// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/net.h>
#include <linux/io_uring.h>

#include "io_uring.h"
#include "notif.h"
#include "rsrc.h"

static const struct ubuf_info_ops io_ubuf_ops;

static void io_notif_tw_complete(struct io_tw_req tw_req, io_tw_token_t tw)
{
        struct io_kiocb *notif = tw_req.req;
        struct io_notif_data *nd = io_notif_to_data(notif);
        struct io_ring_ctx *ctx = notif->ctx;

        lockdep_assert_held(&ctx->uring_lock);

        do {
                notif = cmd_to_io_kiocb(nd);

                if (WARN_ON_ONCE(ctx != notif->ctx))
                        return;
                lockdep_assert(refcount_read(&nd->uarg.refcnt) == 0);

                if (unlikely(nd->zc_report) && (nd->zc_copied || !nd->zc_used))
                        notif->cqe.res |= IORING_NOTIF_USAGE_ZC_COPIED;

                if (nd->account_pages && notif->ctx->user) {
                        __io_unaccount_mem(notif->ctx->user, nd->account_pages);
                        nd->account_pages = 0;
                }

                nd = nd->next;
                io_req_task_complete((struct io_tw_req){notif}, tw);
        } while (nd);
}

void io_tx_ubuf_complete(struct sk_buff *skb, struct ubuf_info *uarg,
                         bool success)
{
        struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
        struct io_kiocb *notif = cmd_to_io_kiocb(nd);
        unsigned tw_flags;

        if (nd->zc_report) {
                if (success && !nd->zc_used && skb)
                        WRITE_ONCE(nd->zc_used, true);
                else if (!success && !nd->zc_copied)
                        WRITE_ONCE(nd->zc_copied, true);
        }

        if (!refcount_dec_and_test(&uarg->refcnt))
                return;

        if (nd->head != nd) {
                io_tx_ubuf_complete(skb, &nd->head->uarg, success);
                return;
        }

        tw_flags = nd->next ? 0 : IOU_F_TWQ_LAZY_WAKE;
        notif->io_task_work.func = io_notif_tw_complete;
        __io_req_task_work_add(notif, tw_flags);
}

static int io_link_skb(struct sk_buff *skb, struct ubuf_info *uarg)
{
        struct io_notif_data *nd, *prev_nd;
        struct io_kiocb *prev_notif, *notif;
        struct ubuf_info *prev_uarg = skb_zcopy(skb);

        nd = container_of(uarg, struct io_notif_data, uarg);
        notif = cmd_to_io_kiocb(nd);

        if (!prev_uarg) {
                net_zcopy_get(&nd->uarg);
                skb_zcopy_init(skb, &nd->uarg);
                return 0;
        }
        /* handle it separately as we can't link a notif to itself */
        if (unlikely(prev_uarg == &nd->uarg))
                return 0;
        /* we can't join two links together, just request a fresh skb */
        if (unlikely(nd->head != nd || nd->next))
                return -EEXIST;
        /* don't mix zc providers */
        if (unlikely(prev_uarg->ops != &io_ubuf_ops))
                return -EEXIST;

        prev_nd = container_of(prev_uarg, struct io_notif_data, uarg);
        prev_notif = cmd_to_io_kiocb(prev_nd);

        /* make sure all notifications can be finished in the same task_work */
        if (unlikely(notif->ctx != prev_notif->ctx ||
                     notif->tctx != prev_notif->tctx))
                return -EEXIST;

        nd->head = prev_nd->head;
        nd->next = prev_nd->next;
        prev_nd->next = nd;
        net_zcopy_get(&nd->head->uarg);
        return 0;
}

static const struct ubuf_info_ops io_ubuf_ops = {
        .complete = io_tx_ubuf_complete,
        .link_skb = io_link_skb,
};

struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        struct io_kiocb *notif;
        struct io_notif_data *nd;

        if (unlikely(!io_alloc_req(ctx, &notif)))
                return NULL;
        notif->ctx = ctx;
        notif->opcode = IORING_OP_NOP;
        notif->flags = 0;
        notif->file = NULL;
        notif->tctx = current->io_uring;
        io_get_task_refs(1);
        notif->file_node = NULL;
        notif->buf_node = NULL;

        nd = io_notif_to_data(notif);
        nd->zc_report = false;
        nd->account_pages = 0;
        nd->next = NULL;
        nd->head = nd;

        nd->uarg.flags = IO_NOTIF_UBUF_FLAGS;
        nd->uarg.ops = &io_ubuf_ops;
        refcount_set(&nd->uarg.refcnt, 1);
        return notif;
}