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 415662367B6 for ; Fri, 8 Aug 2025 12:05:08 +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=1754654709; cv=none; b=YPkK5it1V2D63k0V7B3oq7CqNQ+k/aGdePSml3bkZetFsT4Pg0iUwU19EhRDO6bgAp99d7ZAeCI0OTXLyil0ePsXwSUa8WLioYHlJy2GmScyVuTi4u92B+JJbd7XntVkGCZsjY07t4H/mWGMLh3QYweAwFu3HoOAgim1TmmCYN0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754654709; c=relaxed/simple; bh=HrzlevnFXWocxTcFC9Mwwk2djJHL1hbuTHKY+RrWQts=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=qpAJq3RXZp7xn3mDLiRbYqcPjk/3rDgR8oFuFV2o3pMtgLj3HG6wvAuhJ/QTf/4Tb1Xn+hpQbCQAL/s1neo4w3mxEAW8Ucutm679CuGuUNAt2CH77Sp97L596wsjTDnCMHLxI8zdmOF7B3JeKUHc31mgMXw31W2wgMbUvfVhy4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SlL19d2S; 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="SlL19d2S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 802AFC4CEED; Fri, 8 Aug 2025 12:05:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754654708; bh=HrzlevnFXWocxTcFC9Mwwk2djJHL1hbuTHKY+RrWQts=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=SlL19d2SV5VcIPg+/J0KWRDYuxTiJTl9tKpEB32ddWwiSxbJ/V7QKd2g4hMjjUNEG cLhClR7FOHTBRGmIg2AhkCnE+mmlI8oxBEIaAajHuK0JjK2c9aqdx3wuCkcr8q/b0F j2nHztbBiz9vsFnMV1YD2MTpOAwr76q/AEvDOle4dF2AUmFOEbsHthX1vXYi/S8mU6 +05/PyOIXtCBMb4R7ecCc8/DOrA4/saTNE/KahhPdWvi4sb8r8Ih6N8W8EViXkRYUd WAL86mwL6EaluGFv/8wIBmWaykmn8bFrjOshXUnj/M87zmWalAFh95HYV8sugDFvCE M6xqXnzY/45Dw== Message-ID: Subject: Re: [PATCH v5 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: Fri, 08 Aug 2025 08:05:07 -0400 In-Reply-To: <20250807162544.17191-4-snitzer@kernel.org> References: <20250807162544.17191-1-snitzer@kernel.org> <20250807162544.17191-4-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_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 Ditto here. Looks like this falls back to buffered I/O until patch #6? > Signed-off-by: Mike Snitzer > --- > fs/nfsd/debugfs.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++ > fs/nfsd/nfsd.h | 9 ++++++++ > fs/nfsd/vfs.c | 19 +++++++++++++--- > 3 files changed, 83 insertions(+), 3 deletions(-) >=20 > diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c > index 84b0c8b559dc9..c07f71d4e84f4 100644 > --- a/fs/nfsd/debugfs.c > +++ b/fs/nfsd/debugfs.c > @@ -27,11 +27,66 @@ 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: > + nfsd_io_cache_read =3D NFSD_IO_UNSPECIFIED; > + 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 +99,7 @@ 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..26b6d96258711 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 > @@ -1099,17 +1100,29 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, str= uct svc_fh *fhp, > size_t len; > =20 > init_sync_kiocb(&kiocb, file); > + > + if (nfsd_io_cache_read =3D=3D NFSD_IO_DIRECT) { > + /* Verify ondisk DIO alignment, memory addrs checked below */ > + if (nf->nf_dio_mem_align && nf->nf_dio_read_offset_align && > + (((offset | *count) & (nf->nf_dio_read_offset_align - 1)) =3D=3D 0= )) > + kiocb.ki_flags =3D IOCB_DIRECT; > + } else if (nfsd_io_cache_read =3D=3D NFSD_IO_DONTCACHE) > + kiocb.ki_flags =3D IOCB_DONTCACHE; > + > kiocb.ki_pos =3D offset; > =20 > v =3D 0; > total =3D *count; > while (total) { > len =3D min_t(size_t, total, PAGE_SIZE - base); > - bvec_set_page(&rqstp->rq_bvec[v], *(rqstp->rq_next_page++), > - len, base); > + bvec_set_page(&rqstp->rq_bvec[v], *(rqstp->rq_next_page++), len, base)= ; > + /* No need to verify memory is DIO-aligned since bv_offset is 0 */ > + if (unlikely((kiocb.ki_flags & IOCB_DIRECT) && base && > + (base & (nf->nf_dio_mem_align - 1)))) > + kiocb.ki_flags &=3D ~IOCB_DIRECT; > total -=3D len; > - ++v; > base =3D 0; > + v++; > } > WARN_ON_ONCE(v > rqstp->rq_maxpages); > =20 --=20 Jeff Layton