// SPDX-License-Identifier: GPL-2.0
/*
 * (C) 2001 Clemson University and The University of Chicago
 *
 * See COPYING in top-level directory.
 */
#include "protocol.h"
#include "orangefs-kernel.h"
#include "orangefs-bufmap.h"

struct slot_map {
        int c;
        wait_queue_head_t q;
        int count;
        unsigned long *map;
};

static struct slot_map rw_map = {
        .c = -1,
        .q = __WAIT_QUEUE_HEAD_INITIALIZER(rw_map.q)
};
static struct slot_map readdir_map = {
        .c = -1,
        .q = __WAIT_QUEUE_HEAD_INITIALIZER(readdir_map.q)
};


static void install(struct slot_map *m, int count, unsigned long *map)
{
        spin_lock(&m->q.lock);
        m->c = m->count = count;
        m->map = map;
        wake_up_all_locked(&m->q);
        spin_unlock(&m->q.lock);
}

static void mark_killed(struct slot_map *m)
{
        spin_lock(&m->q.lock);
        m->c -= m->count + 1;
        spin_unlock(&m->q.lock);
}

static void run_down(struct slot_map *m)
{
        DEFINE_WAIT(wait);
        spin_lock(&m->q.lock);
        if (m->c != -1) {
                for (;;) {
                        if (likely(list_empty(&wait.entry)))
                                __add_wait_queue_entry_tail(&m->q, &wait);
                        set_current_state(TASK_UNINTERRUPTIBLE);

                        if (m->c == -1)
                                break;

                        spin_unlock(&m->q.lock);
                        schedule();
                        spin_lock(&m->q.lock);
                }
                __remove_wait_queue(&m->q, &wait);
                __set_current_state(TASK_RUNNING);
        }
        m->map = NULL;
        spin_unlock(&m->q.lock);
}

static void put(struct slot_map *m, int slot)
{
        int v;
        spin_lock(&m->q.lock);
        __clear_bit(slot, m->map);
        v = ++m->c;
        if (v > 0)
                wake_up_locked(&m->q);
        if (unlikely(v == -1))     /* finished dying */
                wake_up_all_locked(&m->q);
        spin_unlock(&m->q.lock);
}

static int wait_for_free(struct slot_map *m)
{
        long left = slot_timeout_secs * HZ;
        DEFINE_WAIT(wait);

        do {
                long n = left, t;
                if (likely(list_empty(&wait.entry)))
                        __add_wait_queue_entry_tail_exclusive(&m->q, &wait);
                set_current_state(TASK_INTERRUPTIBLE);

                if (m->c > 0)
                        break;

                if (m->c < 0) {
                        /* we are waiting for map to be installed */
                        /* it would better be there soon, or we go away */
                        if (n > ORANGEFS_BUFMAP_WAIT_TIMEOUT_SECS * HZ)
                                n = ORANGEFS_BUFMAP_WAIT_TIMEOUT_SECS * HZ;
                }
                spin_unlock(&m->q.lock);
                t = schedule_timeout(n);
                spin_lock(&m->q.lock);
                if (unlikely(!t) && n != left && m->c < 0)
                        left = t;
                else
                        left = t + (left - n);
                if (signal_pending(current))
                        left = -EINTR;
        } while (left > 0);

        if (!list_empty(&wait.entry))
                list_del(&wait.entry);
        else if (left <= 0 && waitqueue_active(&m->q))
                __wake_up_locked_key(&m->q, TASK_INTERRUPTIBLE, NULL);
        __set_current_state(TASK_RUNNING);

        if (likely(left > 0))
                return 0;

        return left < 0 ? -EINTR : -ETIMEDOUT;
}

static int get(struct slot_map *m)
{
        int res = 0;
        spin_lock(&m->q.lock);
        if (unlikely(m->c <= 0))
                res = wait_for_free(m);
        if (likely(!res)) {
                m->c--;
                res = find_first_zero_bit(m->map, m->count);
                __set_bit(res, m->map);
        }
        spin_unlock(&m->q.lock);
        return res;
}

/* used to describe mapped buffers */
struct orangefs_bufmap_desc {
        void __user *uaddr;             /* user space address pointer */
        struct page **page_array;       /* array of mapped pages */
        int array_count;                /* size of above arrays */
        struct list_head list_link;
};

static struct orangefs_bufmap {
        int desc_size;
        int desc_shift;
        int desc_count;
        int total_size;
        int page_count;

        struct page **page_array;
        struct orangefs_bufmap_desc *desc_array;

        /* array to track usage of buffer descriptors */
        unsigned long *buffer_index_array;

        /* array to track usage of buffer descriptors for readdir */
#define N DIV_ROUND_UP(ORANGEFS_READDIR_DEFAULT_DESC_COUNT, BITS_PER_LONG)
        unsigned long readdir_index_array[N];
#undef N
} *__orangefs_bufmap;

static DEFINE_SPINLOCK(orangefs_bufmap_lock);

static void
orangefs_bufmap_unmap(struct orangefs_bufmap *bufmap)
{
        int i;

        for (i = 0; i < bufmap->page_count; i++)
                put_page(bufmap->page_array[i]);
}

static void
orangefs_bufmap_free(struct orangefs_bufmap *bufmap)
{
        kfree(bufmap->page_array);
        kfree(bufmap->desc_array);
        kfree(bufmap->buffer_index_array);
        kfree(bufmap);
}

/*
 * XXX: Can the size and shift change while the caller gives up the
 * XXX: lock between calling this and doing something useful?
 */

int orangefs_bufmap_size_query(void)
{
        struct orangefs_bufmap *bufmap;
        int size = 0;
        spin_lock(&orangefs_bufmap_lock);
        bufmap = __orangefs_bufmap;
        if (bufmap)
                size = bufmap->desc_size;
        spin_unlock(&orangefs_bufmap_lock);
        return size;
}

int orangefs_bufmap_shift_query(void)
{
        struct orangefs_bufmap *bufmap;
        int shift = 0;
        spin_lock(&orangefs_bufmap_lock);
        bufmap = __orangefs_bufmap;
        if (bufmap)
                shift = bufmap->desc_shift;
        spin_unlock(&orangefs_bufmap_lock);
        return shift;
}

static DECLARE_WAIT_QUEUE_HEAD(bufmap_waitq);
static DECLARE_WAIT_QUEUE_HEAD(readdir_waitq);

static struct orangefs_bufmap *
orangefs_bufmap_alloc(struct ORANGEFS_dev_map_desc *user_desc)
{
        struct orangefs_bufmap *bufmap;

        bufmap = kzalloc(sizeof(*bufmap), GFP_KERNEL);
        if (!bufmap)
                goto out;

        bufmap->total_size = user_desc->total_size;
        bufmap->desc_count = user_desc->count;
        bufmap->desc_size = user_desc->size;
        bufmap->desc_shift = ilog2(bufmap->desc_size);

        bufmap->buffer_index_array =
                kzalloc(DIV_ROUND_UP(bufmap->desc_count, BITS_PER_LONG), GFP_KERNEL);
        if (!bufmap->buffer_index_array)
                goto out_free_bufmap;

        bufmap->desc_array =
                kcalloc(bufmap->desc_count, sizeof(struct orangefs_bufmap_desc),
                        GFP_KERNEL);
        if (!bufmap->desc_array)
                goto out_free_index_array;

        bufmap->page_count = bufmap->total_size / PAGE_SIZE;

        /* allocate storage to track our page mappings */
        bufmap->page_array =
                kcalloc(bufmap->page_count, sizeof(struct page *), GFP_KERNEL);
        if (!bufmap->page_array)
                goto out_free_desc_array;

        return bufmap;

out_free_desc_array:
        kfree(bufmap->desc_array);
out_free_index_array:
        kfree(bufmap->buffer_index_array);
out_free_bufmap:
        kfree(bufmap);
out:
        return NULL;
}

static int
orangefs_bufmap_map(struct orangefs_bufmap *bufmap,
                struct ORANGEFS_dev_map_desc *user_desc)
{
        int pages_per_desc = bufmap->desc_size / PAGE_SIZE;
        int offset = 0, ret, i;

        /* map the pages */
        ret = get_user_pages_fast((unsigned long)user_desc->ptr,
                             bufmap->page_count, FOLL_WRITE, bufmap->page_array);

        if (ret < 0)
                return ret;

        if (ret != bufmap->page_count) {
                gossip_err("orangefs error: asked for %d pages, only got %d.\n",
                                bufmap->page_count, ret);

                for (i = 0; i < ret; i++) {
                        SetPageError(bufmap->page_array[i]);
                        put_page(bufmap->page_array[i]);
                }
                return -ENOMEM;
        }

        /*
         * ideally we want to get kernel space pointers for each page, but
         * we can't kmap that many pages at once if highmem is being used.
         * so instead, we just kmap/kunmap the page address each time the
         * kaddr is needed.
         */
        for (i = 0; i < bufmap->page_count; i++)
                flush_dcache_page(bufmap->page_array[i]);

        /* build a list of available descriptors */
        for (offset = 0, i = 0; i < bufmap->desc_count; i++) {
                bufmap->desc_array[i].page_array = &bufmap->page_array[offset];
                bufmap->desc_array[i].array_count = pages_per_desc;
                bufmap->desc_array[i].uaddr =
                    (user_desc->ptr + (i * pages_per_desc * PAGE_SIZE));
                offset += pages_per_desc;
        }

        return 0;
}

/*
 * orangefs_bufmap_initialize()
 *
 * initializes the mapped buffer interface
 *
 * returns 0 on success, -errno on failure
 */
int orangefs_bufmap_initialize(struct ORANGEFS_dev_map_desc *user_desc)
{
        struct orangefs_bufmap *bufmap;
        int ret = -EINVAL;

        gossip_debug(GOSSIP_BUFMAP_DEBUG,
                     "orangefs_bufmap_initialize: called (ptr ("
                     "%p) sz (%d) cnt(%d).\n",
                     user_desc->ptr,
                     user_desc->size,
                     user_desc->count);

        if (user_desc->total_size < 0 ||
            user_desc->size < 0 ||
            user_desc->count < 0)
                goto out;

        /*
         * sanity check alignment and size of buffer that caller wants to
         * work with
         */
        if (PAGE_ALIGN((unsigned long)user_desc->ptr) !=
            (unsigned long)user_desc->ptr) {
                gossip_err("orangefs error: memory alignment (front). %p\n",
                           user_desc->ptr);
                goto out;
        }

        if (PAGE_ALIGN(((unsigned long)user_desc->ptr + user_desc->total_size))
            != (unsigned long)(user_desc->ptr + user_desc->total_size)) {
                gossip_err("orangefs error: memory alignment (back).(%p + %d)\n",
                           user_desc->ptr,
                           user_desc->total_size);
                goto out;
        }

        if (user_desc->total_size != (user_desc->size * user_desc->count)) {
                gossip_err("orangefs error: user provided an oddly sized buffer: (%d, %d, %d)\n",
                           user_desc->total_size,
                           user_desc->size,
                           user_desc->count);
                goto out;
        }

        if ((user_desc->size % PAGE_SIZE) != 0) {
                gossip_err("orangefs error: bufmap size not page size divisible (%d).\n",
                           user_desc->size);
                goto out;
        }

        ret = -ENOMEM;
        bufmap = orangefs_bufmap_alloc(user_desc);
        if (!bufmap)
                goto out;

        ret = orangefs_bufmap_map(bufmap, user_desc);
        if (ret)
                goto out_free_bufmap;


        spin_lock(&orangefs_bufmap_lock);
        if (__orangefs_bufmap) {
                spin_unlock(&orangefs_bufmap_lock);
                gossip_err("orangefs: error: bufmap already initialized.\n");
                ret = -EINVAL;
                goto out_unmap_bufmap;
        }
        __orangefs_bufmap = bufmap;
        install(&rw_map,
                bufmap->desc_count,
                bufmap->buffer_index_array);
        install(&readdir_map,
                ORANGEFS_READDIR_DEFAULT_DESC_COUNT,
                bufmap->readdir_index_array);
        spin_unlock(&orangefs_bufmap_lock);

        gossip_debug(GOSSIP_BUFMAP_DEBUG,
                     "orangefs_bufmap_initialize: exiting normally\n");
        return 0;

out_unmap_bufmap:
        orangefs_bufmap_unmap(bufmap);
out_free_bufmap:
        orangefs_bufmap_free(bufmap);
out:
        return ret;
}

/*
 * orangefs_bufmap_finalize()
 *
 * shuts down the mapped buffer interface and releases any resources
 * associated with it
 *
 * no return value
 */
void orangefs_bufmap_finalize(void)
{
        struct orangefs_bufmap *bufmap = __orangefs_bufmap;
        if (!bufmap)
                return;
        gossip_debug(GOSSIP_BUFMAP_DEBUG, "orangefs_bufmap_finalize: called\n");
        mark_killed(&rw_map);
        mark_killed(&readdir_map);
        gossip_debug(GOSSIP_BUFMAP_DEBUG,
                     "orangefs_bufmap_finalize: exiting normally\n");
}

void orangefs_bufmap_run_down(void)
{
        struct orangefs_bufmap *bufmap = __orangefs_bufmap;
        if (!bufmap)
                return;
        run_down(&rw_map);
        run_down(&readdir_map);
        spin_lock(&orangefs_bufmap_lock);
        __orangefs_bufmap = NULL;
        spin_unlock(&orangefs_bufmap_lock);
        orangefs_bufmap_unmap(bufmap);
        orangefs_bufmap_free(bufmap);
}

/*
 * orangefs_bufmap_get()
 *
 * gets a free mapped buffer descriptor, will sleep until one becomes
 * available if necessary
 *
 * returns slot on success, -errno on failure
 */
int orangefs_bufmap_get(void)
{
        return get(&rw_map);
}

/*
 * orangefs_bufmap_put()
 *
 * returns a mapped buffer descriptor to the collection
 *
 * no return value
 */
void orangefs_bufmap_put(int buffer_index)
{
        put(&rw_map, buffer_index);
}

/*
 * orangefs_readdir_index_get()
 *
 * gets a free descriptor, will sleep until one becomes
 * available if necessary.
 * Although the readdir buffers are not mapped into kernel space
 * we could do that at a later point of time. Regardless, these
 * indices are used by the client-core.
 *
 * returns slot on success, -errno on failure
 */
int orangefs_readdir_index_get(void)
{
        return get(&readdir_map);
}

void orangefs_readdir_index_put(int buffer_index)
{
        put(&readdir_map, buffer_index);
}

/*
 * we've been handed an iovec, we need to copy it to
 * the shared memory descriptor at "buffer_index".
 */
int orangefs_bufmap_copy_from_iovec(struct iov_iter *iter,
                                int buffer_index,
                                size_t size)
{
        struct orangefs_bufmap_desc *to;
        int i;

        gossip_debug(GOSSIP_BUFMAP_DEBUG,
                     "%s: buffer_index:%d: size:%zu:\n",
                     __func__, buffer_index, size);

        to = &__orangefs_bufmap->desc_array[buffer_index];
        for (i = 0; size; i++) {
                struct page *page = to->page_array[i];
                size_t n = size;
                if (n > PAGE_SIZE)
                        n = PAGE_SIZE;
                if (copy_page_from_iter(page, 0, n, iter) != n)
                        return -EFAULT;
                size -= n;
        }
        return 0;
}

/*
 * we've been handed an iovec, we need to fill it from
 * the shared memory descriptor at "buffer_index".
 */
int orangefs_bufmap_copy_to_iovec(struct iov_iter *iter,
                                    int buffer_index,
                                    size_t size)
{
        struct orangefs_bufmap_desc *from;
        int i;

        from = &__orangefs_bufmap->desc_array[buffer_index];
        gossip_debug(GOSSIP_BUFMAP_DEBUG,
                     "%s: buffer_index:%d: size:%zu:\n",
                     __func__, buffer_index, size);


        for (i = 0; size; i++) {
                struct page *page = from->page_array[i];
                size_t n = size;
                if (n > PAGE_SIZE)
                        n = PAGE_SIZE;
                n = copy_page_to_iter(page, 0, n, iter);
                if (!n)
                        return -EFAULT;
                size -= n;
        }
        return 0;
}

void orangefs_bufmap_page_fill(void *page_to,
                                int buffer_index,
                                int slot_index)
{
        struct orangefs_bufmap_desc *from;
        void *page_from;

        from = &__orangefs_bufmap->desc_array[buffer_index];
        page_from = kmap_atomic(from->page_array[slot_index]);
        memcpy(page_to, page_from, PAGE_SIZE);
        kunmap_atomic(page_from);
}