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 35DD835A2A3 for ; Mon, 18 Aug 2025 14:33:11 +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=1755527592; cv=none; b=F18WEaBLrruIbN9w/wH/YW0xgclxprLUuB0jjc4u6tlLcs3lz3QeM+XshLRYwNWC9ZlGo0P/ekKVIWGiVyz/XjsbY2v6DN+oSGEhLfBXlOJMaaE7ch8fl93V44Pvz8GGHWFNmkvSPxpPhlMRiH+FgvJE3+Z5/w+xVpBnPNOECFU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755527592; c=relaxed/simple; bh=rcH34hbHSg/rEc+XH549K/H7ajY7fFoz5L4lTZA7/8U=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=qE9K0okFCUeJa/10gZA5a6vqudj2MVbEn4GW3KpqAP2sHVqpyrjLvfhBiYvg29Q12OsF49p9R75W8pCGSmz23UvrSTMZmkLQ11eMlfMDqjPIkJNukHaKDXv4M0DJBJG6peva0uP1vtxqdmOZL1MO7mBibTokvthvDSm3BktqZ54= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=itGw5IeD; 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="itGw5IeD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63B72C4CEEB; Mon, 18 Aug 2025 14:33:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755527591; bh=rcH34hbHSg/rEc+XH549K/H7ajY7fFoz5L4lTZA7/8U=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=itGw5IeDTGk+XCJhHQ7XMQug1rnYNV+ylo8Y4d8SjRmUlOP5c1PJcBZjEisOoRCfM yMUk93A7d3/9ZJztCeRCM/d+M7bwrI0LRcj+yVED6WuUrJGINjuOHari1FHqgXJbbE /aP0ajrwy0QGhPA0fafrhtv12+fb0kqY+K+fQDS8hwSBAyly3Y2tlZ8zXnRKHLjKj7 rsPoyA4o6fnk61aUvrqGwgnNZ7TzQdP0wWizOwuBxqhmo4/HPgc5a46Ad6Qou+yOHu C7/xERzmiQLX98OMA9Eu7fB2/Pv9o/TFIr63SnqMh7Re8E8L0qhtXGWD2LhwiZ7QpY 2GylXYTsLK74g== Message-ID: <8fb5d28a95c88285fbec27a9db04843a0dbc05e8.camel@kernel.org> Subject: Re: [PATCH v7 3/7] NFSD: add io_cache_read controls to debugfs interface From: Jeff Layton To: Mike Snitzer , Chuck Lever Cc: linux-nfs@vger.kernel.org Date: Mon, 18 Aug 2025 10:33:10 -0400 In-Reply-To: <20250815144607.50967-4-snitzer@kernel.org> References: <20250815144607.50967-1-snitzer@kernel.org> <20250815144607.50967-4-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 > read 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_read may be set by writing to: > /sys/kernel/debug/nfsd/io_cache_read >=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 read must be aligned relative to the > underlying block device's dma_alignment. >=20 > Signed-off-by: Mike Snitzer > --- > fs/nfsd/debugfs.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++ > fs/nfsd/nfsd.h | 9 ++++++++ > fs/nfsd/vfs.c | 18 +++++++++++++++ > 3 files changed, 84 insertions(+) >=20 > diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c > index 84b0c8b559dc9..3cadd45868b48 100644 > --- a/fs/nfsd/debugfs.c > +++ b/fs/nfsd/debugfs.c > @@ -27,11 +27,65 @@ 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) { > + /* > + * Cannot use NFSD_IO_DONTCACHE or NFSD_IO_DIRECT > + * 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: > + * %1: NFS READ will use buffered IO > + * %2: NFS READ will use dontcache (buffered IO w/ dropbehind) > + * %3: NFS READ 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_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: > + case NFSD_IO_DIRECT: > + /* > + * Must disable splice_read when enabling > + * NFSD_IO_DONTCACHE or NFSD_IO_DIRECT. > + */ > + 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"); > + > void nfsd_debugfs_exit(void) > { > debugfs_remove_recursive(nfsd_top_dir); > @@ -44,4 +98,7 @@ 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", S_IWUSR | S_IRUGO, > + nfsd_top_dir, NULL, &nfsd_io_cache_read_fops); > } > diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h > index 1cd0bed57bc2f..6ef799405145f 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 { > + NFSD_IO_UNSPECIFIED =3D 0, > + NFSD_IO_BUFFERED, > + NFSD_IO_DONTCACHE, > + NFSD_IO_DIRECT, > +}; > + > +extern u64 nfsd_io_cache_read __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 79439ad93880a..8ea8b80097195 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -49,6 +49,7 @@ > #define NFSDDBG_FACILITY NFSDDBG_FILEOP > =20 > bool nfsd_disable_splice_read __read_mostly; > +u64 nfsd_io_cache_read __read_mostly; > =20 > /** > * nfserrno - Map Linux errnos to NFS errnos > @@ -1099,6 +1100,23 @@ __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_DIRECT: > + /* Verify ondisk and memory DIO alignment */ > + if (nf->nf_dio_mem_align && nf->nf_dio_read_offset_align && > + (((offset | *count) & (nf->nf_dio_read_offset_align - 1)) =3D=3D 0= ) && > + (base & (nf->nf_dio_mem_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; > + } > + > kiocb.ki_pos =3D offset; > =20 > v =3D 0; I'd still prefer a text-based interface, but I can live with it. Reviewed-by: Jeff Layton