From patchwork Mon May 17 18:35:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 12262799 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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 2CF6CC43462 for ; Mon, 17 May 2021 18:35:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 01783611ED for ; Mon, 17 May 2021 18:35:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239353AbhEQShK (ORCPT ); Mon, 17 May 2021 14:37:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237246AbhEQShJ (ORCPT ); Mon, 17 May 2021 14:37:09 -0400 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0D93C061573 for ; Mon, 17 May 2021 11:35:52 -0700 (PDT) Received: by mail-pj1-x1030.google.com with SMTP id gb21-20020a17090b0615b029015d1a863a91so116395pjb.2 for ; Mon, 17 May 2021 11:35:52 -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=4+7lsPmjBUnhLejnGPlyPiIC1GkPnGJh960LplBN6Jw=; b=cpCt5UMYzdRStfQ7fEAX/2coAsS3qk3Y9uZbOhldv6IPhXnTisf1stAASdTFv/5SNv Qo4kt0HytiEXvpS85JRMW/4V3TYYi3+K3OMAdVs5GKy+vYH9vREpzuMPZ6K7dID/yuzT esMmEmp/glLij6JhmjHcMNw2yg37m2RvUmZgzBlf0NHJm3XIJxl4Qk0KtsSllLLm1J4x qVOM98gTJOdIE5cJolCIFCe827oGhwJ6lkOzEzJO16fAapkJQwwWYRwr1LJGECrQLS91 HluAyl3D7aB177+MYpszDODH/w+1dW9/fXLU21Uf0OGY8UajZmoeWqD8iuC+Sky4cYmN pu4A== 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=4+7lsPmjBUnhLejnGPlyPiIC1GkPnGJh960LplBN6Jw=; b=szhPm0foOvwJZf3iwbfkdF4BwpC5XKzcd3LhxUT+aW+Oy8AdqJ+D2dI1i1bqKqNTNp 6DhGgwHSY/4jOgbgzSOA0LfbpKN+BQuIesTL5iE5mok6NNl8uEl2EEG0gQBDGORPjqVM MTXSIxHKTdHMBhkXCcPGWvsfix/V5znE7jRIBLbvjgeWZUrVagnt3AAWzcTKSvFKnEII OOF5bpL8Y4w0mGrLt7j4vIaoo4OvKUsEvNiq44PmqwZR5ETJDwwI3ARgJ7bWngCodNnb Cs45TlH81MLDGElnJkjLZZlfKv/Fj/HSsSclFXLmDzGaNoiTmvr1VjRODj+vqRD2F5sc 34XQ== X-Gm-Message-State: AOAM533PGvV4uFzAiA4cQM1/EO2gg1M5HffCZPsHe582ZpTjwKqBWA4Z l0hlHJ2P/EvAc3iYHASKlEHM1kPP4mpqHA== X-Google-Smtp-Source: ABdhPJz0Ib9O8RxGNqZDyVcfdnINifdUBp5jBhxu1fPJ5yI69ujVXvVvPmgJ86Yebght+2XdX8zLvg== X-Received: by 2002:a17:902:6b81:b029:ea:dcc5:b841 with SMTP id p1-20020a1709026b81b02900eadcc5b841mr1446115plk.29.1621276549640; Mon, 17 May 2021 11:35:49 -0700 (PDT) Received: from relinquished.tfbnw.net ([2620:10d:c090:400::5:19a9]) by smtp.gmail.com with ESMTPSA id v15sm5498763pfm.187.2021.05.17.11.35.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 May 2021 11:35:48 -0700 (PDT) From: Omar Sandoval To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig Cc: Linus Torvalds , Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: [PATCH RERESEND v9 3/9] fs: add RWF_ENCODED for reading/writing compressed data Date: Mon, 17 May 2021 11:35:21 -0700 Message-Id: <85abdef1969c6502960abe41830ef0dcdb4db0dc.1621276134.git.osandov@fb.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: References: MIME-Version: 1.0 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. Reviewed-by: Josef Bacik Signed-off-by: Omar Sandoval --- Documentation/filesystems/encoded_io.rst | 240 +++++++++++++++++++++++ Documentation/filesystems/index.rst | 1 + fs/read_write.c | 168 ++++++++++++++-- include/linux/encoded_io.h | 17 ++ include/linux/fs.h | 13 ++ include/uapi/linux/encoded_io.h | 30 +++ include/uapi/linux/fs.h | 5 +- 7 files changed, 460 insertions(+), 14 deletions(-) create mode 100644 Documentation/filesystems/encoded_io.rst create mode 100644 include/linux/encoded_io.h create mode 100644 include/uapi/linux/encoded_io.h diff --git a/Documentation/filesystems/encoded_io.rst b/Documentation/filesystems/encoded_io.rst new file mode 100644 index 000000000000..38f1dc940331 --- /dev/null +++ b/Documentation/filesystems/encoded_io.rst @@ -0,0 +1,240 @@ +=========== +Encoded I/O +=========== + +Several filesystems (e.g., Btrfs) support transparent encoding (e.g., +compression, encryption) of data on disk: written data is encoded by the kernel +before it is written to disk, and read data is decoded before being returned to +the user. In some cases, it is useful to skip this encoding step. For example, +the user may want to read the compressed contents of a file or write +pre-compressed data directly to a file. This is referred to as "encoded I/O". + +User API +======== + +Encoded I/O is specified with the ``RWF_ENCODED`` flag to ``preadv2()`` and +``pwritev2()``. If ``RWF_ENCODED`` is specified, then ``iov[0].iov_base`` +points to an ``encoded_iov`` structure, defined in ```` +as:: + + struct encoded_iov { + __aligned_u64 len; + __aligned_u64 unencoded_len; + __aligned_u64 unencoded_offset; + __u32 compression; + __u32 encryption; + }; + +This may be extended in the future, so ``iov[0].iov_len`` must be set to +``sizeof(struct encoded_iov)`` for forward/backward compatibility. The +remaining buffers contain the encoded data. + +``compression`` and ``encryption`` are the encoding fields. ``compression`` is +``ENCODED_IOV_COMPRESSION_NONE`` (zero) or a filesystem-specific +``ENCODED_IOV_COMPRESSION_*`` constant; see `Filesystem support`_ below. +``encryption`` is currently always ``ENCODED_IOV_ENCRYPTION_NONE`` (zero). + +``unencoded_len`` is the length of the unencoded (i.e., decrypted and +decompressed) data. ``unencoded_offset`` is the offset from the first byte of +the unencoded data to the first byte of logical data in the file (less than or +equal to ``unencoded_len``). ``len`` is the length of the data in the file +(less than or equal to ``unencoded_len - unencoded_offset``). See `Extent +layout`_ below for some examples. + +If the unencoded data is actually longer than ``unencoded_len``, then it is +truncated; if it is shorter, then it is extended with zeroes. + +``pwritev2()`` uses the metadata specified in ``iov[0]``, writes the encoded +data from the remaining buffers, and returns the number of encoded bytes +written (that is, the sum of ``iov[n].iov_len for 1 <= n < iovcnt``; partial +writes will not occur). At least one encoding field must be non-zero. Note that +the encoded data is not validated when it is written; if it is not valid (e.g., +it cannot be decompressed), then a subsequent read may return an error. If the +offset argument to ``pwritev2()`` is -1, then the file offset is incremented by +``len``. If ``iov[0].iov_len`` is less than ``sizeof(struct encoded_iov)`` in +the kernel, then any fields unknown to user space are treated as if they were +zero; if it is greater and any fields unknown to the kernel are non-zero, then +``pwritev2()`` returns -1 and sets errno to ``E2BIG``. + +``preadv2()`` populates the metadata in ``iov[0]``, the encoded data in the +remaining buffers, and returns the number of encoded bytes read. This will only +return one extent per call. This can also read data which is not encoded; all +encoding fields will be zero in that case. If the offset argument to +``preadv2()`` is -1, then the file offset is incremented by ``len``. If +``iov[0].iov_len`` is less than ``sizeof(struct encoded_iov)`` in the kernel +and any fields unknown to user space are non-zero, then ``preadv2()`` returns +-1 and sets errno to ``E2BIG``; if it is greater, then any fields unknown to +the kernel are returned as zero. If the provided buffers are not large enough +to return an entire encoded extent, then ``preadv2()`` returns -1 and sets +errno to ``ENOBUFS``. + +As the filesystem page cache typically contains decoded data, encoded I/O +bypasses the page cache. + +Extent layout +------------- + +By using ``len``, ``unencoded_len``, and ``unencoded_offset``, it is possible +to refer to a subset of an unencoded extent. + +In the simplest case, ``len`` is equal to ``unencoded_len`` and +``unencoded_offset`` is zero. This means that the entire unencoded extent is +used. + +However, suppose we read 50 bytes into a file which contains a single +compressed extent. The filesystem must still return the entire compressed +extent for us to be able to decompress it, so ``unencoded_len`` would be the +length of the entire decompressed extent. However, because the read was at +offset 50, the first 50 bytes should be ignored. Therefore, +``unencoded_offset`` would be 50, and ``len`` would accordingly be +``unencoded_len - 50``. + +Additionally, suppose we want to create an encrypted file with length 500, but +the file is encrypted with a block cipher using a block size of 4096. The +unencoded data would therefore include the appropriate padding, and +``unencoded_len`` would be 4096. However, to represent the logical size of the +file, ``len`` would be 500 (and ``unencoded_offset`` would be 0). + +Similar situations can arise in other cases: + +* If the filesystem pads data to the filesystem block size before compressing, + then compressed files with a size unaligned to the filesystem block size will + end with an extent with ``len < unencoded_len``. + +* Extents cloned from the middle of a larger encoded extent with + ``FICLONERANGE`` may have a non-zero ``unencoded_offset`` and/or + ``len < unencoded_len``. + +* If the middle of an encoded extent is overwritten, the filesystem may create + extents with a non-zero ``unencoded_offset`` and/or ``len < unencoded_len`` + for the parts that were not overwritten. + +Security +-------- + +Encoded I/O creates the potential for some security issues: + +* Encoded writes allow writing arbitrary data which the kernel will decode on a + subsequent read. Decompression algorithms are complex and may have bugs that + can be exploited by maliciously crafted data. +* Encoded reads may return data that is not logically present in the file (see + the discussion of ``len`` vs ``unencoded_len`` above). It may not be intended + for this data to be readable. + +Therefore, encoded I/O requires privilege. Namely, the ``RWF_ENCODED`` flag may +only be used if the file description has the ``O_ALLOW_ENCODED`` file status +flag set, and the ``O_ALLOW_ENCODED`` flag may only be set by a thread with the +``CAP_SYS_ADMIN`` capability. The ``O_ALLOW_ENCODED`` flag can be set by +``open()`` or ``fcntl()``. It can also be cleared by ``fcntl()``; clearing it +does not require ``CAP_SYS_ADMIN``. Note that it is not cleared on ``fork()`` +or ``execve()``. One may wish to use ``O_CLOEXEC`` with ``O_ALLOW_ENCODED``. + +Filesystem support +------------------ + +Encoded I/O is supported on the following filesystems: + +Btrfs (since Linux 5.14) +~~~~~~~~~~~~~~~~~~~~~~~~ + +Btrfs supports encoded reads and writes of compressed data. The data is encoded +as follows: + +* If ``compression`` is ``ENCODED_IOV_COMPRESSION_BTRFS_ZLIB``, then the encoded + data is a single zlib stream. +* If ``compression`` is ``ENCODED_IOV_COMPRESSION_BTRFS_ZSTD``, then the + encoded data is a single zstd frame compressed with the windowLog compression + parameter set to no more than 17. +* If ``compression`` is one of ``ENCODED_IOV_COMPRESSION_BTRFS_LZO_4K``, + ``ENCODED_IOV_COMPRESSION_BTRFS_LZO_8K``, + ``ENCODED_IOV_COMPRESSION_BTRFS_LZO_16K``, + ``ENCODED_IOV_COMPRESSION_BTRFS_LZO_32K``, or + ``ENCODED_IOV_COMPRESSION_BTRFS_LZO_64K``, then the encoded data is + compressed page by page (using the page size indicated by the name of the + constant) with LZO1X and wrapped in the format documented in the Linux kernel + source file ``fs/btrfs/lzo.c``. + +Additionally, there are some restrictions on ``pwritev2()``: + +* ``offset`` (or the current file offset if ``offset`` is -1) must be aligned + to the sector size of the filesystem. +* ``len`` must be aligned to the sector size of the filesystem unless the data + ends at or beyond the current end of the file. +* ``unencoded_len`` and the length of the encoded data must each be no more + than 128 KiB. This limit may increase in the future. +* The length of the encoded data must be less than or equal to + ``unencoded_len.`` +* If using LZO, the filesystem's page size must match the compression page + size. + +Implementation +============== + +This section describes the requirements for filesystems implementing encoded +I/O. + +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 d4853cb919d2..670c673c5956 100644 --- a/Documentation/filesystems/index.rst +++ b/Documentation/filesystems/index.rst @@ -54,6 +54,7 @@ filesystem implementations. fscrypt fsverity netfs_library + encoded_io Filesystems =========== diff --git a/fs/read_write.c b/fs/read_write.c index 9db7adf160d2..f8db16e01227 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -20,6 +20,7 @@ #include #include #include +#include #include "internal.h" #include @@ -1632,24 +1633,15 @@ int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count) 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. - */ -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 */ @@ -1659,8 +1651,22 @@ 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 appropriate error code that caller should return or + * zero in case that write should be allowed. + */ +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; @@ -1691,3 +1697,139 @@ int generic_file_rw_checks(struct file *file_in, struct file *file_out) return 0; } + +/** + * 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); + 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); diff --git a/include/linux/encoded_io.h b/include/linux/encoded_io.h new file mode 100644 index 000000000000..a8cfc0108ba0 --- /dev/null +++ b/include/linux/encoded_io.h @@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_ENCODED_IO_H +#define _LINUX_ENCODED_IO_H + +#include + +struct encoded_iov; +struct iov_iter; +struct kiocb; +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 *); + +#endif /* _LINUX_ENCODED_IO_H */ diff --git a/include/linux/fs.h b/include/linux/fs.h index c3c88fdb9b2a..2a9ab11baaed 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -181,6 +181,9 @@ 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) + /* * Attribute flags. These should be or-ed together to figure out what * has been changed! @@ -311,6 +314,7 @@ enum rw_hint { #define IOCB_SYNC (__force int) RWF_SYNC #define IOCB_NOWAIT (__force int) RWF_NOWAIT #define IOCB_APPEND (__force int) RWF_APPEND +#define IOCB_ENCODED (__force int) RWF_ENCODED /* non-RWF related bits - start at 16 */ #define IOCB_EVENTFD (1 << 16) @@ -3223,6 +3227,13 @@ extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *); extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *); extern int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count); +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_file_rw_checks(struct file *file_in, struct file *file_out); ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *to, ssize_t already_read); @@ -3528,6 +3539,8 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags) return -EOPNOTSUPP; kiocb_flags |= IOCB_NOIO; } + if ((flags & RWF_ENCODED) && !(ki->ki_filp->f_mode & FMODE_ENCODED_IO)) + return -EOPNOTSUPP; kiocb_flags |= (__force int) (flags & RWF_SUPPORTED); if (flags & RWF_SYNC) kiocb_flags |= IOCB_DSYNC; diff --git a/include/uapi/linux/encoded_io.h b/include/uapi/linux/encoded_io.h new file mode 100644 index 000000000000..cf741453dba4 --- /dev/null +++ b/include/uapi/linux/encoded_io.h @@ -0,0 +1,30 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_ENCODED_IO_H +#define _UAPI_LINUX_ENCODED_IO_H + +#include + +#define ENCODED_IOV_COMPRESSION_NONE 0 +#define ENCODED_IOV_COMPRESSION_BTRFS_ZLIB 1 +#define ENCODED_IOV_COMPRESSION_BTRFS_ZSTD 2 +#define ENCODED_IOV_COMPRESSION_BTRFS_LZO_4K 3 +#define ENCODED_IOV_COMPRESSION_BTRFS_LZO_8K 4 +#define ENCODED_IOV_COMPRESSION_BTRFS_LZO_16K 5 +#define ENCODED_IOV_COMPRESSION_BTRFS_LZO_32K 6 +#define ENCODED_IOV_COMPRESSION_BTRFS_LZO_64K 7 +#define ENCODED_IOV_COMPRESSION_TYPES 8 + +#define ENCODED_IOV_ENCRYPTION_NONE 0 +#define ENCODED_IOV_ENCRYPTION_TYPES 1 + +struct encoded_iov { + __aligned_u64 len; + __aligned_u64 unencoded_len; + __aligned_u64 unencoded_offset; + __u32 compression; + __u32 encryption; +}; + +#define ENCODED_IOV_SIZE_VER0 32 + +#endif /* _UAPI_LINUX_ENCODED_IO_H */ diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 4c32e97dcdf0..0ef3a073c9b4 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -300,8 +300,11 @@ 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 */