Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1859 insertions, 0 deletions

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
new file mode 100644
index 000000000..6e3011330
--- /dev/null
+++ b/lib/iov_iter.c
@@ -0,0 +1,1859 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <crypto/hash.h>
+#include <linux/export.h>
+#include <linux/bvec.h>
+#include <linux/fault-inject-usercopy.h>
+#include <linux/uio.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/splice.h>
+#include <linux/compat.h>
+#include <net/checksum.h>
+#include <linux/scatterlist.h>
+#include <linux/instrumented.h>
+
+#define PIPE_PARANOIA /* for now */
+
+#define iterate_iovec(i, n, __v, __p, skip, STEP) {	\
+	size_t left;					\
+	size_t wanted = n;				\
+	__p = i->iov;					\
+	__v.iov_len = min(n, __p->iov_len - skip);	\
+	if (likely(__v.iov_len)) {			\
+		__v.iov_base = __p->iov_base + skip;	\
+		left = (STEP);				\
+		__v.iov_len -= left;			\
+		skip += __v.iov_len;			\
+		n -= __v.iov_len;			\
+	} else {					\
+		left = 0;				\
+	}						\
+	while (unlikely(!left && n)) {			\
+		__p++;					\
+		__v.iov_len = min(n, __p->iov_len);	\
+		if (unlikely(!__v.iov_len))		\
+			continue;			\
+		__v.iov_base = __p->iov_base;		\
+		left = (STEP);				\
+		__v.iov_len -= left;			\
+		skip = __v.iov_len;			\
+		n -= __v.iov_len;			\
+	}						\
+	n = wanted - n;					\
+}
+
+#define iterate_kvec(i, n, __v, __p, skip, STEP) {	\
+	size_t wanted = n;				\
+	__p = i->kvec;					\
+	__v.iov_len = min(n, __p->iov_len - skip);	\
+	if (likely(__v.iov_len)) {			\
+		__v.iov_base = __p->iov_base + skip;	\
+		(void)(STEP);				\
+		skip += __v.iov_len;			\
+		n -= __v.iov_len;			\
+	}						\
+	while (unlikely(n)) {				\
+		__p++;					\
+		__v.iov_len = min(n, __p->iov_len);	\
+		if (unlikely(!__v.iov_len))		\
+			continue;			\
+		__v.iov_base = __p->iov_base;		\
+		(void)(STEP);				\
+		skip = __v.iov_len;			\
+		n -= __v.iov_len;			\
+	}						\
+	n = wanted;					\
+}
+
+#define iterate_bvec(i, n, __v, __bi, skip, STEP) {	\
+	struct bvec_iter __start;			\
+	__start.bi_size = n;				\
+	__start.bi_bvec_done = skip;			\
+	__start.bi_idx = 0;				\
+	for_each_bvec(__v, i->bvec, __bi, __start) {	\
+		if (!__v.bv_len)			\
+			continue;			\
+		(void)(STEP);				\
+	}						\
+}
+
+#define iterate_all_kinds(i, n, v, I, B, K) {			\
+	if (likely(n)) {					\
+		size_t skip = i->iov_offset;			\
+		if (unlikely(i->type & ITER_BVEC)) {		\
+			struct bio_vec v;			\
+			struct bvec_iter __bi;			\
+			iterate_bvec(i, n, v, __bi, skip, (B))	\
+		} else if (unlikely(i->type & ITER_KVEC)) {	\
+			const struct kvec *kvec;		\
+			struct kvec v;				\
+			iterate_kvec(i, n, v, kvec, skip, (K))	\
+		} else if (unlikely(i->type & ITER_DISCARD)) {	\
+		} else {					\
+			const struct iovec *iov;		\
+			struct iovec v;				\
+			iterate_iovec(i, n, v, iov, skip, (I))	\
+		}						\
+	}							\
+}
+
+#define iterate_and_advance(i, n, v, I, B, K) {			\
+	if (unlikely(i->count < n))				\
+		n = i->count;					\
+	if (i->count) {						\
+		size_t skip = i->iov_offset;			\
+		if (unlikely(i->type & ITER_BVEC)) {		\
+			const struct bio_vec *bvec = i->bvec;	\
+			struct bio_vec v;			\
+			struct bvec_iter __bi;			\
+			iterate_bvec(i, n, v, __bi, skip, (B))	\
+			i->bvec = __bvec_iter_bvec(i->bvec, __bi);	\
+			i->nr_segs -= i->bvec - bvec;		\
+			skip = __bi.bi_bvec_done;		\
+		} else if (unlikely(i->type & ITER_KVEC)) {	\
+			const struct kvec *kvec;		\
+			struct kvec v;				\
+			iterate_kvec(i, n, v, kvec, skip, (K))	\
+			if (skip == kvec->iov_len) {		\
+				kvec++;				\
+				skip = 0;			\
+			}					\
+			i->nr_segs -= kvec - i->kvec;		\
+			i->kvec = kvec;				\
+		} else if (unlikely(i->type & ITER_DISCARD)) {	\
+			skip += n;				\
+		} else {					\
+			const struct iovec *iov;		\
+			struct iovec v;				\
+			iterate_iovec(i, n, v, iov, skip, (I))	\
+			if (skip == iov->iov_len) {		\
+				iov++;				\
+				skip = 0;			\
+			}					\
+			i->nr_segs -= iov - i->iov;		\
+			i->iov = iov;				\
+		}						\
+		i->count -= n;					\
+		i->iov_offset = skip;				\
+	}							\
+}
+
+static int copyout(void __user *to, const void *from, size_t n)
+{
+	if (should_fail_usercopy())
+		return n;
+	if (access_ok(to, n)) {
+		instrument_copy_to_user(to, from, n);
+		n = raw_copy_to_user(to, from, n);
+	}
+	return n;
+}
+
+static int copyin(void *to, const void __user *from, size_t n)
+{
+	if (should_fail_usercopy())
+		return n;
+	if (access_ok(from, n)) {
+		instrument_copy_from_user(to, from, n);
+		n = raw_copy_from_user(to, from, n);
+	}
+	return n;
+}
+
+static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i)
+{
+	size_t skip, copy, left, wanted;
+	const struct iovec *iov;
+	char __user *buf;
+	void *kaddr, *from;
+
+	if (unlikely(bytes > i->count))
+		bytes = i->count;
+
+	if (unlikely(!bytes))
+		return 0;
+
+	might_fault();
+	wanted = bytes;
+	iov = i->iov;
+	skip = i->iov_offset;
+	buf = iov->iov_base + skip;
+	copy = min(bytes, iov->iov_len - skip);
+
+	if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
+		kaddr = kmap_atomic(page);
+		from = kaddr + offset;
+
+		/* first chunk, usually the only one */
+		left = copyout(buf, from, copy);
+		copy -= left;
+		skip += copy;
+		from += copy;
+		bytes -= copy;
+
+		while (unlikely(!left && bytes)) {
+			iov++;
+			buf = iov->iov_base;
+			copy = min(bytes, iov->iov_len);
+			left = copyout(buf, from, copy);
+			copy -= left;
+			skip = copy;
+			from += copy;
+			bytes -= copy;
+		}
+		if (likely(!bytes)) {
+			kunmap_atomic(kaddr);
+			goto done;
+		}
+		offset = from - kaddr;
+		buf += copy;
+		kunmap_atomic(kaddr);
+		copy = min(bytes, iov->iov_len - skip);
+	}
+	/* Too bad - revert to non-atomic kmap */
+
+	kaddr = kmap(page);
+	from = kaddr + offset;
+	left = copyout(buf, from, copy);
+	copy -= left;
+	skip += copy;
+	from += copy;
+	bytes -= copy;
+	while (unlikely(!left && bytes)) {
+		iov++;
+		buf = iov->iov_base;
+		copy = min(bytes, iov->iov_len);
+		left = copyout(buf, from, copy);
+		copy -= left;
+		skip = copy;
+		from += copy;
+		bytes -= copy;
+	}
+	kunmap(page);
+
+done:
+	if (skip == iov->iov_len) {
+		iov++;
+		skip = 0;
+	}
+	i->count -= wanted - bytes;
+	i->nr_segs -= iov - i->iov;
+	i->iov = iov;
+	i->iov_offset = skip;
+	return wanted - bytes;
+}
+
+static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i)
+{
+	size_t skip, copy, left, wanted;
+	const struct iovec *iov;
+	char __user *buf;
+	void *kaddr, *to;
+
+	if (unlikely(bytes > i->count))
+		bytes = i->count;
+
+	if (unlikely(!bytes))
+		return 0;
+
+	might_fault();
+	wanted = bytes;
+	iov = i->iov;
+	skip = i->iov_offset;
+	buf = iov->iov_base + skip;
+	copy = min(bytes, iov->iov_len - skip);
+
+	if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
+		kaddr = kmap_atomic(page);
+		to = kaddr + offset;
+
+		/* first chunk, usually the only one */
+		left = copyin(to, buf, copy);
+		copy -= left;
+		skip += copy;
+		to += copy;
+		bytes -= copy;
+
+		while (unlikely(!left && bytes)) {
+			iov++;
+			buf = iov->iov_base;
+			copy = min(bytes, iov->iov_len);
+			left = copyin(to, buf, copy);
+			copy -= left;
+			skip = copy;
+			to += copy;
+			bytes -= copy;
+		}
+		if (likely(!bytes)) {
+			kunmap_atomic(kaddr);
+			goto done;
+		}
+		offset = to - kaddr;
+		buf += copy;
+		kunmap_atomic(kaddr);
+		copy = min(bytes, iov->iov_len - skip);
+	}
+	/* Too bad - revert to non-atomic kmap */
+
+	kaddr = kmap(page);
+	to = kaddr + offset;
+	left = copyin(to, buf, copy);
+	copy -= left;
+	skip += copy;
+	to += copy;
+	bytes -= copy;
+	while (unlikely(!left && bytes)) {
+		iov++;
+		buf = iov->iov_base;
+		copy = min(bytes, iov->iov_len);
+		left = copyin(to, buf, copy);
+		copy -= left;
+		skip = copy;
+		to += copy;
+		bytes -= copy;
+	}
+	kunmap(page);
+
+done:
+	if (skip == iov->iov_len) {
+		iov++;
+		skip = 0;
+	}
+	i->count -= wanted - bytes;
+	i->nr_segs -= iov - i->iov;
+	i->iov = iov;
+	i->iov_offset = skip;
+	return wanted - bytes;
+}
+
+#ifdef PIPE_PARANOIA
+static bool sanity(const struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_head = pipe->head;
+	unsigned int p_tail = pipe->tail;
+	unsigned int p_mask = pipe->ring_size - 1;
+	unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
+	unsigned int i_head = i->head;
+	unsigned int idx;
+
+	if (i->iov_offset) {
+		struct pipe_buffer *p;
+		if (unlikely(p_occupancy == 0))
+			goto Bad;	// pipe must be non-empty
+		if (unlikely(i_head != p_head - 1))
+			goto Bad;	// must be at the last buffer...
+
+		p = &pipe->bufs[i_head & p_mask];
+		if (unlikely(p->offset + p->len != i->iov_offset))
+			goto Bad;	// ... at the end of segment
+	} else {
+		if (i_head != p_head)
+			goto Bad;	// must be right after the last buffer
+	}
+	return true;
+Bad:
+	printk(KERN_ERR "idx = %d, offset = %zd\n", i_head, i->iov_offset);
+	printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
+			p_head, p_tail, pipe->ring_size);
+	for (idx = 0; idx < pipe->ring_size; idx++)
+		printk(KERN_ERR "[%p %p %d %d]\n",
+			pipe->bufs[idx].ops,
+			pipe->bufs[idx].page,
+			pipe->bufs[idx].offset,
+			pipe->bufs[idx].len);
+	WARN_ON(1);
+	return false;
+}
+#else
+#define sanity(i) true
+#endif
+
+static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	struct pipe_buffer *buf;
+	unsigned int p_tail = pipe->tail;
+	unsigned int p_mask = pipe->ring_size - 1;
+	unsigned int i_head = i->head;
+	size_t off;
+
+	if (unlikely(bytes > i->count))
+		bytes = i->count;
+
+	if (unlikely(!bytes))
+		return 0;
+
+	if (!sanity(i))
+		return 0;
+
+	off = i->iov_offset;
+	buf = &pipe->bufs[i_head & p_mask];
+	if (off) {
+		if (offset == off && buf->page == page) {
+			/* merge with the last one */
+			buf->len += bytes;
+			i->iov_offset += bytes;
+			goto out;
+		}
+		i_head++;
+		buf = &pipe->bufs[i_head & p_mask];
+	}
+	if (pipe_full(i_head, p_tail, pipe->max_usage))
+		return 0;
+
+	buf->ops = &page_cache_pipe_buf_ops;
+	buf->flags = 0;
+	get_page(page);
+	buf->page = page;
+	buf->offset = offset;
+	buf->len = bytes;
+
+	pipe->head = i_head + 1;
+	i->iov_offset = offset + bytes;
+	i->head = i_head;
+out:
+	i->count -= bytes;
+	return bytes;
+}
+
+/*
+ * Fault in one or more iovecs of the given iov_iter, to a maximum length of
+ * bytes.  For each iovec, fault in each page that constitutes the iovec.
+ *
+ * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
+ * because it is an invalid address).
+ */
+int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
+{
+	size_t skip = i->iov_offset;
+	const struct iovec *iov;
+	int err;
+	struct iovec v;
+
+	if (iter_is_iovec(i)) {
+		iterate_iovec(i, bytes, v, iov, skip, ({
+			err = fault_in_pages_readable(v.iov_base, v.iov_len);
+			if (unlikely(err))
+			return err;
+		0;}))
+	}
+	return 0;
+}
+EXPORT_SYMBOL(iov_iter_fault_in_readable);
+
+void iov_iter_init(struct iov_iter *i, unsigned int direction,
+			const struct iovec *iov, unsigned long nr_segs,
+			size_t count)
+{
+	WARN_ON(direction & ~(READ | WRITE));
+	direction &= READ | WRITE;
+
+	/* It will get better.  Eventually... */
+	if (uaccess_kernel()) {
+		i->type = ITER_KVEC | direction;
+		i->kvec = (struct kvec *)iov;
+	} else {
+		i->type = ITER_IOVEC | direction;
+		i->iov = iov;
+	}
+	i->nr_segs = nr_segs;
+	i->iov_offset = 0;
+	i->count = count;
+}
+EXPORT_SYMBOL(iov_iter_init);
+
+static void memzero_page(struct page *page, size_t offset, size_t len)
+{
+	char *addr = kmap_atomic(page);
+	memset(addr + offset, 0, len);
+	kunmap_atomic(addr);
+}
+
+static inline bool allocated(struct pipe_buffer *buf)
+{
+	return buf->ops == &default_pipe_buf_ops;
+}
+
+static inline void data_start(const struct iov_iter *i,
+			      unsigned int *iter_headp, size_t *offp)
+{
+	unsigned int p_mask = i->pipe->ring_size - 1;
+	unsigned int iter_head = i->head;
+	size_t off = i->iov_offset;
+
+	if (off && (!allocated(&i->pipe->bufs[iter_head & p_mask]) ||
+		    off == PAGE_SIZE)) {
+		iter_head++;
+		off = 0;
+	}
+	*iter_headp = iter_head;
+	*offp = off;
+}
+
+static size_t push_pipe(struct iov_iter *i, size_t size,
+			int *iter_headp, size_t *offp)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_tail = pipe->tail;
+	unsigned int p_mask = pipe->ring_size - 1;
+	unsigned int iter_head;
+	size_t off;
+	ssize_t left;
+
+	if (unlikely(size > i->count))
+		size = i->count;
+	if (unlikely(!size))
+		return 0;
+
+	left = size;
+	data_start(i, &iter_head, &off);
+	*iter_headp = iter_head;
+	*offp = off;
+	if (off) {
+		left -= PAGE_SIZE - off;
+		if (left <= 0) {
+			pipe->bufs[iter_head & p_mask].len += size;
+			return size;
+		}
+		pipe->bufs[iter_head & p_mask].len = PAGE_SIZE;
+		iter_head++;
+	}
+	while (!pipe_full(iter_head, p_tail, pipe->max_usage)) {
+		struct pipe_buffer *buf = &pipe->bufs[iter_head & p_mask];
+		struct page *page = alloc_page(GFP_USER);
+		if (!page)
+			break;
+
+		buf->ops = &default_pipe_buf_ops;
+		buf->flags = 0;
+		buf->page = page;
+		buf->offset = 0;
+		buf->len = min_t(ssize_t, left, PAGE_SIZE);
+		left -= buf->len;
+		iter_head++;
+		pipe->head = iter_head;
+
+		if (left == 0)
+			return size;
+	}
+	return size - left;
+}
+
+static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
+				struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_mask = pipe->ring_size - 1;
+	unsigned int i_head;
+	size_t n, off;
+
+	if (!sanity(i))
+		return 0;
+
+	bytes = n = push_pipe(i, bytes, &i_head, &off);
+	if (unlikely(!n))
+		return 0;
+	do {
+		size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
+		memcpy_to_page(pipe->bufs[i_head & p_mask].page, off, addr, chunk);
+		i->head = i_head;
+		i->iov_offset = off + chunk;
+		n -= chunk;
+		addr += chunk;
+		off = 0;
+		i_head++;
+	} while (n);
+	i->count -= bytes;
+	return bytes;
+}
+
+static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
+			      __wsum sum, size_t off)
+{
+	__wsum next = csum_partial_copy_nocheck(from, to, len);
+	return csum_block_add(sum, next, off);
+}
+
+static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
+					 struct csum_state *csstate,
+					 struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_mask = pipe->ring_size - 1;
+	__wsum sum = csstate->csum;
+	size_t off = csstate->off;
+	unsigned int i_head;
+	size_t n, r;
+
+	if (!sanity(i))
+		return 0;
+
+	bytes = n = push_pipe(i, bytes, &i_head, &r);
+	if (unlikely(!n))
+		return 0;
+	do {
+		size_t chunk = min_t(size_t, n, PAGE_SIZE - r);
+		char *p = kmap_atomic(pipe->bufs[i_head & p_mask].page);
+		sum = csum_and_memcpy(p + r, addr, chunk, sum, off);
+		kunmap_atomic(p);
+		i->head = i_head;
+		i->iov_offset = r + chunk;
+		n -= chunk;
+		off += chunk;
+		addr += chunk;
+		r = 0;
+		i_head++;
+	} while (n);
+	i->count -= bytes;
+	csstate->csum = sum;
+	csstate->off = off;
+	return bytes;
+}
+
+size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+	const char *from = addr;
+	if (unlikely(iov_iter_is_pipe(i)))
+		return copy_pipe_to_iter(addr, bytes, i);
+	if (iter_is_iovec(i))
+		might_fault();
+	iterate_and_advance(i, bytes, v,
+		copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
+		memcpy_to_page(v.bv_page, v.bv_offset,
+			       (from += v.bv_len) - v.bv_len, v.bv_len),
+		memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
+	)
+
+	return bytes;
+}
+EXPORT_SYMBOL(_copy_to_iter);
+
+#ifdef CONFIG_ARCH_HAS_COPY_MC
+static int copyout_mc(void __user *to, const void *from, size_t n)
+{
+	if (access_ok(to, n)) {
+		instrument_copy_to_user(to, from, n);
+		n = copy_mc_to_user((__force void *) to, from, n);
+	}
+	return n;
+}
+
+static unsigned long copy_mc_to_page(struct page *page, size_t offset,
+		const char *from, size_t len)
+{
+	unsigned long ret;
+	char *to;
+
+	to = kmap_atomic(page);
+	ret = copy_mc_to_kernel(to + offset, from, len);
+	kunmap_atomic(to);
+
+	return ret;
+}
+
+static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
+				struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_mask = pipe->ring_size - 1;
+	unsigned int i_head;
+	size_t n, off, xfer = 0;
+
+	if (!sanity(i))
+		return 0;
+
+	bytes = n = push_pipe(i, bytes, &i_head, &off);
+	if (unlikely(!n))
+		return 0;
+	do {
+		size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
+		unsigned long rem;
+
+		rem = copy_mc_to_page(pipe->bufs[i_head & p_mask].page,
+					    off, addr, chunk);
+		i->head = i_head;
+		i->iov_offset = off + chunk - rem;
+		xfer += chunk - rem;
+		if (rem)
+			break;
+		n -= chunk;
+		addr += chunk;
+		off = 0;
+		i_head++;
+	} while (n);
+	i->count -= xfer;
+	return xfer;
+}
+
+/**
+ * _copy_mc_to_iter - copy to iter with source memory error exception handling
+ * @addr: source kernel address
+ * @bytes: total transfer length
+ * @iter: destination iterator
+ *
+ * The pmem driver deploys this for the dax operation
+ * (dax_copy_to_iter()) for dax reads (bypass page-cache and the
+ * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
+ * successfully copied.
+ *
+ * The main differences between this and typical _copy_to_iter().
+ *
+ * * Typical tail/residue handling after a fault retries the copy
+ *   byte-by-byte until the fault happens again. Re-triggering machine
+ *   checks is potentially fatal so the implementation uses source
+ *   alignment and poison alignment assumptions to avoid re-triggering
+ *   hardware exceptions.
+ *
+ * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
+ *   Compare to copy_to_iter() where only ITER_IOVEC attempts might return
+ *   a short copy.
+ */
+size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+	const char *from = addr;
+	unsigned long rem, curr_addr, s_addr = (unsigned long) addr;
+
+	if (unlikely(iov_iter_is_pipe(i)))
+		return copy_mc_pipe_to_iter(addr, bytes, i);
+	if (iter_is_iovec(i))
+		might_fault();
+	iterate_and_advance(i, bytes, v,
+		copyout_mc(v.iov_base, (from += v.iov_len) - v.iov_len,
+			   v.iov_len),
+		({
+		rem = copy_mc_to_page(v.bv_page, v.bv_offset,
+				      (from += v.bv_len) - v.bv_len, v.bv_len);
+		if (rem) {
+			curr_addr = (unsigned long) from;
+			bytes = curr_addr - s_addr - rem;
+			return bytes;
+		}
+		}),
+		({
+		rem = copy_mc_to_kernel(v.iov_base, (from += v.iov_len)
+					- v.iov_len, v.iov_len);
+		if (rem) {
+			curr_addr = (unsigned long) from;
+			bytes = curr_addr - s_addr - rem;
+			return bytes;
+		}
+		})
+	)
+
+	return bytes;
+}
+EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
+#endif /* CONFIG_ARCH_HAS_COPY_MC */
+
+size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
+{
+	char *to = addr;
+	if (unlikely(iov_iter_is_pipe(i))) {
+		WARN_ON(1);
+		return 0;
+	}
+	if (iter_is_iovec(i))
+		might_fault();
+	iterate_and_advance(i, bytes, v,
+		copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len),
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+	)
+
+	return bytes;
+}
+EXPORT_SYMBOL(_copy_from_iter);
+
+bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
+{
+	char *to = addr;
+	if (unlikely(iov_iter_is_pipe(i))) {
+		WARN_ON(1);
+		return false;
+	}
+	if (unlikely(i->count < bytes))
+		return false;
+
+	if (iter_is_iovec(i))
+		might_fault();
+	iterate_all_kinds(i, bytes, v, ({
+		if (copyin((to += v.iov_len) - v.iov_len,
+				      v.iov_base, v.iov_len))
+			return false;
+		0;}),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len),
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+	)
+
+	iov_iter_advance(i, bytes);
+	return true;
+}
+EXPORT_SYMBOL(_copy_from_iter_full);
+
+size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
+{
+	char *to = addr;
+	if (unlikely(iov_iter_is_pipe(i))) {
+		WARN_ON(1);
+		return 0;
+	}
+	iterate_and_advance(i, bytes, v,
+		__copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
+					 v.iov_base, v.iov_len),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len),
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+	)
+
+	return bytes;
+}
+EXPORT_SYMBOL(_copy_from_iter_nocache);
+
+#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
+/**
+ * _copy_from_iter_flushcache - write destination through cpu cache
+ * @addr: destination kernel address
+ * @bytes: total transfer length
+ * @iter: source iterator
+ *
+ * The pmem driver arranges for filesystem-dax to use this facility via
+ * dax_copy_from_iter() for ensuring that writes to persistent memory
+ * are flushed through the CPU cache. It is differentiated from
+ * _copy_from_iter_nocache() in that guarantees all data is flushed for
+ * all iterator types. The _copy_from_iter_nocache() only attempts to
+ * bypass the cache for the ITER_IOVEC case, and on some archs may use
+ * instructions that strand dirty-data in the cache.
+ */
+size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
+{
+	char *to = addr;
+	if (unlikely(iov_iter_is_pipe(i))) {
+		WARN_ON(1);
+		return 0;
+	}
+	iterate_and_advance(i, bytes, v,
+		__copy_from_user_flushcache((to += v.iov_len) - v.iov_len,
+					 v.iov_base, v.iov_len),
+		memcpy_page_flushcache((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len),
+		memcpy_flushcache((to += v.iov_len) - v.iov_len, v.iov_base,
+			v.iov_len)
+	)
+
+	return bytes;
+}
+EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
+#endif
+
+bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
+{
+	char *to = addr;
+	if (unlikely(iov_iter_is_pipe(i))) {
+		WARN_ON(1);
+		return false;
+	}
+	if (unlikely(i->count < bytes))
+		return false;
+	iterate_all_kinds(i, bytes, v, ({
+		if (__copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
+					     v.iov_base, v.iov_len))
+			return false;
+		0;}),
+		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len),
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+	)
+
+	iov_iter_advance(i, bytes);
+	return true;
+}
+EXPORT_SYMBOL(_copy_from_iter_full_nocache);
+
+static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
+{
+	struct page *head;
+	size_t v = n + offset;
+
+	/*
+	 * The general case needs to access the page order in order
+	 * to compute the page size.
+	 * However, we mostly deal with order-0 pages and thus can
+	 * avoid a possible cache line miss for requests that fit all
+	 * page orders.
+	 */
+	if (n <= v && v <= PAGE_SIZE)
+		return true;
+
+	head = compound_head(page);
+	v += (page - head) << PAGE_SHIFT;
+
+	if (likely(n <= v && v <= (page_size(head))))
+		return true;
+	WARN_ON(1);
+	return false;
+}
+
+size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i)
+{
+	if (unlikely(!page_copy_sane(page, offset, bytes)))
+		return 0;
+	if (i->type & (ITER_BVEC|ITER_KVEC)) {
+		void *kaddr = kmap_atomic(page);
+		size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
+		kunmap_atomic(kaddr);
+		return wanted;
+	} else if (unlikely(iov_iter_is_discard(i))) {
+		if (unlikely(i->count < bytes))
+			bytes = i->count;
+		i->count -= bytes;
+		return bytes;
+	} else if (likely(!iov_iter_is_pipe(i)))
+		return copy_page_to_iter_iovec(page, offset, bytes, i);
+	else
+		return copy_page_to_iter_pipe(page, offset, bytes, i);
+}
+EXPORT_SYMBOL(copy_page_to_iter);
+
+size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i)
+{
+	if (unlikely(!page_copy_sane(page, offset, bytes)))
+		return 0;
+	if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
+		WARN_ON(1);
+		return 0;
+	}
+	if (i->type & (ITER_BVEC|ITER_KVEC)) {
+		void *kaddr = kmap_atomic(page);
+		size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
+		kunmap_atomic(kaddr);
+		return wanted;
+	} else
+		return copy_page_from_iter_iovec(page, offset, bytes, i);
+}
+EXPORT_SYMBOL(copy_page_from_iter);
+
+static size_t pipe_zero(size_t bytes, struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_mask = pipe->ring_size - 1;
+	unsigned int i_head;
+	size_t n, off;
+
+	if (!sanity(i))
+		return 0;
+
+	bytes = n = push_pipe(i, bytes, &i_head, &off);
+	if (unlikely(!n))
+		return 0;
+
+	do {
+		size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
+		memzero_page(pipe->bufs[i_head & p_mask].page, off, chunk);
+		i->head = i_head;
+		i->iov_offset = off + chunk;
+		n -= chunk;
+		off = 0;
+		i_head++;
+	} while (n);
+	i->count -= bytes;
+	return bytes;
+}
+
+size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
+{
+	if (unlikely(iov_iter_is_pipe(i)))
+		return pipe_zero(bytes, i);
+	iterate_and_advance(i, bytes, v,
+		clear_user(v.iov_base, v.iov_len),
+		memzero_page(v.bv_page, v.bv_offset, v.bv_len),
+		memset(v.iov_base, 0, v.iov_len)
+	)
+
+	return bytes;
+}
+EXPORT_SYMBOL(iov_iter_zero);
+
+size_t iov_iter_copy_from_user_atomic(struct page *page,
+		struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+	char *kaddr = kmap_atomic(page), *p = kaddr + offset;
+	if (unlikely(!page_copy_sane(page, offset, bytes))) {
+		kunmap_atomic(kaddr);
+		return 0;
+	}
+	if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
+		kunmap_atomic(kaddr);
+		WARN_ON(1);
+		return 0;
+	}
+	iterate_all_kinds(i, bytes, v,
+		copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
+		memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
+				 v.bv_offset, v.bv_len),
+		memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
+	)
+	kunmap_atomic(kaddr);
+	return bytes;
+}
+EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
+
+static inline void pipe_truncate(struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_tail = pipe->tail;
+	unsigned int p_head = pipe->head;
+	unsigned int p_mask = pipe->ring_size - 1;
+
+	if (!pipe_empty(p_head, p_tail)) {
+		struct pipe_buffer *buf;
+		unsigned int i_head = i->head;
+		size_t off = i->iov_offset;
+
+		if (off) {
+			buf = &pipe->bufs[i_head & p_mask];
+			buf->len = off - buf->offset;
+			i_head++;
+		}
+		while (p_head != i_head) {
+			p_head--;
+			pipe_buf_release(pipe, &pipe->bufs[p_head & p_mask]);
+		}
+
+		pipe->head = p_head;
+	}
+}
+
+static void pipe_advance(struct iov_iter *i, size_t size)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	if (unlikely(i->count < size))
+		size = i->count;
+	if (size) {
+		struct pipe_buffer *buf;
+		unsigned int p_mask = pipe->ring_size - 1;
+		unsigned int i_head = i->head;
+		size_t off = i->iov_offset, left = size;
+
+		if (off) /* make it relative to the beginning of buffer */
+			left += off - pipe->bufs[i_head & p_mask].offset;
+		while (1) {
+			buf = &pipe->bufs[i_head & p_mask];
+			if (left <= buf->len)
+				break;
+			left -= buf->len;
+			i_head++;
+		}
+		i->head = i_head;
+		i->iov_offset = buf->offset + left;
+	}
+	i->count -= size;
+	/* ... and discard everything past that point */
+	pipe_truncate(i);
+}
+
+void iov_iter_advance(struct iov_iter *i, size_t size)
+{
+	if (unlikely(iov_iter_is_pipe(i))) {
+		pipe_advance(i, size);
+		return;
+	}
+	if (unlikely(iov_iter_is_discard(i))) {
+		i->count -= size;
+		return;
+	}
+	iterate_and_advance(i, size, v, 0, 0, 0)
+}
+EXPORT_SYMBOL(iov_iter_advance);
+
+void iov_iter_revert(struct iov_iter *i, size_t unroll)
+{
+	if (!unroll)
+		return;
+	if (WARN_ON(unroll > MAX_RW_COUNT))
+		return;
+	i->count += unroll;
+	if (unlikely(iov_iter_is_pipe(i))) {
+		struct pipe_inode_info *pipe = i->pipe;
+		unsigned int p_mask = pipe->ring_size - 1;
+		unsigned int i_head = i->head;
+		size_t off = i->iov_offset;
+		while (1) {
+			struct pipe_buffer *b = &pipe->bufs[i_head & p_mask];
+			size_t n = off - b->offset;
+			if (unroll < n) {
+				off -= unroll;
+				break;
+			}
+			unroll -= n;
+			if (!unroll && i_head == i->start_head) {
+				off = 0;
+				break;
+			}
+			i_head--;
+			b = &pipe->bufs[i_head & p_mask];
+			off = b->offset + b->len;
+		}
+		i->iov_offset = off;
+		i->head = i_head;
+		pipe_truncate(i);
+		return;
+	}
+	if (unlikely(iov_iter_is_discard(i)))
+		return;
+	if (unroll <= i->iov_offset) {
+		i->iov_offset -= unroll;
+		return;
+	}
+	unroll -= i->iov_offset;
+	if (iov_iter_is_bvec(i)) {
+		const struct bio_vec *bvec = i->bvec;
+		while (1) {
+			size_t n = (--bvec)->bv_len;
+			i->nr_segs++;
+			if (unroll <= n) {
+				i->bvec = bvec;
+				i->iov_offset = n - unroll;
+				return;
+			}
+			unroll -= n;
+		}
+	} else { /* same logics for iovec and kvec */
+		const struct iovec *iov = i->iov;
+		while (1) {
+			size_t n = (--iov)->iov_len;
+			i->nr_segs++;
+			if (unroll <= n) {
+				i->iov = iov;
+				i->iov_offset = n - unroll;
+				return;
+			}
+			unroll -= n;
+		}
+	}
+}
+EXPORT_SYMBOL(iov_iter_revert);
+
+/*
+ * Return the count of just the current iov_iter segment.
+ */
+size_t iov_iter_single_seg_count(const struct iov_iter *i)
+{
+	if (unlikely(iov_iter_is_pipe(i)))
+		return i->count;	// it is a silly place, anyway
+	if (i->nr_segs == 1)
+		return i->count;
+	if (unlikely(iov_iter_is_discard(i)))
+		return i->count;
+	else if (iov_iter_is_bvec(i))
+		return min(i->count, i->bvec->bv_len - i->iov_offset);
+	else
+		return min(i->count, i->iov->iov_len - i->iov_offset);
+}
+EXPORT_SYMBOL(iov_iter_single_seg_count);
+
+void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
+			const struct kvec *kvec, unsigned long nr_segs,
+			size_t count)
+{
+	WARN_ON(direction & ~(READ | WRITE));
+	i->type = ITER_KVEC | (direction & (READ | WRITE));
+	i->kvec = kvec;
+	i->nr_segs = nr_segs;
+	i->iov_offset = 0;
+	i->count = count;
+}
+EXPORT_SYMBOL(iov_iter_kvec);
+
+void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
+			const struct bio_vec *bvec, unsigned long nr_segs,
+			size_t count)
+{
+	WARN_ON(direction & ~(READ | WRITE));
+	i->type = ITER_BVEC | (direction & (READ | WRITE));
+	i->bvec = bvec;
+	i->nr_segs = nr_segs;
+	i->iov_offset = 0;
+	i->count = count;
+}
+EXPORT_SYMBOL(iov_iter_bvec);
+
+void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
+			struct pipe_inode_info *pipe,
+			size_t count)
+{
+	BUG_ON(direction != READ);
+	WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
+	i->type = ITER_PIPE | READ;
+	i->pipe = pipe;
+	i->head = pipe->head;
+	i->iov_offset = 0;
+	i->count = count;
+	i->start_head = i->head;
+}
+EXPORT_SYMBOL(iov_iter_pipe);
+
+/**
+ * iov_iter_discard - Initialise an I/O iterator that discards data
+ * @i: The iterator to initialise.
+ * @direction: The direction of the transfer.
+ * @count: The size of the I/O buffer in bytes.
+ *
+ * Set up an I/O iterator that just discards everything that's written to it.
+ * It's only available as a READ iterator.
+ */
+void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
+{
+	BUG_ON(direction != READ);
+	i->type = ITER_DISCARD | READ;
+	i->count = count;
+	i->iov_offset = 0;
+}
+EXPORT_SYMBOL(iov_iter_discard);
+
+unsigned long iov_iter_alignment(const struct iov_iter *i)
+{
+	unsigned long res = 0;
+	size_t size = i->count;
+
+	if (unlikely(iov_iter_is_pipe(i))) {
+		unsigned int p_mask = i->pipe->ring_size - 1;
+
+		if (size && i->iov_offset && allocated(&i->pipe->bufs[i->head & p_mask]))
+			return size | i->iov_offset;
+		return size;
+	}
+	iterate_all_kinds(i, size, v,
+		(res |= (unsigned long)v.iov_base | v.iov_len, 0),
+		res |= v.bv_offset | v.bv_len,
+		res |= (unsigned long)v.iov_base | v.iov_len
+	)
+	return res;
+}
+EXPORT_SYMBOL(iov_iter_alignment);
+
+unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
+{
+	unsigned long res = 0;
+	size_t size = i->count;
+
+	if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
+		WARN_ON(1);
+		return ~0U;
+	}
+
+	iterate_all_kinds(i, size, v,
+		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
+			(size != v.iov_len ? size : 0), 0),
+		(res |= (!res ? 0 : (unsigned long)v.bv_offset) |
+			(size != v.bv_len ? size : 0)),
+		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
+			(size != v.iov_len ? size : 0))
+		);
+	return res;
+}
+EXPORT_SYMBOL(iov_iter_gap_alignment);
+
+static inline ssize_t __pipe_get_pages(struct iov_iter *i,
+				size_t maxsize,
+				struct page **pages,
+				int iter_head,
+				size_t *start)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	unsigned int p_mask = pipe->ring_size - 1;
+	ssize_t n = push_pipe(i, maxsize, &iter_head, start);
+	if (!n)
+		return -EFAULT;
+
+	maxsize = n;
+	n += *start;
+	while (n > 0) {
+		get_page(*pages++ = pipe->bufs[iter_head & p_mask].page);
+		iter_head++;
+		n -= PAGE_SIZE;
+	}
+
+	return maxsize;
+}
+
+static ssize_t pipe_get_pages(struct iov_iter *i,
+		   struct page **pages, size_t maxsize, unsigned maxpages,
+		   size_t *start)
+{
+	unsigned int iter_head, npages;
+	size_t capacity;
+
+	if (!maxsize)
+		return 0;
+
+	if (!sanity(i))
+		return -EFAULT;
+
+	data_start(i, &iter_head, start);
+	/* Amount of free space: some of this one + all after this one */
+	npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
+	capacity = min(npages, maxpages) * PAGE_SIZE - *start;
+
+	return __pipe_get_pages(i, min(maxsize, capacity), pages, iter_head, start);
+}
+
+ssize_t iov_iter_get_pages(struct iov_iter *i,
+		   struct page **pages, size_t maxsize, unsigned maxpages,
+		   size_t *start)
+{
+	if (maxsize > i->count)
+		maxsize = i->count;
+
+	if (unlikely(iov_iter_is_pipe(i)))
+		return pipe_get_pages(i, pages, maxsize, maxpages, start);
+	if (unlikely(iov_iter_is_discard(i)))
+		return -EFAULT;
+
+	iterate_all_kinds(i, maxsize, v, ({
+		unsigned long addr = (unsigned long)v.iov_base;
+		size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
+		int n;
+		int res;
+
+		if (len > maxpages * PAGE_SIZE)
+			len = maxpages * PAGE_SIZE;
+		addr &= ~(PAGE_SIZE - 1);
+		n = DIV_ROUND_UP(len, PAGE_SIZE);
+		res = get_user_pages_fast(addr, n,
+				iov_iter_rw(i) != WRITE ?  FOLL_WRITE : 0,
+				pages);
+		if (unlikely(res <= 0))
+			return res;
+		return (res == n ? len : res * PAGE_SIZE) - *start;
+	0;}),({
+		/* can't be more than PAGE_SIZE */
+		*start = v.bv_offset;
+		get_page(*pages = v.bv_page);
+		return v.bv_len;
+	}),({
+		return -EFAULT;
+	})
+	)
+	return 0;
+}
+EXPORT_SYMBOL(iov_iter_get_pages);
+
+static struct page **get_pages_array(size_t n)
+{
+	return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
+}
+
+static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
+		   struct page ***pages, size_t maxsize,
+		   size_t *start)
+{
+	struct page **p;
+	unsigned int iter_head, npages;
+	ssize_t n;
+
+	if (!maxsize)
+		return 0;
+
+	if (!sanity(i))
+		return -EFAULT;
+
+	data_start(i, &iter_head, start);
+	/* Amount of free space: some of this one + all after this one */
+	npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
+	n = npages * PAGE_SIZE - *start;
+	if (maxsize > n)
+		maxsize = n;
+	else
+		npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
+	p = get_pages_array(npages);
+	if (!p)
+		return -ENOMEM;
+	n = __pipe_get_pages(i, maxsize, p, iter_head, start);
+	if (n > 0)
+		*pages = p;
+	else
+		kvfree(p);
+	return n;
+}
+
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
+		   struct page ***pages, size_t maxsize,
+		   size_t *start)
+{
+	struct page **p;
+
+	if (maxsize > i->count)
+		maxsize = i->count;
+
+	if (unlikely(iov_iter_is_pipe(i)))
+		return pipe_get_pages_alloc(i, pages, maxsize, start);
+	if (unlikely(iov_iter_is_discard(i)))
+		return -EFAULT;
+
+	iterate_all_kinds(i, maxsize, v, ({
+		unsigned long addr = (unsigned long)v.iov_base;
+		size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
+		int n;
+		int res;
+
+		addr &= ~(PAGE_SIZE - 1);
+		n = DIV_ROUND_UP(len, PAGE_SIZE);
+		p = get_pages_array(n);
+		if (!p)
+			return -ENOMEM;
+		res = get_user_pages_fast(addr, n,
+				iov_iter_rw(i) != WRITE ?  FOLL_WRITE : 0, p);
+		if (unlikely(res <= 0)) {
+			kvfree(p);
+			*pages = NULL;
+			return res;
+		}
+		*pages = p;
+		return (res == n ? len : res * PAGE_SIZE) - *start;
+	0;}),({
+		/* can't be more than PAGE_SIZE */
+		*start = v.bv_offset;
+		*pages = p = get_pages_array(1);
+		if (!p)
+			return -ENOMEM;
+		get_page(*p = v.bv_page);
+		return v.bv_len;
+	}),({
+		return -EFAULT;
+	})
+	)
+	return 0;
+}
+EXPORT_SYMBOL(iov_iter_get_pages_alloc);
+
+size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
+			       struct iov_iter *i)
+{
+	char *to = addr;
+	__wsum sum, next;
+	size_t off = 0;
+	sum = *csum;
+	if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
+		WARN_ON(1);
+		return 0;
+	}
+	iterate_and_advance(i, bytes, v, ({
+		next = csum_and_copy_from_user(v.iov_base,
+					       (to += v.iov_len) - v.iov_len,
+					       v.iov_len);
+		if (next) {
+			sum = csum_block_add(sum, next, off);
+			off += v.iov_len;
+		}
+		next ? 0 : v.iov_len;
+	}), ({
+		char *p = kmap_atomic(v.bv_page);
+		sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
+				      p + v.bv_offset, v.bv_len,
+				      sum, off);
+		kunmap_atomic(p);
+		off += v.bv_len;
+	}),({
+		sum = csum_and_memcpy((to += v.iov_len) - v.iov_len,
+				      v.iov_base, v.iov_len,
+				      sum, off);
+		off += v.iov_len;
+	})
+	)
+	*csum = sum;
+	return bytes;
+}
+EXPORT_SYMBOL(csum_and_copy_from_iter);
+
+bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
+			       struct iov_iter *i)
+{
+	char *to = addr;
+	__wsum sum, next;
+	size_t off = 0;
+	sum = *csum;
+	if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
+		WARN_ON(1);
+		return false;
+	}
+	if (unlikely(i->count < bytes))
+		return false;
+	iterate_all_kinds(i, bytes, v, ({
+		next = csum_and_copy_from_user(v.iov_base,
+					       (to += v.iov_len) - v.iov_len,
+					       v.iov_len);
+		if (!next)
+			return false;
+		sum = csum_block_add(sum, next, off);
+		off += v.iov_len;
+		0;
+	}), ({
+		char *p = kmap_atomic(v.bv_page);
+		sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
+				      p + v.bv_offset, v.bv_len,
+				      sum, off);
+		kunmap_atomic(p);
+		off += v.bv_len;
+	}),({
+		sum = csum_and_memcpy((to += v.iov_len) - v.iov_len,
+				      v.iov_base, v.iov_len,
+				      sum, off);
+		off += v.iov_len;
+	})
+	)
+	*csum = sum;
+	iov_iter_advance(i, bytes);
+	return true;
+}
+EXPORT_SYMBOL(csum_and_copy_from_iter_full);
+
+size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
+			     struct iov_iter *i)
+{
+	struct csum_state *csstate = _csstate;
+	const char *from = addr;
+	__wsum sum, next;
+	size_t off;
+
+	if (unlikely(iov_iter_is_pipe(i)))
+		return csum_and_copy_to_pipe_iter(addr, bytes, _csstate, i);
+
+	sum = csstate->csum;
+	off = csstate->off;
+	if (unlikely(iov_iter_is_discard(i))) {
+		WARN_ON(1);	/* for now */
+		return 0;
+	}
+	iterate_and_advance(i, bytes, v, ({
+		next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
+					     v.iov_base,
+					     v.iov_len);
+		if (next) {
+			sum = csum_block_add(sum, next, off);
+			off += v.iov_len;
+		}
+		next ? 0 : v.iov_len;
+	}), ({
+		char *p = kmap_atomic(v.bv_page);
+		sum = csum_and_memcpy(p + v.bv_offset,
+				      (from += v.bv_len) - v.bv_len,
+				      v.bv_len, sum, off);
+		kunmap_atomic(p);
+		off += v.bv_len;
+	}),({
+		sum = csum_and_memcpy(v.iov_base,
+				     (from += v.iov_len) - v.iov_len,
+				     v.iov_len, sum, off);
+		off += v.iov_len;
+	})
+	)
+	csstate->csum = sum;
+	csstate->off = off;
+	return bytes;
+}
+EXPORT_SYMBOL(csum_and_copy_to_iter);
+
+size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
+		struct iov_iter *i)
+{
+#ifdef CONFIG_CRYPTO_HASH
+	struct ahash_request *hash = hashp;
+	struct scatterlist sg;
+	size_t copied;
+
+	copied = copy_to_iter(addr, bytes, i);
+	sg_init_one(&sg, addr, copied);
+	ahash_request_set_crypt(hash, &sg, NULL, copied);
+	crypto_ahash_update(hash);
+	return copied;
+#else
+	return 0;
+#endif
+}
+EXPORT_SYMBOL(hash_and_copy_to_iter);
+
+int iov_iter_npages(const struct iov_iter *i, int maxpages)
+{
+	size_t size = i->count;
+	int npages = 0;
+
+	if (!size)
+		return 0;
+	if (unlikely(iov_iter_is_discard(i)))
+		return 0;
+
+	if (unlikely(iov_iter_is_pipe(i))) {
+		struct pipe_inode_info *pipe = i->pipe;
+		unsigned int iter_head;
+		size_t off;
+
+		if (!sanity(i))
+			return 0;
+
+		data_start(i, &iter_head, &off);
+		/* some of this one + all after this one */
+		npages = pipe_space_for_user(iter_head, pipe->tail, pipe);
+		if (npages >= maxpages)
+			return maxpages;
+	} else iterate_all_kinds(i, size, v, ({
+		unsigned long p = (unsigned long)v.iov_base;
+		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
+			- p / PAGE_SIZE;
+		if (npages >= maxpages)
+			return maxpages;
+	0;}),({
+		npages++;
+		if (npages >= maxpages)
+			return maxpages;
+	}),({
+		unsigned long p = (unsigned long)v.iov_base;
+		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
+			- p / PAGE_SIZE;
+		if (npages >= maxpages)
+			return maxpages;
+	})
+	)
+	return npages;
+}
+EXPORT_SYMBOL(iov_iter_npages);
+
+const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
+{
+	*new = *old;
+	if (unlikely(iov_iter_is_pipe(new))) {
+		WARN_ON(1);
+		return NULL;
+	}
+	if (unlikely(iov_iter_is_discard(new)))
+		return NULL;
+	if (iov_iter_is_bvec(new))
+		return new->bvec = kmemdup(new->bvec,
+				    new->nr_segs * sizeof(struct bio_vec),
+				    flags);
+	else
+		/* iovec and kvec have identical layout */
+		return new->iov = kmemdup(new->iov,
+				   new->nr_segs * sizeof(struct iovec),
+				   flags);
+}
+EXPORT_SYMBOL(dup_iter);
+
+static int copy_compat_iovec_from_user(struct iovec *iov,
+		const struct iovec __user *uvec, unsigned long nr_segs)
+{
+	const struct compat_iovec __user *uiov =
+		(const struct compat_iovec __user *)uvec;
+	int ret = -EFAULT, i;
+
+	if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
+		return -EFAULT;
+
+	for (i = 0; i < nr_segs; i++) {
+		compat_uptr_t buf;
+		compat_ssize_t len;
+
+		unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
+		unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
+
+		/* check for compat_size_t not fitting in compat_ssize_t .. */
+		if (len < 0) {
+			ret = -EINVAL;
+			goto uaccess_end;
+		}
+		iov[i].iov_base = compat_ptr(buf);
+		iov[i].iov_len = len;
+	}
+
+	ret = 0;
+uaccess_end:
+	user_access_end();
+	return ret;
+}
+
+static int copy_iovec_from_user(struct iovec *iov,
+		const struct iovec __user *uvec, unsigned long nr_segs)
+{
+	unsigned long seg;
+
+	if (copy_from_user(iov, uvec, nr_segs * sizeof(*uvec)))
+		return -EFAULT;
+	for (seg = 0; seg < nr_segs; seg++) {
+		if ((ssize_t)iov[seg].iov_len < 0)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+struct iovec *iovec_from_user(const struct iovec __user *uvec,
+		unsigned long nr_segs, unsigned long fast_segs,
+		struct iovec *fast_iov, bool compat)
+{
+	struct iovec *iov = fast_iov;
+	int ret;
+
+	/*
+	 * SuS says "The readv() function *may* fail if the iovcnt argument was
+	 * less than or equal to 0, or greater than {IOV_MAX}.  Linux has
+	 * traditionally returned zero for zero segments, so...
+	 */
+	if (nr_segs == 0)
+		return iov;
+	if (nr_segs > UIO_MAXIOV)
+		return ERR_PTR(-EINVAL);
+	if (nr_segs > fast_segs) {
+		iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
+		if (!iov)
+			return ERR_PTR(-ENOMEM);
+	}
+
+	if (compat)
+		ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
+	else
+		ret = copy_iovec_from_user(iov, uvec, nr_segs);
+	if (ret) {
+		if (iov != fast_iov)
+			kfree(iov);
+		return ERR_PTR(ret);
+	}
+
+	return iov;
+}
+
+ssize_t __import_iovec(int type, const struct iovec __user *uvec,
+		 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
+		 struct iov_iter *i, bool compat)
+{
+	ssize_t total_len = 0;
+	unsigned long seg;
+	struct iovec *iov;
+
+	iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
+	if (IS_ERR(iov)) {
+		*iovp = NULL;
+		return PTR_ERR(iov);
+	}
+
+	/*
+	 * According to the Single Unix Specification we should return EINVAL if
+	 * an element length is < 0 when cast to ssize_t or if the total length
+	 * would overflow the ssize_t return value of the system call.
+	 *
+	 * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
+	 * overflow case.
+	 */
+	for (seg = 0; seg < nr_segs; seg++) {
+		ssize_t len = (ssize_t)iov[seg].iov_len;
+
+		if (!access_ok(iov[seg].iov_base, len)) {
+			if (iov != *iovp)
+				kfree(iov);
+			*iovp = NULL;
+			return -EFAULT;
+		}
+
+		if (len > MAX_RW_COUNT - total_len) {
+			len = MAX_RW_COUNT - total_len;
+			iov[seg].iov_len = len;
+		}
+		total_len += len;
+	}
+
+	iov_iter_init(i, type, iov, nr_segs, total_len);
+	if (iov == *iovp)
+		*iovp = NULL;
+	else
+		*iovp = iov;
+	return total_len;
+}
+
+/**
+ * import_iovec() - Copy an array of &struct iovec from userspace
+ *     into the kernel, check that it is valid, and initialize a new
+ *     &struct iov_iter iterator to access it.
+ *
+ * @type: One of %READ or %WRITE.
+ * @uvec: Pointer to the userspace array.
+ * @nr_segs: Number of elements in userspace array.
+ * @fast_segs: Number of elements in @iov.
+ * @iovp: (input and output parameter) Pointer to pointer to (usually small
+ *     on-stack) kernel array.
+ * @i: Pointer to iterator that will be initialized on success.
+ *
+ * If the array pointed to by *@iov is large enough to hold all @nr_segs,
+ * then this function places %NULL in *@iov on return. Otherwise, a new
+ * array will be allocated and the result placed in *@iov. This means that
+ * the caller may call kfree() on *@iov regardless of whether the small
+ * on-stack array was used or not (and regardless of whether this function
+ * returns an error or not).
+ *
+ * Return: Negative error code on error, bytes imported on success
+ */
+ssize_t import_iovec(int type, const struct iovec __user *uvec,
+		 unsigned nr_segs, unsigned fast_segs,
+		 struct iovec **iovp, struct iov_iter *i)
+{
+	return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
+			      in_compat_syscall());
+}
+EXPORT_SYMBOL(import_iovec);
+
+int import_single_range(int rw, void __user *buf, size_t len,
+		 struct iovec *iov, struct iov_iter *i)
+{
+	if (len > MAX_RW_COUNT)
+		len = MAX_RW_COUNT;
+	if (unlikely(!access_ok(buf, len)))
+		return -EFAULT;
+
+	iov->iov_base = buf;
+	iov->iov_len = len;
+	iov_iter_init(i, rw, iov, 1, len);
+	return 0;
+}
+EXPORT_SYMBOL(import_single_range);
+
+/**
+ * iov_iter_restore() - Restore a &struct iov_iter to the same state as when
+ *     iov_iter_save_state() was called.
+ *
+ * @i: &struct iov_iter to restore
+ * @state: state to restore from
+ *
+ * Used after iov_iter_save_state() to bring restore @i, if operations may
+ * have advanced it.
+ *
+ * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
+ */
+void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
+{
+	if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) &&
+			 !iov_iter_is_kvec(i))
+		return;
+	i->iov_offset = state->iov_offset;
+	i->count = state->count;
+	/*
+	 * For the *vec iters, nr_segs + iov is constant - if we increment
+	 * the vec, then we also decrement the nr_segs count. Hence we don't
+	 * need to track both of these, just one is enough and we can deduct
+	 * the other from that. ITER_KVEC and ITER_IOVEC are the same struct
+	 * size, so we can just increment the iov pointer as they are unionzed.
+	 * ITER_BVEC _may_ be the same size on some archs, but on others it is
+	 * not. Be safe and handle it separately.
+	 */
+	BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
+	if (iov_iter_is_bvec(i))
+		i->bvec -= state->nr_segs - i->nr_segs;
+	else
+		i->iov -= state->nr_segs - i->nr_segs;
+	i->nr_segs = state->nr_segs;
+}