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 B30E232D0CF for ; Thu, 16 Oct 2025 16:10:28 +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=1760631028; cv=none; b=RyW6IJSm+sWBxsSDHmUO9Z5wvL03O8iLk/9JzAOAXPZbk6Kc0qgYi5KAASHe6PFu9aF1ZnIZpvliyq1nHTwtlZfY6w58FO5kjfu0/cxmkVMLHAMkIsBPDcrwK3VSd1md9tMLwggF6HOuGay2HgrEDw4KI1y90uFgFm5CmAHquJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760631028; c=relaxed/simple; bh=4Z8g9EaKz5y2kcVZ7VRrbbeUOpifC+SLLrkbZ8Of6l0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Pn9KBW3xp0BGiStd3rgprW4CRvqxszp+F77/C+1GYEY2jo/Wzy7gnPWcgD6qyg0coYdJVfn9akTKJJ30RGnK0qeVwl0MeYEh8FMiNlwC4OvjqCCBH4UA2WD0MdmyDMXIBPXX6I8Wxd8o8c1iCsQFzy6+5B7nEWk1c8kqjum3zjo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sqggobzz; 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="sqggobzz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96183C4CEF1; Thu, 16 Oct 2025 16:10:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760631028; bh=4Z8g9EaKz5y2kcVZ7VRrbbeUOpifC+SLLrkbZ8Of6l0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=sqggobzzGBEnnbd1d3e0ZaV6p2lXTTxlGI8yQiEX50ioUmyoV4pH6mVWCqKR1fhXv ipcsGOPt0e73WyFAjixYbCa1fStHNkDC1Fz+OfkrjpiJzXa08xYesBSQ2Am3pDqxl5 K8/3bneQyneDte5np3tL1RoaldruKeket09DrejE1EfNnLNj8BGnJ0jgVoItuSbs4X pq6k2iXhUbuWiAZAhihXZt3us/kj/U6nZR8EcT0QeBKf9Kdd7Na/7jXPxy+VO+uMoP wW3QVXPAbcTxxc2p3gZa2+ceLPuxjEEPE5w8J99vsSLOmsbNxQXNFJr4spAbPgIWbr nWA9A1dSiQZVA== Message-ID: Subject: Re: [PATCH v3] NFSD: Implement NFSD_IO_DIRECT for NFS WRITE From: Jeff Layton To: Mike Snitzer , Chuck Lever Cc: NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , linux-nfs@vger.kernel.org, Chuck Lever Date: Thu, 16 Oct 2025 12:10:26 -0400 In-Reply-To: References: <20251013190113.252097-1-cel@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 YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf CBYyUE8QJpvTZyfUHNYldXlrjO6n5MdOempLqWpfOmcGkwnyNRBR46g/jf8KnPRwXs509yAqDB6sE LZH+yWr9LQZEwARAQABtCVKZWZmIExheXRvbiA8amxheXRvbkBwb29jaGllcmVkcy5uZXQ+iQI7BB MBAgAlAhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAUCTpXWPAIZAQAKCRAADmhBGVaCFc65D/4 gBLNMHopQYgG/9RIM3kgFCCQV0pLv0hcg1cjr+bPI5f1PzJoOVi9s0wBDHwp8+vtHgYhM54yt43uI 7Htij0RHFL5eFqoVT4TSfAg2qlvNemJEOY0e4daljjmZM7UtmpGs9NN0r9r50W82eb5Kw5bc/r0km R/arUS2st+ecRsCnwAOj6HiURwIgfDMHGPtSkoPpu3DDp/cjcYUg3HaOJuTjtGHFH963B+f+hyQ2B rQZBBE76ErgTDJ2Db9Ey0kw7VEZ4I2nnVUY9B5dE2pJFVO5HJBMp30fUGKvwaKqYCU2iAKxdmJXRI ONb7dSde8LqZahuunPDMZyMA5+mkQl7kpIpR6kVDIiqmxzRuPeiMP7O2FCUlS2DnJnRVrHmCljLkZ Wf7ZUA22wJpepBligemtSRSbqCyZ3B48zJ8g5B8xLEntPo/NknSJaYRvfEQqGxgk5kkNWMIMDkfQO lDSXZvoxqU9wFH/9jTv1/6p8dHeGM0BsbBLMqQaqnWiVt5mG92E1zkOW69LnoozE6Le+12DsNW7Rj iR5K+27MObjXEYIW7FIvNN/TQ6U1EOsdxwB8o//Yfc3p2QqPr5uS93SDDan5ehH59BnHpguTc27Xi QQZ9EGiieCUx6Zh2ze3X2UW9YNzE15uKwkkuEIj60NvQRmEDfweYfOfPVOueC+iFifbQgSmVmZiBM YXl0b24gPGpsYXl0b25AcmVkaGF0LmNvbT6JAjgEEwECACIFAk6V0q0CGwMGCwkIBwMCBhUIAgkKC wQWAgMBAh4BAheAAAoJEAAOaEEZVoIViKUQALpvsacTMWWOd7SlPFzIYy2/fjvKlfB/Xs4YdNcf9q LqF+lk2RBUHdR/dGwZpvw/OLmnZ8TryDo2zXVJNWEEUFNc7wQpl3i78r6UU/GUY/RQmOgPhs3epQC 3PMJj4xFx+VuVcf/MXgDDdBUHaCTT793hyBeDbQuciARDJAW24Q1RCmjcwWIV/pgrlFa4lAXsmhoa c8UPc82Ijrs6ivlTweFf16VBc4nSLX5FB3ls7S5noRhm5/Zsd4PGPgIHgCZcPgkAnU1S/A/rSqf3F LpU+CbVBDvlVAnOq9gfNF+QiTlOHdZVIe4gEYAU3CUjbleywQqV02BKxPVM0C5/oVjMVx3bri75n1 TkBYGmqAXy9usCkHIsG5CBHmphv9MHmqMZQVsxvCzfnI5IO1+7MoloeeW/lxuyd0pU88dZsV/riHw 87i2GJUJtVlMl5IGBNFpqoNUoqmvRfEMeXhy/kUX4Xc03I1coZIgmwLmCSXwx9MaCPFzV/dOOrju2 xjO+2sYyB5BNtxRqUEyXglpujFZqJxxau7E0eXoYgoY9gtFGsspzFkVNntamVXEWVVgzJJr/EWW0y +jNd54MfPRqH+eCGuqlnNLktSAVz1MvVRY1dxUltSlDZT7P2bUoMorIPu8p7ZCg9dyX1+9T6Muc5d Hxf/BBP/ir+3e8JTFQBFOiLNdFtB9KZWZmIExheXRvbiA8amxheXRvbkBzYW1iYS5vcmc+iQI4BBM BAgAiBQJOldK9AhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRAADmhBGVaCFWgWD/0ZRi4h N9FK2BdQs9RwNnFZUr7JidAWfCrs37XrA/56olQl3ojn0fQtrP4DbTmCuh0SfMijB24psy1GnkPep naQ6VRf7Dxg/Y8muZELSOtsv2CKt3/02J1BBitrkkqmHyni5fLLYYg6fub0T/8Kwo1qGPdu1hx2BQ RERYtQ/S5d/T0cACdlzi6w8rs5f09hU9Tu4qV1JLKmBTgUWKN969HPRkxiojLQziHVyM/weR5Reu6 FZVNuVBGqBD+sfk/c98VJHjsQhYJijcsmgMb1NohAzwrBKcSGKOWJToGEO/1RkIN8tqGnYNp2G+aR 685D0chgTl1WzPRM6mFG1+n2b2RR95DxumKVpwBwdLPoCkI24JkeDJ7lXSe3uFWISstFGt0HL8Eew P8RuGC8s5h7Ct91HMNQTbjgA+Vi1foWUVXpEintAKgoywaIDlJfTZIl6Ew8ETN/7DLy8bXYgq0Xzh aKg3CnOUuGQV5/nl4OAX/3jocT5Cz/OtAiNYj5mLPeL5z2ZszjoCAH6caqsF2oLyAnLqRgDgR+wTQ T6gMhr2IRsl+cp8gPHBwQ4uZMb+X00c/Amm9VfviT+BI7B66cnC7Zv6Gvmtu2rEjWDGWPqUgccB7h dMKnKDthkA227/82tYoFiFMb/NwtgGrn5n2vwJyKN6SEoygGrNt0SI84y6hEVbQlSmVmZiBMYXl0b 24gPGpsYXl0b25AcHJpbWFyeWRhdGEuY29tPokCOQQTAQIAIwUCU4xmKQIbAwcLCQgHAwIBBhUIAg kKCwQWAgMBAh4BAheAAAoJEAAOaEEZVoIV1H0P/j4OUTwFd7BBbpoSp695qb6HqCzWMuExsp8nZjr uymMaeZbGr3OWMNEXRI1FWNHMtcMHWLP/RaDqCJil28proO+PQ/yPhsr2QqJcW4nr91tBrv/MqItu AXLYlsgXqp4BxLP67bzRJ1Bd2x0bWXurpEXY//VBOLnODqThGEcL7jouwjmnRh9FTKZfBDpFRaEfD FOXIfAkMKBa/c9TQwRpx2DPsl3eFWVCNuNGKeGsirLqCxUg5kWTxEorROppz9oU4HPicL6rRH22Ce 6nOAON2vHvhkUuO3GbffhrcsPD4DaYup4ic+DxWm+DaSSRJ+e1yJvwi6NmQ9P9UAuLG93S2MdNNbo sZ9P8k2mTOVKMc+GooI9Ve/vH8unwitwo7ORMVXhJeU6Q0X7zf3SjwDq2lBhn1DSuTsn2DbsNTiDv qrAaCvbsTsw+SZRwF85eG67eAwouYk+dnKmp1q57LDKMyzysij2oDKbcBlwB/TeX16p8+LxECv51a sjS9TInnipssssUDrHIvoTTXWcz7Y5wIngxDFwT8rPY3EggzLGfK5Zx2Q5S/N0FfmADmKknG/D8qG IcJE574D956tiUDKN4I+/g125ORR1v7bP+OIaayAvq17RP+qcAqkxc0x8iCYVCYDouDyNvWPGRhbL UO7mlBpjW9jK9e2fvZY9iw3QzIPGKtClKZWZmIExheXRvbiA8amVmZi5sYXl0b25AcHJpbWFyeWRh dGEuY29tPokCOQQTAQIAIwUCU4xmUAIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEAAOa EEZVoIVzJoQALFCS6n/FHQS+hIzHIb56JbokhK0AFqoLVzLKzrnaeXhE5isWcVg0eoV2oTScIwUSU apy94if69tnUo4Q7YNt8/6yFM6hwZAxFjOXR0ciGE3Q+Z1zi49Ox51yjGMQGxlakV9ep4sV/d5a50 M+LFTmYSAFp6HY23JN9PkjVJC4PUv5DYRbOZ6Y1+TfXKBAewMVqtwT1Y+LPlfmI8dbbbuUX/kKZ5d dhV2736fgyfpslvJKYl0YifUOVy4D1G/oSycyHkJG78OvX4JKcf2kKzVvg7/Rnv+AueCfFQ6nGwPn 0P91I7TEOC4XfZ6a1K3uTp4fPPs1Wn75X7K8lzJP/p8lme40uqwAyBjk+IA5VGd+CVRiyJTpGZwA0 jwSYLyXboX+Dqm9pSYzmC9+/AE7lIgpWj+3iNisp1SWtHc4pdtQ5EU2SEz8yKvDbD0lNDbv4ljI7e flPsvN6vOrxz24mCliEco5DwhpaaSnzWnbAPXhQDWb/lUgs/JNk8dtwmvWnqCwRqElMLVisAbJmC0 BhZ/Ab4sph3EaiZfdXKhiQqSGdK4La3OTJOJYZphPdGgnkvDV9Pl1QZ0ijXQrVIy3zd6VCNaKYq7B AKidn5g/2Q8oio9Tf4XfdZ9dtwcB+bwDJFgvvDYaZ5bI3ln4V3EyW5i2NfXazz/GA/I/ZtbsigCFc 8ftCBKZWZmIExheXRvbiA8amxheXRvbkBrZXJuZWwub3JnPokCOAQTAQIAIgUCWe8u6AIbAwYLCQg HAwIGFQgCCQoLBBYCAwECHgECF4AACgkQAA5oQRlWghUuCg/+Lb/xGxZD2Q1oJVAE37uW308UpVSD 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 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-10-15 at 18:13 -0400, Mike Snitzer wrote: > If NFSD_IO_DIRECT is used, split any misaligned WRITE into a start, > middle and end as needed. The large middle extent is DIO-aligned and > the start and/or end are misaligned. Synchronous buffered IO (with > preference towards using DONTCACHE) is used for the misaligned extents > and O_DIRECT is used for the middle DIO-aligned extent. >=20 > nfsd_issue_write_dio() promotes @stable_how to NFS_FILE_SYNC, which > allows the client to drop its dirty data and avoid needing an extra > COMMIT operation. >=20 > If vfs_iocb_iter_write() returns -ENOTBLK, due to its inability to > invalidate the page cache on behalf of the DIO WRITE, then > nfsd_issue_write_dio() will fall back to using buffered IO. >=20 > These changes served as the original starting point for the NFS > client's misaligned O_DIRECT support that landed with commit > c817248fc831 ("nfs/localio: add proper O_DIRECT support for READ and > WRITE"). But NFSD's support is simpler because it currently doesn't > use AIO completion. >=20 > Signed-off-by: Mike Snitzer > --- > fs/nfsd/debugfs.c | 1 + > fs/nfsd/trace.h | 1 + > fs/nfsd/vfs.c | 218 ++++++++++++++++++++++++++++++++++++++++++++-- > 3 files changed, 215 insertions(+), 5 deletions(-) >=20 > Changes since v2: > - rebased ontop of "[PATCH v1] NFSD: Enable return of an updated stable_h= ow to NFS clients" > - set both IOCB_DSYNC and IOCB_SYNC (rather than just IOCB_SYNC) in nfsd_= issue_write_dio() > - update nfsd_issue_write_dio() to promote @stable_how to NFS_FILE_SYNC > - push call to trace_nfsd_write_direct down from nfsd_direct_write to nfs= d_issue_write_dio=20 > - fix comment block style to have naked '/*' on first line >=20 > diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c > index 00eb1ecef6ac..7f44689e0a53 100644 > --- a/fs/nfsd/debugfs.c > +++ b/fs/nfsd/debugfs.c > @@ -108,6 +108,7 @@ static int nfsd_io_cache_write_set(void *data, u64 va= l) > switch (val) { > case NFSD_IO_BUFFERED: > case NFSD_IO_DONTCACHE: > + case NFSD_IO_DIRECT: > nfsd_io_cache_write =3D val; > break; > default: > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h > index bfd41236aff2..ad74439d0105 100644 > --- a/fs/nfsd/trace.h > +++ b/fs/nfsd/trace.h > @@ -469,6 +469,7 @@ DEFINE_NFSD_IO_EVENT(read_io_done); > DEFINE_NFSD_IO_EVENT(read_done); > DEFINE_NFSD_IO_EVENT(write_start); > DEFINE_NFSD_IO_EVENT(write_opened); > +DEFINE_NFSD_IO_EVENT(write_direct); > DEFINE_NFSD_IO_EVENT(write_io_done); > DEFINE_NFSD_IO_EVENT(write_done); > DEFINE_NFSD_IO_EVENT(commit_start); > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index a3dee33a7233..ba7cb698ac68 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -1253,6 +1253,210 @@ static int wait_for_concurrent_writes(struct file= *file) > return err; > } > =20 > +struct nfsd_write_dio { > + ssize_t start_len; /* Length for misaligned first extent */ > + ssize_t middle_len; /* Length for DIO-aligned middle extent */ > + ssize_t end_len; /* Length for misaligned last extent */ > +}; > + > +static bool > +nfsd_is_write_dio_possible(loff_t offset, unsigned long len, > + struct nfsd_file *nf, struct nfsd_write_dio *write_dio) > +{ > + const u32 dio_blocksize =3D nf->nf_dio_offset_align; > + loff_t start_end, orig_end, middle_end; > + > + if (unlikely(!nf->nf_dio_mem_align || !dio_blocksize)) > + return false; > + if (unlikely(dio_blocksize > PAGE_SIZE)) > + return false; > + if (unlikely(len < dio_blocksize)) > + return false; > + > + start_end =3D round_up(offset, dio_blocksize); > + orig_end =3D offset + len; > + middle_end =3D round_down(orig_end, dio_blocksize); > + > + write_dio->start_len =3D start_end - offset; > + write_dio->middle_len =3D middle_end - start_end; > + write_dio->end_len =3D orig_end - middle_end; > + > + return true; > +} > + > +static bool nfsd_iov_iter_aligned_bvec(const struct iov_iter *i, > + unsigned int addr_mask, unsigned int len_mask) > +{ > + const struct bio_vec *bvec =3D i->bvec; > + size_t skip =3D i->iov_offset; > + size_t size =3D i->count; > + > + if (size & len_mask) > + return false; > + do { > + size_t len =3D bvec->bv_len; > + > + if (len > size) > + len =3D size; > + if ((unsigned long)(bvec->bv_offset + skip) & addr_mask) > + return false; > + bvec++; > + size -=3D len; > + skip =3D 0; > + } while (size); > + > + return true; > +} > + > +/* > + * Setup as many as 3 iov_iter based on extents described by @write_dio. > + * Returns the number of iov_iter that were setup. > + */ > +static int > +nfsd_setup_write_dio_iters(struct iov_iter **iterp, bool *iter_is_dio_al= igned, > + struct bio_vec *rq_bvec, unsigned int nvecs, > + unsigned long cnt, struct nfsd_write_dio *write_dio, > + struct nfsd_file *nf) > +{ > + int n_iters =3D 0; > + struct iov_iter *iters =3D *iterp; > + > + /* Setup misaligned start? */ > + if (write_dio->start_len) { > + iov_iter_bvec(&iters[n_iters], ITER_SOURCE, rq_bvec, nvecs, cnt); > + iters[n_iters].count =3D write_dio->start_len; > + iter_is_dio_aligned[n_iters] =3D false; > + ++n_iters; > + } > + > + /* Setup DIO-aligned middle */ > + iov_iter_bvec(&iters[n_iters], ITER_SOURCE, rq_bvec, nvecs, cnt); > + if (write_dio->start_len) > + iov_iter_advance(&iters[n_iters], write_dio->start_len); > + iters[n_iters].count -=3D write_dio->end_len; > + iter_is_dio_aligned[n_iters] =3D > + nfsd_iov_iter_aligned_bvec(&iters[n_iters], > + nf->nf_dio_mem_align-1, nf->nf_dio_offset_align-1); > + if (unlikely(!iter_is_dio_aligned[n_iters])) > + return 0; /* no DIO-aligned IO possible */ > + ++n_iters; > + > + /* Setup misaligned end? */ > + if (write_dio->end_len) { > + iov_iter_bvec(&iters[n_iters], ITER_SOURCE, rq_bvec, nvecs, cnt); > + iov_iter_advance(&iters[n_iters], > + write_dio->start_len + write_dio->middle_len); > + iter_is_dio_aligned[n_iters] =3D false; > + ++n_iters; > + } > + > + return n_iters; > +} > + > +static int > +nfsd_buffered_write(struct svc_rqst *rqstp, struct file *file, > + unsigned int nvecs, unsigned long *cnt, > + struct kiocb *kiocb) > +{ > + struct iov_iter iter; > + int host_err; > + > + iov_iter_bvec(&iter, ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt); > + host_err =3D vfs_iocb_iter_write(file, kiocb, &iter); > + if (host_err < 0) > + return host_err; > + *cnt =3D host_err; > + > + return 0; > +} > + > +static int > +nfsd_issue_write_dio(struct svc_rqst *rqstp, struct svc_fh *fhp, struct = nfsd_file *nf, > + u32 *stable_how, unsigned int nvecs, unsigned long *cnt, > + struct kiocb *kiocb, struct nfsd_write_dio *write_dio) > +{ > + struct file *file =3D nf->nf_file; > + bool iter_is_dio_aligned[3]; > + struct iov_iter iter_stack[3]; > + struct iov_iter *iter =3D iter_stack; > + unsigned int n_iters =3D 0; > + unsigned long in_count =3D *cnt; > + loff_t in_offset =3D kiocb->ki_pos; > + ssize_t host_err; > + > + n_iters =3D nfsd_setup_write_dio_iters(&iter, iter_is_dio_aligned, > + rqstp->rq_bvec, nvecs, *cnt, write_dio, nf); > + if (unlikely(!n_iters)) > + return nfsd_buffered_write(rqstp, file, nvecs, cnt, kiocb); > + > + trace_nfsd_write_direct(rqstp, fhp, in_offset, in_count); > + > + /* > + * Any buffered IO issued here will be misaligned, use > + * sync IO to ensure it has completed before returning. > + * Also update @stable_how to avoid need for COMMIT. > + */ > + kiocb->ki_flags |=3D (IOCB_DSYNC|IOCB_SYNC); > + *stable_how =3D NFS_FILE_SYNC; > + > + *cnt =3D 0; > + for (int i =3D 0; i < n_iters; i++) { > + if (iter_is_dio_aligned[i]) > + kiocb->ki_flags |=3D IOCB_DIRECT; > + else > + kiocb->ki_flags &=3D ~IOCB_DIRECT; > + > + host_err =3D vfs_iocb_iter_write(file, kiocb, &iter[i]); > + if (host_err < 0) { > + /* > + * VFS will return -ENOTBLK if DIO WRITE fails to > + * invalidate the page cache. Retry using buffered IO. > + */ > + if (unlikely(host_err =3D=3D -ENOTBLK)) { > + kiocb->ki_flags &=3D ~IOCB_DIRECT; > + *cnt =3D in_count; > + kiocb->ki_pos =3D in_offset; > + return nfsd_buffered_write(rqstp, file, > + nvecs, cnt, kiocb); > + } else if (unlikely(host_err =3D=3D -EINVAL)) { > + struct inode *inode =3D d_inode(fhp->fh_dentry); > + > + pr_info_ratelimited("nfsd: Direct I/O alignment failure on %s/%ld\n"= , > + inode->i_sb->s_id, inode->i_ino); > + host_err =3D -ESERVERFAULT; > + } > + return host_err; > + } > + *cnt +=3D host_err; > + if (host_err < iter[i].count) /* partial write? */ > + break; > + } > + > + return 0; > +} > + > +static noinline_for_stack int > +nfsd_direct_write(struct svc_rqst *rqstp, struct svc_fh *fhp, > + struct nfsd_file *nf, u32 *stable_how, unsigned int nvecs, > + unsigned long *cnt, struct kiocb *kiocb) > +{ > + struct nfsd_write_dio write_dio; > + > + /* > + * Check if IOCB_DONTCACHE can be used when issuing buffered IO; > + * if so, set it to preserve intent of NFSD_IO_DIRECT (it will > + * be ignored for any DIO issued here). > + */ > + if (nf->nf_file->f_op->fop_flags & FOP_DONTCACHE) > + kiocb->ki_flags |=3D IOCB_DONTCACHE; > + > + if (nfsd_is_write_dio_possible(kiocb->ki_pos, *cnt, nf, &write_dio)) > + return nfsd_issue_write_dio(rqstp, fhp, nf, stable_how, nvecs, > + cnt, kiocb, &write_dio); > + > + return nfsd_buffered_write(rqstp, nf->nf_file, nvecs, cnt, kiocb); > +} > + > /** > * nfsd_vfs_write - write data to an already-open file > * @rqstp: RPC execution context > @@ -1281,7 +1485,6 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_f= h *fhp, > u32 stable =3D *stable_how; > struct kiocb kiocb; > struct svc_export *exp; > - struct iov_iter iter; > errseq_t since; > __be32 nfserr; > int host_err; > @@ -1318,25 +1521,30 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc= _fh *fhp, > kiocb.ki_flags |=3D IOCB_DSYNC; > =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); > + > since =3D READ_ONCE(file->f_wb_err); > if (verf) > nfsd_copy_write_verifier(verf, nn); > =20 > switch (nfsd_io_cache_write) { > - case NFSD_IO_BUFFERED: > + case NFSD_IO_DIRECT: > + host_err =3D nfsd_direct_write(rqstp, fhp, nf, stable_how, > + nvecs, cnt, &kiocb); > + stable =3D *stable_how; > break; > case NFSD_IO_DONTCACHE: > if (file->f_op->fop_flags & FOP_DONTCACHE) > kiocb.ki_flags |=3D IOCB_DONTCACHE; > + fallthrough; /* must call nfsd_buffered_write */ > + case NFSD_IO_BUFFERED: > + host_err =3D nfsd_buffered_write(rqstp, file, > + nvecs, cnt, &kiocb); > break; > } > - host_err =3D vfs_iocb_iter_write(file, &kiocb, &iter); > if (host_err < 0) { > commit_reset_write_verifier(nn, rqstp, host_err); > goto out_nfserr; > } > - *cnt =3D host_err; > nfsd_stats_io_write_add(nn, exp, *cnt); > fsnotify_modify(file); > host_err =3D filemap_check_wb_err(file->f_mapping, since); LGTM Reviewed-by: Jeff Layton