From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26579CA9EAF for ; Tue, 22 Oct 2019 01:37:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DCB43214B2 for ; Tue, 22 Oct 2019 01:37:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730065AbfJVBhe (ORCPT ); Mon, 21 Oct 2019 21:37:34 -0400 Received: from mx2a.mailbox.org ([80.241.60.219]:51563 "EHLO mx2a.mailbox.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727264AbfJVBhd (ORCPT ); Mon, 21 Oct 2019 21:37:33 -0400 Received: from smtp2.mailbox.org (smtp2.mailbox.org [80.241.60.241]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by mx2a.mailbox.org (Postfix) with ESMTPS id 9A2FCA3414; Tue, 22 Oct 2019 03:37:30 +0200 (CEST) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp2.mailbox.org ([80.241.60.241]) by spamfilter02.heinlein-hosting.de (spamfilter02.heinlein-hosting.de [80.241.56.116]) (amavisd-new, port 10030) with ESMTP id dyNrI7RqNmMC; Tue, 22 Oct 2019 03:37:27 +0200 (CEST) Date: Tue, 22 Oct 2019 12:37:17 +1100 From: Aleksa Sarai To: "Darrick J. Wong" Cc: Omar Sandoval , linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Dave Chinner , Jann Horn , linux-api@vger.kernel.org, kernel-team@fb.com Subject: Re: [RFC PATCH v2 2/5] fs: add RWF_ENCODED for reading/writing compressed data Message-ID: <20191022013717.enwdmox4b7la4i74@yavin.dot.cyphar.com> References: <7f98cf5409cf2b583cd5b3451fc739fd3428873b.1571164762.git.osandov@fb.com> <20191021182806.GA6706@magnolia> <20191021183831.mbe4q2beqo76fqxm@yavin.dot.cyphar.com> <20191021190010.GC6726@magnolia> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="tel3pez3twjkfp2c" Content-Disposition: inline In-Reply-To: <20191021190010.GC6726@magnolia> Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org --tel3pez3twjkfp2c Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2019-10-21, Darrick J. Wong wrote: > On Tue, Oct 22, 2019 at 05:38:31AM +1100, Aleksa Sarai wrote: > > On 2019-10-21, Darrick J. Wong wrote: > > > On Tue, Oct 15, 2019 at 11:42:40AM -0700, Omar Sandoval wrote: > > > > From: Omar Sandoval > > > >=20 > > > > Btrfs supports transparent compression: data written by the user ca= n be > > > > compressed when written to disk and decompressed when read back. > > > > However, we'd like to add an interface to write pre-compressed data > > > > directly to the filesystem, and the matching interface to read > > > > compressed data without decompressing it. This adds support for > > > > so-called "encoded I/O" via preadv2() and pwritev2(). > > > >=20 > > > > A new RWF_ENCODED flags indicates that a read or write is "encoded"= =2E If > > > > this flag is set, iov[0].iov_base points to a struct encoded_iov wh= ich > > > > is used for metadata: namely, the compression algorithm, unencoded > > > > (i.e., decompressed) length, and what subrange of the unencoded data > > > > should be used (needed for truncated or hole-punched extents and wh= en > > > > reading in the middle of an extent). For reads, the filesystem retu= rns > > > > this information; for writes, the caller provides it to the filesys= tem. > > > > iov[0].iov_len must be set to sizeof(struct encoded_iov), which can= be > > > > used to extend the interface in the future. The remaining iovecs co= ntain > > > > the encoded extent. > > > >=20 > > > > Filesystems must indicate that they support encoded writes by setti= ng > > > > FMODE_ENCODED_IO in ->file_open(). > > > >=20 > > > > Signed-off-by: Omar Sandoval > > > > --- > > > > include/linux/fs.h | 14 +++++++ > > > > include/uapi/linux/fs.h | 26 ++++++++++++- > > > > mm/filemap.c | 82 ++++++++++++++++++++++++++++++++++---= ---- > > > > 3 files changed, 108 insertions(+), 14 deletions(-) > > > >=20 > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > > > index e0d909d35763..54681f21e05e 100644 > > > > --- a/include/linux/fs.h > > > > +++ b/include/linux/fs.h > > > > @@ -175,6 +175,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, = loff_t offset, > > > > /* File does not contribute to nr_files count */ > > > > #define FMODE_NOACCOUNT ((__force fmode_t)0x20000000) > > > > =20 > > > > +/* File supports encoded IO */ > > > > +#define FMODE_ENCODED_IO ((__force fmode_t)0x40000000) > > > > + > > > > /* > > > > * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector > > > > * that indicates that they should check the contents of the iovec= are > > > > @@ -314,6 +317,7 @@ enum rw_hint { > > > > #define IOCB_SYNC (1 << 5) > > > > #define IOCB_WRITE (1 << 6) > > > > #define IOCB_NOWAIT (1 << 7) > > > > +#define IOCB_ENCODED (1 << 8) > > > > =20 > > > > struct kiocb { > > > > struct file *ki_filp; > > > > @@ -3088,6 +3092,11 @@ extern int sb_min_blocksize(struct super_blo= ck *, int); > > > > extern int generic_file_mmap(struct file *, struct vm_area_struct = *); > > > > extern int generic_file_readonly_mmap(struct file *, struct vm_are= a_struct *); > > > > extern ssize_t generic_write_checks(struct kiocb *, struct iov_ite= r *); > > > > +struct encoded_iov; > > > > +extern int generic_encoded_write_checks(struct kiocb *, struct enc= oded_iov *); > > > > +extern ssize_t check_encoded_read(struct kiocb *, struct iov_iter = *); > > > > +extern int import_encoded_write(struct kiocb *, struct encoded_iov= *, > > > > + struct iov_iter *); > > > > extern int generic_remap_checks(struct file *file_in, loff_t pos_i= n, > > > > struct file *file_out, loff_t pos_out, > > > > loff_t *count, unsigned int remap_flags); > > > > @@ -3403,6 +3412,11 @@ static inline int kiocb_set_rw_flags(struct = kiocb *ki, rwf_t flags) > > > > return -EOPNOTSUPP; > > > > ki->ki_flags |=3D IOCB_NOWAIT; > > > > } > > > > + if (flags & RWF_ENCODED) { > > > > + if (!(ki->ki_filp->f_mode & FMODE_ENCODED_IO)) > > > > + return -EOPNOTSUPP; > > > > + ki->ki_flags |=3D IOCB_ENCODED; > > > > + } > > > > if (flags & RWF_HIPRI) > > > > ki->ki_flags |=3D IOCB_HIPRI; > > > > if (flags & RWF_DSYNC) > > > > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > > > > index 379a612f8f1d..ed92a8a257cb 100644 > > > > --- a/include/uapi/linux/fs.h > > > > +++ b/include/uapi/linux/fs.h > > > > @@ -284,6 +284,27 @@ struct fsxattr { > > > > =20 > > > > typedef int __bitwise __kernel_rwf_t; > > > > =20 > > > > +enum { > > > > + ENCODED_IOV_COMPRESSION_NONE, > > > > + ENCODED_IOV_COMPRESSION_ZLIB, > > > > + ENCODED_IOV_COMPRESSION_LZO, > > > > + ENCODED_IOV_COMPRESSION_ZSTD, > > > > + ENCODED_IOV_COMPRESSION_TYPES =3D ENCODED_IOV_COMPRESSION_ZSTD, > > > > +}; > > > > + > > > > +enum { > > > > + ENCODED_IOV_ENCRYPTION_NONE, > > > > + ENCODED_IOV_ENCRYPTION_TYPES =3D ENCODED_IOV_ENCRYPTION_NONE, > > > > +}; > > > > + > > > > +struct encoded_iov { > > > > + __u64 len; > > > > + __u64 unencoded_len; > > > > + __u64 unencoded_offset; > > > > + __u32 compression; > > > > + __u32 encryption; > > >=20 > > > Can we add some must-be-zero padding space at the end here for whomev= er > > > comes along next wanting to add more encoding info? > >=20 > > I would suggest to copy the extension design of copy_struct_from_user(). > > Adding must-be-zero padding is a less-ideal solution to the extension > > problem than length-based extension. >=20 > Come to think of it, you /do/ have to specify iov_len so... yeah, do > that instead; we can always extend the structure later. >=20 > > Also (I might be wrong) but shouldn't the __u64s be __aligned_u64 (as > > with syscall structure arguments)? >=20 > No idea, that's the first I've heard of that type and it doesn't > seem to be used by the fs code. Why would we care about alignment for > an incore structure? When passing u64s from userspace, it's generally considered a good idea to use __aligned_u64 -- the main reason is that 32-bit userspace on a 64-bit kernel will use different structure alignment for 64-bit fields. This means you'd need to implement a bunch of COMPAT_SYSCALL-like handling for that case. It's much simpler to use __aligned_u64 (and on the plus side I don't think you need to add any fields to ensure the padding is zero). > >=20 > > > (And maybe a manpage and some basic testing, to reiterate Dave...) > > >=20 > > > --D > > >=20 > > > > +}; > > > > + > > > > /* high priority request, poll if possible */ > > > > #define RWF_HIPRI ((__force __kernel_rwf_t)0x00000001) > > > > =20 > > > > @@ -299,8 +320,11 @@ typedef int __bitwise __kernel_rwf_t; > > > > /* per-IO O_APPEND */ > > > > #define RWF_APPEND ((__force __kernel_rwf_t)0x00000010) > > > > =20 > > > > +/* encoded (e.g., compressed or encrypted) IO */ > > > > +#define RWF_ENCODED ((__force __kernel_rwf_t)0x00000020) > > > > + > > > > /* mask of flags supported by the kernel */ > > > > #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWA= IT |\ > > > > - RWF_APPEND) > > > > + RWF_APPEND | RWF_ENCODED) > > > > =20 > > > > #endif /* _UAPI_LINUX_FS_H */ > > > > diff --git a/mm/filemap.c b/mm/filemap.c > > > > index 1146fcfa3215..d2e6d9caf353 100644 > > > > --- a/mm/filemap.c > > > > +++ b/mm/filemap.c > > > > @@ -2948,24 +2948,15 @@ static int generic_write_check_limits(struc= t file *file, loff_t pos, > > > > return 0; > > > > } > > > > =20 > > > > -/* > > > > - * Performs necessary checks before doing a write > > > > - * > > > > - * Can adjust writing position or amount of bytes to write. > > > > - * Returns appropriate error code that caller should return or > > > > - * zero in case that write should be allowed. > > > > - */ > > > > -inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov= _iter *from) > > > > +static int generic_write_checks_common(struct kiocb *iocb, loff_t = *count) > > > > { > > > > struct file *file =3D iocb->ki_filp; > > > > struct inode *inode =3D file->f_mapping->host; > > > > - loff_t count; > > > > - int ret; > > > > =20 > > > > if (IS_SWAPFILE(inode)) > > > > return -ETXTBSY; > > > > =20 > > > > - if (!iov_iter_count(from)) > > > > + if (!*count) > > > > return 0; > > > > =20 > > > > /* FIXME: this is for backwards compatibility with 2.4 */ > > > > @@ -2975,8 +2966,21 @@ inline ssize_t generic_write_checks(struct k= iocb *iocb, struct iov_iter *from) > > > > if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIR= ECT)) > > > > return -EINVAL; > > > > =20 > > > > - count =3D iov_iter_count(from); > > > > - ret =3D generic_write_check_limits(file, iocb->ki_pos, &count); > > > > + return generic_write_check_limits(iocb->ki_filp, iocb->ki_pos, co= unt); > > > > +} > > > > + > > > > +/* > > > > + * Performs necessary checks before doing a write > > > > + * > > > > + * Can adjust writing position or amount of bytes to write. > > > > + * Returns a negative errno or the new number of bytes to write. > > > > + */ > > > > +inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov= _iter *from) > > > > +{ > > > > + loff_t count =3D iov_iter_count(from); > > > > + int ret; > > > > + > > > > + ret =3D generic_write_checks_common(iocb, &count); > > > > if (ret) > > > > return ret; > > > > =20 > > > > @@ -2985,6 +2989,58 @@ inline ssize_t generic_write_checks(struct k= iocb *iocb, struct iov_iter *from) > > > > } > > > > EXPORT_SYMBOL(generic_write_checks); > > > > =20 > > > > +int generic_encoded_write_checks(struct kiocb *iocb, > > > > + struct encoded_iov *encoded) > > > > +{ > > > > + loff_t count =3D encoded->unencoded_len; > > > > + int ret; > > > > + > > > > + ret =3D generic_write_checks_common(iocb, &count); > > > > + if (ret) > > > > + return ret; > > > > + > > > > + if (count !=3D encoded->unencoded_len) { > > > > + /* > > > > + * The write got truncated by generic_write_checks_common(). We > > > > + * can't do a partial encoded write. > > > > + */ > > > > + return -EFBIG; > > > > + } > > > > + return 0; > > > > +} > > > > +EXPORT_SYMBOL(generic_encoded_write_checks); > > > > + > > > > +ssize_t check_encoded_read(struct kiocb *iocb, struct iov_iter *it= er) > > > > +{ > > > > + if (!(iocb->ki_filp->f_flags & O_ENCODED)) > > > > + return -EPERM; > > > > + if (iov_iter_single_seg_count(iter) !=3D sizeof(struct encoded_io= v)) > > > > + return -EINVAL; > > > > + return iov_iter_count(iter) - sizeof(struct encoded_iov); > > > > +} > > > > +EXPORT_SYMBOL(check_encoded_read); > > > > + > > > > +int import_encoded_write(struct kiocb *iocb, struct encoded_iov *e= ncoded, > > > > + struct iov_iter *from) > > > > +{ > > > > + if (!(iocb->ki_filp->f_flags & O_ENCODED)) > > > > + return -EPERM; > > > > + if (iov_iter_single_seg_count(from) !=3D sizeof(*encoded)) > > > > + return -EINVAL; > > > > + if (copy_from_iter(encoded, sizeof(*encoded), from) !=3D sizeof(*= encoded)) > > > > + return -EFAULT; > > > > + if (encoded->compression =3D=3D ENCODED_IOV_COMPRESSION_NONE && > > > > + encoded->encryption =3D=3D ENCODED_IOV_ENCRYPTION_NONE) > > > > + return -EINVAL; > > > > + if (encoded->compression > ENCODED_IOV_COMPRESSION_TYPES || > > > > + encoded->encryption > ENCODED_IOV_ENCRYPTION_TYPES) > > > > + return -EINVAL; > > > > + if (encoded->unencoded_offset >=3D encoded->unencoded_len) > > > > + return -EINVAL; > > > > + return 0; > > > > +} > > > > +EXPORT_SYMBOL(import_encoded_write); > > > > + > > > > /* > > > > * Performs necessary checks before doing a clone. > > > > * --=20 Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH --tel3pez3twjkfp2c Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQSxZm6dtfE8gxLLfYqdlLljIbnQEgUCXa5dSQAKCRCdlLljIbnQ EmxRAPsGpqeyAWpLA0wtXYC//gRIdEqupPZnfJCvZPvY3+Bw6AEAo8W6ZMfu8/XN i9uZlXnDzE5uE0/SQfeliX1xRJWUbgM= =jjFU -----END PGP SIGNATURE----- --tel3pez3twjkfp2c--