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Message-Id: <20200724184501.1651378-2-satyat@google.com>
Date: Fri, 24 Jul 2020 18:44:55 +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 v6 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.
Also introduce fscrypt_limit_io_blocks() to limit how many blocks can be
added to a bio being prepared for direct I/O. This is needed for
filesystems that use the iomap direct I/O implementation to avoid DUN
wraparound in the middle of a bio (which is possible with the
IV_INO_LBLK_32 IV generation method). Elsewhere fscrypt_mergeable_bio()
is used for this, but iomap operates on logical ranges directly, so
filesystems using iomap won't have a chance to call fscrypt_mergeable_bio()
on every block added to a bio. So we need this function which limits a
logical range in one go.
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 | 74 ++++++++++++++++++++++++++++++++++++++++
include/linux/fscrypt.h | 18 ++++++++++
3 files changed, 100 insertions(+)
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index 9212325763b0..f72f22a718b2 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_blocks(). fscrypt_limit_io_blocks()
+ * 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..4cdf807b89b9 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 +363,76 @@ 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_blocks() - limit I/O blocks to avoid discontiguous DUNs
+ * @inode: the file on which I/O is being done
+ * @lblk: the block at which the I/O is being started from
+ * @nr_blocks: the number of blocks we want to submit starting at @pos
+ *
+ * Determine the limit to the number of blocks that can be submitted in the bio
+ * targeting @pos without causing a data unit number (DUN) discontinuity.
+ *
+ * This is normally just @nr_blocks, as normally the DUNs just increment along
+ * with the logical blocks. (Or the file is not encrypted.)
+ *
+ * In rare cases, fscrypt can be using an IV generation method that allows the
+ * DUN to wrap around within logically continuous blocks, and that wraparound
+ * will occur. If this happens, a value less than @nr_blocks will be returned
+ * so that the wraparound doesn't occur in the middle of the bio.
+ *
+ * Return: the actual number of blocks that can be submitted
+ */
+u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks)
+{
+ const struct fscrypt_info *ci = inode->i_crypt_info;
+ u32 dun;
+
+ if (!fscrypt_inode_uses_inline_crypto(inode))
+ return nr_blocks;
+
+ if (nr_blocks <= 1)
+ return nr_blocks;
+
+ if (!(fscrypt_policy_flags(&ci->ci_policy) &
+ FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))
+ return nr_blocks;
+
+ /* With IV_INO_LBLK_32, the DUN can wrap around from U32_MAX to 0. */
+
+ dun = ci->ci_hashed_ino + lblk;
+
+ return min_t(u64, nr_blocks, (u64)U32_MAX + 1 - dun);
+}
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index bb257411365f..5de122ec0464 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -559,6 +559,10 @@ 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);
+
+u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks);
+
#else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
static inline bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode)
@@ -587,6 +591,20 @@ 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 u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk,
+ u64 nr_blocks)
+{
+ return nr_blocks;
+}
#endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
/**
--
2.28.0.rc0.142.g3c755180ce-goog
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