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Message-Id: <20200717013518.59219-2-satyat@google.com> Date: Fri, 17 Jul 2020 01:35:12 +0000 From: Satya Tangirala <satyat@...gle.com> To: linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, linux-ext4@...r.kernel.org Cc: linux-xfs@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>, Satya Tangirala <satyat@...gle.com> Subject: [PATCH v2 1/7] fscrypt: Add functions for direct I/O support From: Eric Biggers <ebiggers@...gle.com> Introduce fscrypt_dio_supported() to check whether a direct I/O request is unsupported due to encryption constraints, and fscrypt_limit_io_pages() to check how many pages may be added to a bio being prepared for direct I/O. The IV_INO_LBLK_32 fscrypt policy introduced the possibility that DUNs in logically continuous file blocks might wrap from 0xffffffff to 0. Since this was particularly difficult to handle when block_size != PAGE_SIZE, fscrypt only supports blk-crypto en/decryption with the IV_INO_LBLK_32 policy when block_size == PAGE_SIZE, and ensures that the DUN never wraps around within any submitted bio. fscrypt_limit_io_pages() can be used to determine the number of logically contiguous blocks/pages that may be added to the bio without causing the DUN to wrap around within the bio. This is an alternative to calling fscrypt_mergeable_bio() on each page in a range of logically contiguous pages. Signed-off-by: Eric Biggers <ebiggers@...gle.com> Co-developed-by: Satya Tangirala <satyat@...gle.com> Signed-off-by: Satya Tangirala <satyat@...gle.com> --- fs/crypto/crypto.c | 8 ++++ fs/crypto/inline_crypt.c | 80 ++++++++++++++++++++++++++++++++++++++++ include/linux/fscrypt.h | 19 ++++++++++ 3 files changed, 107 insertions(+) diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index a52cf32733ab..fb34364360b3 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -69,6 +69,14 @@ void fscrypt_free_bounce_page(struct page *bounce_page) } EXPORT_SYMBOL(fscrypt_free_bounce_page); +/* + * Generate the IV for the given logical block number within the given file. + * For filenames encryption, lblk_num == 0. + * + * Keep this in sync with fscrypt_limit_io_pages(). fscrypt_limit_io_pages() + * needs to know about any IV generation methods where the low bits of IV don't + * simply contain the lblk_num (e.g., IV_INO_LBLK_32). + */ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, const struct fscrypt_info *ci) { diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c index d7aecadf33c1..f5af6a63e04c 100644 --- a/fs/crypto/inline_crypt.c +++ b/fs/crypto/inline_crypt.c @@ -16,6 +16,7 @@ #include <linux/blkdev.h> #include <linux/buffer_head.h> #include <linux/sched/mm.h> +#include <linux/uio.h> #include "fscrypt_private.h" @@ -362,3 +363,82 @@ bool fscrypt_mergeable_bio_bh(struct bio *bio, return fscrypt_mergeable_bio(bio, inode, next_lblk); } EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh); + +/** + * fscrypt_dio_supported() - check whether a direct I/O request is unsupported + * due to encryption constraints + * @iocb: the file and position the I/O is targeting + * @iter: the I/O data segment(s) + * + * Return: true if direct I/O is supported + */ +bool fscrypt_dio_supported(struct kiocb *iocb, struct iov_iter *iter) +{ + const struct inode *inode = file_inode(iocb->ki_filp); + const unsigned int blocksize = i_blocksize(inode); + + /* If the file is unencrypted, no veto from us. */ + if (!fscrypt_needs_contents_encryption(inode)) + return true; + + /* We only support direct I/O with inline crypto, not fs-layer crypto */ + if (!fscrypt_inode_uses_inline_crypto(inode)) + return false; + + /* + * Since the granularity of encryption is filesystem blocks, the I/O + * must be block aligned -- not just disk sector aligned. + */ + if (!IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(iter), blocksize)) + return false; + + return true; +} +EXPORT_SYMBOL_GPL(fscrypt_dio_supported); + +/** + * fscrypt_limit_io_pages() - limit I/O pages to avoid discontiguous DUNs + * @inode: the file on which I/O is being done + * @pos: the file position (in bytes) at which the I/O is being done + * @nr_pages: the number of pages we want to submit starting at @pos + * + * Determine the limit to the number of pages that can be submitted in the bio + * targeting @pos without causing a data unit number (DUN) discontinuity. + * + * For IV generation methods that can't cause DUN wraparounds + * within logically continuous data blocks, the maximum number of pages is + * simply @nr_pages. For those IV generation methods that *might* cause DUN + * wraparounds, the returned number of pages is the largest possible number of + * pages (less than @nr_pages) that can be added to the bio without causing a + * DUN wraparound within the bio. + * + * Return: the actual number of pages that can be submitted + */ +int fscrypt_limit_io_pages(const struct inode *inode, loff_t pos, int nr_pages) +{ + const struct fscrypt_info *ci = inode->i_crypt_info; + u32 dun; + + if (!fscrypt_inode_uses_inline_crypto(inode)) + return nr_pages; + + if (nr_pages <= 1) + return nr_pages; + + if (!(fscrypt_policy_flags(&ci->ci_policy) & + FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) + return nr_pages; + + /* + * fscrypt_select_encryption_impl() ensures that block_size == PAGE_SIZE + * when using FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32. + */ + if (WARN_ON_ONCE(i_blocksize(inode) != PAGE_SIZE)) + return 1; + + /* With IV_INO_LBLK_32, the DUN can wrap around from U32_MAX to 0. */ + + dun = ci->ci_hashed_ino + (pos >> inode->i_blkbits); + + return min_t(u64, nr_pages, (u64)U32_MAX + 1 - dun); +} diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index bb257411365f..c205c214b35e 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -559,6 +559,11 @@ bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode, bool fscrypt_mergeable_bio_bh(struct bio *bio, const struct buffer_head *next_bh); +bool fscrypt_dio_supported(struct kiocb *iocb, struct iov_iter *iter); + +int fscrypt_limit_io_pages(const struct inode *inode, loff_t pos, + int nr_pages); + #else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */ static inline bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode) @@ -587,6 +592,20 @@ static inline bool fscrypt_mergeable_bio_bh(struct bio *bio, { return true; } + +static inline bool fscrypt_dio_supported(struct kiocb *iocb, + struct iov_iter *iter) +{ + const struct inode *inode = file_inode(iocb->ki_filp); + + return !fscrypt_needs_contents_encryption(inode); +} + +static inline int fscrypt_limit_io_pages(const struct inode *inode, loff_t pos, + int nr_pages) +{ + return nr_pages; +} #endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */ /** -- 2.28.0.rc0.105.gf9edc3c819-goog
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