From patchwork Wed Nov 20 18:24:23 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 11254623 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 70A5F1871 for ; Wed, 20 Nov 2019 18:24:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E42320878 for ; Wed, 20 Nov 2019 18:24:58 +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="uGKzKYqm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728482AbfKTSY5 (ORCPT ); Wed, 20 Nov 2019 13:24:57 -0500 Received: from mail-pg1-f193.google.com ([209.85.215.193]:37958 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728391AbfKTSY5 (ORCPT ); Wed, 20 Nov 2019 13:24:57 -0500 Received: by mail-pg1-f193.google.com with SMTP id 15so134641pgh.5 for ; Wed, 20 Nov 2019 10:24:55 -0800 (PST) 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=8XzHxPi137x/pI2bsQL0zdjTY440X6mKNZblWdV6sp4=; b=uGKzKYqmJGH7hI2tDaniyhEGGulXqY53tmyyMJ6u1QC9wf4UWQdvv73v4TXPFgfP1d SLVzeT7GtMNTZTO7mklH1Fx0FgVvm/zP4VrpgsGoM4lXUVITZ2Xa6tw3+qLyCflrlMXe AOdfLUO9Ybns0MeFETognL7BEakGHn09bWHEQCaFga9wY2Rlz/CKn4qkg2/ckyUhWws2 gKMHeaGSL5VdH3Y+VBufRtLbm4zQvzekc2YS2eEcR2wNwefNGF8+abYgZEG9ajNmNw0y D6/5d7h46exwPpnJ6GfgDMDjW2171+M0MzHkd3o4M/lps18MzUT56BsuJvSZCDK0js7d Uuxw== 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=8XzHxPi137x/pI2bsQL0zdjTY440X6mKNZblWdV6sp4=; b=Cy7WokGO2n9wIcJ55PFCMIGo3CHKdR2dtXYjTftkEWtbfpCrxV3nu2qFKq6AWPyPUQ fZvr48zSX6PtvCsni7eWoe78OdbHEYKumichTex93Yv1MG5BuGI9xwhmOKZ4GgAcM9AB zF8m5QEzobrK6lt02GnGB9nAUrCyNsluHwh2O9R//QHcQO21wqgu4Z20hrIVATb64GZa J+/yTDIWHeVXG66jeqb82Xti/L5gMsN2sMlQmgHepl2vwClvdzekSauGhbNECsb/S0bw KKAUFaGwvgSSibx6LwJbilZxYBxQjyBz0KZQ4i0z7HJDicAmAvo+BWlTXvFLl7/PHGPg Jiwg== X-Gm-Message-State: APjAAAUC6BkY0BOGYW/eyC4ZPGL/dZIMC2LKGMfDFZyGeei5vPYO3kxu vkmoz0JPZlRmPW7k7+4U2M2kGGdP1ZQ= X-Google-Smtp-Source: APXvYqwFl2Y4PqQ4ZTgsWnt5DRDAiKjHqjz6UVVx2FEKN5ekCIRvh29PxvFoCftAn0iP1Qf5sUerLQ== X-Received: by 2002:a65:62d3:: with SMTP id m19mr4696325pgv.270.1574274294198; Wed, 20 Nov 2019 10:24:54 -0800 (PST) Received: from vader.thefacebook.com ([2620:10d:c090:180::1a46]) by smtp.gmail.com with ESMTPSA id q34sm7937866pjb.15.2019.11.20.10.24.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Nov 2019 10:24:53 -0800 (PST) From: Omar Sandoval To: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org Cc: Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: [RFC PATCH v3 03/12] fs: add RWF_ENCODED for reading/writing compressed data Date: Wed, 20 Nov 2019 10:24:23 -0800 Message-Id: <07f9cc1969052e94818fa50019e7589d206d1d18.1574273658.git.osandov@fb.com> X-Mailer: git-send-email 2.24.0 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 --- Documentation/filesystems/encoded_io.rst | 79 +++++++++++ Documentation/filesystems/index.rst | 1 + include/linux/fs.h | 16 +++ include/uapi/linux/fs.h | 33 ++++- mm/filemap.c | 165 +++++++++++++++++++++-- 5 files changed, 280 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..3ed1ba6e34de --- /dev/null +++ b/Documentation/filesystems/encoded_io.rst @@ -0,0 +1,79 @@ +=========== +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``. +* If ``encoded_iov->len`` is greater than ``encoded_iov->unencoded_len - + encoded_iov->unencoded_offset``, then the user will treat the remainder as + zero-filled. Therefore, holes may be returned by setting ``encoded_iov->len`` + to the size of the hole, setting ``encoded_iov->unencoded_len`` to zero, and + copying no data to the user. + +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 2c3a9f761205..ac9a46fc6120 100644 --- a/Documentation/filesystems/index.rst +++ b/Documentation/filesystems/index.rst @@ -37,6 +37,7 @@ filesystem implementations. journalling fscrypt fsverity + encoded_io Filesystems =========== diff --git a/include/linux/fs.h b/include/linux/fs.h index e0d909d35763..b4f8949d3588 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) +/* 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) struct kiocb { struct file *ki_filp; @@ -3088,6 +3092,13 @@ 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); @@ -3403,6 +3414,11 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags) return -EOPNOTSUPP; ki->ki_flags |= IOCB_NOWAIT; } + if (flags & RWF_ENCODED) { + if (!(ki->ki_filp->f_mode & FMODE_ENCODED_IO)) + return -EOPNOTSUPP; + ki->ki_flags |= IOCB_ENCODED; + } if (flags & RWF_HIPRI) ki->ki_flags |= IOCB_HIPRI; if (flags & RWF_DSYNC) diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 379a612f8f1d..775d18bb0efc 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -284,6 +284,34 @@ struct fsxattr { typedef int __bitwise __kernel_rwf_t; +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 + /* high priority request, poll if possible */ #define RWF_HIPRI ((__force __kernel_rwf_t)0x00000001) @@ -299,8 +327,11 @@ 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 85b7d087eb45..78b8535b58dd 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2949,24 +2949,15 @@ 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 */ @@ -2976,8 +2967,21 @@ 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; @@ -2986,6 +2990,141 @@ 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_len && + encoded->unencoded_offset >= encoded->unencoded_len) + 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. *