfs_init(void) > =20 > debugfs_create_file("disable-splice-read", S_IWUSR | S_IRUGO, > nfsd_top_dir, NULL, &nfsd_dsr_fops); > + > + debugfs_create_file("io_cache_read", 0644, nfsd_top_dir, NULL, > + &nfsd_io_cache_read_fops); > + > + debugfs_create_file("io_cache_write", 0644, nfsd_top_dir, NULL, > + &nfsd_io_cache_write_fops); > } > diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h > index 1cd0bed57bc2..809729d41e08 100644 > --- a/fs/nfsd/nfsd.h > +++ b/fs/nfsd/nfsd.h > @@ -153,6 +153,15 @@ static inline void nfsd_debugfs_exit(void) {} > =20 > extern bool nfsd_disable_splice_read __read_mostly; > =20 > +enum { > + /* Any new NFSD_IO enum value must be added at the end */ > + NFSD_IO_BUFFERED, > + NFSD_IO_DONTCACHE, > +}; > + > +extern u64 nfsd_io_cache_read __read_mostly; > +extern u64 nfsd_io_cache_write __read_mostly; > + > extern int nfsd_max_blksize; > =20 > static inline int nfsd_v4client(struct svc_rqst *rq) > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index 3cd3b9e069f4..714777c221ed 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -49,6 +49,8 @@ > #define NFSDDBG_FACILITY NFSDDBG_FILEOP > =20 > bool nfsd_disable_splice_read __read_mostly; > +u64 nfsd_io_cache_read __read_mostly =3D NFSD_IO_BUFFERED; > +u64 nfsd_io_cache_write __read_mostly =3D NFSD_IO_BUFFERED; > =20 > /** > * nfserrno - Map Linux errnos to NFS errnos > @@ -1099,6 +1101,16 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, stru= ct svc_fh *fhp, > size_t len; > =20 > init_sync_kiocb(&kiocb, file); > + > + switch (nfsd_io_cache_read) { > + case NFSD_IO_BUFFERED: > + break; > + case NFSD_IO_DONTCACHE: > + if (file->f_op->fop_flags & FOP_DONTCACHE) > + kiocb.ki_flags =3D IOCB_DONTCACHE; > + break; > + } > + > kiocb.ki_pos =3D offset; > =20 > v =3D 0; > @@ -1224,6 +1236,15 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_= fh *fhp, > since =3D READ_ONCE(file->f_wb_err); > if (verf) > nfsd_copy_write_verifier(verf, nn); > + > + switch (nfsd_io_cache_write) { > + case NFSD_IO_BUFFERED: > + break; > + case NFSD_IO_DONTCACHE: > + if (file->f_op->fop_flags & FOP_DONTCACHE) > + kiocb.ki_flags |=3D IOCB_DONTCACHE; > + break; > + } > host_err =3D vfs_iocb_iter_write(file, &kiocb, &iter); > if (host_err < 0) { > commit_reset_write_verifier(nn, rqstp, host_err); Could we get this into v6.18? Reviewed-by: Jeff Layton