[RFC PATCH 0/4] userspace PI passthrough via io_uring

[RFC PATCH 0/4] userspace PI passthrough via io_uring

[Bob Liu]

This RFC provides a rough implementation of a mechanism to allow
userspace to attach protection information (e.g. T10 DIF) data to a
disk write and to receive the information alongside a disk read.
The interface is an extension to the io_uring interface:
two new commands (IORING_OP_READV{WRITEV}_PI) are provided.
The last struct iovec in the arg list is interpreted to point to a buffer
containing the the PI data.

Patch #1 add two new commands to io_uring.
Patch #2 introduces two helper funcs in bio-integrity.
Patch #3 implement the PI passthrough in direct-io of block-dev.
(Similar extensions may add to fs/direct-io.c and fs/maps/directio.c)
Patch #4 add io_uring use space test case to liburing.

Welcome any feedbacks.
Thanks!

There was attempt before[1], but was based on AIO at that time.
[1] https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg27537.html

Bob Liu (3):
  io_uring: add IORING_OP_READ{WRITE}V_PI cmd
  bio-integrity: introduce two funcs handle protect information
  block_dev: support protect information passthrough

 block/bio-integrity.c         | 77 +++++++++++++++++++++++++++++++++++++++++++
 fs/block_dev.c                | 17 ++++++++++
 fs/io_uring.c                 | 12 +++++++
 include/linux/bio.h           | 14 ++++++++
 include/linux/fs.h            |  1 +
 include/uapi/linux/io_uring.h |  2 ++
 6 files changed, 123 insertions(+)

-- 
2.9.5

[PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Bob Liu]

Add read and write with protect information command.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 fs/io_uring.c                 | 12 ++++++++++++
 include/linux/fs.h            |  1 +
 include/uapi/linux/io_uring.h |  2 ++
 3 files changed, 15 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 562e3a1..c43d96a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -630,12 +630,14 @@ static inline bool io_prep_async_work(struct io_kiocb *req,
 
 	switch (req->opcode) {
 	case IORING_OP_WRITEV:
+	case IORING_OP_WRITEV_PI:
 	case IORING_OP_WRITE_FIXED:
 		/* only regular files should be hashed for writes */
 		if (req->flags & REQ_F_ISREG)
 			do_hashed = true;
 		/* fall-through */
 	case IORING_OP_READV:
+	case IORING_OP_READV_PI:
 	case IORING_OP_READ_FIXED:
 	case IORING_OP_SENDMSG:
 	case IORING_OP_RECVMSG:
@@ -1505,6 +1507,12 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	kiocb->ki_pos = READ_ONCE(sqe->off);
 	kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
 	kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp));
+	if (req->opcode == IORING_OP_READV_PI ||
+			req->opcode == IORING_OP_WRITEV_PI) {
+		if (!(req->file->f_flags & O_DIRECT))
+			return -EINVAL;
+		kiocb->ki_flags |= IOCB_USE_PI;
+	}
 
 	ioprio = READ_ONCE(sqe->ioprio);
 	if (ioprio) {
@@ -3065,10 +3073,12 @@ static int io_req_defer_prep(struct io_kiocb *req,
 	case IORING_OP_NOP:
 		break;
 	case IORING_OP_READV:
+	case IORING_OP_READV_PI:
 	case IORING_OP_READ_FIXED:
 		ret = io_read_prep(req, sqe, true);
 		break;
 	case IORING_OP_WRITEV:
+	case IORING_OP_WRITEV_PI:
 	case IORING_OP_WRITE_FIXED:
 		ret = io_write_prep(req, sqe, true);
 		break;
@@ -3156,6 +3166,7 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	case IORING_OP_NOP:
 		ret = io_nop(req);
 		break;
+	case IORING_OP_READV_PI:
 	case IORING_OP_READV:
 	case IORING_OP_READ_FIXED:
 		if (sqe) {
@@ -3166,6 +3177,7 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		ret = io_read(req, nxt, force_nonblock);
 		break;
 	case IORING_OP_WRITEV:
+	case IORING_OP_WRITEV_PI:
 	case IORING_OP_WRITE_FIXED:
 		if (sqe) {
 			ret = io_write_prep(req, sqe, force_nonblock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 98e0349..65fda07 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -314,6 +314,7 @@ enum rw_hint {
 #define IOCB_SYNC		(1 << 5)
 #define IOCB_WRITE		(1 << 6)
 #define IOCB_NOWAIT		(1 << 7)
+#define IOCB_USE_PI		(1 << 8)
 
 struct kiocb {
 	struct file		*ki_filp;
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index a3300e1..98fa3f1 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -62,6 +62,8 @@ enum {
 	IORING_OP_NOP,
 	IORING_OP_READV,
 	IORING_OP_WRITEV,
+	IORING_OP_READV_PI,
+	IORING_OP_WRITEV_PI,
 	IORING_OP_FSYNC,
 	IORING_OP_READ_FIXED,
 	IORING_OP_WRITE_FIXED,
-- 
2.9.5

[PATCH 2/4] bio-integrity: introduce two funcs handle protect information

[Bob Liu]

Introduce two funcs handle protect information passthrough from
user space.

iter_slice_protect_info() will slice the last segment as protect
information.

bio_integrity_prep_from_iovec() attach the protect information to
a bio.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 block/bio-integrity.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/bio.h   | 14 ++++++++++
 2 files changed, 91 insertions(+)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 575df98..0b22c5d 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -12,6 +12,7 @@
 #include <linux/bio.h>
 #include <linux/workqueue.h>
 #include <linux/slab.h>
+#include <linux/uio.h>
 #include "blk.h"
 
 #define BIP_INLINE_VECS	4
@@ -305,6 +306,53 @@ bool bio_integrity_prep(struct bio *bio)
 }
 EXPORT_SYMBOL(bio_integrity_prep);
 
+int bio_integrity_prep_from_iovec(struct bio *bio, struct iovec *pi_iov)
+{
+	struct blk_integrity *bi = blk_get_integrity(bio->bi_disk);
+	struct bio_integrity_payload *bip;
+	struct page *user_pi_page;
+	int nr_vec_page = 0;
+	int ret = 0, interval = 0;
+
+	if (!pi_iov || !pi_iov->iov_base)
+		return 1;
+
+	nr_vec_page = (pi_iov->iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if (nr_vec_page > 1) {
+		printk("Now only support 1 page containing integrity "
+			"metadata, while requires %d pages.\n", nr_vec_page);
+		return 1;
+	}
+
+	interval = bio_integrity_intervals(bi, bio_sectors(bio));
+	if ((interval * bi->tuple_size) != pi_iov->iov_len)
+		return 1;
+
+	bip = bio_integrity_alloc(bio, GFP_NOIO, nr_vec_page);
+	if (IS_ERR(bip))
+		return PTR_ERR(bip);
+
+	bip->bip_iter.bi_size = pi_iov->iov_len;
+	bip->bio_iter = bio->bi_iter;
+	bip_set_seed(bip, bio->bi_iter.bi_sector);
+
+	if (bi->flags & BLK_INTEGRITY_IP_CHECKSUM)
+		bip->bip_flags |= BIP_IP_CHECKSUM;
+
+	ret = get_user_pages_fast((unsigned long)(pi_iov->iov_base), nr_vec_page,
+			op_is_write(bio_op(bio)) ?  FOLL_WRITE : 0,
+			&user_pi_page);
+	if (unlikely(ret < 0))
+		return 1;
+
+	ret = bio_integrity_add_page(bio, user_pi_page, pi_iov->iov_len, 0);
+	if (unlikely(ret != pi_iov->iov_len))
+		return -ENOMEM;
+
+	return 0;
+}
+EXPORT_SYMBOL(bio_integrity_prep_from_iovec);
+
 /**
  * bio_integrity_verify_fn - Integrity I/O completion worker
  * @work:	Work struct stored in bio to be verified
@@ -378,6 +426,35 @@ void bio_integrity_advance(struct bio *bio, unsigned int bytes_done)
 }
 
 /**
+ * iter_slice_protect_info
+ *
+ * Description: slice protection information from iter.
+ * The last iovec contains protection information pass from user space.
+ */
+int iter_slice_protect_info(struct iov_iter *iter, int nr_pages,
+		struct iovec **pi_iov)
+{
+	size_t len = 0;
+
+	/* TBD: now only support one bio. */
+	if (!iter_is_iovec(iter) || nr_pages >= BIO_MAX_PAGES - 1)
+		return 1;
+
+	/* Last iovec contains protection information. */
+	iter->nr_segs--;
+	*pi_iov = (struct iovec *)(iter->iov + iter->nr_segs);
+
+	len = (*pi_iov)->iov_len;
+	if (len > 0 && len < iter->count) {
+		iter->count -= len;
+		return 0;
+	}
+
+	return 1;
+}
+EXPORT_SYMBOL(iter_slice_protect_info);
+
+/**
  * bio_integrity_trim - Trim integrity vector
  * @bio:	bio whose integrity vector to update
  *
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 3cdb84c..6172b13 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -749,6 +749,8 @@ static inline bool bioset_initialized(struct bio_set *bs)
 extern struct bio_integrity_payload *bio_integrity_alloc(struct bio *, gfp_t, unsigned int);
 extern int bio_integrity_add_page(struct bio *, struct page *, unsigned int, unsigned int);
 extern bool bio_integrity_prep(struct bio *);
+extern int bio_integrity_prep_from_iovec(struct bio *bio, struct iovec *pi_iov);
+extern int iter_slice_protect_info(struct iov_iter *iter, int nr_pages, struct iovec **pi_iov);
 extern void bio_integrity_advance(struct bio *, unsigned int);
 extern void bio_integrity_trim(struct bio *);
 extern int bio_integrity_clone(struct bio *, struct bio *, gfp_t);
@@ -778,6 +780,18 @@ static inline bool bio_integrity_prep(struct bio *bio)
 	return true;
 }
 
+static inline int bio_integrity_prep_from_iovec(struct bio *bio,
+		struct iovec *pi_iov)
+{
+	return 0;
+}
+
+static inline int iter_slice_protect_info(struct iov_iter *iter, int nr_pages,
+		struct iovec **pi_iov)
+{
+	return 0;
+}
+
 static inline int bio_integrity_clone(struct bio *bio, struct bio *bio_src,
 				      gfp_t gfp_mask)
 {
-- 
2.9.5

[PATCH 3/4] block_dev: support protect information passthrough

[Bob Liu]

Support protect information passed from use sapce, on direct io
is considered now.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 fs/block_dev.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 69bf2fb..10e3299 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -348,6 +348,13 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 	loff_t pos = iocb->ki_pos;
 	blk_qc_t qc = BLK_QC_T_NONE;
 	int ret = 0;
+	struct iovec *pi_iov;
+
+	if (iocb->ki_flags & IOCB_USE_PI) {
+		ret = iter_slice_protect_info(iter, nr_pages, &pi_iov);
+		if (ret)
+			return -EINVAL;
+	}
 
 	if ((pos | iov_iter_alignment(iter)) &
 	    (bdev_logical_block_size(bdev) - 1))
@@ -411,6 +418,16 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 				polled = true;
 			}
 
+			/* Add protection information to bio */
+			if (iocb->ki_flags & IOCB_USE_PI) {
+				ret = bio_integrity_prep_from_iovec(bio, pi_iov);
+				if (ret) {
+					bio->bi_status = BLK_STS_IOERR;
+					bio_endio(bio);
+					break;
+				}
+			}
+
 			qc = submit_bio(bio);
 
 			if (polled)
-- 
2.9.5

[PATCH 4/4] liburing/test: add testcase for protect information passthrough

[Bob Liu]

Demonstrate how to use IORING_OP_READ{WRITE}V_PI cmd.
Write data together with protection information, then read back and compare
results.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 src/include/liburing.h          |  16 ++
 src/include/liburing/io_uring.h |   2 +
 test/Makefile                   |   4 +-
 test/pi_passthrough.c           | 267 ++++++++++++++++++++++++++++++++
 4 files changed, 287 insertions(+), 2 deletions(-)
 create mode 100644 test/pi_passthrough.c

diff --git a/src/include/liburing.h b/src/include/liburing.h
index 2f1e968..2967c5b 100644
--- a/src/include/liburing.h
+++ b/src/include/liburing.h
@@ -206,6 +206,14 @@ static inline void io_uring_prep_rw(int op, struct io_uring_sqe *sqe, int fd,
 	sqe->__pad2[0] = sqe->__pad2[1] = sqe->__pad2[2] = 0;
 }
 
+static inline void io_uring_prep_readv_pi(struct io_uring_sqe *sqe, int fd,
+				       const struct iovec *iovecs,
+				       unsigned nr_vecs, off_t offset)
+{
+	io_uring_prep_rw(IORING_OP_READV_PI, sqe, fd, iovecs, nr_vecs, offset);
+}
+
+
 static inline void io_uring_prep_readv(struct io_uring_sqe *sqe, int fd,
 				       const struct iovec *iovecs,
 				       unsigned nr_vecs, off_t offset)
@@ -228,6 +236,14 @@ static inline void io_uring_prep_writev(struct io_uring_sqe *sqe, int fd,
 	io_uring_prep_rw(IORING_OP_WRITEV, sqe, fd, iovecs, nr_vecs, offset);
 }
 
+static inline void io_uring_prep_writev_pi(struct io_uring_sqe *sqe, int fd,
+					const struct iovec *iovecs,
+					unsigned nr_vecs, off_t offset)
+{
+	io_uring_prep_rw(IORING_OP_WRITEV_PI, sqe, fd, iovecs, nr_vecs, offset);
+}
+
+
 static inline void io_uring_prep_write_fixed(struct io_uring_sqe *sqe, int fd,
 					     const void *buf, unsigned nbytes,
 					     off_t offset, int buf_index)
diff --git a/src/include/liburing/io_uring.h b/src/include/liburing/io_uring.h
index 3f7961c..f5bb46f 100644
--- a/src/include/liburing/io_uring.h
+++ b/src/include/liburing/io_uring.h
@@ -86,6 +86,8 @@ enum {
 	IORING_OP_NOP,
 	IORING_OP_READV,
 	IORING_OP_WRITEV,
+	IORING_OP_READV_PI,
+	IORING_OP_WRITEV_PI,
 	IORING_OP_FSYNC,
 	IORING_OP_READ_FIXED,
 	IORING_OP_WRITE_FIXED,
diff --git a/test/Makefile b/test/Makefile
index 4a0bb4e..0bf29ec 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -13,7 +13,7 @@ all_targets += poll poll-cancel ring-leak fsync io_uring_setup io_uring_register
 		send_recvmsg a4c0b3decb33-test 500f9fbadef8-test timeout \
 		sq-space_left stdout cq-ready cq-peek-batch file-register \
 		cq-size 8a9973408177-test a0908ae19763-test 232c93d07b74-test \
-		socket-rw accept timeout-overflow defer read-write io-cancel \
+		socket-rw accept timeout-overflow defer read-write pi_passthrough io-cancel \
 		link-timeout cq-overflow link_drain fc2a85cb02ef-test \
 		poll-link accept-link fixed-link poll-cancel-ton teardowns \
 		poll-many b5837bd5311d-test accept-test d77a67ed5f27-test \
@@ -40,7 +40,7 @@ test_srcs := poll.c poll-cancel.c ring-leak.c fsync.c io_uring_setup.c \
 	500f9fbadef8-test.c timeout.c sq-space_left.c stdout.c cq-ready.c\
 	cq-peek-batch.c file-register.c cq-size.c 8a9973408177-test.c \
 	a0908ae19763-test.c 232c93d07b74-test.c socket-rw.c accept.c \
-	timeout-overflow.c defer.c read-write.c io-cancel.c link-timeout.c \
+	timeout-overflow.c defer.c read-write.c pi_passthrough.c io-cancel.c link-timeout.c \
 	cq-overflow.c link_drain.c fc2a85cb02ef-test.c poll-link.c \
 	accept-link.c fixed-link.c poll-cancel-ton.c teardowns.c poll-many.c \
 	b5837bd5311d-test.c accept-test.c d77a67ed5f27-test.c connect.c \
diff --git a/test/pi_passthrough.c b/test/pi_passthrough.c
new file mode 100644
index 0000000..27d679a
--- /dev/null
+++ b/test/pi_passthrough.c
@@ -0,0 +1,267 @@
+/*
+ * Simple app that demonstrates how to setup an io_uring interface,
+ * submit and complete IO against it, and then tear it down.
+ *
+ * gcc -Wall -O2 -D_GNU_SOURCE -o pi_passthrough pi_passthrough.c -luring
+ * modprobe scsi_debug.ko dif=1 guard=1 dev_size_mb=1024 num_parts=1 ato=1 dix=31
+ */
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include "liburing.h"
+
+#define NR_SECTOR   11
+#define SECTOR_SIZE 512
+#define BUF_SIZE    (NR_SECTOR * SECTOR_SIZE)
+
+/* Will be round up power of 2 */
+#define QD	    (NR_SECTOR + 1 )
+
+struct sd_dif_tuple {
+       uint16_t guard_tag;	/* Checksum */
+       uint16_t app_tag;	/* Opaque storage */
+       uint32_t ref_tag;	/* Target LBA or indirect LBA */
+};
+
+
+typedef unsigned short __sum16;
+static inline unsigned short from32to16(unsigned int x)
+{
+        /* add up 16-bit and 16-bit for 16+c bit */
+        x = (x & 0xffff) + (x >> 16);
+        /* add up carry.. */
+        x = (x & 0xffff) + (x >> 16);
+        return x;
+}
+
+static unsigned int do_csum(const unsigned char *buff, int len)
+{
+	int odd, count;
+	unsigned long result = 0;
+
+	if (len <= 0)
+		goto out;
+	odd = 1 & (unsigned long) buff;
+	if (odd) {
+#ifdef __LITTLE_ENDIAN
+		result = *buff;
+#else
+		result += (*buff << 8);
+#endif
+		len--;
+		buff++;
+	}
+	count = len >> 1;		/* nr of 16-bit words.. */
+	if (count) {
+		if (2 & (unsigned long) buff) {
+			result += *(unsigned short *) buff;
+			count--;
+			len -= 2;
+			buff += 2;
+		}
+		count >>= 1;		/* nr of 32-bit words.. */
+		if (count) {
+			unsigned long carry = 0;
+			do {
+				unsigned long w = *(unsigned int *) buff;
+				count--;
+				buff += 4;
+				result += carry;
+				result += w;
+				carry = (w > result);
+			} while (count);
+			result += carry;
+			result = (result & 0xffff) + (result >> 16);
+		}
+		if (len & 2) {
+			result += *(unsigned short *) buff;
+			buff += 2;
+		}
+	}
+	if (len & 1)
+#ifdef __LITTLE_ENDIAN
+		result += *buff;
+#else
+		result += (*buff << 8);
+#endif
+	result = from32to16(result);
+	if (odd)
+		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+out:
+	return result;
+}
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+__sum16 ip_compute_csum(const void *buff, int len)
+{
+	return (__sum16)~do_csum(buff, len);
+}
+
+static void stamp_pi_buffer(struct sd_dif_tuple *t, uint16_t csum,
+			    uint16_t tag, uint32_t sector)
+{
+	//t->guard_tag = htons(csum);
+	t->guard_tag = csum;
+	t->app_tag = getpid();
+	t->ref_tag = htonl(sector);
+}
+
+static void dump_buffer(char *buf, size_t len)
+{
+	size_t off;
+	char *p;
+
+	for (p = buf; p < buf + len; p++) {
+		off = p - buf;
+		if (off % 32 == 0) {
+			if (p != buf)
+				printf("\n");
+			printf("%05zu:", off);
+		}
+		printf(" %02x", *p & 0xFF);
+	}
+	printf("\n");
+}
+
+int io_rw(int fd, int write, void *buf, size_t len,
+		void *mbuf, size_t pi_buflen)
+{
+	struct io_uring ring;
+	struct io_uring_sqe *sqe;
+	struct io_uring_cqe *cqe;
+	struct iovec *iovecs;
+	int i, ret, pending, done, offset=0;
+
+	iovecs = calloc(QD, sizeof(struct iovec));
+	for (i = 0; i < QD - 1; i++) {
+		iovecs[i].iov_base = buf + i * SECTOR_SIZE;
+		iovecs[i].iov_len = SECTOR_SIZE;
+	}
+	/* Last iovecs store protect information */
+	iovecs[i].iov_base = mbuf;
+	iovecs[i].iov_len  = pi_buflen;
+
+	if (write) {
+		__sum16 ip_csum;
+		int out_fd = 0;
+		out_fd = open("/dev/random", O_RDONLY);
+		if (out_fd < 0) {
+			perror("open");
+			return 1;
+		}
+
+		ret = read(out_fd, buf, len);
+		printf("read %d bytes from file\n", ret);
+		for( i = 0; i < NR_SECTOR; i++) {
+			ip_csum = ip_compute_csum(buf + i*SECTOR_SIZE, SECTOR_SIZE);
+			printf("ip_csum:0x%x\n", ip_csum);
+
+			stamp_pi_buffer(mbuf + i * sizeof(struct sd_dif_tuple),
+					ip_csum,0x0, i & 0xffffffff);
+		}
+	}
+
+	ret = io_uring_queue_init(1, &ring, 0);
+	if (ret < 0) {
+		fprintf(stderr, "queue_init: %s\n", strerror(-ret));
+		return 1;
+	}
+
+	sqe = io_uring_get_sqe(&ring);
+	if (!sqe)
+		return 1;
+	if(write)
+		io_uring_prep_writev_pi(sqe, fd, iovecs, QD, offset);
+	else
+		io_uring_prep_readv_pi(sqe, fd, iovecs, QD, offset);
+
+	ret = io_uring_submit(&ring);
+	if (ret < 0) {
+		fprintf(stderr, "io_uring_submit: %s\n", strerror(-ret));
+		return 1;
+	}
+
+	done = 0;
+	pending = ret;
+	for (i = 0; i < pending; i++) {
+		ret = io_uring_wait_cqe(&ring, &cqe);
+		if (ret < 0) {
+			fprintf(stderr, "io_uring_wait_cqe: %s\n", strerror(-ret));
+			return 1;
+		}
+
+		done++;
+		ret = 0;
+		if (cqe->res != SECTOR_SIZE) {
+			fprintf(stderr, "ceq->res=%d, wanted %d\n",
+					cqe->res, SECTOR_SIZE);
+			ret = 1;
+		}
+		io_uring_cqe_seen(&ring, cqe);
+		if (ret)
+			break;
+	}
+	io_uring_queue_exit(&ring);
+	printf("Submitted=%d, completed=%d\n", pending, done);
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	int fd;
+	int page_size = 4096;
+	size_t pi_buflen;
+	void *buf, *mbuf;
+	void *buf2, *mbuf2; //read back
+
+	if (argc < 2) {
+		printf("%s: file\n", argv[0]);
+		return 1;
+	}
+
+	fd = open(argv[1], O_RDWR |O_SYNC| O_DIRECT);
+	if (fd < 0) {
+		perror("open");
+		return 1;
+	}
+
+	/* write with protect information */
+	pi_buflen =  NR_SECTOR * sizeof(struct sd_dif_tuple);
+	if (posix_memalign(&buf, page_size, BUF_SIZE) ||
+			posix_memalign(&mbuf, page_size, pi_buflen) ) {
+		perror("memalign");
+		return 1;
+	}
+	io_rw(fd, 1, buf, BUF_SIZE, mbuf, pi_buflen);
+
+	/* read out protect information */
+	if (posix_memalign(&buf2, page_size, BUF_SIZE) ||
+			posix_memalign(&mbuf2, page_size, pi_buflen) ) {
+		perror("memalign");
+		return 1;
+	}
+	io_rw(fd, 0, buf2, BUF_SIZE, mbuf2, pi_buflen);
+	close(fd);
+
+	/* Compare result. */
+	if(memcmp(buf, buf2, BUF_SIZE)) {
+		printf("err!! protect date mismatch!!\n");
+		dump_buffer(buf, BUF_SIZE);
+		dump_buffer(mbuf, pi_buflen);
+	}
+	if(memcmp(mbuf, mbuf2, pi_buflen)) {
+		printf("err!! protect date mismatch!!\n");
+		dump_buffer(buf2, BUF_SIZE);
+		dump_buffer(mbuf2, pi_buflen);
+	}
+	printf("test succ!!\n");
+
+	return 0;
+}
-- 
2.17.1

Re: [PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Jens Axboe]

On 2/26/20 1:37 AM, Bob Liu wrote:
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index a3300e1..98fa3f1 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -62,6 +62,8 @@ enum {
>  	IORING_OP_NOP,
>  	IORING_OP_READV,
>  	IORING_OP_WRITEV,
> +	IORING_OP_READV_PI,
> +	IORING_OP_WRITEV_PI,
>  	IORING_OP_FSYNC,
>  	IORING_OP_READ_FIXED,
>  	IORING_OP_WRITE_FIXED,

So this one renumbers everything past IORING_OP_WRITEV, breaking the
ABI in a very bad way. I'm guessing that was entirely unintentional?
Any new command must go at the end of the list.

You're also not updating io_op_defs[] with the two new commands,
which means it won't compile at all. I'm guessing you tested this on
an older version of the kernel which didn't have io_op_defs[]?

-- 
Jens Axboe

Re: [RFC PATCH 0/4] userspace PI passthrough via io_uring

[Jens Axboe]

On 2/26/20 1:37 AM, Bob Liu wrote:
> This RFC provides a rough implementation of a mechanism to allow
> userspace to attach protection information (e.g. T10 DIF) data to a
> disk write and to receive the information alongside a disk read.
> The interface is an extension to the io_uring interface:
> two new commands (IORING_OP_READV{WRITEV}_PI) are provided.
> The last struct iovec in the arg list is interpreted to point to a buffer
> containing the the PI data.
> 
> Patch #1 add two new commands to io_uring.
> Patch #2 introduces two helper funcs in bio-integrity.
> Patch #3 implement the PI passthrough in direct-io of block-dev.
> (Similar extensions may add to fs/direct-io.c and fs/maps/directio.c)
> Patch #4 add io_uring use space test case to liburing.

No strong feelings on the support in general, the io_uring bits are
trivial enough (once fixed up, per comments in that patch) that I
have no objections on that front.

I'd really like Martin to render an opinion on the API (PI info in
last vec), since he's the integrity guy.

-- 
Jens Axboe

Re: [PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Christoph Hellwig]

On Wed, Feb 26, 2020 at 07:24:06AM -0700, Jens Axboe wrote:
> On 2/26/20 1:37 AM, Bob Liu wrote:
> > diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> > index a3300e1..98fa3f1 100644
> > --- a/include/uapi/linux/io_uring.h
> > +++ b/include/uapi/linux/io_uring.h
> > @@ -62,6 +62,8 @@ enum {
> >  	IORING_OP_NOP,
> >  	IORING_OP_READV,
> >  	IORING_OP_WRITEV,
> > +	IORING_OP_READV_PI,
> > +	IORING_OP_WRITEV_PI,
> >  	IORING_OP_FSYNC,
> >  	IORING_OP_READ_FIXED,
> >  	IORING_OP_WRITE_FIXED,
> 
> So this one renumbers everything past IORING_OP_WRITEV, breaking the
> ABI in a very bad way. I'm guessing that was entirely unintentional?
> Any new command must go at the end of the list.
> 
> You're also not updating io_op_defs[] with the two new commands,
> which means it won't compile at all. I'm guessing you tested this on
> an older version of the kernel which didn't have io_op_defs[]?

And the real question is why we need ops insted of just a flag and
using previously reserved fields for the PI pointer.

Re: [PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Jens Axboe]

On 2/26/20 8:57 AM, Christoph Hellwig wrote:
> On Wed, Feb 26, 2020 at 07:24:06AM -0700, Jens Axboe wrote:
>> On 2/26/20 1:37 AM, Bob Liu wrote:
>>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>>> index a3300e1..98fa3f1 100644
>>> --- a/include/uapi/linux/io_uring.h
>>> +++ b/include/uapi/linux/io_uring.h
>>> @@ -62,6 +62,8 @@ enum {
>>>  	IORING_OP_NOP,
>>>  	IORING_OP_READV,
>>>  	IORING_OP_WRITEV,
>>> +	IORING_OP_READV_PI,
>>> +	IORING_OP_WRITEV_PI,
>>>  	IORING_OP_FSYNC,
>>>  	IORING_OP_READ_FIXED,
>>>  	IORING_OP_WRITE_FIXED,
>>
>> So this one renumbers everything past IORING_OP_WRITEV, breaking the
>> ABI in a very bad way. I'm guessing that was entirely unintentional?
>> Any new command must go at the end of the list.
>>
>> You're also not updating io_op_defs[] with the two new commands,
>> which means it won't compile at all. I'm guessing you tested this on
>> an older version of the kernel which didn't have io_op_defs[]?
> 
> And the real question is why we need ops insted of just a flag and
> using previously reserved fields for the PI pointer.

Yeah, should probably be a RWF_ flag instead, and a 64-bit SQE field
for the PI data. The 'last iovec is PI' is kind of icky.

-- 
Jens Axboe

Re: [PATCH 2/4] bio-integrity: introduce two funcs handle protect information

[Darrick J. Wong]

On Wed, Feb 26, 2020 at 04:37:17PM +0800, Bob Liu wrote:
> Introduce two funcs handle protect information passthrough from
> user space.
> 
> iter_slice_protect_info() will slice the last segment as protect
> information.
> 
> bio_integrity_prep_from_iovec() attach the protect information to
> a bio.
> 
> Signed-off-by: Bob Liu <bob.liu@oracle.com>
> ---
>  block/bio-integrity.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/bio.h   | 14 ++++++++++
>  2 files changed, 91 insertions(+)
> 
> diff --git a/block/bio-integrity.c b/block/bio-integrity.c
> index 575df98..0b22c5d 100644
> --- a/block/bio-integrity.c
> +++ b/block/bio-integrity.c
> @@ -12,6 +12,7 @@
>  #include <linux/bio.h>
>  #include <linux/workqueue.h>
>  #include <linux/slab.h>
> +#include <linux/uio.h>
>  #include "blk.h"
>  
>  #define BIP_INLINE_VECS	4
> @@ -305,6 +306,53 @@ bool bio_integrity_prep(struct bio *bio)
>  }
>  EXPORT_SYMBOL(bio_integrity_prep);
>  
> +int bio_integrity_prep_from_iovec(struct bio *bio, struct iovec *pi_iov)
> +{
> +	struct blk_integrity *bi = blk_get_integrity(bio->bi_disk);
> +	struct bio_integrity_payload *bip;
> +	struct page *user_pi_page;
> +	int nr_vec_page = 0;
> +	int ret = 0, interval = 0;
> +
> +	if (!pi_iov || !pi_iov->iov_base)
> +		return 1;
> +
> +	nr_vec_page = (pi_iov->iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +	if (nr_vec_page > 1) {
> +		printk("Now only support 1 page containing integrity "
> +			"metadata, while requires %d pages.\n", nr_vec_page);
> +		return 1;

I would've thought this would be -EINVAL or something given the -ENOMEM
below...?

> +	}
> +
> +	interval = bio_integrity_intervals(bi, bio_sectors(bio));
> +	if ((interval * bi->tuple_size) != pi_iov->iov_len)
> +		return 1;
> +
> +	bip = bio_integrity_alloc(bio, GFP_NOIO, nr_vec_page);
> +	if (IS_ERR(bip))
> +		return PTR_ERR(bip);
> +
> +	bip->bip_iter.bi_size = pi_iov->iov_len;
> +	bip->bio_iter = bio->bi_iter;
> +	bip_set_seed(bip, bio->bi_iter.bi_sector);
> +
> +	if (bi->flags & BLK_INTEGRITY_IP_CHECKSUM)
> +		bip->bip_flags |= BIP_IP_CHECKSUM;
> +
> +	ret = get_user_pages_fast((unsigned long)(pi_iov->iov_base), nr_vec_page,
> +			op_is_write(bio_op(bio)) ?  FOLL_WRITE : 0,
> +			&user_pi_page);
> +	if (unlikely(ret < 0))
> +		return 1;
> +
> +	ret = bio_integrity_add_page(bio, user_pi_page, pi_iov->iov_len, 0);
> +	if (unlikely(ret != pi_iov->iov_len))
> +		return -ENOMEM;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(bio_integrity_prep_from_iovec);
> +
>  /**
>   * bio_integrity_verify_fn - Integrity I/O completion worker
>   * @work:	Work struct stored in bio to be verified
> @@ -378,6 +426,35 @@ void bio_integrity_advance(struct bio *bio, unsigned int bytes_done)
>  }
>  
>  /**
> + * iter_slice_protect_info
> + *
> + * Description: slice protection information from iter.
> + * The last iovec contains protection information pass from user space.

What do the return values here mean?

Also kinda wondering about the slice & dice of the iovec here, but
<shrug> I guess this is RFC. :)

--D

> + */
> +int iter_slice_protect_info(struct iov_iter *iter, int nr_pages,
> +		struct iovec **pi_iov)
> +{
> +	size_t len = 0;
> +
> +	/* TBD: now only support one bio. */
> +	if (!iter_is_iovec(iter) || nr_pages >= BIO_MAX_PAGES - 1)
> +		return 1;
> +
> +	/* Last iovec contains protection information. */
> +	iter->nr_segs--;
> +	*pi_iov = (struct iovec *)(iter->iov + iter->nr_segs);
> +
> +	len = (*pi_iov)->iov_len;
> +	if (len > 0 && len < iter->count) {
> +		iter->count -= len;
> +		return 0;
> +	}
> +
> +	return 1;
> +}
> +EXPORT_SYMBOL(iter_slice_protect_info);
> +
> +/**
>   * bio_integrity_trim - Trim integrity vector
>   * @bio:	bio whose integrity vector to update
>   *
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 3cdb84c..6172b13 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -749,6 +749,8 @@ static inline bool bioset_initialized(struct bio_set *bs)
>  extern struct bio_integrity_payload *bio_integrity_alloc(struct bio *, gfp_t, unsigned int);
>  extern int bio_integrity_add_page(struct bio *, struct page *, unsigned int, unsigned int);
>  extern bool bio_integrity_prep(struct bio *);
> +extern int bio_integrity_prep_from_iovec(struct bio *bio, struct iovec *pi_iov);
> +extern int iter_slice_protect_info(struct iov_iter *iter, int nr_pages, struct iovec **pi_iov);
>  extern void bio_integrity_advance(struct bio *, unsigned int);
>  extern void bio_integrity_trim(struct bio *);
>  extern int bio_integrity_clone(struct bio *, struct bio *, gfp_t);
> @@ -778,6 +780,18 @@ static inline bool bio_integrity_prep(struct bio *bio)
>  	return true;
>  }
>  
> +static inline int bio_integrity_prep_from_iovec(struct bio *bio,
> +		struct iovec *pi_iov)
> +{
> +	return 0;
> +}
> +
> +static inline int iter_slice_protect_info(struct iov_iter *iter, int nr_pages,
> +		struct iovec **pi_iov)
> +{
> +	return 0;
> +}
> +
>  static inline int bio_integrity_clone(struct bio *bio, struct bio *bio_src,
>  				      gfp_t gfp_mask)
>  {
> -- 
> 2.9.5
> 

Re: [PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Darrick J. Wong]

On Wed, Feb 26, 2020 at 08:58:46AM -0700, Jens Axboe wrote:
> On 2/26/20 8:57 AM, Christoph Hellwig wrote:
> > On Wed, Feb 26, 2020 at 07:24:06AM -0700, Jens Axboe wrote:
> >> On 2/26/20 1:37 AM, Bob Liu wrote:
> >>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> >>> index a3300e1..98fa3f1 100644
> >>> --- a/include/uapi/linux/io_uring.h
> >>> +++ b/include/uapi/linux/io_uring.h
> >>> @@ -62,6 +62,8 @@ enum {
> >>>  	IORING_OP_NOP,
> >>>  	IORING_OP_READV,
> >>>  	IORING_OP_WRITEV,
> >>> +	IORING_OP_READV_PI,
> >>> +	IORING_OP_WRITEV_PI,
> >>>  	IORING_OP_FSYNC,
> >>>  	IORING_OP_READ_FIXED,
> >>>  	IORING_OP_WRITE_FIXED,
> >>
> >> So this one renumbers everything past IORING_OP_WRITEV, breaking the
> >> ABI in a very bad way. I'm guessing that was entirely unintentional?
> >> Any new command must go at the end of the list.
> >>
> >> You're also not updating io_op_defs[] with the two new commands,
> >> which means it won't compile at all. I'm guessing you tested this on
> >> an older version of the kernel which didn't have io_op_defs[]?
> > 
> > And the real question is why we need ops insted of just a flag and
> > using previously reserved fields for the PI pointer.
> 
> Yeah, should probably be a RWF_ flag instead, and a 64-bit SQE field
> for the PI data. The 'last iovec is PI' is kind of icky.

Heh, I was about to send in nearly the same comment. :)

--D

> -- 
> Jens Axboe
> 

Re: [PATCH 3/4] block_dev: support protect information passthrough

[Darrick J. Wong]

On Wed, Feb 26, 2020 at 04:37:18PM +0800, Bob Liu wrote:
> Support protect information passed from use sapce, on direct io
> is considered now.
> 
> Signed-off-by: Bob Liu <bob.liu@oracle.com>
> ---
>  fs/block_dev.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 69bf2fb..10e3299 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -348,6 +348,13 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
>  	loff_t pos = iocb->ki_pos;
>  	blk_qc_t qc = BLK_QC_T_NONE;
>  	int ret = 0;
> +	struct iovec *pi_iov;
> +
> +	if (iocb->ki_flags & IOCB_USE_PI) {
> +		ret = iter_slice_protect_info(iter, nr_pages, &pi_iov);
> +		if (ret)
> +			return -EINVAL;
> +	}
>  
>  	if ((pos | iov_iter_alignment(iter)) &
>  	    (bdev_logical_block_size(bdev) - 1))
> @@ -411,6 +418,16 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
>  				polled = true;
>  			}
>  
> +			/* Add protection information to bio */
> +			if (iocb->ki_flags & IOCB_USE_PI) {
> +				ret = bio_integrity_prep_from_iovec(bio, pi_iov);
> +				if (ret) {
> +					bio->bi_status = BLK_STS_IOERR;
> +					bio_endio(bio);

If you're just going to mash all the error codes into IOERR, then this
could very well become bio_io_error() ?

--D

> +					break;
> +				}
> +			}
> +
>  			qc = submit_bio(bio);
>  
>  			if (polled)
> -- 
> 2.9.5
> 

Re: [PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Christoph Hellwig]

On Wed, Feb 26, 2020 at 08:58:46AM -0700, Jens Axboe wrote:
> Yeah, should probably be a RWF_ flag instead, and a 64-bit SQE field
> for the PI data. The 'last iovec is PI' is kind of icky.

Abusing an iovec (although I though of the first once when looking
into it) looks really horrible, but has two huge advantages:

 - it doesn't require passing another argument all the way down
   the I/O stack
 - it works with all the vectored interfaces that take a flag
   argument, so not just io_uring, but also preadv2/pwritev2 and aio.
   And while I don't care too much about the last I think preadv2
   and pwritev2 are valuable to support.

Re: [PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Bob Liu]

On 2/26/20 10:24 PM, Jens Axboe wrote:
> On 2/26/20 1:37 AM, Bob Liu wrote:
>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>> index a3300e1..98fa3f1 100644
>> --- a/include/uapi/linux/io_uring.h
>> +++ b/include/uapi/linux/io_uring.h
>> @@ -62,6 +62,8 @@ enum {
>>  	IORING_OP_NOP,
>>  	IORING_OP_READV,
>>  	IORING_OP_WRITEV,
>> +	IORING_OP_READV_PI,
>> +	IORING_OP_WRITEV_PI,
>>  	IORING_OP_FSYNC,
>>  	IORING_OP_READ_FIXED,
>>  	IORING_OP_WRITE_FIXED,
> 
> So this one renumbers everything past IORING_OP_WRITEV, breaking the
> ABI in a very bad way. I'm guessing that was entirely unintentional?
> Any new command must go at the end of the list.
> 
> You're also not updating io_op_defs[] with the two new commands,
> which means it won't compile at all. I'm guessing you tested this on
> an older version of the kernel which didn't have io_op_defs[]?
> 

Yep, will rebase to the latest version next time.

Re: [PATCH 1/4] io_uring: add IORING_OP_READ{WRITE}V_PI cmd

[Bob Liu]

On 2/27/20 12:53 AM, Christoph Hellwig wrote:
> On Wed, Feb 26, 2020 at 08:58:46AM -0700, Jens Axboe wrote:
>> Yeah, should probably be a RWF_ flag instead, and a 64-bit SQE field
>> for the PI data. The 'last iovec is PI' is kind of icky.
> 
> Abusing an iovec (although I though of the first once when looking
> into it) looks really horrible, but has two huge advantages:
> 
>  - it doesn't require passing another argument all the way down
>    the I/O stack
>  - it works with all the vectored interfaces that take a flag
>    argument, so not just io_uring, but also preadv2/pwritev2 and aio.
>    And while I don't care too much about the last I think preadv2
>    and pwritev2 are valuable to support.
> 

Indeed, actually the 'last iovec is PI' idea was learned from Darrick's original
patch which support PI passthrough via aio.
https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg27537.html

Re: [PATCH 2/4] bio-integrity: introduce two funcs handle protect information

[Bob Liu]

On 2/27/20 12:03 AM, Darrick J. Wong wrote:
> On Wed, Feb 26, 2020 at 04:37:17PM +0800, Bob Liu wrote:
>> Introduce two funcs handle protect information passthrough from
>> user space.
>>
>> iter_slice_protect_info() will slice the last segment as protect
>> information.
>>
>> bio_integrity_prep_from_iovec() attach the protect information to
>> a bio.
>>
>> Signed-off-by: Bob Liu <bob.liu@oracle.com>
>> ---
>>  block/bio-integrity.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/bio.h   | 14 ++++++++++
>>  2 files changed, 91 insertions(+)
>>
>> diff --git a/block/bio-integrity.c b/block/bio-integrity.c
>> index 575df98..0b22c5d 100644
>> --- a/block/bio-integrity.c
>> +++ b/block/bio-integrity.c
>> @@ -12,6 +12,7 @@
>>  #include <linux/bio.h>
>>  #include <linux/workqueue.h>
>>  #include <linux/slab.h>
>> +#include <linux/uio.h>
>>  #include "blk.h"
>>  
>>  #define BIP_INLINE_VECS	4
>> @@ -305,6 +306,53 @@ bool bio_integrity_prep(struct bio *bio)
>>  }
>>  EXPORT_SYMBOL(bio_integrity_prep);
>>  
>> +int bio_integrity_prep_from_iovec(struct bio *bio, struct iovec *pi_iov)
>> +{
>> +	struct blk_integrity *bi = blk_get_integrity(bio->bi_disk);
>> +	struct bio_integrity_payload *bip;
>> +	struct page *user_pi_page;
>> +	int nr_vec_page = 0;
>> +	int ret = 0, interval = 0;
>> +
>> +	if (!pi_iov || !pi_iov->iov_base)
>> +		return 1;
>> +
>> +	nr_vec_page = (pi_iov->iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
>> +	if (nr_vec_page > 1) {
>> +		printk("Now only support 1 page containing integrity "
>> +			"metadata, while requires %d pages.\n", nr_vec_page);
>> +		return 1;
> 
> I would've thought this would be -EINVAL or something given the -ENOMEM
> below...?
> 
>> +	}
>> +
>> +	interval = bio_integrity_intervals(bi, bio_sectors(bio));
>> +	if ((interval * bi->tuple_size) != pi_iov->iov_len)
>> +		return 1;
>> +
>> +	bip = bio_integrity_alloc(bio, GFP_NOIO, nr_vec_page);
>> +	if (IS_ERR(bip))
>> +		return PTR_ERR(bip);
>> +
>> +	bip->bip_iter.bi_size = pi_iov->iov_len;
>> +	bip->bio_iter = bio->bi_iter;
>> +	bip_set_seed(bip, bio->bi_iter.bi_sector);
>> +
>> +	if (bi->flags & BLK_INTEGRITY_IP_CHECKSUM)
>> +		bip->bip_flags |= BIP_IP_CHECKSUM;
>> +
>> +	ret = get_user_pages_fast((unsigned long)(pi_iov->iov_base), nr_vec_page,
>> +			op_is_write(bio_op(bio)) ?  FOLL_WRITE : 0,
>> +			&user_pi_page);
>> +	if (unlikely(ret < 0))
>> +		return 1;
>> +
>> +	ret = bio_integrity_add_page(bio, user_pi_page, pi_iov->iov_len, 0);
>> +	if (unlikely(ret != pi_iov->iov_len))
>> +		return -ENOMEM;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL(bio_integrity_prep_from_iovec);
>> +
>>  /**
>>   * bio_integrity_verify_fn - Integrity I/O completion worker
>>   * @work:	Work struct stored in bio to be verified
>> @@ -378,6 +426,35 @@ void bio_integrity_advance(struct bio *bio, unsigned int bytes_done)
>>  }
>>  
>>  /**
>> + * iter_slice_protect_info
>> + *
>> + * Description: slice protection information from iter.
>> + * The last iovec contains protection information pass from user space.
> 
> What do the return values here mean?
> 

Will update.

> Also kinda wondering about the slice & dice of the iovec here, but
> <shrug> I guess this is RFC. :)
> 

Hmm, I also very hesitate to put it here or lib/iov_iter.c. 

> --D
> 
>> + */
>> +int iter_slice_protect_info(struct iov_iter *iter, int nr_pages,
>> +		struct iovec **pi_iov)
>> +{
>> +	size_t len = 0;
>> +
>> +	/* TBD: now only support one bio. */
>> +	if (!iter_is_iovec(iter) || nr_pages >= BIO_MAX_PAGES - 1)
>> +		return 1;
>> +
>> +	/* Last iovec contains protection information. */
>> +	iter->nr_segs--;
>> +	*pi_iov = (struct iovec *)(iter->iov + iter->nr_segs);
>> +
>> +	len = (*pi_iov)->iov_len;
>> +	if (len > 0 && len < iter->count) {
>> +		iter->count -= len;
>> +		return 0;
>> +	}
>> +
>> +	return 1;
>> +}
>> +EXPORT_SYMBOL(iter_slice_protect_info);
>> +
>> +/**
>>   * bio_integrity_trim - Trim integrity vector
>>   * @bio:	bio whose integrity vector to update
>>   *
>> diff --git a/include/linux/bio.h b/include/linux/bio.h
>> index 3cdb84c..6172b13 100644
>> --- a/include/linux/bio.h
>> +++ b/include/linux/bio.h
>> @@ -749,6 +749,8 @@ static inline bool bioset_initialized(struct bio_set *bs)
>>  extern struct bio_integrity_payload *bio_integrity_alloc(struct bio *, gfp_t, unsigned int);
>>  extern int bio_integrity_add_page(struct bio *, struct page *, unsigned int, unsigned int);
>>  extern bool bio_integrity_prep(struct bio *);
>> +extern int bio_integrity_prep_from_iovec(struct bio *bio, struct iovec *pi_iov);
>> +extern int iter_slice_protect_info(struct iov_iter *iter, int nr_pages, struct iovec **pi_iov);
>>  extern void bio_integrity_advance(struct bio *, unsigned int);
>>  extern void bio_integrity_trim(struct bio *);
>>  extern int bio_integrity_clone(struct bio *, struct bio *, gfp_t);
>> @@ -778,6 +780,18 @@ static inline bool bio_integrity_prep(struct bio *bio)
>>  	return true;
>>  }
>>  
>> +static inline int bio_integrity_prep_from_iovec(struct bio *bio,
>> +		struct iovec *pi_iov)
>> +{
>> +	return 0;
>> +}
>> +
>> +static inline int iter_slice_protect_info(struct iov_iter *iter, int nr_pages,
>> +		struct iovec **pi_iov)
>> +{
>> +	return 0;
>> +}
>> +
>>  static inline int bio_integrity_clone(struct bio *bio, struct bio *bio_src,
>>  				      gfp_t gfp_mask)
>>  {
>> -- 
>> 2.9.5
>>