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>
		43	#include <libadt/hash_table.h>
2590	jermar	44
2596	jermar	45	/** Futex protecting the VFS node hash table. */
		46	atomic_t nodes_futex = FUTEX_INITIALIZER;
		47
		48	#define NODES_BUCKETS_LOG 8
		49	#define NODES_BUCKETS (1 << NODES_BUCKETS_LOG)
		50
		51	/** VFS node hash table containing all active, in-memory VFS nodes. */
		52	hash_table_t nodes;
		53
		54	#define KEY_FS_HANDLE 0
		55	#define KEY_DEV_HANDLE 1
		56	#define KEY_INDEX 2
		57
		58	static hash_index_t nodes_hash(unsigned long []);
		59	static int nodes_compare(unsigned long [], hash_count_t, link_t *);
		60	static void nodes_remove_callback(link_t *);
		61
		62	/** VFS node hash table operations. */
		63	hash_table_operations_t nodes_ops = {
		64	.hash = nodes_hash,
		65	.compare = nodes_compare,
		66	.remove_callback = nodes_remove_callback
		67	};
		68
		69	/** Initialize the VFS node hash table.
		70	*
		71	* @return Return true on success, false on failure.
		72	*/
		73	bool vfs_nodes_init(void)
		74	{
		75	return hash_table_create(&nodes, NODES_BUCKETS, 3, &nodes_ops);
		76	}
		77
		78	static inline void _vfs_node_addref(vfs_node_t *node)
		79	{
		80	node->refcnt++;
		81	}
		82
2593	jermar	83	/** Increment reference count of a VFS node.
		84	*
		85	* @param node VFS node that will have its refcnt incremented.
		86	*/
		87	void vfs_node_addref(vfs_node_t *node)
		88	{
2596	jermar	89	futex_down(&nodes_futex);
		90	_vfs_node_addref(node);
		91	futex_up(&nodes_futex);
2593	jermar	92	}
		93
		94	/** Decrement reference count of a VFS node.
		95	*
		96	* This function handles the case when the reference count drops to zero.
		97	*
		98	* @param node VFS node that will have its refcnt decremented.
		99	*/
		100	void vfs_node_delref(vfs_node_t *node)
		101	{
2596	jermar	102	futex_down(&nodes_futex);
		103	if (node->refcnt-- == 1) {
		104	unsigned long key[] = {
		105	[KEY_FS_HANDLE] = node->fs_handle,
		106	[KEY_DEV_HANDLE] = node->dev_handle,
		107	[KEY_INDEX] = node->index
		108	};
		109	hash_table_remove(&nodes, key, 3);
		110	}
		111	futex_up(&nodes_futex);
2593	jermar	112	}
		113
		114	/** Find VFS node.
		115	*
		116	* This function will try to lookup the given triplet in the VFS node hash
		117	* table. In case the triplet is not found there, a new VFS node is created.
		118	* In any case, the VFS node will have its reference count incremented. Every
		119	* node returned by this call should be eventually put back by calling
		120	* vfs_node_put() on it.
		121	*
		122	* @param triplet Triplet encoding the identity of the VFS node.
		123	*
		124	* @return VFS node corresponding to the given triplet.
		125	*/
2590	jermar	126	vfs_node_t vfs_node_get(vfs_triplet_t triplet)
		127	{
2596	jermar	128	unsigned long key[] = {
		129	[KEY_FS_HANDLE] = triplet->fs_handle,
		130	[KEY_DEV_HANDLE] = triplet->dev_handle,
		131	[KEY_INDEX] = triplet->index
		132	};
		133	link_t *tmp;
		134	vfs_node_t *node;
		135
		136	futex_down(&nodes_futex);
		137	tmp = hash_table_find(&nodes, key);
		138	if (!tmp) {
		139	node = (vfs_node_t *) malloc(sizeof(vfs_node_t));
		140	if (!node) {
		141	futex_up(&nodes_futex);
		142	return NULL;
		143	}
		144	memset(node, 0, sizeof(vfs_node_t));
		145	node->fs_handle = triplet->fs_handle;
		146	node->dev_handle = triplet->fs_handle;
		147	node->index = triplet->index;
		148	link_initialize(&node->nh_link);
2679	jermar	149	futex_initialize(&node->contents_futex, 1);
2596	jermar	150	hash_table_insert(&nodes, key, &node->nh_link);
		151	} else {
		152	node = hash_table_get_instance(tmp, vfs_node_t, nh_link);
		153	}
		154	_vfs_node_addref(node);
		155	futex_up(&nodes_futex);
		156
		157	return node;
2590	jermar	158	}
		159
2593	jermar	160	/** Return VFS node when no longer needed by the caller.
		161	*
		162	* This function will remove the reference on the VFS node created by
		163	* vfs_node_get(). This function can only be called as a closing bracket to the
		164	* preceding vfs_node_get() call.
		165	*
		166	* @param node VFS node being released.
		167	*/
		168	void vfs_node_put(vfs_node_t *node)
		169	{
		170	vfs_node_delref(node);
		171	}
		172
2596	jermar	173	hash_index_t nodes_hash(unsigned long key[])
		174	{
		175	hash_index_t a = key[KEY_FS_HANDLE] << (NODES_BUCKETS_LOG / 4);
		176	hash_index_t b = (a \| key[KEY_DEV_HANDLE]) << (NODES_BUCKETS_LOG / 2);
		177
2652	jermar	178	return (b \| key[KEY_INDEX]) & (NODES_BUCKETS - 1);
2596	jermar	179	}
		180
		181	int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)
		182	{
		183	vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
		184	return (node->fs_handle == key[KEY_FS_HANDLE]) &&
		185	(node->dev_handle == key[KEY_DEV_HANDLE]) &&
		186	(node->index == key[KEY_INDEX]);
		187	}
		188
		189	void nodes_remove_callback(link_t *item)
		190	{
		191	vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
		192	free(node);
		193	}
		194
2590	jermar	195	/**
		196	* @}
		197	*/

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(root)//trunk/uspace/srv/vfs/vfs_node.c – Rev 2679