From patchwork Fri Aug 21 07:38:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 11728433 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6559C1392 for ; Fri, 21 Aug 2020 07:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FC1C207DF for ; Fri, 21 Aug 2020 07:39:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="wz1QmbUY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728169AbgHUHjR (ORCPT ); Fri, 21 Aug 2020 03:39:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728131AbgHUHi7 (ORCPT ); Fri, 21 Aug 2020 03:38:59 -0400 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F1A7C06138B for ; Fri, 21 Aug 2020 00:38:59 -0700 (PDT) Received: by mail-pl1-x641.google.com with SMTP id h2so524570plr.0 for ; Fri, 21 Aug 2020 00:38:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=x7nmOKKnzuw08JzbWz9S0vd+MFbiT4hw/Chd9PX4ZOw=; b=wz1QmbUYJKU+Q7LFSB1tYfwiECD8FKoD5F6G3knrVhNPhSt3w+2lkmzQVEp3NflNuK xKqcWtwJpod9vm/nDGTClJ/KR8QgElBtCOT4YTPlnDSdW3dMFO/02QGVM3sS0ESn/lNk x0gZG9lmVXf3tIZmg8KRwZUSHY9cyqFXX+qAtodabQNN/LDeABOQVLSVBAdCTcLTUFYB CBP3TTZHKDvHJRA1wK+u000/JzbU3wsHsKxqTbH5SazNMUQ7o/cn9zfP70OoadAehs64 96rv+0aTyAnAH67NQ/QwqNux7x9B0Hb9FTSBq/RXWoRkxTdYod70auTvl2GwAYX8dW5t 38Ow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=x7nmOKKnzuw08JzbWz9S0vd+MFbiT4hw/Chd9PX4ZOw=; b=Iz7D6XbRp+tt70Nhvtd8hOoFpb2jp6wqcY/UYp0yMRVGSGcwxerEVnvlVow8stVzWX WyYwyGcKrKEsp5td0WuMc8Rhp2EP6rrgmFTYNOh7zb9Hs3CGWbF6rezzPXojY8j20JvZ Qh9I1z8Pocq75x2Xa9EqlHEO5BGMwTChlirw9doXdkkE89kyWFrGdmDgOlF7x0zaVjuT 4AGd/KNbwMBS9Wej4qoev2cFWrnfyv0TxI4/JJnJdraxSneyfqEhwFnvTDtPhrjmCG8F u+42/JPnaB93vS2aKDOAY28BsoZ2+aYKpWV9SADTymOZYi+roLu7h60Lp8KKVdFzMrUO WXLg== X-Gm-Message-State: AOAM530kH8PRYXtBEw3PQTPYAPOUImsAfzThKmGusjglk3GwSAa3Sxd3 svLfl1JHofi6T57vXgX86yQNugZgtsdvwA== X-Google-Smtp-Source: ABdhPJzNq5b0oCyp5wN5loyDfbwwJJc2y7r3fFrA/34tycWTESDg8chxCrwnWO1bAGqsKLSyvM4Png== X-Received: by 2002:a17:90a:4dca:: with SMTP id r10mr1430612pjl.200.1597995537889; Fri, 21 Aug 2020 00:38:57 -0700 (PDT) Received: from exodia.tfbnw.net ([2620:10d:c090:400::5:f2a4]) by smtp.gmail.com with ESMTPSA id t10sm1220867pgp.15.2020.08.21.00.38.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2020 00:38:56 -0700 (PDT) From: Omar Sandoval To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig Cc: Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v5 3/9] fs: add RWF_ENCODED for reading/writing compressed data Date: Fri, 21 Aug 2020 00:38:34 -0700 Message-Id: <9020a583581b644ae86b7c05de6a39fd5204f06d.1597993855.git.osandov@osandov.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: References: MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Omar Sandoval Btrfs supports transparent compression: data written by the user can 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(). A new RWF_ENCODED flags indicates that a read or write is "encoded". If this flag is set, iov[0].iov_base points to a struct encoded_iov which 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 when reading in the middle of an extent). For reads, the filesystem returns this information; for writes, the caller provides it to the filesystem. iov[0].iov_len must be set to sizeof(struct encoded_iov), which can be used to extend the interface in the future a la copy_struct_from_user(). The remaining iovecs contain the encoded extent. This adds the VFS helpers for supporting encoded I/O and documentation for filesystem support. Signed-off-by: Omar Sandoval Reviewed-by: Josef Bacik --- Documentation/filesystems/encoded_io.rst | 74 ++++++++++ Documentation/filesystems/index.rst | 1 + include/linux/fs.h | 16 +++ include/uapi/linux/fs.h | 33 ++++- mm/filemap.c | 166 +++++++++++++++++++++-- 5 files changed, 276 insertions(+), 14 deletions(-) create mode 100644 Documentation/filesystems/encoded_io.rst diff --git a/Documentation/filesystems/encoded_io.rst b/Documentation/filesystems/encoded_io.rst new file mode 100644 index 000000000000..50405276d866 --- /dev/null +++ b/Documentation/filesystems/encoded_io.rst @@ -0,0 +1,74 @@ +=========== +Encoded I/O +=========== + +Encoded I/O is a mechanism for reading and writing encoded (e.g., compressed +and/or encrypted) data directly from/to the filesystem. The userspace interface +is thoroughly described in the :manpage:`encoded_io(7)` man page; this document +describes the requirements for filesystem support. + +First of all, a filesystem supporting encoded I/O must indicate this by setting +the ``FMODE_ENCODED_IO`` flag in its ``file_open`` file operation:: + + static int foo_file_open(struct inode *inode, struct file *filp) + { + ... + filep->f_mode |= FMODE_ENCODED_IO; + ... + } + +Encoded I/O goes through ``read_iter`` and ``write_iter``, designated by the +``IOCB_ENCODED`` flag in ``kiocb->ki_flags``. + +Reads +===== + +Encoded ``read_iter`` should: + +1. Call ``generic_encoded_read_checks()`` to validate the file and buffers + provided by userspace. +2. Initialize the ``encoded_iov`` appropriately. +3. Copy it to the user with ``copy_encoded_iov_to_iter()``. +4. Copy the encoded data to the user. +5. Advance ``kiocb->ki_pos`` by ``encoded_iov->len``. +6. Return the size of the encoded data read, not including the ``encoded_iov``. + +There are a few details to be aware of: + +* Encoded ``read_iter`` should support reading unencoded data if the extent is + not encoded. +* If the buffers provided by the user are not large enough to contain an entire + encoded extent, then ``read_iter`` should return ``-ENOBUFS``. This is to + avoid confusing userspace with truncated data that cannot be properly + decoded. +* Reads in the middle of an encoded extent can be returned by setting + ``encoded_iov->unencoded_offset`` to non-zero. +* Truncated unencoded data (e.g., because the file does not end on a block + boundary) may be returned by setting ``encoded_iov->len`` to a value smaller + value than ``encoded_iov->unencoded_len - encoded_iov->unencoded_offset``. + +Writes +====== + +Encoded ``write_iter`` should (in addition to the usual accounting/checks done +by ``write_iter``): + +1. Call ``copy_encoded_iov_from_iter()`` to get and validate the + ``encoded_iov``. +2. Call ``generic_encoded_write_checks()`` instead of + ``generic_write_checks()``. +3. Check that the provided encoding in ``encoded_iov`` is supported. +4. Advance ``kiocb->ki_pos`` by ``encoded_iov->len``. +5. Return the size of the encoded data written. + +Again, there are a few details: + +* Encoded ``write_iter`` doesn't need to support writing unencoded data. +* ``write_iter`` should either write all of the encoded data or none of it; it + must not do partial writes. +* ``write_iter`` doesn't need to validate the encoded data; a subsequent read + may return, e.g., ``-EIO`` if the data is not valid. +* The user may lie about the unencoded size of the data; a subsequent read + should truncate or zero-extend the unencoded data rather than returning an + error. +* Be careful of page cache coherency. diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst index 4c536e66dc4c..9adbbc3c7441 100644 --- a/Documentation/filesystems/index.rst +++ b/Documentation/filesystems/index.rst @@ -55,6 +55,7 @@ filesystem implementations. journalling fscrypt fsverity + encoded_io Filesystems =========== diff --git a/include/linux/fs.h b/include/linux/fs.h index e019ea2f1347..a3fe6fa9687c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -178,6 +178,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, /* File supports async buffered reads */ #define FMODE_BUF_RASYNC ((__force fmode_t)0x40000000) +/* File supports encoded IO */ +#define FMODE_ENCODED_IO ((__force fmode_t)0x80000000) + /* * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector * that indicates that they should check the contents of the iovec are @@ -321,6 +324,7 @@ enum rw_hint { /* iocb->ki_waitq is valid */ #define IOCB_WAITQ (1 << 8) #define IOCB_NOIO (1 << 9) +#define IOCB_ENCODED (1 << 10) struct kiocb { struct file *ki_filp; @@ -3006,6 +3010,13 @@ extern int sb_min_blocksize(struct super_block *, int); extern int generic_file_mmap(struct file *, struct vm_area_struct *); extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *); extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *); +struct encoded_iov; +extern int generic_encoded_write_checks(struct kiocb *, + const struct encoded_iov *); +extern int copy_encoded_iov_from_iter(struct encoded_iov *, struct iov_iter *); +extern ssize_t generic_encoded_read_checks(struct kiocb *, struct iov_iter *); +extern int copy_encoded_iov_to_iter(const struct encoded_iov *, + struct iov_iter *); extern int generic_remap_checks(struct file *file_in, loff_t pos_in, struct file *file_out, loff_t pos_out, loff_t *count, unsigned int remap_flags); @@ -3324,6 +3335,11 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags) return -EOPNOTSUPP; kiocb_flags |= IOCB_NOWAIT | IOCB_NOIO; } + if (flags & RWF_ENCODED) { + if (!(ki->ki_filp->f_mode & FMODE_ENCODED_IO)) + return -EOPNOTSUPP; + kiocb_flags |= IOCB_ENCODED; + } if (flags & RWF_HIPRI) kiocb_flags |= IOCB_HIPRI; if (flags & RWF_DSYNC) diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index f44eb0a04afd..972390d3089d 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -279,6 +279,34 @@ struct fsxattr { SYNC_FILE_RANGE_WAIT_BEFORE | \ SYNC_FILE_RANGE_WAIT_AFTER) +enum { + ENCODED_IOV_COMPRESSION_NONE, +#define ENCODED_IOV_COMPRESSION_NONE ENCODED_IOV_COMPRESSION_NONE + ENCODED_IOV_COMPRESSION_ZLIB, +#define ENCODED_IOV_COMPRESSION_ZLIB ENCODED_IOV_COMPRESSION_ZLIB + ENCODED_IOV_COMPRESSION_LZO, +#define ENCODED_IOV_COMPRESSION_LZO ENCODED_IOV_COMPRESSION_LZO + ENCODED_IOV_COMPRESSION_ZSTD, +#define ENCODED_IOV_COMPRESSION_ZSTD ENCODED_IOV_COMPRESSION_ZSTD + ENCODED_IOV_COMPRESSION_TYPES = ENCODED_IOV_COMPRESSION_ZSTD, +}; + +enum { + ENCODED_IOV_ENCRYPTION_NONE, +#define ENCODED_IOV_ENCRYPTION_NONE ENCODED_IOV_ENCRYPTION_NONE + ENCODED_IOV_ENCRYPTION_TYPES = ENCODED_IOV_ENCRYPTION_NONE, +}; + +struct encoded_iov { + __aligned_u64 len; + __aligned_u64 unencoded_len; + __aligned_u64 unencoded_offset; + __u32 compression; + __u32 encryption; +}; + +#define ENCODED_IOV_SIZE_VER0 32 + /* * Flags for preadv2/pwritev2: */ @@ -300,8 +328,11 @@ typedef int __bitwise __kernel_rwf_t; /* per-IO O_APPEND */ #define RWF_APPEND ((__force __kernel_rwf_t)0x00000010) +/* encoded (e.g., compressed and/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_NOWAIT |\ - RWF_APPEND) + RWF_APPEND | RWF_ENCODED) #endif /* _UAPI_LINUX_FS_H */ diff --git a/mm/filemap.c b/mm/filemap.c index 1aaea26556cc..f28b42888144 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3022,24 +3022,15 @@ static int generic_write_check_limits(struct file *file, loff_t pos, return 0; } -/* - * 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 = iocb->ki_filp; struct inode *inode = file->f_mapping->host; - loff_t count; - int ret; if (IS_SWAPFILE(inode)) return -ETXTBSY; - if (!iov_iter_count(from)) + if (!*count) return 0; /* FIXME: this is for backwards compatibility with 2.4 */ @@ -3049,8 +3040,21 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT)) return -EINVAL; - count = iov_iter_count(from); - ret = generic_write_check_limits(file, iocb->ki_pos, &count); + return generic_write_check_limits(iocb->ki_filp, iocb->ki_pos, count); +} + +/* + * 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 = iov_iter_count(from); + int ret; + + ret = generic_write_checks_common(iocb, &count); if (ret) return ret; @@ -3059,6 +3063,142 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) } EXPORT_SYMBOL(generic_write_checks); +/** + * generic_encoded_write_checks() - check an encoded write + * @iocb: I/O context. + * @encoded: Encoding metadata. + * + * This should be called by RWF_ENCODED write implementations rather than + * generic_write_checks(). Unlike generic_write_checks(), it returns -EFBIG + * instead of adjusting the size of the write. + * + * Return: 0 on success, -errno on error. + */ +int generic_encoded_write_checks(struct kiocb *iocb, + const struct encoded_iov *encoded) +{ + loff_t count = encoded->len; + int ret; + + if (!(iocb->ki_filp->f_flags & O_ALLOW_ENCODED)) + return -EPERM; + + ret = generic_write_checks_common(iocb, &count); + if (ret) + return ret; + + if (count != encoded->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); + +/** + * copy_encoded_iov_from_iter() - copy a &struct encoded_iov from userspace + * @encoded: Returned encoding metadata. + * @from: Source iterator. + * + * This copies in the &struct encoded_iov and does some basic sanity checks. + * This should always be used rather than a plain copy_from_iter(), as it does + * the proper handling for backward- and forward-compatibility. + * + * Return: 0 on success, -EFAULT if access to userspace failed, -E2BIG if the + * copied structure contained non-zero fields that this kernel doesn't + * support, -EINVAL if the copied structure was invalid. + */ +int copy_encoded_iov_from_iter(struct encoded_iov *encoded, + struct iov_iter *from) +{ + size_t usize; + int ret; + + usize = iov_iter_single_seg_count(from); + if (usize > PAGE_SIZE) + return -E2BIG; + if (usize < ENCODED_IOV_SIZE_VER0) + return -EINVAL; + ret = copy_struct_from_iter(encoded, sizeof(*encoded), from, usize); + if (ret) + return ret; + + if (encoded->compression == ENCODED_IOV_COMPRESSION_NONE && + encoded->encryption == 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 > encoded->unencoded_len) + return -EINVAL; + if (encoded->len > encoded->unencoded_len - encoded->unencoded_offset) + return -EINVAL; + return 0; +} +EXPORT_SYMBOL(copy_encoded_iov_from_iter); + +/** + * generic_encoded_read_checks() - sanity check an RWF_ENCODED read + * @iocb: I/O context. + * @iter: Destination iterator for read. + * + * This should always be called by RWF_ENCODED read implementations before + * returning any data. + * + * Return: Number of bytes available to return encoded data in @iter on success, + * -EPERM if the file was not opened with O_ALLOW_ENCODED, -EINVAL if + * the size of the &struct encoded_iov iovec is invalid. + */ +ssize_t generic_encoded_read_checks(struct kiocb *iocb, struct iov_iter *iter) +{ + size_t usize; + + if (!(iocb->ki_filp->f_flags & O_ALLOW_ENCODED)) + return -EPERM; + usize = iov_iter_single_seg_count(iter); + if (usize > PAGE_SIZE || usize < ENCODED_IOV_SIZE_VER0) + return -EINVAL; + return iov_iter_count(iter) - usize; +} +EXPORT_SYMBOL(generic_encoded_read_checks); + +/** + * copy_encoded_iov_to_iter() - copy a &struct encoded_iov to userspace + * @encoded: Encoding metadata to return. + * @to: Destination iterator. + * + * This should always be used by RWF_ENCODED read implementations rather than a + * plain copy_to_iter(), as it does the proper handling for backward- and + * forward-compatibility. The iterator must be sanity-checked with + * generic_encoded_read_checks() before this is called. + * + * Return: 0 on success, -EFAULT if access to userspace failed, -E2BIG if there + * were non-zero fields in @encoded that the user buffer could not + * accommodate. + */ +int copy_encoded_iov_to_iter(const struct encoded_iov *encoded, + struct iov_iter *to) +{ + size_t ksize = sizeof(*encoded); + size_t usize = iov_iter_single_seg_count(to); + size_t size = min(ksize, usize); + + /* We already sanity-checked usize in generic_encoded_read_checks(). */ + + if (usize < ksize && + memchr_inv((char *)encoded + usize, 0, ksize - usize)) + return -E2BIG; + if (copy_to_iter(encoded, size, to) != size || + (usize > ksize && + iov_iter_zero(usize - ksize, to) != usize - ksize)) + return -EFAULT; + return 0; +} +EXPORT_SYMBOL(copy_encoded_iov_to_iter); + /* * Performs necessary checks before doing a clone. *