// 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 (unlikely(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);
	bitmap_free(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 = bitmap_zalloc(bufmap->desc_count, 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:
	bitmap_free(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, 1, 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;
}