// SPDX-License-Identifier: GPL-2.0-only
/*
 * This file contians vfs file ops for 9P2000.
 *
 *  Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
 *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/filelock.h>
#include <linux/sched.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/pagemap.h>
#include <linux/utsname.h>
#include <linux/uaccess.h>
#include <linux/uio.h>
#include <linux/slab.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>

#include "v9fs.h"
#include "v9fs_vfs.h"
#include "fid.h"
#include "cache.h"

static const struct vm_operations_struct v9fs_mmap_file_vm_ops;

/**
 * v9fs_file_open - open a file (or directory)
 * @inode: inode to be opened
 * @file: file being opened
 *
 */

int v9fs_file_open(struct inode *inode, struct file *file)
{
        int err;
        struct v9fs_session_info *v9ses;
        struct p9_fid *fid;
        int omode;
        int o_append;

        p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, file);
        v9ses = v9fs_inode2v9ses(inode);
        if (v9fs_proto_dotl(v9ses)) {
                omode = v9fs_open_to_dotl_flags(file->f_flags);
                o_append = P9_DOTL_APPEND;
        } else {
                omode = v9fs_uflags2omode(file->f_flags,
                                        v9fs_proto_dotu(v9ses));
                o_append = P9_OAPPEND;
        }
        fid = file->private_data;
        if (!fid) {
                fid = v9fs_fid_clone(file_dentry(file));
                if (IS_ERR(fid))
                        return PTR_ERR(fid);

                if ((v9ses->cache & CACHE_WRITEBACK) && (omode & P9_OWRITE)) {
                        int writeback_omode = (omode & ~(P9_OWRITE | o_append)) | P9_ORDWR;

                        p9_debug(P9_DEBUG_CACHE, "write-only file with writeback enabled, try opening O_RDWR\n");

                        err = p9_client_open(fid, writeback_omode);
                        if (err < 0) {
                                p9_debug(P9_DEBUG_CACHE, "could not open O_RDWR, disabling caches\n");
                                err = p9_client_open(fid, omode);
                                fid->mode |= P9L_DIRECT;
                        }
                } else {
                        err = p9_client_open(fid, omode);
                }
                if (err < 0) {
                        p9_fid_put(fid);
                        return err;
                }
                if ((file->f_flags & O_APPEND) &&
                        (!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses)))
                        generic_file_llseek(file, 0, SEEK_END);

                file->private_data = fid;
        }

#ifdef CONFIG_9P_FSCACHE
        if (v9ses->cache & CACHE_FSCACHE)
                fscache_use_cookie(v9fs_inode_cookie(V9FS_I(inode)),
                                   file->f_mode & FMODE_WRITE);
#endif
        v9fs_fid_add_modes(fid, v9ses->flags, v9ses->cache, file->f_flags);
        v9fs_open_fid_add(inode, &fid);
        return 0;
}

/**
 * v9fs_file_lock - lock a file (or directory)
 * @filp: file to be locked
 * @cmd: lock command
 * @fl: file lock structure
 *
 * Bugs: this looks like a local only lock, we should extend into 9P
 *       by using open exclusive
 */

static int v9fs_file_lock(struct file *filp, int cmd, struct file_lock *fl)
{
        struct inode *inode = file_inode(filp);

        p9_debug(P9_DEBUG_VFS, "filp: %p lock: %p\n", filp, fl);

        if ((IS_SETLK(cmd) || IS_SETLKW(cmd)) && fl->c.flc_type != F_UNLCK) {
                filemap_write_and_wait(inode->i_mapping);
                invalidate_mapping_pages(&inode->i_data, 0, -1);
        }

        return 0;
}

static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
{
        struct p9_flock flock;
        struct p9_fid *fid;
        uint8_t status = P9_LOCK_ERROR;
        int res = 0;
        struct v9fs_session_info *v9ses;

        fid = filp->private_data;
        BUG_ON(fid == NULL);

        BUG_ON((fl->c.flc_flags & FL_POSIX) != FL_POSIX);

        res = locks_lock_file_wait(filp, fl);
        if (res < 0)
                goto out;

        /* convert posix lock to p9 tlock args */
        memset(&flock, 0, sizeof(flock));
        /* map the lock type */
        switch (fl->c.flc_type) {
        case F_RDLCK:
                flock.type = P9_LOCK_TYPE_RDLCK;
                break;
        case F_WRLCK:
                flock.type = P9_LOCK_TYPE_WRLCK;
                break;
        case F_UNLCK:
                flock.type = P9_LOCK_TYPE_UNLCK;
                break;
        }
        flock.start = fl->fl_start;
        if (fl->fl_end == OFFSET_MAX)
                flock.length = 0;
        else
                flock.length = fl->fl_end - fl->fl_start + 1;
        flock.proc_id = fl->c.flc_pid;
        flock.client_id = fid->clnt->name;
        if (IS_SETLKW(cmd))
                flock.flags = P9_LOCK_FLAGS_BLOCK;

        v9ses = v9fs_inode2v9ses(file_inode(filp));

        /*
         * if its a blocked request and we get P9_LOCK_BLOCKED as the status
         * for lock request, keep on trying
         */
        for (;;) {
                res = p9_client_lock_dotl(fid, &flock, &status);
                if (res < 0)
                        goto out_unlock;

                if (status != P9_LOCK_BLOCKED)
                        break;
                if (status == P9_LOCK_BLOCKED && !IS_SETLKW(cmd))
                        break;
                if (schedule_timeout_interruptible(v9ses->session_lock_timeout)
                                != 0)
                        break;
                /*
                 * p9_client_lock_dotl overwrites flock.client_id with the
                 * server message, free and reuse the client name
                 */
                if (flock.client_id != fid->clnt->name) {
                        kfree(flock.client_id);
                        flock.client_id = fid->clnt->name;
                }
        }

        /* map 9p status to VFS status */
        switch (status) {
        case P9_LOCK_SUCCESS:
                res = 0;
                break;
        case P9_LOCK_BLOCKED:
                res = -EAGAIN;
                break;
        default:
                WARN_ONCE(1, "unknown lock status code: %d\n", status);
                fallthrough;
        case P9_LOCK_ERROR:
        case P9_LOCK_GRACE:
                res = -ENOLCK;
                break;
        }

out_unlock:
        /*
         * incase server returned error for lock request, revert
         * it locally
         */
        if (res < 0 && fl->c.flc_type != F_UNLCK) {
                unsigned char type = fl->c.flc_type;

                fl->c.flc_type = F_UNLCK;
                /* Even if this fails we want to return the remote error */
                locks_lock_file_wait(filp, fl);
                fl->c.flc_type = type;
        }
        if (flock.client_id != fid->clnt->name)
                kfree(flock.client_id);
out:
        return res;
}

static int v9fs_file_getlock(struct file *filp, struct file_lock *fl)
{
        struct p9_getlock glock;
        struct p9_fid *fid;
        int res = 0;

        fid = filp->private_data;
        BUG_ON(fid == NULL);

        posix_test_lock(filp, fl);
        /*
         * if we have a conflicting lock locally, no need to validate
         * with server
         */
        if (fl->c.flc_type != F_UNLCK)
                return res;

        /* convert posix lock to p9 tgetlock args */
        memset(&glock, 0, sizeof(glock));
        glock.type  = P9_LOCK_TYPE_UNLCK;
        glock.start = fl->fl_start;
        if (fl->fl_end == OFFSET_MAX)
                glock.length = 0;
        else
                glock.length = fl->fl_end - fl->fl_start + 1;
        glock.proc_id = fl->c.flc_pid;
        glock.client_id = fid->clnt->name;

        res = p9_client_getlock_dotl(fid, &glock);
        if (res < 0)
                goto out;
        /* map 9p lock type to os lock type */
        switch (glock.type) {
        case P9_LOCK_TYPE_RDLCK:
                fl->c.flc_type = F_RDLCK;
                break;
        case P9_LOCK_TYPE_WRLCK:
                fl->c.flc_type = F_WRLCK;
                break;
        case P9_LOCK_TYPE_UNLCK:
                fl->c.flc_type = F_UNLCK;
                break;
        }
        if (glock.type != P9_LOCK_TYPE_UNLCK) {
                fl->fl_start = glock.start;
                if (glock.length == 0)
                        fl->fl_end = OFFSET_MAX;
                else
                        fl->fl_end = glock.start + glock.length - 1;
                fl->c.flc_pid = -glock.proc_id;
        }
out:
        if (glock.client_id != fid->clnt->name)
                kfree(glock.client_id);
        return res;
}

/**
 * v9fs_file_lock_dotl - lock a file (or directory)
 * @filp: file to be locked
 * @cmd: lock command
 * @fl: file lock structure
 *
 */

static int v9fs_file_lock_dotl(struct file *filp, int cmd, struct file_lock *fl)
{
        struct inode *inode = file_inode(filp);
        int ret = -ENOLCK;

        p9_debug(P9_DEBUG_VFS, "filp: %p cmd:%d lock: %p name: %pD\n",
                 filp, cmd, fl, filp);

        if ((IS_SETLK(cmd) || IS_SETLKW(cmd)) && fl->c.flc_type != F_UNLCK) {
                filemap_write_and_wait(inode->i_mapping);
                invalidate_mapping_pages(&inode->i_data, 0, -1);
        }

        if (IS_SETLK(cmd) || IS_SETLKW(cmd))
                ret = v9fs_file_do_lock(filp, cmd, fl);
        else if (IS_GETLK(cmd))
                ret = v9fs_file_getlock(filp, fl);
        else
                ret = -EINVAL;
        return ret;
}

/**
 * v9fs_file_flock_dotl - lock a file
 * @filp: file to be locked
 * @cmd: lock command
 * @fl: file lock structure
 *
 */

static int v9fs_file_flock_dotl(struct file *filp, int cmd,
        struct file_lock *fl)
{
        struct inode *inode = file_inode(filp);
        int ret = -ENOLCK;

        p9_debug(P9_DEBUG_VFS, "filp: %p cmd:%d lock: %p name: %pD\n",
                 filp, cmd, fl, filp);

        if (!(fl->c.flc_flags & FL_FLOCK))
                goto out_err;

        if ((IS_SETLK(cmd) || IS_SETLKW(cmd)) && fl->c.flc_type != F_UNLCK) {
                filemap_write_and_wait(inode->i_mapping);
                invalidate_mapping_pages(&inode->i_data, 0, -1);
        }
        /* Convert flock to posix lock */
        fl->c.flc_flags |= FL_POSIX;
        fl->c.flc_flags ^= FL_FLOCK;

        if (IS_SETLK(cmd) | IS_SETLKW(cmd))
                ret = v9fs_file_do_lock(filp, cmd, fl);
        else
                ret = -EINVAL;
out_err:
        return ret;
}

/**
 * v9fs_file_read_iter - read from a file
 * @iocb: The operation parameters
 * @to: The buffer to read into
 *
 */
static ssize_t
v9fs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct p9_fid *fid = iocb->ki_filp->private_data;

        p9_debug(P9_DEBUG_VFS, "fid %d count %zu offset %lld\n",
                 fid->fid, iov_iter_count(to), iocb->ki_pos);

        if (fid->mode & P9L_DIRECT)
                return netfs_unbuffered_read_iter(iocb, to);

        p9_debug(P9_DEBUG_VFS, "(cached)\n");
        return netfs_file_read_iter(iocb, to);
}

/*
 * v9fs_file_splice_read - splice-read from a file
 * @in: The 9p file to read from
 * @ppos: Where to find/update the file position
 * @pipe: The pipe to splice into
 * @len: The maximum amount of data to splice
 * @flags: SPLICE_F_* flags
 */
static ssize_t v9fs_file_splice_read(struct file *in, loff_t *ppos,
                                     struct pipe_inode_info *pipe,
                                     size_t len, unsigned int flags)
{
        struct p9_fid *fid = in->private_data;

        p9_debug(P9_DEBUG_VFS, "fid %d count %zu offset %lld\n",
                 fid->fid, len, *ppos);

        if (fid->mode & P9L_DIRECT)
                return copy_splice_read(in, ppos, pipe, len, flags);
        return filemap_splice_read(in, ppos, pipe, len, flags);
}

/**
 * v9fs_file_write_iter - write to a file
 * @iocb: The operation parameters
 * @from: The data to write
 *
 */
static ssize_t
v9fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct file *file = iocb->ki_filp;
        struct p9_fid *fid = file->private_data;

        p9_debug(P9_DEBUG_VFS, "fid %d\n", fid->fid);

        if (fid->mode & (P9L_DIRECT | P9L_NOWRITECACHE))
                return netfs_unbuffered_write_iter(iocb, from);

        p9_debug(P9_DEBUG_CACHE, "(cached)\n");
        return netfs_file_write_iter(iocb, from);
}

static int v9fs_file_fsync(struct file *filp, loff_t start, loff_t end,
                           int datasync)
{
        struct p9_fid *fid;
        struct inode *inode = filp->f_mapping->host;
        struct p9_wstat wstat;
        int retval;

        retval = file_write_and_wait_range(filp, start, end);
        if (retval)
                return retval;

        inode_lock(inode);
        p9_debug(P9_DEBUG_VFS, "filp %p datasync %x\n", filp, datasync);

        fid = filp->private_data;
        v9fs_blank_wstat(&wstat);

        retval = p9_client_wstat(fid, &wstat);
        inode_unlock(inode);

        return retval;
}

int v9fs_file_fsync_dotl(struct file *filp, loff_t start, loff_t end,
                         int datasync)
{
        struct p9_fid *fid;
        struct inode *inode = filp->f_mapping->host;
        int retval;

        retval = file_write_and_wait_range(filp, start, end);
        if (retval)
                return retval;

        inode_lock(inode);
        p9_debug(P9_DEBUG_VFS, "filp %p datasync %x\n", filp, datasync);

        fid = filp->private_data;

        retval = p9_client_fsync(fid, datasync);
        inode_unlock(inode);

        return retval;
}

static int
v9fs_file_mmap_prepare(struct vm_area_desc *desc)
{
        int retval;
        struct file *filp = desc->file;
        struct inode *inode = file_inode(filp);
        struct v9fs_session_info *v9ses = v9fs_inode2v9ses(inode);

        p9_debug(P9_DEBUG_MMAP, "filp :%p\n", filp);

        if (!(v9ses->cache & CACHE_WRITEBACK)) {
                p9_debug(P9_DEBUG_CACHE, "(read-only mmap mode)");
                return generic_file_readonly_mmap_prepare(desc);
        }

        retval = generic_file_mmap_prepare(desc);
        if (!retval)
                desc->vm_ops = &v9fs_mmap_file_vm_ops;

        return retval;
}

static vm_fault_t
v9fs_vm_page_mkwrite(struct vm_fault *vmf)
{
        return netfs_page_mkwrite(vmf, NULL);
}

static void v9fs_mmap_vm_close(struct vm_area_struct *vma)
{
        if (!(vma->vm_flags & VM_SHARED))
                return;

        p9_debug(P9_DEBUG_VFS, "9p VMA close, %p, flushing", vma);

        filemap_fdatawrite_range(file_inode(vma->vm_file)->i_mapping,
                        (loff_t)vma->vm_pgoff * PAGE_SIZE,
                        (loff_t)vma->vm_pgoff * PAGE_SIZE +
                                (vma->vm_end - vma->vm_start - 1));
}

static const struct vm_operations_struct v9fs_mmap_file_vm_ops = {
        .close = v9fs_mmap_vm_close,
        .fault = filemap_fault,
        .map_pages = filemap_map_pages,
        .page_mkwrite = v9fs_vm_page_mkwrite,
};

const struct file_operations v9fs_file_operations = {
        .llseek = generic_file_llseek,
        .read_iter = v9fs_file_read_iter,
        .write_iter = v9fs_file_write_iter,
        .open = v9fs_file_open,
        .release = v9fs_dir_release,
        .lock = v9fs_file_lock,
        .mmap_prepare = generic_file_readonly_mmap_prepare,
        .splice_read = v9fs_file_splice_read,
        .splice_write = iter_file_splice_write,
        .fsync = v9fs_file_fsync,
};

const struct file_operations v9fs_file_operations_dotl = {
        .llseek = generic_file_llseek,
        .read_iter = v9fs_file_read_iter,
        .write_iter = v9fs_file_write_iter,
        .open = v9fs_file_open,
        .release = v9fs_dir_release,
        .lock = v9fs_file_lock_dotl,
        .flock = v9fs_file_flock_dotl,
        .mmap_prepare = v9fs_file_mmap_prepare,
        .splice_read = v9fs_file_splice_read,
        .splice_write = iter_file_splice_write,
        .fsync = v9fs_file_fsync_dotl,
};