fs/orangefs/orangefs-bufmap.c - linux - Git at Google

 // 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, 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;
 }
	// 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, 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;
	}