// SPDX-License-Identifier: GPL-2.0
/*
 * File operations for Coda.
 * Original version: (C) 1996 Peter Braam 
 * Rewritten for Linux 2.1: (C) 1997 Carnegie Mellon University
 *
 * Carnegie Mellon encourages users of this code to contribute improvements
 * to the Coda project. Contact Peter Braam <coda@cs.cmu.edu>.
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/stat.h>
#include <linux/cred.h>
#include <linux/errno.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/uio.h>

#include <linux/coda.h>
#include "coda_psdev.h"
#include "coda_linux.h"
#include "coda_int.h"

struct coda_vm_ops {
        atomic_t refcnt;
        struct file *coda_file;
        const struct vm_operations_struct *host_vm_ops;
        struct vm_operations_struct vm_ops;
};

static ssize_t
coda_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *coda_file = iocb->ki_filp;
        struct inode *coda_inode = file_inode(coda_file);
        struct coda_file_info *cfi = coda_ftoc(coda_file);
        loff_t ki_pos = iocb->ki_pos;
        size_t count = iov_iter_count(to);
        ssize_t ret;

        ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
                                  &cfi->cfi_access_intent,
                                  count, ki_pos, CODA_ACCESS_TYPE_READ);
        if (ret)
                goto finish_read;

        ret = vfs_iter_read(cfi->cfi_container, to, &iocb->ki_pos, 0);

finish_read:
        venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
                            &cfi->cfi_access_intent,
                            count, ki_pos, CODA_ACCESS_TYPE_READ_FINISH);
        return ret;
}

static ssize_t
coda_file_write_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *coda_file = iocb->ki_filp;
        struct inode *coda_inode = file_inode(coda_file);
        struct coda_file_info *cfi = coda_ftoc(coda_file);
        struct file *host_file = cfi->cfi_container;
        loff_t ki_pos = iocb->ki_pos;
        size_t count = iov_iter_count(to);
        ssize_t ret;

        ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
                                  &cfi->cfi_access_intent,
                                  count, ki_pos, CODA_ACCESS_TYPE_WRITE);
        if (ret)
                goto finish_write;

        file_start_write(host_file);
        inode_lock(coda_inode);
        ret = vfs_iter_write(cfi->cfi_container, to, &iocb->ki_pos, 0);
        coda_inode->i_size = file_inode(host_file)->i_size;
        coda_inode->i_blocks = (coda_inode->i_size + 511) >> 9;
        coda_inode->i_mtime = coda_inode->i_ctime = current_time(coda_inode);
        inode_unlock(coda_inode);
        file_end_write(host_file);

finish_write:
        venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
                            &cfi->cfi_access_intent,
                            count, ki_pos, CODA_ACCESS_TYPE_WRITE_FINISH);
        return ret;
}

static void
coda_vm_open(struct vm_area_struct *vma)
{
        struct coda_vm_ops *cvm_ops =
                container_of(vma->vm_ops, struct coda_vm_ops, vm_ops);

        atomic_inc(&cvm_ops->refcnt);

        if (cvm_ops->host_vm_ops && cvm_ops->host_vm_ops->open)
                cvm_ops->host_vm_ops->open(vma);
}

static void
coda_vm_close(struct vm_area_struct *vma)
{
        struct coda_vm_ops *cvm_ops =
                container_of(vma->vm_ops, struct coda_vm_ops, vm_ops);

        if (cvm_ops->host_vm_ops && cvm_ops->host_vm_ops->close)
                cvm_ops->host_vm_ops->close(vma);

        if (atomic_dec_and_test(&cvm_ops->refcnt)) {
                vma->vm_ops = cvm_ops->host_vm_ops;
                fput(cvm_ops->coda_file);
                kfree(cvm_ops);
        }
}

static int
coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma)
{
        struct inode *coda_inode = file_inode(coda_file);
        struct coda_file_info *cfi = coda_ftoc(coda_file);
        struct file *host_file = cfi->cfi_container;
        struct inode *host_inode = file_inode(host_file);
        struct coda_inode_info *cii;
        struct coda_vm_ops *cvm_ops;
        loff_t ppos;
        size_t count;
        int ret;

        if (!host_file->f_op->mmap)
                return -ENODEV;

        if (WARN_ON(coda_file != vma->vm_file))
                return -EIO;

        count = vma->vm_end - vma->vm_start;
        ppos = vma->vm_pgoff * PAGE_SIZE;

        ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
                                  &cfi->cfi_access_intent,
                                  count, ppos, CODA_ACCESS_TYPE_MMAP);
        if (ret)
                return ret;

        cvm_ops = kmalloc(sizeof(struct coda_vm_ops), GFP_KERNEL);
        if (!cvm_ops)
                return -ENOMEM;

        cii = ITOC(coda_inode);
        spin_lock(&cii->c_lock);
        coda_file->f_mapping = host_file->f_mapping;
        if (coda_inode->i_mapping == &coda_inode->i_data)
                coda_inode->i_mapping = host_inode->i_mapping;

        /* only allow additional mmaps as long as userspace isn't changing
         * the container file on us! */
        else if (coda_inode->i_mapping != host_inode->i_mapping) {
                spin_unlock(&cii->c_lock);
                kfree(cvm_ops);
                return -EBUSY;
        }

        /* keep track of how often the coda_inode/host_file has been mmapped */
        cii->c_mapcount++;
        cfi->cfi_mapcount++;
        spin_unlock(&cii->c_lock);

        vma->vm_file = get_file(host_file);
        ret = call_mmap(vma->vm_file, vma);

        if (ret) {
                /* if call_mmap fails, our caller will put host_file so we
                 * should drop the reference to the coda_file that we got.
                 */
                fput(coda_file);
                kfree(cvm_ops);
        } else {
                /* here we add redirects for the open/close vm_operations */
                cvm_ops->host_vm_ops = vma->vm_ops;
                if (vma->vm_ops)
                        cvm_ops->vm_ops = *vma->vm_ops;

                cvm_ops->vm_ops.open = coda_vm_open;
                cvm_ops->vm_ops.close = coda_vm_close;
                cvm_ops->coda_file = coda_file;
                atomic_set(&cvm_ops->refcnt, 1);

                vma->vm_ops = &cvm_ops->vm_ops;
        }
        return ret;
}

int coda_open(struct inode *coda_inode, struct file *coda_file)
{
        struct file *host_file = NULL;
        int error;
        unsigned short flags = coda_file->f_flags & (~O_EXCL);
        unsigned short coda_flags = coda_flags_to_cflags(flags);
        struct coda_file_info *cfi;

        cfi = kmalloc(sizeof(struct coda_file_info), GFP_KERNEL);
        if (!cfi)
                return -ENOMEM;

        error = venus_open(coda_inode->i_sb, coda_i2f(coda_inode), coda_flags,
                           &host_file);
        if (!host_file)
                error = -EIO;

        if (error) {
                kfree(cfi);
                return error;
        }

        host_file->f_flags |= coda_file->f_flags & (O_APPEND | O_SYNC);

        cfi->cfi_magic = CODA_MAGIC;
        cfi->cfi_mapcount = 0;
        cfi->cfi_container = host_file;
        /* assume access intents are supported unless we hear otherwise */
        cfi->cfi_access_intent = true;

        BUG_ON(coda_file->private_data != NULL);
        coda_file->private_data = cfi;
        return 0;
}

int coda_release(struct inode *coda_inode, struct file *coda_file)
{
        unsigned short flags = (coda_file->f_flags) & (~O_EXCL);
        unsigned short coda_flags = coda_flags_to_cflags(flags);
        struct coda_file_info *cfi;
        struct coda_inode_info *cii;
        struct inode *host_inode;
        int err;

        cfi = coda_ftoc(coda_file);

        err = venus_close(coda_inode->i_sb, coda_i2f(coda_inode),
                          coda_flags, coda_file->f_cred->fsuid);

        host_inode = file_inode(cfi->cfi_container);
        cii = ITOC(coda_inode);

        /* did we mmap this file? */
        spin_lock(&cii->c_lock);
        if (coda_inode->i_mapping == &host_inode->i_data) {
                cii->c_mapcount -= cfi->cfi_mapcount;
                if (!cii->c_mapcount)
                        coda_inode->i_mapping = &coda_inode->i_data;
        }
        spin_unlock(&cii->c_lock);

        fput(cfi->cfi_container);
        kfree(coda_file->private_data);
        coda_file->private_data = NULL;

        /* VFS fput ignores the return value from file_operations->release, so
         * there is no use returning an error here */
        return 0;
}

int coda_fsync(struct file *coda_file, loff_t start, loff_t end, int datasync)
{
        struct file *host_file;
        struct inode *coda_inode = file_inode(coda_file);
        struct coda_file_info *cfi;
        int err;

        if (!(S_ISREG(coda_inode->i_mode) || S_ISDIR(coda_inode->i_mode) ||
              S_ISLNK(coda_inode->i_mode)))
                return -EINVAL;

        err = filemap_write_and_wait_range(coda_inode->i_mapping, start, end);
        if (err)
                return err;
        inode_lock(coda_inode);

        cfi = coda_ftoc(coda_file);
        host_file = cfi->cfi_container;

        err = vfs_fsync(host_file, datasync);
        if (!err && !datasync)
                err = venus_fsync(coda_inode->i_sb, coda_i2f(coda_inode));
        inode_unlock(coda_inode);

        return err;
}

const struct file_operations coda_file_operations = {
        .llseek         = generic_file_llseek,
        .read_iter      = coda_file_read_iter,
        .write_iter     = coda_file_write_iter,
        .mmap           = coda_file_mmap,
        .open           = coda_open,
        .release        = coda_release,
        .fsync          = coda_fsync,
        .splice_read    = generic_file_splice_read,
};