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/*

 * Copyright (c) 2008 Jakub Jermar

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in the

 *   documentation and/or other materials provided with the distribution.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/** @addtogroup fs

 * @{

 */ 

/**

 * @file	fat_idx.c

 * @brief	Layer for translating FAT entities to VFS node indices.

 */

#include "fat.h"

#include "../../vfs/vfs.h"

#include <errno.h>

#include <string.h>

#include <adt/hash_table.h>

#include <adt/list.h>

#include <assert.h>

#include <fibril_sync.h>

/** Each instance of this type describes one interval of freed VFS indices. */

typedef struct {

	link_t		link;

	fs_index_t	first;

	fs_index_t	last;

} freed_t;

/**

 * Each instance of this type describes state of all VFS indices that

 * are currently unused.

 */

typedef struct {

	link_t		link;

	dev_handle_t	dev_handle;

	/** Next unassigned index. */

	fs_index_t	next;

	/** Number of remaining unassigned indices. */

	uint64_t	remaining;

	/** Sorted list of intervals of freed indices. */

	link_t		freed_head;

} unused_t;

/** Mutex protecting the list of unused structures. */

static FIBRIL_MUTEX_INITIALIZE(unused_lock);

/** List of unused structures. */

static LIST_INITIALIZE(unused_head);

static void unused_initialize(unused_t *u, dev_handle_t dev_handle)

{

	link_initialize(&u->link);

	u->dev_handle = dev_handle;

	u->next = 0;

	u->remaining = ((uint64_t)((fs_index_t)-1)) + 1;

	list_initialize(&u->freed_head);

}

static unused_t *unused_find(dev_handle_t dev_handle, bool lock)

{

	unused_t *u;

	link_t *l;

	if (lock)

		fibril_mutex_lock(&unused_lock);

	for (l = unused_head.next; l != &unused_head; l = l->next) {

		u = list_get_instance(l, unused_t, link);

		if (u->dev_handle == dev_handle) 

			return u;

	}

	if (lock)

		fibril_mutex_unlock(&unused_lock);

	return NULL;

}

/** Mutex protecting the up_hash and ui_hash. */

static FIBRIL_MUTEX_INITIALIZE(used_lock);

/**

 * Global hash table of all used fat_idx_t structures.

 * The index structures are hashed by the dev_handle, parent node's first

 * cluster and index within the parent directory.

 */ 

static hash_table_t up_hash;

#define UPH_BUCKETS_LOG	12

#define UPH_BUCKETS	(1 << UPH_BUCKETS_LOG)

#define UPH_DH_KEY	0

#define UPH_PFC_KEY	1

#define UPH_PDI_KEY	2

static hash_index_t pos_hash(unsigned long key[])

{

	dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];

	fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];

	unsigned pdi = (unsigned)key[UPH_PDI_KEY];

	hash_index_t h;

	/*

	 * The least significant half of all bits are the least significant bits

	 * of the parent node's first cluster.

	 *

	 * The least significant half of the most significant half of all bits

	 * are the least significant bits of the node's dentry index within the

	 * parent directory node.

	 *

	 * The most significant half of the most significant half of all bits

	 * are the least significant bits of the device handle.

	 */

	h = pfc & ((1 << (UPH_BUCKETS_LOG / 2)) - 1);

	h |= (pdi & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<

	    (UPH_BUCKETS_LOG / 2); 

	h |= (dev_handle & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<

	    (3 * (UPH_BUCKETS_LOG / 4));

	return h;

}

static int pos_compare(unsigned long key[], hash_count_t keys, link_t *item)

{

	dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];

	fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];

	unsigned pdi = (unsigned)key[UPH_PDI_KEY];

	fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uph_link);

	return (dev_handle == fidx->dev_handle) && (pfc == fidx->pfc) &&

	    (pdi == fidx->pdi);

}

static void pos_remove_callback(link_t *item)

{

	/* nothing to do */

}

static hash_table_operations_t uph_ops = {

	.hash = pos_hash,

	.compare = pos_compare,

	.remove_callback = pos_remove_callback,

};

/**

 * Global hash table of all used fat_idx_t structures.

 * The index structures are hashed by the dev_handle and index.

 */

static hash_table_t ui_hash;

#define UIH_BUCKETS_LOG	12

#define UIH_BUCKETS	(1 << UIH_BUCKETS_LOG)

#define UIH_DH_KEY	0

#define UIH_INDEX_KEY	1

static hash_index_t idx_hash(unsigned long key[])

{

	dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];

	fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];

	hash_index_t h;

	h = dev_handle & ((1 << (UIH_BUCKETS_LOG / 2)) - 1);

	h |= (index & ((1 << (UIH_BUCKETS_LOG / 2)) - 1)) <<

	    (UIH_BUCKETS_LOG / 2);

	return h;

}

static int idx_compare(unsigned long key[], hash_count_t keys, link_t *item)

{

	dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];

	fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];

	fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uih_link);

	return (dev_handle == fidx->dev_handle) && (index == fidx->index);

}

static void idx_remove_callback(link_t *item)

{

	/* nothing to do */

}

static hash_table_operations_t uih_ops = {

	.hash = idx_hash,

	.compare = idx_compare,

	.remove_callback = idx_remove_callback,

};

/** Allocate a VFS index which is not currently in use. */

static bool fat_index_alloc(dev_handle_t dev_handle, fs_index_t *index)

{

	unused_t *u;

	assert(index);

	u = unused_find(dev_handle, true);

	if (!u)

		return false;	

	if (list_empty(&u->freed_head)) {

		if (u->remaining) { 

			/*

			 * There are no freed indices, allocate one directly

			 * from the counter.

			 */

			*index = u->next++;

			--u->remaining;

			fibril_mutex_unlock(&unused_lock);

			return true;

		}

	} else {

		/* There are some freed indices which we can reuse. */

		freed_t *f = list_get_instance(u->freed_head.next, freed_t,

		    link);

		*index = f->first;

		if (f->first++ == f->last) {

			/* Destroy the interval. */

			list_remove(&f->link);

			free(f);

		}

		fibril_mutex_unlock(&unused_lock);

		return true;

	}

	/*

	 * We ran out of indices, which is extremely unlikely with FAT16, but

	 * theoretically still possible (e.g. too many open unlinked nodes or

	 * too many zero-sized nodes).

	 */

	fibril_mutex_unlock(&unused_lock);

	return false;

}

/** If possible, coalesce two intervals of freed indices. */

static void try_coalesce_intervals(link_t *l, link_t *r, link_t *cur)

{

	freed_t *fl = list_get_instance(l, freed_t, link);

	freed_t *fr = list_get_instance(r, freed_t, link);

	if (fl->last + 1 == fr->first) {

		if (cur == l) {

			fl->last = fr->last;

			list_remove(r);

			free(r);

		} else {

			fr->first = fl->first;

			list_remove(l);

			free(l);

		}

	}

}

/** Free a VFS index, which is no longer in use. */

static void fat_index_free(dev_handle_t dev_handle, fs_index_t index)

{

	unused_t *u;

	u = unused_find(dev_handle, true);

	assert(u);

	if (u->next == index + 1) {

		/* The index can be returned directly to the counter. */

		u->next--;

		u->remaining++;

	} else {

		/*

		 * The index must be returned either to an existing freed

		 * interval or a new interval must be created.

		 */

		link_t *lnk;

		freed_t *n;

		for (lnk = u->freed_head.next; lnk != &u->freed_head;

		    lnk = lnk->next) {

			freed_t *f = list_get_instance(lnk, freed_t, link);

			if (f->first == index + 1) {

				f->first--;

				if (lnk->prev != &u->freed_head)

					try_coalesce_intervals(lnk->prev, lnk,

					    lnk);

				fibril_mutex_unlock(&unused_lock);

				return;

			}

			if (f->last == index - 1) {

				f->last++;

				if (lnk->next != &u->freed_head)

					try_coalesce_intervals(lnk, lnk->next,

					    lnk);

				fibril_mutex_unlock(&unused_lock);

				return;

			}

			if (index > f->first) {

				n = malloc(sizeof(freed_t));

				/* TODO: sleep until allocation succeeds */

				assert(n);

				link_initialize(&n->link);

				n->first = index;

				n->last = index;

				list_insert_before(&n->link, lnk);

				fibril_mutex_unlock(&unused_lock);

				return;

			}

		}

		/* The index will form the last interval. */

		n = malloc(sizeof(freed_t));

		/* TODO: sleep until allocation succeeds */

		assert(n);

		link_initialize(&n->link);

		n->first = index;

		n->last = index;

		list_append(&n->link, &u->freed_head);

	}

	fibril_mutex_unlock(&unused_lock);

}

static fat_idx_t *fat_idx_create(dev_handle_t dev_handle)

{

	fat_idx_t *fidx;

	fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));

	if (!fidx) 

		return NULL;

	if (!fat_index_alloc(dev_handle, &fidx->index)) {

		free(fidx);

		return NULL;

	}

	link_initialize(&fidx->uph_link);

	link_initialize(&fidx->uih_link);

	fibril_mutex_initialize(&fidx->lock);

	fidx->dev_handle = dev_handle;

	fidx->pfc = FAT_CLST_RES0;	/* no parent yet */

	fidx->pdi = 0;

	fidx->nodep = NULL;

	return fidx;

}

fat_idx_t *fat_idx_get_new(dev_handle_t dev_handle)

{

	fat_idx_t *fidx;

	fibril_mutex_lock(&used_lock);

	fidx = fat_idx_create(dev_handle);

	if (!fidx) {

		fibril_mutex_unlock(&used_lock);

		return NULL;

	}

	unsigned long ikey[] = {

		[UIH_DH_KEY] = dev_handle,

		[UIH_INDEX_KEY] = fidx->index,

	};

	hash_table_insert(&ui_hash, ikey, &fidx->uih_link);

	fibril_mutex_lock(&fidx->lock);

	fibril_mutex_unlock(&used_lock);

	return fidx;

}

fat_idx_t *

fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)

{

	fat_idx_t *fidx;

	link_t *l;

	unsigned long pkey[] = {

		[UPH_DH_KEY] = dev_handle,

		[UPH_PFC_KEY] = pfc,

		[UPH_PDI_KEY] = pdi,

	};

	fibril_mutex_lock(&used_lock);

	l = hash_table_find(&up_hash, pkey);

	if (l) {

		fidx = hash_table_get_instance(l, fat_idx_t, uph_link);

	} else {

		fidx = fat_idx_create(dev_handle);

		if (!fidx) {

			fibril_mutex_unlock(&used_lock);

			return NULL;

		}

		unsigned long ikey[] = {

			[UIH_DH_KEY] = dev_handle,

			[UIH_INDEX_KEY] = fidx->index,

		};

		fidx->pfc = pfc;

		fidx->pdi = pdi;

		hash_table_insert(&up_hash, pkey, &fidx->uph_link);

		hash_table_insert(&ui_hash, ikey, &fidx->uih_link);

	}

	fibril_mutex_lock(&fidx->lock);

	fibril_mutex_unlock(&used_lock);

	return fidx;

}

void fat_idx_hashin(fat_idx_t *idx)

{

	unsigned long pkey[] = {

		[UPH_DH_KEY] = idx->dev_handle,

		[UPH_PFC_KEY] = idx->pfc,

		[UPH_PDI_KEY] = idx->pdi,

	};

	fibril_mutex_lock(&used_lock);

	hash_table_insert(&up_hash, pkey, &idx->uph_link);

	fibril_mutex_unlock(&used_lock);

}

void fat_idx_hashout(fat_idx_t *idx)

{

	unsigned long pkey[] = {

		[UPH_DH_KEY] = idx->dev_handle,

		[UPH_PFC_KEY] = idx->pfc,

		[UPH_PDI_KEY] = idx->pdi,

	};

	fibril_mutex_lock(&used_lock);

	hash_table_remove(&up_hash, pkey, 3);

	fibril_mutex_unlock(&used_lock);

}

fat_idx_t *

fat_idx_get_by_index(dev_handle_t dev_handle, fs_index_t index)

{

	fat_idx_t *fidx = NULL;

	link_t *l;

	unsigned long ikey[] = {

		[UIH_DH_KEY] = dev_handle,

		[UIH_INDEX_KEY] = index,

	};

	fibril_mutex_lock(&used_lock);

	l = hash_table_find(&ui_hash, ikey);

	if (l) {

		fidx = hash_table_get_instance(l, fat_idx_t, uih_link);

		futex_down(&fidx->lock);

	}

	fibril_mutex_unlock(&used_lock);

	return fidx;

}

/** Destroy the index structure.

 *

 * @param idx		The index structure to be destroyed.

 */

void fat_idx_destroy(fat_idx_t *idx)

{

	unsigned long ikey[] = {

		[UIH_DH_KEY] = idx->dev_handle,

		[UIH_INDEX_KEY] = idx->index,

	};

	assert(idx->pfc == FAT_CLST_RES0);

	fibril_mutex_lock(&used_lock);

	/*

	 * Since we can only free unlinked nodes, the index structure is not

	 * present in the position hash (uph). We therefore hash it out from

	 * the index hash only.

	 */

	hash_table_remove(&ui_hash, ikey, 2);

	fibril_mutex_unlock(&used_lock);

	/* Release the VFS index. */

	fat_index_free(idx->dev_handle, idx->index);

	/* Deallocate the structure. */

	free(idx);

}

int fat_idx_init(void)

{

	if (!hash_table_create(&up_hash, UPH_BUCKETS, 3, &uph_ops)) 

		return ENOMEM;

	if (!hash_table_create(&ui_hash, UIH_BUCKETS, 2, &uih_ops)) {

		hash_table_destroy(&up_hash);

		return ENOMEM;

	}

	return EOK;

}

void fat_idx_fini(void)

{

	/* We assume the hash tables are empty. */

	hash_table_destroy(&up_hash);

	hash_table_destroy(&ui_hash);

}

int fat_idx_init_by_dev_handle(dev_handle_t dev_handle)

{

	unused_t *u;

	int rc = EOK;

	u = (unused_t *) malloc(sizeof(unused_t));

	if (!u)

		return ENOMEM;

	unused_initialize(u, dev_handle);

	fibril_mutex_lock(&unused_lock);

	if (!unused_find(dev_handle, false))

		list_append(&u->link, &unused_head);

	else

		rc = EEXIST;

	fibril_mutex_unlock(&unused_lock);

	return rc;

}

void fat_idx_fini_by_dev_handle(dev_handle_t dev_handle)

{

	unused_t *u;

	u = unused_find(dev_handle, true);

	assert(u);

	list_remove(&u->link);

	fibril_mutex_unlock(&unused_lock);

	while (!list_empty(&u->freed_head)) {

		freed_t *f;

		f = list_get_instance(u->freed_head.next, freed_t, link);

		list_remove(&f->link);

		free(f);

	}

	free(u); 

}

/**

 * @}

 */