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 A3A04220F3F for ; Mon, 18 Aug 2025 14:34:46 +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=1755527686; cv=none; b=mY5nPI/2SP9PKeiRc4z1lk5nEqW8m0K2n25C6PQfeh2MqDjVEfaTdAhKZk7H8Kz8awJNNZP6nC4+g8QZMloXjzcQne1p8Kttfrj+yU4cav3K7oJAdk3V6Gk+qJ7LN9rZz3M9g4r+QKrUoI5mFSeYqkOraMVMRE5/5YAFKylnZUU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755527686; c=relaxed/simple; bh=VZBqntlU/HPwqXSKITwFQoIsK7gOHOlcZV4fu/iLwZw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=LbCD2mv7ZYd3ZIxjwpy1+4i9vvZ1AKZh6iGf5VVWXvwOumtEsicvhWaVrWru63PgW/iQjC6gvMoHt9J5X9+b8Y2TX5QyyjiguyPKrXzkRTLQJHG2zzlyXnjfYJhNmgI1O1CQhbJh1rVb6ffBanFVJVEAzSgCJYJVOuLChnrgmFw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IMKOgsyv; 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="IMKOgsyv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F02DBC4CEEB; Mon, 18 Aug 2025 14:34:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755527686; bh=VZBqntlU/HPwqXSKITwFQoIsK7gOHOlcZV4fu/iLwZw=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=IMKOgsyvV+dpYe1XhMrW52t19dYHl1uF0k+P1sxbDgNVAwF4ZtQcSLn+wmuo/8pgU s6yxNYdZi3+qFNDp5wul176kXKrNGA+GLn/ZYepLN/kZ8amIhjniR/aAja6/VubCpX hGc+eTq3U5Yb5hxOE8E21PGEgt0QY6rRRovPILG5BJR1otIF+seKUs58cjqZHMaxGp nu2LuRaPCX+jxTJhU7136/EkF6vZJ//XYsmxp1ZtrX2j2kJ8B0ISfN/xwrn8+pboSA lSRCxJX2LXttU2h2j2nEvgOLWc9USGUcc+hGvzLt+XPT9HNA50rH6/C04ba78qvA40 yOnHMnMsggR9A== Message-ID: <69f8ed5effe369932e4f6a7f9884dc63189a826e.camel@kernel.org> Subject: Re: [PATCH v7 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: Mon, 18 Aug 2025 10:34:45 -0400 In-Reply-To: <20250815144607.50967-5-snitzer@kernel.org> References: <20250815144607.50967-1-snitzer@kernel.org> <20250815144607.50967-5-snitzer@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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NFSD's debugfs interface so that: Any data > written by NFSD will either be: > - 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. >=20 > Signed-off-by: Mike Snitzer > --- > fs/nfsd/debugfs.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > fs/nfsd/nfsd.h | 1 + > fs/nfsd/vfs.c | 16 ++++++++++++++++ > 3 files changed, 60 insertions(+) >=20 > diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c > index 3cadd45868b48..8878c3519b30c 100644 > --- a/fs/nfsd/debugfs.c > +++ b/fs/nfsd/debugfs.c > @@ -86,6 +86,46 @@ 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: > + 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); > @@ -101,4 +141,7 @@ 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 8ea8b80097195..c340708fbab4d 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 > @@ -1242,6 +1243,21 @@ 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_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; > + fallthrough; > + case NFSD_IO_UNSPECIFIED: > + case NFSD_IO_BUFFERED: > + break; > + } > host_err =3D vfs_iocb_iter_write(file, &kiocb, &iter); > if (host_err < 0) { > commit_reset_write_verifier(nn, rqstp, host_err); Ditto here on text vs. numeric interface, but I can live with it. Reviewed-by: Jeff Layton