WebSVN – HelenOS – Blame – //trunk/uspace/srv/vfs/vfs_node.c

Rev	Author	Line No.	Line
2590	jermar	1	/*
		2	* Copyright (c) 2007 Jakub Jermar
		3	* All rights reserved.
		4	*
		5	* Redistribution and use in source and binary forms, with or without
		6	* modification, are permitted provided that the following conditions
		7	* are met:
		8	*
		9	* - Redistributions of source code must retain the above copyright
		10	* notice, this list of conditions and the following disclaimer.
		11	* - Redistributions in binary form must reproduce the above copyright
		12	* notice, this list of conditions and the following disclaimer in the
		13	* documentation and/or other materials provided with the distribution.
		14	* - The name of the author may not be used to endorse or promote products
		15	* derived from this software without specific prior written permission.
		16	*
		17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
		18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
		19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
		20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
		21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
		22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
		23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
		24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
		25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
		26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
		27	*/
		28
		29	/** @addtogroup fs
		30	* @{
		31	*/
		32
		33	/**
		34	* @file vfs_node.c
		35	* @brief Various operations on VFS nodes have their home in this file.
		36	*/
		37
		38	#include "vfs.h"
2596	jermar	39	#include <stdlib.h>
		40	#include <string.h>
		41	#include <atomic.h>
		42	#include <futex.h>
2680	jermar	43	#include <rwlock.h>
2596	jermar	44	#include <libadt/hash_table.h>
2590	jermar	45
2596	jermar	46	/** Futex protecting the VFS node hash table. */
		47	atomic_t nodes_futex = FUTEX_INITIALIZER;
		48
		49	#define NODES_BUCKETS_LOG 8
		50	#define NODES_BUCKETS (1 << NODES_BUCKETS_LOG)
		51
		52	/** VFS node hash table containing all active, in-memory VFS nodes. */
		53	hash_table_t nodes;
		54
		55	#define KEY_FS_HANDLE 0
		56	#define KEY_DEV_HANDLE 1
		57	#define KEY_INDEX 2
		58
		59	static hash_index_t nodes_hash(unsigned long []);
		60	static int nodes_compare(unsigned long [], hash_count_t, link_t *);
		61	static void nodes_remove_callback(link_t *);
		62
		63	/** VFS node hash table operations. */
		64	hash_table_operations_t nodes_ops = {
		65	.hash = nodes_hash,
		66	.compare = nodes_compare,
		67	.remove_callback = nodes_remove_callback
		68	};
		69
		70	/** Initialize the VFS node hash table.
		71	*
		72	* @return Return true on success, false on failure.
		73	*/
		74	bool vfs_nodes_init(void)
		75	{
		76	return hash_table_create(&nodes, NODES_BUCKETS, 3, &nodes_ops);
		77	}
		78
		79	static inline void _vfs_node_addref(vfs_node_t *node)
		80	{
		81	node->refcnt++;
		82	}
		83
2593	jermar	84	/** Increment reference count of a VFS node.
		85	*
		86	* @param node VFS node that will have its refcnt incremented.
		87	*/
		88	void vfs_node_addref(vfs_node_t *node)
		89	{
2596	jermar	90	futex_down(&nodes_futex);
		91	_vfs_node_addref(node);
		92	futex_up(&nodes_futex);
2593	jermar	93	}
		94
		95	/** Decrement reference count of a VFS node.
		96	*
		97	* This function handles the case when the reference count drops to zero.
		98	*
		99	* @param node VFS node that will have its refcnt decremented.
		100	*/
		101	void vfs_node_delref(vfs_node_t *node)
		102	{
2596	jermar	103	futex_down(&nodes_futex);
		104	if (node->refcnt-- == 1) {
		105	unsigned long key[] = {
		106	[KEY_FS_HANDLE] = node->fs_handle,
		107	[KEY_DEV_HANDLE] = node->dev_handle,
		108	[KEY_INDEX] = node->index
		109	};
		110	hash_table_remove(&nodes, key, 3);
		111	}
		112	futex_up(&nodes_futex);
2593	jermar	113	}
		114
		115	/** Find VFS node.
		116	*
		117	* This function will try to lookup the given triplet in the VFS node hash
		118	* table. In case the triplet is not found there, a new VFS node is created.
		119	* In any case, the VFS node will have its reference count incremented. Every
		120	* node returned by this call should be eventually put back by calling
		121	* vfs_node_put() on it.
		122	*
		123	* @param triplet Triplet encoding the identity of the VFS node.
		124	*
		125	* @return VFS node corresponding to the given triplet.
		126	*/
2590	jermar	127	vfs_node_t vfs_node_get(vfs_triplet_t triplet)
		128	{
2596	jermar	129	unsigned long key[] = {
		130	[KEY_FS_HANDLE] = triplet->fs_handle,
		131	[KEY_DEV_HANDLE] = triplet->dev_handle,
		132	[KEY_INDEX] = triplet->index
		133	};
		134	link_t *tmp;
		135	vfs_node_t *node;
		136
		137	futex_down(&nodes_futex);
		138	tmp = hash_table_find(&nodes, key);
		139	if (!tmp) {
		140	node = (vfs_node_t *) malloc(sizeof(vfs_node_t));
		141	if (!node) {
		142	futex_up(&nodes_futex);
		143	return NULL;
		144	}
		145	memset(node, 0, sizeof(vfs_node_t));
		146	node->fs_handle = triplet->fs_handle;
		147	node->dev_handle = triplet->fs_handle;
		148	node->index = triplet->index;
		149	link_initialize(&node->nh_link);
2680	jermar	150	rwlock_initialize(&node->contents_rwlock);
2596	jermar	151	hash_table_insert(&nodes, key, &node->nh_link);
		152	} else {
		153	node = hash_table_get_instance(tmp, vfs_node_t, nh_link);
		154	}
		155	_vfs_node_addref(node);
		156	futex_up(&nodes_futex);
		157
		158	return node;
2590	jermar	159	}
		160
2593	jermar	161	/** Return VFS node when no longer needed by the caller.
		162	*
		163	* This function will remove the reference on the VFS node created by
		164	* vfs_node_get(). This function can only be called as a closing bracket to the
		165	* preceding vfs_node_get() call.
		166	*
		167	* @param node VFS node being released.
		168	*/
		169	void vfs_node_put(vfs_node_t *node)
		170	{
		171	vfs_node_delref(node);
		172	}
		173
2596	jermar	174	hash_index_t nodes_hash(unsigned long key[])
		175	{
		176	hash_index_t a = key[KEY_FS_HANDLE] << (NODES_BUCKETS_LOG / 4);
		177	hash_index_t b = (a \| key[KEY_DEV_HANDLE]) << (NODES_BUCKETS_LOG / 2);
		178
2652	jermar	179	return (b \| key[KEY_INDEX]) & (NODES_BUCKETS - 1);
2596	jermar	180	}
		181
		182	int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)
		183	{
		184	vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
		185	return (node->fs_handle == key[KEY_FS_HANDLE]) &&
		186	(node->dev_handle == key[KEY_DEV_HANDLE]) &&
		187	(node->index == key[KEY_INDEX]);
		188	}
		189
		190	void nodes_remove_callback(link_t *item)
		191	{
		192	vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
		193	free(node);
		194	}
		195
2590	jermar	196	/**
		197	* @}
		198	*/

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(root)//trunk/uspace/srv/vfs/vfs_node.c – Rev 2680