// SPDX-License-Identifier: GPL-2.0-only
/*
 * This file contians vfs address (mmap) ops for 9P2000.
 *
 *  Copyright (C) 2005 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/file.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/pagemap.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/uio.h>
#include <linux/netfs.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include <trace/events/netfs.h>

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

/*
 * Writeback calls this when it finds a folio that needs uploading.  This isn't
 * called if writeback only has copy-to-cache to deal with.
 */
static void v9fs_begin_writeback(struct netfs_io_request *wreq)
{
        struct p9_fid *fid;

        fid = v9fs_fid_find_inode(wreq->inode, true, INVALID_UID, true);
        if (!fid) {
                WARN_ONCE(1, "folio expected an open fid inode->i_ino=%lx\n",
                          wreq->inode->i_ino);
                return;
        }

        wreq->wsize = fid->clnt->msize - P9_IOHDRSZ;
        if (fid->iounit)
                wreq->wsize = min(wreq->wsize, fid->iounit);
        wreq->netfs_priv = fid;
        wreq->io_streams[0].avail = true;
}

/*
 * Issue a subrequest to write to the server.
 */
static void v9fs_issue_write(struct netfs_io_subrequest *subreq)
{
        struct p9_fid *fid = subreq->rreq->netfs_priv;
        int err, len;

        len = p9_client_write(fid, subreq->start, &subreq->io_iter, &err);
        if (len > 0)
                __set_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);
        netfs_write_subrequest_terminated(subreq, len ?: err);
}

/**
 * v9fs_issue_read - Issue a read from 9P
 * @subreq: The read to make
 */
static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
{
        struct netfs_io_request *rreq = subreq->rreq;
        struct p9_fid *fid = rreq->netfs_priv;
        unsigned long long pos = subreq->start + subreq->transferred;
        int total, err;

        total = p9_client_read(fid, pos, &subreq->io_iter, &err);

        /* if we just extended the file size, any portion not in
         * cache won't be on server and is zeroes */
        if (subreq->rreq->origin != NETFS_UNBUFFERED_READ &&
            subreq->rreq->origin != NETFS_DIO_READ)
                __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
        if (pos + total >= i_size_read(rreq->inode))
                __set_bit(NETFS_SREQ_HIT_EOF, &subreq->flags);
        if (!err && total) {
                subreq->transferred += total;
                __set_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);
        }

        subreq->error = err;
        netfs_read_subreq_terminated(subreq);
}

/**
 * v9fs_init_request - Initialise a request
 * @rreq: The read request
 * @file: The file being read from
 */
static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
{
        struct p9_fid *fid;
        bool writing = (rreq->origin == NETFS_READ_FOR_WRITE ||
                        rreq->origin == NETFS_WRITETHROUGH ||
                        rreq->origin == NETFS_UNBUFFERED_WRITE ||
                        rreq->origin == NETFS_DIO_WRITE);

        if (rreq->origin == NETFS_WRITEBACK)
                return 0; /* We don't get the write handle until we find we
                           * have actually dirty data and not just
                           * copy-to-cache data.
                           */

        if (file) {
                fid = file->private_data;
                if (!fid)
                        goto no_fid;
                p9_fid_get(fid);
        } else {
                fid = v9fs_fid_find_inode(rreq->inode, writing, INVALID_UID, true);
                if (!fid)
                        goto no_fid;
        }

        rreq->wsize = fid->clnt->msize - P9_IOHDRSZ;
        if (fid->iounit)
                rreq->wsize = min(rreq->wsize, fid->iounit);

        /* we might need to read from a fid that was opened write-only
         * for read-modify-write of page cache, use the writeback fid
         * for that */
        WARN_ON(rreq->origin == NETFS_READ_FOR_WRITE && !(fid->mode & P9_ORDWR));
        rreq->netfs_priv = fid;
        return 0;

no_fid:
        WARN_ONCE(1, "folio expected an open fid inode->i_ino=%lx\n",
                  rreq->inode->i_ino);
        return -EINVAL;
}

/**
 * v9fs_free_request - Cleanup request initialized by v9fs_init_rreq
 * @rreq: The I/O request to clean up
 */
static void v9fs_free_request(struct netfs_io_request *rreq)
{
        struct p9_fid *fid = rreq->netfs_priv;

        p9_fid_put(fid);
}

const struct netfs_request_ops v9fs_req_ops = {
        .init_request           = v9fs_init_request,
        .free_request           = v9fs_free_request,
        .issue_read             = v9fs_issue_read,
        .begin_writeback        = v9fs_begin_writeback,
        .issue_write            = v9fs_issue_write,
};

const struct address_space_operations v9fs_addr_operations = {
        .read_folio             = netfs_read_folio,
        .readahead              = netfs_readahead,
        .dirty_folio            = netfs_dirty_folio,
        .release_folio          = netfs_release_folio,
        .invalidate_folio       = netfs_invalidate_folio,
        .direct_IO              = noop_direct_IO,
        .writepages             = netfs_writepages,
        .migrate_folio          = filemap_migrate_folio,
};