// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/read_write.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/sched/xacct.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include <linux/export.h>
#include <linux/syscalls.h>
#include <linux/pagemap.h>
#include <linux/splice.h>
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/fs.h>
#include "internal.h"

#include <linux/uaccess.h>
#include <asm/unistd.h>

const struct file_operations generic_ro_fops = {
        .llseek         = generic_file_llseek,
        .read_iter      = generic_file_read_iter,
        .mmap           = generic_file_readonly_mmap,
        .splice_read    = generic_file_splice_read,
};

EXPORT_SYMBOL(generic_ro_fops);

static inline bool unsigned_offsets(struct file *file)
{
        return file->f_mode & FMODE_UNSIGNED_OFFSET;
}

/**
 * vfs_setpos - update the file offset for lseek
 * @file:       file structure in question
 * @offset:     file offset to seek to
 * @maxsize:    maximum file size
 *
 * This is a low-level filesystem helper for updating the file offset to
 * the value specified by @offset if the given offset is valid and it is
 * not equal to the current file offset.
 *
 * Return the specified offset on success and -EINVAL on invalid offset.
 */
loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize)
{
        if (offset < 0 && !unsigned_offsets(file))
                return -EINVAL;
        if (offset > maxsize)
                return -EINVAL;

        if (offset != file->f_pos) {
                file->f_pos = offset;
                file->f_version = 0;
        }
        return offset;
}
EXPORT_SYMBOL(vfs_setpos);

/**
 * generic_file_llseek_size - generic llseek implementation for regular files
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 * @size:       max size of this file in file system
 * @eof:        offset used for SEEK_END position
 *
 * This is a variant of generic_file_llseek that allows passing in a custom
 * maximum file size and a custom EOF position, for e.g. hashed directories
 *
 * Synchronization:
 * SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms)
 * SEEK_CUR is synchronized against other SEEK_CURs, but not read/writes.
 * read/writes behave like SEEK_SET against seeks.
 */
loff_t
generic_file_llseek_size(struct file *file, loff_t offset, int whence,
                loff_t maxsize, loff_t eof)
{
        switch (whence) {
        case SEEK_END:
                offset += eof;
                break;
        case SEEK_CUR:
                /*
                 * Here we special-case the lseek(fd, 0, SEEK_CUR)
                 * position-querying operation.  Avoid rewriting the "same"
                 * f_pos value back to the file because a concurrent read(),
                 * write() or lseek() might have altered it
                 */
                if (offset == 0)
                        return file->f_pos;
                /*
                 * f_lock protects against read/modify/write race with other
                 * SEEK_CURs. Note that parallel writes and reads behave
                 * like SEEK_SET.
                 */
                spin_lock(&file->f_lock);
                offset = vfs_setpos(file, file->f_pos + offset, maxsize);
                spin_unlock(&file->f_lock);
                return offset;
        case SEEK_DATA:
                /*
                 * In the generic case the entire file is data, so as long as
                 * offset isn't at the end of the file then the offset is data.
                 */
                if ((unsigned long long)offset >= eof)
                        return -ENXIO;
                break;
        case SEEK_HOLE:
                /*
                 * There is a virtual hole at the end of the file, so as long as
                 * offset isn't i_size or larger, return i_size.
                 */
                if ((unsigned long long)offset >= eof)
                        return -ENXIO;
                offset = eof;
                break;
        }

        return vfs_setpos(file, offset, maxsize);
}
EXPORT_SYMBOL(generic_file_llseek_size);

/**
 * generic_file_llseek - generic llseek implementation for regular files
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 *
 * This is a generic implemenation of ->llseek useable for all normal local
 * filesystems.  It just updates the file offset to the value specified by
 * @offset and @whence.
 */
loff_t generic_file_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *inode = file->f_mapping->host;

        return generic_file_llseek_size(file, offset, whence,
                                        inode->i_sb->s_maxbytes,
                                        i_size_read(inode));
}
EXPORT_SYMBOL(generic_file_llseek);

/**
 * fixed_size_llseek - llseek implementation for fixed-sized devices
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 * @size:       size of the file
 *
 */
loff_t fixed_size_llseek(struct file *file, loff_t offset, int whence, loff_t size)
{
        switch (whence) {
        case SEEK_SET: case SEEK_CUR: case SEEK_END:
                return generic_file_llseek_size(file, offset, whence,
                                                size, size);
        default:
                return -EINVAL;
        }
}
EXPORT_SYMBOL(fixed_size_llseek);

/**
 * no_seek_end_llseek - llseek implementation for fixed-sized devices
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 *
 */
loff_t no_seek_end_llseek(struct file *file, loff_t offset, int whence)
{
        switch (whence) {
        case SEEK_SET: case SEEK_CUR:
                return generic_file_llseek_size(file, offset, whence,
                                                OFFSET_MAX, 0);
        default:
                return -EINVAL;
        }
}
EXPORT_SYMBOL(no_seek_end_llseek);

/**
 * no_seek_end_llseek_size - llseek implementation for fixed-sized devices
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 * @size:       maximal offset allowed
 *
 */
loff_t no_seek_end_llseek_size(struct file *file, loff_t offset, int whence, loff_t size)
{
        switch (whence) {
        case SEEK_SET: case SEEK_CUR:
                return generic_file_llseek_size(file, offset, whence,
                                                size, 0);
        default:
                return -EINVAL;
        }
}
EXPORT_SYMBOL(no_seek_end_llseek_size);

/**
 * noop_llseek - No Operation Performed llseek implementation
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 *
 * This is an implementation of ->llseek useable for the rare special case when
 * userspace expects the seek to succeed but the (device) file is actually not
 * able to perform the seek. In this case you use noop_llseek() instead of
 * falling back to the default implementation of ->llseek.
 */
loff_t noop_llseek(struct file *file, loff_t offset, int whence)
{
        return file->f_pos;
}
EXPORT_SYMBOL(noop_llseek);

loff_t no_llseek(struct file *file, loff_t offset, int whence)
{
        return -ESPIPE;
}
EXPORT_SYMBOL(no_llseek);

loff_t default_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *inode = file_inode(file);
        loff_t retval;

        inode_lock(inode);
        switch (whence) {
                case SEEK_END:
                        offset += i_size_read(inode);
                        break;
                case SEEK_CUR:
                        if (offset == 0) {
                                retval = file->f_pos;
                                goto out;
                        }
                        offset += file->f_pos;
                        break;
                case SEEK_DATA:
                        /*
                         * In the generic case the entire file is data, so as
                         * long as offset isn't at the end of the file then the
                         * offset is data.
                         */
                        if (offset >= inode->i_size) {
                                retval = -ENXIO;
                                goto out;
                        }
                        break;
                case SEEK_HOLE:
                        /*
                         * There is a virtual hole at the end of the file, so
                         * as long as offset isn't i_size or larger, return
                         * i_size.
                         */
                        if (offset >= inode->i_size) {
                                retval = -ENXIO;
                                goto out;
                        }
                        offset = inode->i_size;
                        break;
        }
        retval = -EINVAL;
        if (offset >= 0 || unsigned_offsets(file)) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_version = 0;
                }
                retval = offset;
        }
out:
        inode_unlock(inode);
        return retval;
}
EXPORT_SYMBOL(default_llseek);

loff_t vfs_llseek(struct file *file, loff_t offset, int whence)
{
        loff_t (*fn)(struct file *, loff_t, int);

        fn = no_llseek;
        if (file->f_mode & FMODE_LSEEK) {
                if (file->f_op->llseek)
                        fn = file->f_op->llseek;
        }
        return fn(file, offset, whence);
}
EXPORT_SYMBOL(vfs_llseek);

off_t ksys_lseek(unsigned int fd, off_t offset, unsigned int whence)
{
        off_t retval;
        struct fd f = fdget_pos(fd);
        if (!f.file)
                return -EBADF;

        retval = -EINVAL;
        if (whence <= SEEK_MAX) {
                loff_t res = vfs_llseek(f.file, offset, whence);
                retval = res;
                if (res != (loff_t)retval)
                        retval = -EOVERFLOW;    /* LFS: should only happen on 32 bit platforms */
        }
        fdput_pos(f);
        return retval;
}

SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence)
{
        return ksys_lseek(fd, offset, whence);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(lseek, unsigned int, fd, compat_off_t, offset, unsigned int, whence)
{
        return ksys_lseek(fd, offset, whence);
}
#endif

#ifdef __ARCH_WANT_SYS_LLSEEK
SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned long, offset_high,
                unsigned long, offset_low, loff_t __user *, result,
                unsigned int, whence)
{
        int retval;
        struct fd f = fdget_pos(fd);
        loff_t offset;

        if (!f.file)
                return -EBADF;

        retval = -EINVAL;
        if (whence > SEEK_MAX)
                goto out_putf;

        offset = vfs_llseek(f.file, ((loff_t) offset_high << 32) | offset_low,
                        whence);

        retval = (int)offset;
        if (offset >= 0) {
                retval = -EFAULT;
                if (!copy_to_user(result, &offset, sizeof(offset)))
                        retval = 0;
        }
out_putf:
        fdput_pos(f);
        return retval;
}
#endif

int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t count)
{
        struct inode *inode;
        loff_t pos;
        int retval = -EINVAL;

        inode = file_inode(file);
        if (unlikely((ssize_t) count < 0))
                return retval;
        pos = *ppos;
        if (unlikely(pos < 0)) {
                if (!unsigned_offsets(file))
                        return retval;
                if (count >= -pos) /* both values are in 0..LLONG_MAX */
                        return -EOVERFLOW;
        } else if (unlikely((loff_t) (pos + count) < 0)) {
                if (!unsigned_offsets(file))
                        return retval;
        }

        if (unlikely(inode->i_flctx && mandatory_lock(inode))) {
                retval = locks_mandatory_area(inode, file, pos, pos + count - 1,
                                read_write == READ ? F_RDLCK : F_WRLCK);
                if (retval < 0)
                        return retval;
        }
        return security_file_permission(file,
                                read_write == READ ? MAY_READ : MAY_WRITE);
}

static ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
{
        struct iovec iov = { .iov_base = buf, .iov_len = len };
        struct kiocb kiocb;
        struct iov_iter iter;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        iov_iter_init(&iter, READ, &iov, 1, len);

        ret = call_read_iter(filp, &kiocb, &iter);
        BUG_ON(ret == -EIOCBQUEUED);
        *ppos = kiocb.ki_pos;
        return ret;
}

ssize_t __vfs_read(struct file *file, char __user *buf, size_t count,
                   loff_t *pos)
{
        if (file->f_op->read)
                return file->f_op->read(file, buf, count, pos);
        else if (file->f_op->read_iter)
                return new_sync_read(file, buf, count, pos);
        else
                return -EINVAL;
}

ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
{
        mm_segment_t old_fs;
        ssize_t result;

        old_fs = get_fs();
        set_fs(get_ds());
        /* The cast to a user pointer is valid due to the set_fs() */
        result = vfs_read(file, (void __user *)buf, count, pos);
        set_fs(old_fs);
        return result;
}
EXPORT_SYMBOL(kernel_read);

ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
{
        ssize_t ret;

        if (!(file->f_mode & FMODE_READ))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_READ))
                return -EINVAL;
        if (unlikely(!access_ok(buf, count)))
                return -EFAULT;

        ret = rw_verify_area(READ, file, pos, count);
        if (!ret) {
                if (count > MAX_RW_COUNT)
                        count =  MAX_RW_COUNT;
                ret = __vfs_read(file, buf, count, pos);
                if (ret > 0) {
                        fsnotify_access(file);
                        add_rchar(current, ret);
                }
                inc_syscr(current);
        }

        return ret;
}

static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
{
        struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };
        struct kiocb kiocb;
        struct iov_iter iter;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        iov_iter_init(&iter, WRITE, &iov, 1, len);

        ret = call_write_iter(filp, &kiocb, &iter);
        BUG_ON(ret == -EIOCBQUEUED);
        if (ret > 0)
                *ppos = kiocb.ki_pos;
        return ret;
}

ssize_t __vfs_write(struct file *file, const char __user *p, size_t count,
                    loff_t *pos)
{
        if (file->f_op->write)
                return file->f_op->write(file, p, count, pos);
        else if (file->f_op->write_iter)
                return new_sync_write(file, p, count, pos);
        else
                return -EINVAL;
}

ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
{
        mm_segment_t old_fs;
        const char __user *p;
        ssize_t ret;

        if (!(file->f_mode & FMODE_CAN_WRITE))
                return -EINVAL;

        old_fs = get_fs();
        set_fs(get_ds());
        p = (__force const char __user *)buf;
        if (count > MAX_RW_COUNT)
                count =  MAX_RW_COUNT;
        ret = __vfs_write(file, p, count, pos);
        set_fs(old_fs);
        if (ret > 0) {
                fsnotify_modify(file);
                add_wchar(current, ret);
        }
        inc_syscw(current);
        return ret;
}
EXPORT_SYMBOL(__kernel_write);

ssize_t kernel_write(struct file *file, const void *buf, size_t count,
                            loff_t *pos)
{
        mm_segment_t old_fs;
        ssize_t res;

        old_fs = get_fs();
        set_fs(get_ds());
        /* The cast to a user pointer is valid due to the set_fs() */
        res = vfs_write(file, (__force const char __user *)buf, count, pos);
        set_fs(old_fs);

        return res;
}
EXPORT_SYMBOL(kernel_write);

ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
        ssize_t ret;

        if (!(file->f_mode & FMODE_WRITE))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_WRITE))
                return -EINVAL;
        if (unlikely(!access_ok(buf, count)))
                return -EFAULT;

        ret = rw_verify_area(WRITE, file, pos, count);
        if (!ret) {
                if (count > MAX_RW_COUNT)
                        count =  MAX_RW_COUNT;
                file_start_write(file);
                ret = __vfs_write(file, buf, count, pos);
                if (ret > 0) {
                        fsnotify_modify(file);
                        add_wchar(current, ret);
                }
                inc_syscw(current);
                file_end_write(file);
        }

        return ret;
}

static inline loff_t file_pos_read(struct file *file)
{
        return file->f_pos;
}

static inline void file_pos_write(struct file *file, loff_t pos)
{
        file->f_pos = pos;
}

ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_read(f.file, buf, count, &pos);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }
        return ret;
}

SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)
{
        return ksys_read(fd, buf, count);
}

ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_write(f.file, buf, count, &pos);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }

        return ret;
}

SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
                size_t, count)
{
        return ksys_write(fd, buf, count);
}

ssize_t ksys_pread64(unsigned int fd, char __user *buf, size_t count,
                     loff_t pos)
{
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {
                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PREAD)
                        ret = vfs_read(f.file, buf, count, &pos);
                fdput(f);
        }

        return ret;
}

SYSCALL_DEFINE4(pread64, unsigned int, fd, char __user *, buf,
                        size_t, count, loff_t, pos)
{
        return ksys_pread64(fd, buf, count, pos);
}

ssize_t ksys_pwrite64(unsigned int fd, const char __user *buf,
                      size_t count, loff_t pos)
{
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {
                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PWRITE)  
                        ret = vfs_write(f.file, buf, count, &pos);
                fdput(f);
        }

        return ret;
}

SYSCALL_DEFINE4(pwrite64, unsigned int, fd, const char __user *, buf,
                         size_t, count, loff_t, pos)
{
        return ksys_pwrite64(fd, buf, count, pos);
}

static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
                loff_t *ppos, int type, rwf_t flags)
{
        struct kiocb kiocb;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        ret = kiocb_set_rw_flags(&kiocb, flags);
        if (ret)
                return ret;
        kiocb.ki_pos = *ppos;

        if (type == READ)
                ret = call_read_iter(filp, &kiocb, iter);
        else
                ret = call_write_iter(filp, &kiocb, iter);
        BUG_ON(ret == -EIOCBQUEUED);
        *ppos = kiocb.ki_pos;
        return ret;
}

/* Do it by hand, with file-ops */
static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
                loff_t *ppos, int type, rwf_t flags)
{
        ssize_t ret = 0;

        if (flags & ~RWF_HIPRI)
                return -EOPNOTSUPP;

        while (iov_iter_count(iter)) {
                struct iovec iovec = iov_iter_iovec(iter);
                ssize_t nr;

                if (type == READ) {
                        nr = filp->f_op->read(filp, iovec.iov_base,
                                              iovec.iov_len, ppos);
                } else {
                        nr = filp->f_op->write(filp, iovec.iov_base,
                                               iovec.iov_len, ppos);
                }

                if (nr < 0) {
                        if (!ret)
                                ret = nr;
                        break;
                }
                ret += nr;
                if (nr != iovec.iov_len)
                        break;
                iov_iter_advance(iter, nr);
        }

        return ret;
}

/**
 * rw_copy_check_uvector() - Copy an array of &struct iovec from userspace
 *     into the kernel and check that it is valid.
 *
 * @type: One of %CHECK_IOVEC_ONLY, %READ, or %WRITE.
 * @uvector: Pointer to the userspace array.
 * @nr_segs: Number of elements in userspace array.
 * @fast_segs: Number of elements in @fast_pointer.
 * @fast_pointer: Pointer to (usually small on-stack) kernel array.
 * @ret_pointer: (output parameter) Pointer to a variable that will point to
 *     either @fast_pointer, a newly allocated kernel array, or NULL,
 *     depending on which array was used.
 *
 * This function copies an array of &struct iovec of @nr_segs from
 * userspace into the kernel and checks that each element is valid (e.g.
 * it does not point to a kernel address or cause overflow by being too
 * large, etc.).
 *
 * As an optimization, the caller may provide a pointer to a small
 * on-stack array in @fast_pointer, typically %UIO_FASTIOV elements long
 * (the size of this array, or 0 if unused, should be given in @fast_segs).
 *
 * @ret_pointer will always point to the array that was used, so the
 * caller must take care not to call kfree() on it e.g. in case the
 * @fast_pointer array was used and it was allocated on the stack.
 *
 * Return: The total number of bytes covered by the iovec array on success
 *   or a negative error code on error.
 */
ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
                              unsigned long nr_segs, unsigned long fast_segs,
                              struct iovec *fast_pointer,
                              struct iovec **ret_pointer)
{
        unsigned long seg;
        ssize_t ret;
        struct iovec *iov = fast_pointer;

        /*
         * 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) {
                ret = 0;
                goto out;
        }

        /*
         * First get the "struct iovec" from user memory and
         * verify all the pointers
         */
        if (nr_segs > UIO_MAXIOV) {
                ret = -EINVAL;
                goto out;
        }
        if (nr_segs > fast_segs) {
                iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
                if (iov == NULL) {
                        ret = -ENOMEM;
                        goto out;
                }
        }
        if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
                ret = -EFAULT;
                goto out;
        }

        /*
         * 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.
         */
        ret = 0;
        for (seg = 0; seg < nr_segs; seg++) {
                void __user *buf = iov[seg].iov_base;
                ssize_t len = (ssize_t)iov[seg].iov_len;

                /* see if we we're about to use an invalid len or if
                 * it's about to overflow ssize_t */
                if (len < 0) {
                        ret = -EINVAL;
                        goto out;
                }
                if (type >= 0
                    && unlikely(!access_ok(buf, len))) {
                        ret = -EFAULT;
                        goto out;
                }
                if (len > MAX_RW_COUNT - ret) {
                        len = MAX_RW_COUNT - ret;
                        iov[seg].iov_len = len;
                }
                ret += len;
        }
out:
        *ret_pointer = iov;
        return ret;
}

#ifdef CONFIG_COMPAT
ssize_t compat_rw_copy_check_uvector(int type,
                const struct compat_iovec __user *uvector, unsigned long nr_segs,
                unsigned long fast_segs, struct iovec *fast_pointer,
                struct iovec **ret_pointer)
{
        compat_ssize_t tot_len;
        struct iovec *iov = *ret_pointer = fast_pointer;
        ssize_t ret = 0;
        int seg;

        /*
         * 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)
                goto out;

        ret = -EINVAL;
        if (nr_segs > UIO_MAXIOV)
                goto out;
        if (nr_segs > fast_segs) {
                ret = -ENOMEM;
                iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
                if (iov == NULL)
                        goto out;
        }
        *ret_pointer = iov;

        ret = -EFAULT;
        if (!access_ok(uvector, nr_segs*sizeof(*uvector)))
                goto out;

        /*
         * Single unix specification:
         * We should -EINVAL if an element length is not >= 0 and fitting an
         * ssize_t.
         *
         * In Linux, the total length is limited to MAX_RW_COUNT, there is
         * no overflow possibility.
         */
        tot_len = 0;
        ret = -EINVAL;
        for (seg = 0; seg < nr_segs; seg++) {
                compat_uptr_t buf;
                compat_ssize_t len;

                if (__get_user(len, &uvector->iov_len) ||
                   __get_user(buf, &uvector->iov_base)) {
                        ret = -EFAULT;
                        goto out;
                }
                if (len < 0)    /* size_t not fitting in compat_ssize_t .. */
                        goto out;
                if (type >= 0 &&
                    !access_ok(compat_ptr(buf), len)) {
                        ret = -EFAULT;
                        goto out;
                }
                if (len > MAX_RW_COUNT - tot_len)
                        len = MAX_RW_COUNT - tot_len;
                tot_len += len;
                iov->iov_base = compat_ptr(buf);
                iov->iov_len = (compat_size_t) len;
                uvector++;
                iov++;
        }
        ret = tot_len;

out:
        return ret;
}
#endif

static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,
                loff_t *pos, rwf_t flags)
{
        size_t tot_len;
        ssize_t ret = 0;

        if (!(file->f_mode & FMODE_READ))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_READ))
                return -EINVAL;

        tot_len = iov_iter_count(iter);
        if (!tot_len)
                goto out;
        ret = rw_verify_area(READ, file, pos, tot_len);
        if (ret < 0)
                return ret;

        if (file->f_op->read_iter)
                ret = do_iter_readv_writev(file, iter, pos, READ, flags);
        else
                ret = do_loop_readv_writev(file, iter, pos, READ, flags);
out:
        if (ret >= 0)
                fsnotify_access(file);
        return ret;
}

ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
                           struct iov_iter *iter)
{
        size_t tot_len;
        ssize_t ret = 0;

        if (!file->f_op->read_iter)
                return -EINVAL;
        if (!(file->f_mode & FMODE_READ))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_READ))
                return -EINVAL;

        tot_len = iov_iter_count(iter);
        if (!tot_len)
                goto out;
        ret = rw_verify_area(READ, file, &iocb->ki_pos, tot_len);
        if (ret < 0)
                return ret;

        ret = call_read_iter(file, iocb, iter);
out:
        if (ret >= 0)
                fsnotify_access(file);
        return ret;
}
EXPORT_SYMBOL(vfs_iocb_iter_read);

ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
                rwf_t flags)
{
        if (!file->f_op->read_iter)
                return -EINVAL;
        return do_iter_read(file, iter, ppos, flags);
}
EXPORT_SYMBOL(vfs_iter_read);

static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
                loff_t *pos, rwf_t flags)
{
        size_t tot_len;
        ssize_t ret = 0;

        if (!(file->f_mode & FMODE_WRITE))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_WRITE))
                return -EINVAL;

        tot_len = iov_iter_count(iter);
        if (!tot_len)
                return 0;
        ret = rw_verify_area(WRITE, file, pos, tot_len);
        if (ret < 0)
                return ret;

        if (file->f_op->write_iter)
                ret = do_iter_readv_writev(file, iter, pos, WRITE, flags);
        else
                ret = do_loop_readv_writev(file, iter, pos, WRITE, flags);
        if (ret > 0)
                fsnotify_modify(file);
        return ret;
}

ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
                            struct iov_iter *iter)
{
        size_t tot_len;
        ssize_t ret = 0;

        if (!file->f_op->write_iter)
                return -EINVAL;
        if (!(file->f_mode & FMODE_WRITE))

                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_WRITE))
                return -EINVAL;

        tot_len = iov_iter_count(iter);
        if (!tot_len)
                return 0;
        ret = rw_verify_area(WRITE, file, &iocb->ki_pos, tot_len);
        if (ret < 0)
                return ret;

        ret = call_write_iter(file, iocb, iter);
        if (ret > 0)
                fsnotify_modify(file);

        return ret;
}
EXPORT_SYMBOL(vfs_iocb_iter_write);

ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
                rwf_t flags)
{
        if (!file->f_op->write_iter)
                return -EINVAL;
        return do_iter_write(file, iter, ppos, flags);
}
EXPORT_SYMBOL(vfs_iter_write);

ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
                  unsigned long vlen, loff_t *pos, rwf_t flags)
{
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        struct iov_iter iter;
        ssize_t ret;

        ret = import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
        if (ret >= 0) {
                ret = do_iter_read(file, &iter, pos, flags);
                kfree(iov);
        }

        return ret;
}

static ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,
                   unsigned long vlen, loff_t *pos, rwf_t flags)
{
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        struct iov_iter iter;
        ssize_t ret;

        ret = import_iovec(WRITE, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
        if (ret >= 0) {
                file_start_write(file);
                ret = do_iter_write(file, &iter, pos, flags);
                file_end_write(file);
                kfree(iov);
        }
        return ret;
}

static ssize_t do_readv(unsigned long fd, const struct iovec __user *vec,
                        unsigned long vlen, rwf_t flags)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_readv(f.file, vec, vlen, &pos, flags);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }

        if (ret > 0)
                add_rchar(current, ret);
        inc_syscr(current);
        return ret;
}

static ssize_t do_writev(unsigned long fd, const struct iovec __user *vec,
                         unsigned long vlen, rwf_t flags)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_writev(f.file, vec, vlen, &pos, flags);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }

        if (ret > 0)
                add_wchar(current, ret);
        inc_syscw(current);
        return ret;
}

static inline loff_t pos_from_hilo(unsigned long high, unsigned long low)
{
#define HALF_LONG_BITS (BITS_PER_LONG / 2)
        return (((loff_t)high << HALF_LONG_BITS) << HALF_LONG_BITS) | low;
}

static ssize_t do_preadv(unsigned long fd, const struct iovec __user *vec,
                         unsigned long vlen, loff_t pos, rwf_t flags)
{
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {
                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PREAD)
                        ret = vfs_readv(f.file, vec, vlen, &pos, flags);
                fdput(f);
        }

        if (ret > 0)
                add_rchar(current, ret);
        inc_syscr(current);
        return ret;
}

static ssize_t do_pwritev(unsigned long fd, const struct iovec __user *vec,
                          unsigned long vlen, loff_t pos, rwf_t flags)
{
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {
                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PWRITE)
                        ret = vfs_writev(f.file, vec, vlen, &pos, flags);
                fdput(f);
        }

        if (ret > 0)
                add_wchar(current, ret);
        inc_syscw(current);
        return ret;
}

SYSCALL_DEFINE3(readv, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen)
{
        return do_readv(fd, vec, vlen, 0);
}

SYSCALL_DEFINE3(writev, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen)
{
        return do_writev(fd, vec, vlen, 0);
}

SYSCALL_DEFINE5(preadv, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h)
{
        loff_t pos = pos_from_hilo(pos_h, pos_l);

        return do_preadv(fd, vec, vlen, pos, 0);
}

SYSCALL_DEFINE6(preadv2, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h,
                rwf_t, flags)
{
        loff_t pos = pos_from_hilo(pos_h, pos_l);

        if (pos == -1)
                return do_readv(fd, vec, vlen, flags);

        return do_preadv(fd, vec, vlen, pos, flags);
}

SYSCALL_DEFINE5(pwritev, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h)
{
        loff_t pos = pos_from_hilo(pos_h, pos_l);

        return do_pwritev(fd, vec, vlen, pos, 0);
}

SYSCALL_DEFINE6(pwritev2, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h,
                rwf_t, flags)
{
        loff_t pos = pos_from_hilo(pos_h, pos_l);

        if (pos == -1)
                return do_writev(fd, vec, vlen, flags);

        return do_pwritev(fd, vec, vlen, pos, flags);
}

#ifdef CONFIG_COMPAT
static size_t compat_readv(struct file *file,
                           const struct compat_iovec __user *vec,
                           unsigned long vlen, loff_t *pos, rwf_t flags)
{
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        struct iov_iter iter;
        ssize_t ret;

        ret = compat_import_iovec(READ, vec, vlen, UIO_FASTIOV, &iov, &iter);
        if (ret >= 0) {
                ret = do_iter_read(file, &iter, pos, flags);
                kfree(iov);
        }
        if (ret > 0)
                add_rchar(current, ret);
        inc_syscr(current);
        return ret;
}

static size_t do_compat_readv(compat_ulong_t fd,
                                 const struct compat_iovec __user *vec,
                                 compat_ulong_t vlen, rwf_t flags)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret;
        loff_t pos;

        if (!f.file)
                return -EBADF;
        pos = f.file->f_pos;
        ret = compat_readv(f.file, vec, vlen, &pos, flags);
        if (ret >= 0)
                f.file->f_pos = pos;
        fdput_pos(f);
        return ret;

}

COMPAT_SYSCALL_DEFINE3(readv, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen)
{
        return do_compat_readv(fd, vec, vlen, 0);
}

static long do_compat_preadv64(unsigned long fd,
                                  const struct compat_iovec __user *vec,
                                  unsigned long vlen, loff_t pos, rwf_t flags)
{
        struct fd f;
        ssize_t ret;

        if (pos < 0)
                return -EINVAL;
        f = fdget(fd);
        if (!f.file)
                return -EBADF;
        ret = -ESPIPE;
        if (f.file->f_mode & FMODE_PREAD)
                ret = compat_readv(f.file, vec, vlen, &pos, flags);
        fdput(f);
        return ret;
}

#ifdef __ARCH_WANT_COMPAT_SYS_PREADV64
COMPAT_SYSCALL_DEFINE4(preadv64, unsigned long, fd,
                const struct compat_iovec __user *,vec,
                unsigned long, vlen, loff_t, pos)
{
        return do_compat_preadv64(fd, vec, vlen, pos, 0);
}
#endif

COMPAT_SYSCALL_DEFINE5(preadv, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen, u32, pos_low, u32, pos_high)
{
        loff_t pos = ((loff_t)pos_high << 32) | pos_low;

        return do_compat_preadv64(fd, vec, vlen, pos, 0);
}

#ifdef __ARCH_WANT_COMPAT_SYS_PREADV64V2
COMPAT_SYSCALL_DEFINE5(preadv64v2, unsigned long, fd,
                const struct compat_iovec __user *,vec,
                unsigned long, vlen, loff_t, pos, rwf_t, flags)
{
        return do_compat_preadv64(fd, vec, vlen, pos, flags);
}
#endif

COMPAT_SYSCALL_DEFINE6(preadv2, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen, u32, pos_low, u32, pos_high,
                rwf_t, flags)
{
        loff_t pos = ((loff_t)pos_high << 32) | pos_low;

        if (pos == -1)
                return do_compat_readv(fd, vec, vlen, flags);

        return do_compat_preadv64(fd, vec, vlen, pos, flags);
}

static size_t compat_writev(struct file *file,
                            const struct compat_iovec __user *vec,
                            unsigned long vlen, loff_t *pos, rwf_t flags)
{
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        struct iov_iter iter;
        ssize_t ret;

        ret = compat_import_iovec(WRITE, vec, vlen, UIO_FASTIOV, &iov, &iter);
        if (ret >= 0) {
                file_start_write(file);
                ret = do_iter_write(file, &iter, pos, flags);
                file_end_write(file);
                kfree(iov);
        }
        if (ret > 0)
                add_wchar(current, ret);
        inc_syscw(current);
        return ret;
}

static size_t do_compat_writev(compat_ulong_t fd,
                                  const struct compat_iovec __user* vec,
                                  compat_ulong_t vlen, rwf_t flags)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret;
        loff_t pos;

        if (!f.file)
                return -EBADF;
        pos = f.file->f_pos;
        ret = compat_writev(f.file, vec, vlen, &pos, flags);
        if (ret >= 0)
                f.file->f_pos = pos;
        fdput_pos(f);
        return ret;
}

COMPAT_SYSCALL_DEFINE3(writev, compat_ulong_t, fd,
                const struct compat_iovec __user *, vec,
                compat_ulong_t, vlen)
{
        return do_compat_writev(fd, vec, vlen, 0);
}

static long do_compat_pwritev64(unsigned long fd,
                                   const struct compat_iovec __user *vec,
                                   unsigned long vlen, loff_t pos, rwf_t flags)
{
        struct fd f;
        ssize_t ret;

        if (pos < 0)
                return -EINVAL;
        f = fdget(fd);
        if (!f.file)
                return -EBADF;
        ret = -ESPIPE;
        if (f.file->f_mode & FMODE_PWRITE)
                ret = compat_writev(f.file, vec, vlen, &pos, flags);
        fdput(f);
        return ret;
}

#ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64
COMPAT_SYSCALL_DEFINE4(pwritev64, unsigned long, fd,
                const struct compat_iovec __user *,vec,
                unsigned long, vlen, loff_t, pos)
{
        return do_compat_pwritev64(fd, vec, vlen, pos, 0);
}
#endif

COMPAT_SYSCALL_DEFINE5(pwritev, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen, u32, pos_low, u32, pos_high)
{
        loff_t pos = ((loff_t)pos_high << 32) | pos_low;

        return do_compat_pwritev64(fd, vec, vlen, pos, 0);
}

#ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64V2
COMPAT_SYSCALL_DEFINE5(pwritev64v2, unsigned long, fd,
                const struct compat_iovec __user *,vec,
                unsigned long, vlen, loff_t, pos, rwf_t, flags)
{
        return do_compat_pwritev64(fd, vec, vlen, pos, flags);
}
#endif

COMPAT_SYSCALL_DEFINE6(pwritev2, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen, u32, pos_low, u32, pos_high, rwf_t, flags)
{
        loff_t pos = ((loff_t)pos_high << 32) | pos_low;

        if (pos == -1)
                return do_compat_writev(fd, vec, vlen, flags);

        return do_compat_pwritev64(fd, vec, vlen, pos, flags);
}

#endif

static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
                           size_t count, loff_t max)
{
        struct fd in, out;
        struct inode *in_inode, *out_inode;
        loff_t pos;
        loff_t out_pos;
        ssize_t retval;
        int fl;

        /*
         * Get input file, and verify that it is ok..
         */
        retval = -EBADF;
        in = fdget(in_fd);
        if (!in.file)
                goto out;
        if (!(in.file->f_mode & FMODE_READ))
                goto fput_in;
        retval = -ESPIPE;
        if (!ppos) {
                pos = in.file->f_pos;
        } else {
                pos = *ppos;
                if (!(in.file->f_mode & FMODE_PREAD))
                        goto fput_in;
        }
        retval = rw_verify_area(READ, in.file, &pos, count);
        if (retval < 0)
                goto fput_in;
        if (count > MAX_RW_COUNT)
                count =  MAX_RW_COUNT;

        /*
         * Get output file, and verify that it is ok..
         */
        retval = -EBADF;
        out = fdget(out_fd);
        if (!out.file)
                goto fput_in;
        if (!(out.file->f_mode & FMODE_WRITE))
                goto fput_out;
        retval = -EINVAL;
        in_inode = file_inode(in.file);
        out_inode = file_inode(out.file);
        out_pos = out.file->f_pos;
        retval = rw_verify_area(WRITE, out.file, &out_pos, count);
        if (retval < 0)
                goto fput_out;

        if (!max)
                max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);

        if (unlikely(pos + count > max)) {
                retval = -EOVERFLOW;
                if (pos >= max)
                        goto fput_out;
                count = max - pos;
        }

        fl = 0;
#if 0
        /*
         * We need to debate whether we can enable this or not. The
         * man page documents EAGAIN return for the output at least,
         * and the application is arguably buggy if it doesn't expect
         * EAGAIN on a non-blocking file descriptor.
         */
        if (in.file->f_flags & O_NONBLOCK)
                fl = SPLICE_F_NONBLOCK;
#endif
        file_start_write(out.file);
        retval = do_splice_direct(in.file, &pos, out.file, &out_pos, count, fl);
        file_end_write(out.file);

        if (retval > 0) {
                add_rchar(current, retval);
                add_wchar(current, retval);
                fsnotify_access(in.file);
                fsnotify_modify(out.file);
                out.file->f_pos = out_pos;
                if (ppos)
                        *ppos = pos;
                else
                        in.file->f_pos = pos;
        }

        inc_syscr(current);
        inc_syscw(current);
        if (pos > max)
                retval = -EOVERFLOW;

fput_out:
        fdput(out);
fput_in:
        fdput(in);
out:
        return retval;
}

SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd, off_t __user *, offset, size_t, count)
{
        loff_t pos;
        off_t off;
        ssize_t ret;

        if (offset) {
                if (unlikely(get_user(off, offset)))
                        return -EFAULT;
                pos = off;
                ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}

SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd, loff_t __user *, offset, size_t, count)
{
        loff_t pos;
        ssize_t ret;

        if (offset) {
                if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
                        return -EFAULT;
                ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd,
                compat_off_t __user *, offset, compat_size_t, count)
{
        loff_t pos;
        off_t off;
        ssize_t ret;

        if (offset) {
                if (unlikely(get_user(off, offset)))
                        return -EFAULT;
                pos = off;
                ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}

COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
                compat_loff_t __user *, offset, compat_size_t, count)
{
        loff_t pos;
        ssize_t ret;

        if (offset) {
                if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
                        return -EFAULT;
                ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}
#endif

/**
 * generic_copy_file_range - copy data between two files
 * @file_in:    file structure to read from
 * @pos_in:     file offset to read from
 * @file_out:   file structure to write data to
 * @pos_out:    file offset to write data to
 * @len:        amount of data to copy
 * @flags:      copy flags
 *
 * This is a generic filesystem helper to copy data from one file to another.
 * It has no constraints on the source or destination file owners - the files
 * can belong to different superblocks and different filesystem types. Short
 * copies are allowed.
 *
 * This should be called from the @file_out filesystem, as per the
 * ->copy_file_range() method.
 *
 * Returns the number of bytes copied or a negative error indicating the
 * failure.
 */

ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
                                struct file *file_out, loff_t pos_out,
                                size_t len, unsigned int flags)
{
        return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
                                len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
}
EXPORT_SYMBOL(generic_copy_file_range);

static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
                                  struct file *file_out, loff_t pos_out,
                                  size_t len, unsigned int flags)
{
        /*
         * Although we now allow filesystems to handle cross sb copy, passing
         * a file of the wrong filesystem type to filesystem driver can result
         * in an attempt to dereference the wrong type of ->private_data, so
         * avoid doing that until we really have a good reason.  NFS defines
         * several different file_system_type structures, but they all end up
         * using the same ->copy_file_range() function pointer.
         */
        if (file_out->f_op->copy_file_range &&
            file_out->f_op->copy_file_range == file_in->f_op->copy_file_range)
                return file_out->f_op->copy_file_range(file_in, pos_in,
                                                       file_out, pos_out,
                                                       len, flags);

        return generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
                                       flags);
}

/*
 * copy_file_range() differs from regular file read and write in that it
 * specifically allows return partial success.  When it does so is up to
 * the copy_file_range method.
 */
ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
                            struct file *file_out, loff_t pos_out,
                            size_t len, unsigned int flags)
{
        ssize_t ret;

        if (flags != 0)
                return -EINVAL;

        ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
                                       flags);
        if (unlikely(ret))
                return ret;

        ret = rw_verify_area(READ, file_in, &pos_in, len);
        if (unlikely(ret))
                return ret;

        ret = rw_verify_area(WRITE, file_out, &pos_out, len);
        if (unlikely(ret))
                return ret;

        if (len == 0)
                return 0;

        file_start_write(file_out);

        /*
         * Try cloning first, this is supported by more file systems, and
         * more efficient if both clone and copy are supported (e.g. NFS).
         */
        if (file_in->f_op->remap_file_range &&
            file_inode(file_in)->i_sb == file_inode(file_out)->i_sb) {
                loff_t cloned;

                cloned = file_in->f_op->remap_file_range(file_in, pos_in,
                                file_out, pos_out,
                                min_t(loff_t, MAX_RW_COUNT, len),
                                REMAP_FILE_CAN_SHORTEN);
                if (cloned > 0) {
                        ret = cloned;
                        goto done;
                }
        }

        ret = do_copy_file_range(file_in, pos_in, file_out, pos_out, len,
                                flags);
        WARN_ON_ONCE(ret == -EOPNOTSUPP);
done:
        if (ret > 0) {
                fsnotify_access(file_in);
                add_rchar(current, ret);
                fsnotify_modify(file_out);
                add_wchar(current, ret);
        }

        inc_syscr(current);
        inc_syscw(current);

        file_end_write(file_out);

        return ret;
}
EXPORT_SYMBOL(vfs_copy_file_range);

SYSCALL_DEFINE6(copy_file_range, int, fd_in, loff_t __user *, off_in,
                int, fd_out, loff_t __user *, off_out,
                size_t, len, unsigned int, flags)
{
        loff_t pos_in;
        loff_t pos_out;
        struct fd f_in;
        struct fd f_out;
        ssize_t ret = -EBADF;

        f_in = fdget(fd_in);
        if (!f_in.file)
                goto out2;

        f_out = fdget(fd_out);
        if (!f_out.file)
                goto out1;

        ret = -EFAULT;
        if (off_in) {
                if (copy_from_user(&pos_in, off_in, sizeof(loff_t)))
                        goto out;
        } else {
                pos_in = f_in.file->f_pos;
        }

        if (off_out) {
                if (copy_from_user(&pos_out, off_out, sizeof(loff_t)))
                        goto out;
        } else {
                pos_out = f_out.file->f_pos;
        }

        ret = vfs_copy_file_range(f_in.file, pos_in, f_out.file, pos_out, len,
                                  flags);
        if (ret > 0) {
                pos_in += ret;
                pos_out += ret;

                if (off_in) {
                        if (copy_to_user(off_in, &pos_in, sizeof(loff_t)))
                                ret = -EFAULT;
                } else {
                        f_in.file->f_pos = pos_in;
                }

                if (off_out) {
                        if (copy_to_user(off_out, &pos_out, sizeof(loff_t)))
                                ret = -EFAULT;
                } else {
                        f_out.file->f_pos = pos_out;
                }
        }

out:
        fdput(f_out);
out1:
        fdput(f_in);
out2:
        return ret;
}

static int remap_verify_area(struct file *file, loff_t pos, loff_t len,
                             bool write)
{
        struct inode *inode = file_inode(file);

        if (unlikely(pos < 0 || len < 0))
                return -EINVAL;

         if (unlikely((loff_t) (pos + len) < 0))
                return -EINVAL;

        if (unlikely(inode->i_flctx && mandatory_lock(inode))) {
                loff_t end = len ? pos + len - 1 : OFFSET_MAX;
                int retval;

                retval = locks_mandatory_area(inode, file, pos, end,
                                write ? F_WRLCK : F_RDLCK);
                if (retval < 0)
                        return retval;
        }

        return security_file_permission(file, write ? MAY_WRITE : MAY_READ);
}
/*
 * Ensure that we don't remap a partial EOF block in the middle of something
 * else.  Assume that the offsets have already been checked for block
 * alignment.
 *
 * For deduplication we always scale down to the previous block because we
 * can't meaningfully compare post-EOF contents.
 *
 * For clone we only link a partial EOF block above the destination file's EOF.
 *
 * Shorten the request if possible.
 */
static int generic_remap_check_len(struct inode *inode_in,
                                   struct inode *inode_out,
                                   loff_t pos_out,
                                   loff_t *len,
                                   unsigned int remap_flags)
{
        u64 blkmask = i_blocksize(inode_in) - 1;
        loff_t new_len = *len;

        if ((*len & blkmask) == 0)
                return 0;

        if ((remap_flags & REMAP_FILE_DEDUP) ||
            pos_out + *len < i_size_read(inode_out))
                new_len &= ~blkmask;

        if (new_len == *len)
                return 0;

        if (remap_flags & REMAP_FILE_CAN_SHORTEN) {
                *len = new_len;
                return 0;
        }

        return (remap_flags & REMAP_FILE_DEDUP) ? -EBADE : -EINVAL;
}

/*
 * Read a page's worth of file data into the page cache.  Return the page
 * locked.
 */
static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset)
{
        struct page *page;

        page = read_mapping_page(inode->i_mapping, offset >> PAGE_SHIFT, NULL);
        if (IS_ERR(page))
                return page;
        if (!PageUptodate(page)) {
                put_page(page);
                return ERR_PTR(-EIO);
        }
        lock_page(page);
        return page;
}

/*
 * Compare extents of two files to see if they are the same.
 * Caller must have locked both inodes to prevent write races.
 */
static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
                                         struct inode *dest, loff_t destoff,
                                         loff_t len, bool *is_same)
{
        loff_t src_poff;
        loff_t dest_poff;
        void *src_addr;
        void *dest_addr;
        struct page *src_page;
        struct page *dest_page;
        loff_t cmp_len;
        bool same;
        int error;

        error = -EINVAL;
        same = true;
        while (len) {
                src_poff = srcoff & (PAGE_SIZE - 1);
                dest_poff = destoff & (PAGE_SIZE - 1);
                cmp_len = min(PAGE_SIZE - src_poff,
                              PAGE_SIZE - dest_poff);
                cmp_len = min(cmp_len, len);
                if (cmp_len <= 0)
                        goto out_error;

                src_page = vfs_dedupe_get_page(src, srcoff);
                if (IS_ERR(src_page)) {
                        error = PTR_ERR(src_page);
                        goto out_error;
                }
                dest_page = vfs_dedupe_get_page(dest, destoff);
                if (IS_ERR(dest_page)) {
                        error = PTR_ERR(dest_page);
                        unlock_page(src_page);
                        put_page(src_page);
                        goto out_error;
                }
                src_addr = kmap_atomic(src_page);
                dest_addr = kmap_atomic(dest_page);

                flush_dcache_page(src_page);
                flush_dcache_page(dest_page);

                if (memcmp(src_addr + src_poff, dest_addr + dest_poff, cmp_len))
                        same = false;

                kunmap_atomic(dest_addr);
                kunmap_atomic(src_addr);
                unlock_page(dest_page);
                unlock_page(src_page);
                put_page(dest_page);
                put_page(src_page);

                if (!same)
                        break;

                srcoff += cmp_len;
                destoff += cmp_len;
                len -= cmp_len;
        }

        *is_same = same;
        return 0;

out_error:
        return error;
}

/*
 * Check that the two inodes are eligible for cloning, the ranges make
 * sense, and then flush all dirty data.  Caller must ensure that the
 * inodes have been locked against any other modifications.
 *
 * If there's an error, then the usual negative error code is returned.
 * Otherwise returns 0 with *len set to the request length.
 */
int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
                                  struct file *file_out, loff_t pos_out,
                                  loff_t *len, unsigned int remap_flags)
{
        struct inode *inode_in = file_inode(file_in);
        struct inode *inode_out = file_inode(file_out);
        bool same_inode = (inode_in == inode_out);
        int ret;

        /* Don't touch certain kinds of inodes */
        if (IS_IMMUTABLE(inode_out))
                return -EPERM;

        if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
                return -ETXTBSY;

        /* Don't reflink dirs, pipes, sockets... */
        if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
                return -EISDIR;
        if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
                return -EINVAL;

        /* Zero length dedupe exits immediately; reflink goes to EOF. */
        if (*len == 0) {
                loff_t isize = i_size_read(inode_in);

                if ((remap_flags & REMAP_FILE_DEDUP) || pos_in == isize)
                        return 0;
                if (pos_in > isize)
                        return -EINVAL;
                *len = isize - pos_in;
                if (*len == 0)
                        return 0;
        }

        /* Check that we don't violate system file offset limits. */
        ret = generic_remap_checks(file_in, pos_in, file_out, pos_out, len,
                        remap_flags);
        if (ret)
                return ret;

        /* Wait for the completion of any pending IOs on both files */
        inode_dio_wait(inode_in);
        if (!same_inode)
                inode_dio_wait(inode_out);

        ret = filemap_write_and_wait_range(inode_in->i_mapping,
                        pos_in, pos_in + *len - 1);
        if (ret)
                return ret;

        ret = filemap_write_and_wait_range(inode_out->i_mapping,
                        pos_out, pos_out + *len - 1);
        if (ret)
                return ret;

        /*
         * Check that the extents are the same.
         */

        if (remap_flags & REMAP_FILE_DEDUP) {
                bool            is_same = false;

                ret = vfs_dedupe_file_range_compare(inode_in, pos_in,
                                inode_out, pos_out, *len, &is_same);
                if (ret)
                        return ret;
                if (!is_same)
                        return -EBADE;
        }

        ret = generic_remap_check_len(inode_in, inode_out, pos_out, len,
                        remap_flags);
        if (ret)
                return ret;

        /* If can't alter the file contents, we're done. */
        if (!(remap_flags & REMAP_FILE_DEDUP))
                ret = file_modified(file_out);

        return ret;
}
EXPORT_SYMBOL(generic_remap_file_range_prep);

loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
                           struct file *file_out, loff_t pos_out,
                           loff_t len, unsigned int remap_flags)
{
        loff_t ret;

        WARN_ON_ONCE(remap_flags & REMAP_FILE_DEDUP);

        /*
         * FICLONE/FICLONERANGE ioctls enforce that src and dest files are on
         * the same mount. Practically, they only need to be on the same file
         * system.
         */
        if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
                return -EXDEV;

        ret = generic_file_rw_checks(file_in, file_out);
        if (ret < 0)
                return ret;

        if (!file_in->f_op->remap_file_range)
                return -EOPNOTSUPP;

        ret = remap_verify_area(file_in, pos_in, len, false);
        if (ret)
                return ret;

        ret = remap_verify_area(file_out, pos_out, len, true);
        if (ret)
                return ret;

        ret = file_in->f_op->remap_file_range(file_in, pos_in,
                        file_out, pos_out, len, remap_flags);
        if (ret < 0)
                return ret;

        fsnotify_access(file_in);
        fsnotify_modify(file_out);
        return ret;
}
EXPORT_SYMBOL(do_clone_file_range);

loff_t vfs_clone_file_range(struct file *file_in, loff_t pos_in,
                            struct file *file_out, loff_t pos_out,
                            loff_t len, unsigned int remap_flags)
{
        loff_t ret;

        file_start_write(file_out);
        ret = do_clone_file_range(file_in, pos_in, file_out, pos_out, len,
                                  remap_flags);
        file_end_write(file_out);

        return ret;
}
EXPORT_SYMBOL(vfs_clone_file_range);

loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
                                 struct file *dst_file, loff_t dst_pos,
                                 loff_t len, unsigned int remap_flags)
{
        loff_t ret;

        WARN_ON_ONCE(remap_flags & ~(REMAP_FILE_DEDUP |
                                     REMAP_FILE_CAN_SHORTEN));

        ret = mnt_want_write_file(dst_file);
        if (ret)
                return ret;

        ret = remap_verify_area(dst_file, dst_pos, len, true);
        if (ret < 0)
                goto out_drop_write;

        ret = -EINVAL;
        if (!(capable(CAP_SYS_ADMIN) || (dst_file->f_mode & FMODE_WRITE)))
                goto out_drop_write;

        ret = -EXDEV;
        if (src_file->f_path.mnt != dst_file->f_path.mnt)
                goto out_drop_write;

        ret = -EISDIR;
        if (S_ISDIR(file_inode(dst_file)->i_mode))
                goto out_drop_write;

        ret = -EINVAL;
        if (!dst_file->f_op->remap_file_range)
                goto out_drop_write;

        if (len == 0) {
                ret = 0;
                goto out_drop_write;
        }

        ret = dst_file->f_op->remap_file_range(src_file, src_pos, dst_file,
                        dst_pos, len, remap_flags | REMAP_FILE_DEDUP);
out_drop_write:
        mnt_drop_write_file(dst_file);

        return ret;
}
EXPORT_SYMBOL(vfs_dedupe_file_range_one);

int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
{
        struct file_dedupe_range_info *info;
        struct inode *src = file_inode(file);
        u64 off;
        u64 len;
        int i;
        int ret;
        u16 count = same->dest_count;
        loff_t deduped;

        if (!(file->f_mode & FMODE_READ))
                return -EINVAL;

        if (same->reserved1 || same->reserved2)
                return -EINVAL;

        off = same->src_offset;
        len = same->src_length;

        if (S_ISDIR(src->i_mode))
                return -EISDIR;

        if (!S_ISREG(src->i_mode))
                return -EINVAL;

        if (!file->f_op->remap_file_range)
                return -EOPNOTSUPP;

        ret = remap_verify_area(file, off, len, false);
        if (ret < 0)
                return ret;
        ret = 0;

        if (off + len > i_size_read(src))
                return -EINVAL;

        /* Arbitrary 1G limit on a single dedupe request, can be raised. */
        len = min_t(u64, len, 1 << 30);

        /* pre-format output fields to sane values */
        for (i = 0; i < count; i++) {
                same->info[i].bytes_deduped = 0ULL;
                same->info[i].status = FILE_DEDUPE_RANGE_SAME;
        }

        for (i = 0, info = same->info; i < count; i++, info++) {
                struct fd dst_fd = fdget(info->dest_fd);
                struct file *dst_file = dst_fd.file;

                if (!dst_file) {
                        info->status = -EBADF;
                        goto next_loop;
                }

                if (info->reserved) {
                        info->status = -EINVAL;
                        goto next_fdput;
                }

                deduped = vfs_dedupe_file_range_one(file, off, dst_file,
                                                    info->dest_offset, len,
                                                    REMAP_FILE_CAN_SHORTEN);
                if (deduped == -EBADE)
                        info->status = FILE_DEDUPE_RANGE_DIFFERS;
                else if (deduped < 0)
                        info->status = deduped;
                else
                        info->bytes_deduped = len;

next_fdput:
                fdput(dst_fd);
next_loop:
                if (fatal_signal_pending(current))
                        break;
        }
        return ret;
}
EXPORT_SYMBOL(vfs_dedupe_file_range);