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 9E8551DED4A for ; Fri, 8 Aug 2025 12:03:53 +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=1754654633; cv=none; b=TYE73LpDuqqk1+Zz9sxRmAdwh+Pr30RJhfuTQBBuMLgy3gxX1LjzOj3K+PhOSfscU5JvU/WAooTZ9MnO/iQIJ20DZibwomY1M9v5hR/Myr5wCV+4adchaMbKr5Qf9fBSZQqZyrfB/kqpAzxd/7Pw6Oi86CdMSwcQLuDWonrDkGE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754654633; c=relaxed/simple; bh=ozlK5HlhvziVqUuFEWnVDIM19ChWforubWfhbOkT/M0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=YMKTfGyiOh7TlC+7o+0Jf29W0FnPS1OsLoY60+b7tyVyLwHEjxKfhaSjcTMyul8fgoXxAMMbk7qac4BmxR8g82skJqKzZ5p4TyWprOnYEuLbfvuk5P2qQfPl31WTvsojJ5oN09qYmUjfmycR8uq6pVwjFA30iSj/fFcFymzgLgs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rmnihrUh; 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="rmnihrUh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB7C5C4CEED; Fri, 8 Aug 2025 12:03:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754654633; bh=ozlK5HlhvziVqUuFEWnVDIM19ChWforubWfhbOkT/M0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=rmnihrUhcB2z4NR5GpkhE5KbXgv9U9SvRVpElR+Ib6qBPSLf5GEp2of9A7lb5VmcM VTzb5eXq6OZGuxJJUqfqGHWFSisZhMhlffIoF9Zc7wAZrisXk4QjNuP+v/zm2xGwlJ u8Cu1L0vAw53I8wo8+295rE/ZzalGHr5Wo2HMKKHrTCC4MxEMyO0z8mau4wjhOeyMP Uyq7y43jeprqXOwzJxC9ZlzQQc6VUPApqZW3paN2k7RX6mioQR7cZYZWBUrWmpI/SH TY3i/fXGAWI/Esue8Mn6m6FqVCAt8EkxLHN8PMWmRASmhT/MabaInQ0xr8Gzo4hBYH 1bdcH3nqlMDfA== Message-ID: Subject: Re: [PATCH v5 4/7] NFSD: add io_cache_write controls to debugfs interface From: Jeff Layton To: Mike Snitzer , Chuck Lever Cc: linux-nfs@vger.kernel.org Date: Fri, 08 Aug 2025 08:03:51 -0400 In-Reply-To: <20250807162544.17191-5-snitzer@kernel.org> References: <20250807162544.17191-1-snitzer@kernel.org> <20250807162544.17191-5-snitzer@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV 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cached using page cache (NFSD_IO_BUFFERED=3D1) > - cached but removed from the page cache upon completion > (NFSD_IO_DONTCACHE=3D2). > - not cached (NFSD_IO_DIRECT=3D3) >=20 > io_cache_write may be set by writing to: > /sys/kernel/debug/nfsd/io_cache_write >=20 > If NFSD_IO_DONTCACHE is specified using 2, FOP_DONTCACHE must be > advertised as supported by the underlying filesystem (e.g. XFS), > otherwise all IO flagged with RWF_DONTCACHE will fail with > -EOPNOTSUPP. >=20 > If NFSD_IO_DIRECT is specified using 3, the IO must be aligned > relative to the underlying block device's logical_block_size. Also the > memory buffer used to store the WRITE payload must be aligned relative > to the underlying block device's dma_alignment. And if it isn't, it looks it falls back on doing regular buffered I/O (at least until patch #7)? > Signed-off-by: Mike Snitzer > --- > fs/nfsd/debugfs.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ > fs/nfsd/nfsd.h | 1 + > fs/nfsd/vfs.c | 16 ++++++++++++++++ > 3 files changed, 61 insertions(+) >=20 > diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c > index c07f71d4e84f4..872de65f0e9ac 100644 > --- a/fs/nfsd/debugfs.c > +++ b/fs/nfsd/debugfs.c > @@ -87,6 +87,47 @@ static int nfsd_io_cache_read_set(void *data, u64 val) > DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_read_fops, nfsd_io_cache_read_get= , > nfsd_io_cache_read_set, "%llu\n"); > =20 > +/* > + * /sys/kernel/debug/nfsd/io_cache_write > + * > + * Contents: > + * %1: NFS WRITE will use buffered IO > + * %2: NFS WRITE will use dontcache (buffered IO w/ dropbehind) > + * %3: NFS WRITE will use direct IO > + * > + * The default value of this setting is zero (UNSPECIFIED). > + * 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: > + case NFSD_IO_DIRECT: > + nfsd_io_cache_write =3D val; > + break; > + default: > + nfsd_io_cache_write =3D NFSD_IO_UNSPECIFIED; > + 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); > @@ -102,4 +143,7 @@ void nfsd_debugfs_init(void) > =20 > debugfs_create_file("io_cache_read", S_IWUSR | S_IRUGO, > nfsd_top_dir, NULL, &nfsd_io_cache_read_fops); > + > + debugfs_create_file("io_cache_write", S_IWUSR | S_IRUGO, > + nfsd_top_dir, NULL, &nfsd_io_cache_write_fops); > } > diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h > index 6ef799405145f..fe935b4cda538 100644 > --- a/fs/nfsd/nfsd.h > +++ b/fs/nfsd/nfsd.h > @@ -161,6 +161,7 @@ enum { > }; > =20 > extern u64 nfsd_io_cache_read __read_mostly; > +extern u64 nfsd_io_cache_write __read_mostly; > =20 > extern int nfsd_max_blksize; > =20 > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index 26b6d96258711..5768244c7a3c3 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -50,6 +50,7 @@ > =20 > bool nfsd_disable_splice_read __read_mostly; > u64 nfsd_io_cache_read __read_mostly; > +u64 nfsd_io_cache_write __read_mostly; > =20 > /** > * nfserrno - Map Linux errnos to NFS errnos > @@ -1234,6 +1235,21 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_= fh *fhp, > =20 > nvecs =3D xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, payload); > iov_iter_bvec(&iter, ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt); > + > + switch (nfsd_io_cache_write) { > + case NFSD_IO_DIRECT: > + /* direct I/O must be aligned to device logical sector size */ > + if (nf->nf_dio_mem_align && nf->nf_dio_offset_align && > + (((offset | *cnt) & (nf->nf_dio_offset_align-1)) =3D=3D 0)) > + kiocb.ki_flags |=3D IOCB_DIRECT; > + break; > + case NFSD_IO_DONTCACHE: > + kiocb.ki_flags |=3D IOCB_DONTCACHE; > + break; > + case NFSD_IO_BUFFERED: > + break; > + } > + > since =3D READ_ONCE(file->f_wb_err); > if (verf) > nfsd_copy_write_verifier(verf, nn); Reviewed-by: Jeff Layton