// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/bvec.h>
#include <linux/uio.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/splice.h>
#include <net/checksum.h>
#include <linux/scatterlist.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 (access_ok(to, n)) {
                kasan_check_read(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 (access_ok(from, n)) {
                kasan_check_write(to, 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;
        int idx = i->idx;
        int next = pipe->curbuf + pipe->nrbufs;
        if (i->iov_offset) {
                struct pipe_buffer *p;
                if (unlikely(!pipe->nrbufs))
                        goto Bad;       // pipe must be non-empty
                if (unlikely(idx != ((next - 1) & (pipe->buffers - 1))))
                        goto Bad;       // must be at the last buffer...

                p = &pipe->bufs[idx];
                if (unlikely(p->offset + p->len != i->iov_offset))
                        goto Bad;       // ... at the end of segment
        } else {
                if (idx != (next & (pipe->buffers - 1)))
                        goto Bad;       // must be right after the last buffer
        }
        return true;
Bad:
        printk(KERN_ERR "idx = %d, offset = %zd\n", i->idx, i->iov_offset);
        printk(KERN_ERR "curbuf = %d, nrbufs = %d, buffers = %d\n",
                        pipe->curbuf, pipe->nrbufs, pipe->buffers);
        for (idx = 0; idx < pipe->buffers; 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 inline int next_idx(int idx, struct pipe_inode_info *pipe)
{
        return (idx + 1) & (pipe->buffers - 1);
}

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;
        size_t off;
        int idx;

        if (unlikely(bytes > i->count))
                bytes = i->count;

        if (unlikely(!bytes))
                return 0;

        if (!sanity(i))
                return 0;

        off = i->iov_offset;
        idx = i->idx;
        buf = &pipe->bufs[idx];
        if (off) {
                if (offset == off && buf->page == page) {
                        /* merge with the last one */
                        buf->len += bytes;
                        i->iov_offset += bytes;
                        goto out;
                }
                idx = next_idx(idx, pipe);
                buf = &pipe->bufs[idx];
        }
        if (idx == pipe->curbuf && pipe->nrbufs)
                return 0;
        pipe->nrbufs++;
        buf->ops = &page_cache_pipe_buf_ops;
        get_page(buf->page = page);
        buf->offset = offset;
        buf->len = bytes;
        i->iov_offset = offset + bytes;
        i->idx = idx;
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 (!(i->type & (ITER_BVEC|ITER_KVEC))) {
                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 memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
{
        char *from = kmap_atomic(page);
        memcpy(to, from + offset, len);
        kunmap_atomic(from);
}

static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
{
        char *to = kmap_atomic(page);
        memcpy(to + offset, from, len);
        kunmap_atomic(to);
}

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, int *idxp, size_t *offp)
{
        size_t off = i->iov_offset;
        int idx = i->idx;
        if (off && (!allocated(&i->pipe->bufs[idx]) || off == PAGE_SIZE)) {
                idx = next_idx(idx, i->pipe);
                off = 0;
        }
        *idxp = idx;
        *offp = off;
}

static size_t push_pipe(struct iov_iter *i, size_t size,
                        int *idxp, size_t *offp)
{
        struct pipe_inode_info *pipe = i->pipe;
        size_t off;
        int idx;
        ssize_t left;

        if (unlikely(size > i->count))
                size = i->count;
        if (unlikely(!size))
                return 0;

        left = size;
        data_start(i, &idx, &off);
        *idxp = idx;
        *offp = off;
        if (off) {
                left -= PAGE_SIZE - off;
                if (left <= 0) {
                        pipe->bufs[idx].len += size;
                        return size;
                }
                pipe->bufs[idx].len = PAGE_SIZE;
                idx = next_idx(idx, pipe);
        }
        while (idx != pipe->curbuf || !pipe->nrbufs) {
                struct page *page = alloc_page(GFP_USER);
                if (!page)
                        break;
                pipe->nrbufs++;
                pipe->bufs[idx].ops = &default_pipe_buf_ops;
                pipe->bufs[idx].page = page;
                pipe->bufs[idx].offset = 0;
                if (left <= PAGE_SIZE) {
                        pipe->bufs[idx].len = left;
                        return size;
                }
                pipe->bufs[idx].len = PAGE_SIZE;
                left -= PAGE_SIZE;
                idx = next_idx(idx, pipe);
        }
        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;
        size_t n, off;
        int idx;

        if (!sanity(i))
                return 0;

        bytes = n = push_pipe(i, bytes, &idx, &off);
        if (unlikely(!n))
                return 0;
        for ( ; n; idx = next_idx(idx, pipe), off = 0) {
                size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
                memcpy_to_page(pipe->bufs[idx].page, off, addr, chunk);
                i->idx = idx;
                i->iov_offset = off + chunk;
                n -= chunk;
                addr += chunk;
        }
        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, 0);
        return csum_block_add(sum, next, off);
}

static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
                                __wsum *csum, struct iov_iter *i)
{
        struct pipe_inode_info *pipe = i->pipe;
        size_t n, r;
        size_t off = 0;
        __wsum sum = *csum;
        int idx;

        if (!sanity(i))
                return 0;

        bytes = n = push_pipe(i, bytes, &idx, &r);
        if (unlikely(!n))
                return 0;
        for ( ; n; idx = next_idx(idx, pipe), r = 0) {
                size_t chunk = min_t(size_t, n, PAGE_SIZE - r);
                char *p = kmap_atomic(pipe->bufs[idx].page);
                sum = csum_and_memcpy(p + r, addr, chunk, sum, off);
                kunmap_atomic(p);
                i->idx = idx;
                i->iov_offset = r + chunk;
                n -= chunk;
                off += chunk;
                addr += chunk;
        }
        i->count -= bytes;
        *csum = sum;
        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_UACCESS_MCSAFE
static int copyout_mcsafe(void __user *to, const void *from, size_t n)
{
        if (access_ok(to, n)) {
                kasan_check_read(from, n);
                n = copy_to_user_mcsafe((__force void *) to, from, n);
        }
        return n;
}

static unsigned long memcpy_mcsafe_to_page(struct page *page, size_t offset,
                const char *from, size_t len)
{
        unsigned long ret;
        char *to;

        to = kmap_atomic(page);
        ret = memcpy_mcsafe(to + offset, from, len);
        kunmap_atomic(to);

        return ret;
}

static size_t copy_pipe_to_iter_mcsafe(const void *addr, size_t bytes,
                                struct iov_iter *i)
{
        struct pipe_inode_info *pipe = i->pipe;
        size_t n, off, xfer = 0;
        int idx;

        if (!sanity(i))
                return 0;

        bytes = n = push_pipe(i, bytes, &idx, &off);
        if (unlikely(!n))
                return 0;
        for ( ; n; idx = next_idx(idx, pipe), off = 0) {
                size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
                unsigned long rem;

                rem = memcpy_mcsafe_to_page(pipe->bufs[idx].page, off, addr,
                                chunk);
                i->idx = idx;
                i->iov_offset = off + chunk - rem;
                xfer += chunk - rem;
                if (rem)
                        break;
                n -= chunk;
                addr += chunk;
        }
        i->count -= xfer;
        return xfer;
}

/**
 * _copy_to_iter_mcsafe - copy to user with source-read error exception handling
 * @addr: source kernel address
 * @bytes: total transfer length
 * @iter: destination iterator
 *
 * The pmem driver arranges for filesystem-dax to use this facility via
 * dax_copy_to_iter() for protecting read/write to persistent memory.
 * Unless / until an architecture can guarantee identical performance
 * between _copy_to_iter_mcsafe() and _copy_to_iter() it would be a
 * performance regression to switch more users to the mcsafe version.
 *
 * Otherwise, 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.
 *
 * See MCSAFE_TEST for self-test.
 */
size_t _copy_to_iter_mcsafe(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_pipe_to_iter_mcsafe(addr, bytes, i);
        if (iter_is_iovec(i))
                might_fault();
        iterate_and_advance(i, bytes, v,
                copyout_mcsafe(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
                ({
                rem = memcpy_mcsafe_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 = memcpy_mcsafe(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_to_iter_mcsafe);
#endif /* CONFIG_ARCH_HAS_UACCESS_MCSAFE */

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 << compound_order(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)))
                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;
        size_t n, off;
        int idx;

        if (!sanity(i))
                return 0;

        bytes = n = push_pipe(i, bytes, &idx, &off);
        if (unlikely(!n))
                return 0;

        for ( ; n; idx = next_idx(idx, pipe), off = 0) {
                size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
                memzero_page(pipe->bufs[idx].page, off, chunk);
                i->idx = idx;
                i->iov_offset = off + chunk;
                n -= chunk;
        }
        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;
        if (pipe->nrbufs) {
                size_t off = i->iov_offset;
                int idx = i->idx;
                int nrbufs = (idx - pipe->curbuf) & (pipe->buffers - 1);
                if (off) {
                        pipe->bufs[idx].len = off - pipe->bufs[idx].offset;
                        idx = next_idx(idx, pipe);
                        nrbufs++;
                }
                while (pipe->nrbufs > nrbufs) {
                        pipe_buf_release(pipe, &pipe->bufs[idx]);

                        idx = next_idx(idx, pipe);
                        pipe->nrbufs--;
                }
        }
}

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;
                size_t off = i->iov_offset, left = size;
                int idx = i->idx;
                if (off) /* make it relative to the beginning of buffer */
                        left += off - pipe->bufs[idx].offset;
                while (1) {
                        buf = &pipe->bufs[idx];
                        if (left <= buf->len)
                                break;
                        left -= buf->len;
                        idx = next_idx(idx, pipe);
                }
                i->idx = idx;
                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;
                int idx = i->idx;
                size_t off = i->iov_offset;
                while (1) {
                        size_t n = off - pipe->bufs[idx].offset;
                        if (unroll < n) {
                                off -= unroll;
                                break;
                        }
                        unroll -= n;
                        if (!unroll && idx == i->start_idx) {
                                off = 0;
                                break;
                        }
                        if (!idx--)
                                idx = pipe->buffers - 1;
                        off = pipe->bufs[idx].offset + pipe->bufs[idx].len;
                }
                i->iov_offset = off;
                i->idx = idx;
                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->nrbufs == pipe->buffers);
        i->type = ITER_PIPE | READ;
        i->pipe = pipe;
        i->idx = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
        i->iov_offset = 0;
        i->count = count;
        i->start_idx = i->idx;
}
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))) {
                if (size && i->iov_offset && allocated(&i->pipe->bufs[i->idx]))
                        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 idx,
                                size_t *start)
{
        struct pipe_inode_info *pipe = i->pipe;
        ssize_t n = push_pipe(i, maxsize, &idx, start);
        if (!n)
                return -EFAULT;

        maxsize = n;
        n += *start;
        while (n > 0) {
                get_page(*pages++ = pipe->bufs[idx].page);
                idx = next_idx(idx, pipe);
                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 npages;
        size_t capacity;
        int idx;

        if (!maxsize)
                return 0;

        if (!sanity(i))
                return -EFAULT;

        data_start(i, &idx, start);
        /* some of this one + all after this one */
        npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
        capacity = min(npages,maxpages) * PAGE_SIZE - *start;

        return __pipe_get_pages(i, min(maxsize, capacity), pages, idx, 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;
        ssize_t n;
        int idx;
        int npages;

        if (!maxsize)
                return 0;

        if (!sanity(i))
                return -EFAULT;

        data_start(i, &idx, start);
        /* some of this one + all after this one */
        npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
        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, idx, 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);
                        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, ({
                int err = 0;
                next = csum_and_copy_from_user(v.iov_base,
                                               (to += v.iov_len) - v.iov_len,
                                               v.iov_len, 0, &err);
                if (!err) {
                        sum = csum_block_add(sum, next, off);
                        off += v.iov_len;
                }
                err ? 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;
        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, ({
                int err = 0;
                next = csum_and_copy_from_user(v.iov_base,
                                               (to += v.iov_len) - v.iov_len,
                                               v.iov_len, 0, &err);
                if (err)
                        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 *csump,
                             struct iov_iter *i)
{
        const char *from = addr;
        __wsum *csum = csump;
        __wsum sum, next;
        size_t off = 0;

        if (unlikely(iov_iter_is_pipe(i)))
                return csum_and_copy_to_pipe_iter(addr, bytes, csum, i);

        sum = *csum;
        if (unlikely(iov_iter_is_discard(i))) {
                WARN_ON(1);     /* for now */
                return 0;
        }
        iterate_and_advance(i, bytes, v, ({
                int err = 0;
                next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
                                             v.iov_base,
                                             v.iov_len, 0, &err);
                if (!err) {
                        sum = csum_block_add(sum, next, off);
                        off += v.iov_len;
                }
                err ? v.iov_len : 0;
        }), ({
                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;
        })
        )
        *csum = sum;
        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
        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;
                size_t off;
                int idx;

                if (!sanity(i))
                        return 0;

                data_start(i, &idx, &off);
                /* some of this one + all after this one */
                npages = ((pipe->curbuf - idx - 1) & (pipe->buffers - 1)) + 1;
                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);

/**
 * 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.
 * @uvector: Pointer to the userspace array.
 * @nr_segs: Number of elements in userspace array.
 * @fast_segs: Number of elements in @iov.
 * @iov: (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 * uvector,
                 unsigned nr_segs, unsigned fast_segs,
                 struct iovec **iov, struct iov_iter *i)
{
        ssize_t n;
        struct iovec *p;
        n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
                                  *iov, &p);
        if (n < 0) {
                if (p != *iov)
                        kfree(p);
                *iov = NULL;
                return n;
        }
        iov_iter_init(i, type, p, nr_segs, n);
        *iov = p == *iov ? NULL : p;
        return n;
}
EXPORT_SYMBOL(import_iovec);

#ifdef CONFIG_COMPAT
#include <linux/compat.h>

ssize_t compat_import_iovec(int type,
                const struct compat_iovec __user * uvector,
                unsigned nr_segs, unsigned fast_segs,
                struct iovec **iov, struct iov_iter *i)
{
        ssize_t n;
        struct iovec *p;
        n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
                                  *iov, &p);
        if (n < 0) {
                if (p != *iov)
                        kfree(p);
                *iov = NULL;
                return n;
        }
        iov_iter_init(i, type, p, nr_segs, n);
        *iov = p == *iov ? NULL : p;
        return n;
}
#endif

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);

int iov_iter_for_each_range(struct iov_iter *i, size_t bytes,
                            int (*f)(struct kvec *vec, void *context),
                            void *context)
{
        struct kvec w;
        int err = -EINVAL;
        if (!bytes)
                return 0;

        iterate_all_kinds(i, bytes, v, -EINVAL, ({
                w.iov_base = kmap(v.bv_page) + v.bv_offset;
                w.iov_len = v.bv_len;
                err = f(&w, context);
                kunmap(v.bv_page);
                err;}), ({
                w = v;
                err = f(&w, context);})
        )
        return err;
}
EXPORT_SYMBOL(iov_iter_for_each_range);