// SPDX-License-Identifier: GPL-2.0-only
/* Object lifetime handling and tracing.
 *
 * Copyright (C) 2022 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/delay.h>
#include "internal.h"

static void netfs_free_request(struct work_struct *work);

/*
 * Allocate an I/O request and initialise it.
 */
struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
                                             struct file *file,
                                             loff_t start, size_t len,
                                             enum netfs_io_origin origin)
{
        static atomic_t debug_ids;
        struct inode *inode = file ? file_inode(file) : mapping->host;
        struct netfs_inode *ctx = netfs_inode(inode);
        struct netfs_io_request *rreq;
        mempool_t *mempool = ctx->ops->request_pool ?: &netfs_request_pool;
        struct kmem_cache *cache = mempool->pool_data;
        int ret;

        for (;;) {
                rreq = mempool_alloc(mempool, GFP_KERNEL);
                if (rreq)
                        break;
                msleep(10);
        }

        memset(rreq, 0, kmem_cache_size(cache));
        INIT_WORK(&rreq->cleanup_work, netfs_free_request);
        rreq->start     = start;
        rreq->len       = len;
        rreq->origin    = origin;
        rreq->netfs_ops = ctx->ops;
        rreq->mapping   = mapping;
        rreq->inode     = inode;
        rreq->i_size    = i_size_read(inode);
        rreq->debug_id  = atomic_inc_return(&debug_ids);
        rreq->wsize     = INT_MAX;
        rreq->io_streams[0].sreq_max_len = ULONG_MAX;
        rreq->io_streams[0].sreq_max_segs = 0;
        spin_lock_init(&rreq->lock);
        INIT_LIST_HEAD(&rreq->io_streams[0].subrequests);
        INIT_LIST_HEAD(&rreq->io_streams[1].subrequests);
        init_waitqueue_head(&rreq->waitq);
        refcount_set(&rreq->ref, 2);

        if (origin == NETFS_READAHEAD ||
            origin == NETFS_READPAGE ||
            origin == NETFS_READ_GAPS ||
            origin == NETFS_READ_SINGLE ||
            origin == NETFS_READ_FOR_WRITE ||
            origin == NETFS_UNBUFFERED_READ ||
            origin == NETFS_DIO_READ) {
                INIT_WORK(&rreq->work, netfs_read_collection_worker);
                rreq->io_streams[0].avail = true;
        } else {
                INIT_WORK(&rreq->work, netfs_write_collection_worker);
        }

        __set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
        if (rreq->netfs_ops->init_request) {
                ret = rreq->netfs_ops->init_request(rreq, file);
                if (ret < 0) {
                        mempool_free(rreq, rreq->netfs_ops->request_pool ?: &netfs_request_pool);
                        return ERR_PTR(ret);
                }
        }

        atomic_inc(&ctx->io_count);
        trace_netfs_rreq_ref(rreq->debug_id, refcount_read(&rreq->ref), netfs_rreq_trace_new);
        netfs_proc_add_rreq(rreq);
        netfs_stat(&netfs_n_rh_rreq);
        return rreq;
}

void netfs_get_request(struct netfs_io_request *rreq, enum netfs_rreq_ref_trace what)
{
        int r;

        __refcount_inc(&rreq->ref, &r);
        trace_netfs_rreq_ref(rreq->debug_id, r + 1, what);
}

void netfs_clear_subrequests(struct netfs_io_request *rreq)
{
        struct netfs_io_subrequest *subreq;
        struct netfs_io_stream *stream;
        int s;

        for (s = 0; s < ARRAY_SIZE(rreq->io_streams); s++) {
                stream = &rreq->io_streams[s];
                while (!list_empty(&stream->subrequests)) {
                        subreq = list_first_entry(&stream->subrequests,
                                                  struct netfs_io_subrequest, rreq_link);
                        list_del(&subreq->rreq_link);
                        netfs_put_subrequest(subreq, netfs_sreq_trace_put_clear);
                }
        }
}

static void netfs_free_request_rcu(struct rcu_head *rcu)
{
        struct netfs_io_request *rreq = container_of(rcu, struct netfs_io_request, rcu);

        mempool_free(rreq, rreq->netfs_ops->request_pool ?: &netfs_request_pool);
        netfs_stat_d(&netfs_n_rh_rreq);
}

static void netfs_deinit_request(struct netfs_io_request *rreq)
{
        struct netfs_inode *ictx = netfs_inode(rreq->inode);
        unsigned int i;

        trace_netfs_rreq(rreq, netfs_rreq_trace_free);

        /* Cancel/flush the result collection worker.  That does not carry a
         * ref of its own, so we must wait for it somewhere.
         */
        cancel_work_sync(&rreq->work);

        netfs_proc_del_rreq(rreq);
        netfs_clear_subrequests(rreq);
        if (rreq->netfs_ops->free_request)
                rreq->netfs_ops->free_request(rreq);
        if (rreq->cache_resources.ops)
                rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
        if (rreq->direct_bv) {
                for (i = 0; i < rreq->direct_bv_count; i++) {
                        if (rreq->direct_bv[i].bv_page) {
                                if (rreq->direct_bv_unpin)
                                        unpin_user_page(rreq->direct_bv[i].bv_page);
                        }
                }
                kvfree(rreq->direct_bv);
        }
        rolling_buffer_clear(&rreq->buffer);

        if (atomic_dec_and_test(&ictx->io_count))
                wake_up_var(&ictx->io_count);
}

static void netfs_free_request(struct work_struct *work)
{
        struct netfs_io_request *rreq =
                container_of(work, struct netfs_io_request, cleanup_work);

        netfs_deinit_request(rreq);
        call_rcu(&rreq->rcu, netfs_free_request_rcu);
}

void netfs_put_request(struct netfs_io_request *rreq, enum netfs_rreq_ref_trace what)
{
        unsigned int debug_id;
        bool dead;
        int r;

        if (rreq) {
                debug_id = rreq->debug_id;
                dead = __refcount_dec_and_test(&rreq->ref, &r);
                trace_netfs_rreq_ref(debug_id, r - 1, what);
                if (dead)
                        WARN_ON(!queue_work(system_dfl_wq, &rreq->cleanup_work));
        }
}

/*
 * Free a request (synchronously) that was just allocated but has
 * failed before it could be submitted.
 */
void netfs_put_failed_request(struct netfs_io_request *rreq)
{
        int r = refcount_read(&rreq->ref);

        /* new requests have two references (see
         * netfs_alloc_request(), and this function is only allowed on
         * new request objects
         */
        WARN_ON_ONCE(r != 2);

        trace_netfs_rreq_ref(rreq->debug_id, r, netfs_rreq_trace_put_failed);
        netfs_free_request(&rreq->cleanup_work);
}

/*
 * Allocate and partially initialise an I/O request structure.
 */
struct netfs_io_subrequest *netfs_alloc_subrequest(struct netfs_io_request *rreq)
{
        struct netfs_io_subrequest *subreq;
        mempool_t *mempool = rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool;
        struct kmem_cache *cache = mempool->pool_data;

        for (;;) {
                subreq = mempool_alloc(rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool,
                                       GFP_KERNEL);
                if (subreq)
                        break;
                msleep(10);
        }

        memset(subreq, 0, kmem_cache_size(cache));
        INIT_WORK(&subreq->work, NULL);
        INIT_LIST_HEAD(&subreq->rreq_link);
        refcount_set(&subreq->ref, 2);
        subreq->rreq = rreq;
        subreq->debug_index = atomic_inc_return(&rreq->subreq_counter);
        netfs_get_request(rreq, netfs_rreq_trace_get_subreq);
        netfs_stat(&netfs_n_rh_sreq);
        return subreq;
}

void netfs_get_subrequest(struct netfs_io_subrequest *subreq,
                          enum netfs_sreq_ref_trace what)
{
        int r;

        __refcount_inc(&subreq->ref, &r);
        trace_netfs_sreq_ref(subreq->rreq->debug_id, subreq->debug_index, r + 1,
                             what);
}

static void netfs_free_subrequest(struct netfs_io_subrequest *subreq)
{
        struct netfs_io_request *rreq = subreq->rreq;

        trace_netfs_sreq(subreq, netfs_sreq_trace_free);
        if (rreq->netfs_ops->free_subrequest)
                rreq->netfs_ops->free_subrequest(subreq);
        mempool_free(subreq, rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool);
        netfs_stat_d(&netfs_n_rh_sreq);
        netfs_put_request(rreq, netfs_rreq_trace_put_subreq);
}

void netfs_put_subrequest(struct netfs_io_subrequest *subreq,
                          enum netfs_sreq_ref_trace what)
{
        unsigned int debug_index = subreq->debug_index;
        unsigned int debug_id = subreq->rreq->debug_id;
        bool dead;
        int r;

        dead = __refcount_dec_and_test(&subreq->ref, &r);
        trace_netfs_sreq_ref(debug_id, debug_index, r - 1, what);
        if (dead)
                netfs_free_subrequest(subreq);
}