WebSVN – HelenOS – Blame – /branches/dynload/uspace/srv/vfs/vfs_lookup.c

Rev	Author	Line No.	Line
2698	jermar	1	/*
		2	* Copyright (c) 2008 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_lookup.c
		35	* @brief
		36	*/
		37
		38	#include <ipc/ipc.h>
		39	#include <async.h>
		40	#include <errno.h>
		41	#include <string.h>
		42	#include <bool.h>
		43	#include <futex.h>
		44	#include <libadt/list.h>
		45	#include <atomic.h>
		46	#include "vfs.h"
		47
		48	#define min(a, b) ((a) < (b) ? (a) : (b))
		49
		50	atomic_t plb_futex = FUTEX_INITIALIZER;
		51	link_t plb_head; /*< PLB entry ring buffer. /
		52	uint8_t *plb = NULL;
		53
		54	/** Perform a path lookup.
		55	*
		56	* @param path Path to be resolved; it needn't be an ASCIIZ string.
		57	* @param len Number of path characters pointed by path.
		58	* @param result Empty structure where the lookup result will be stored.
		59	* @param altroot If non-empty, will be used instead of rootfs as the root
		60	* of the whole VFS tree.
		61	*
		62	* @return EOK on success or an error code from errno.h.
		63	*/
		64	int vfs_lookup_internal(char path, size_t len, vfs_lookup_res_t result,
		65	vfs_pair_t *altroot)
		66	{
		67	vfs_pair_t *root;
		68
		69	if (!len)
		70	return EINVAL;
		71
		72	if (altroot)
		73	root = altroot;
		74	else
		75	root = (vfs_pair_t *) &rootfs;
		76
		77	if (!root->fs_handle)
		78	return ENOENT;
		79
		80	futex_down(&plb_futex);
		81
		82	plb_entry_t entry;
		83	link_initialize(&entry.plb_link);
		84	entry.len = len;
		85
		86	off_t first; /* the first free index */
		87	off_t last; /* the last free index */
		88
		89	if (list_empty(&plb_head)) {
		90	first = 0;
		91	last = PLB_SIZE - 1;
		92	} else {
		93	plb_entry_t *oldest = list_get_instance(plb_head.next,
		94	plb_entry_t, plb_link);
		95	plb_entry_t *newest = list_get_instance(plb_head.prev,
		96	plb_entry_t, plb_link);
		97
		98	first = (newest->index + newest->len) % PLB_SIZE;
		99	last = (oldest->index - 1) % PLB_SIZE;
		100	}
		101
		102	if (first <= last) {
		103	if ((last - first) + 1 < len) {
		104	/*
		105	* The buffer cannot absorb the path.
		106	*/
		107	futex_up(&plb_futex);
		108	return ELIMIT;
		109	}
		110	} else {
		111	if (PLB_SIZE - ((first - last) + 1) < len) {
		112	/*
		113	* The buffer cannot absorb the path.
		114	*/
		115	futex_up(&plb_futex);
		116	return ELIMIT;
		117	}
		118	}
		119
		120	/*
		121	* We know the first free index in PLB and we also know that there is
		122	* enough space in the buffer to hold our path.
		123	*/
		124
		125	entry.index = first;
		126	entry.len = len;
		127
		128	/*
		129	* Claim PLB space by inserting the entry into the PLB entry ring
		130	* buffer.
		131	*/
		132	list_append(&entry.plb_link, &plb_head);
		133
		134	futex_up(&plb_futex);
		135
		136	/*
		137	* Copy the path into PLB.
		138	*/
		139	size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
		140	size_t cnt2 = len - cnt1;
		141
		142	memcpy(&plb[first], path, cnt1);
		143	memcpy(plb, &path[cnt1], cnt2);
		144
		145	ipc_call_t answer;
		146	int phone = vfs_grab_phone(root->fs_handle);
		147	aid_t req = async_send_3(phone, VFS_LOOKUP, (ipcarg_t) first,
		148	(ipcarg_t) (first + len - 1) % PLB_SIZE,
		149	(ipcarg_t) root->dev_handle, &answer);
		150	vfs_release_phone(phone);
		151
		152	ipcarg_t rc;
		153	async_wait_for(req, &rc);
		154
		155	futex_down(&plb_futex);
		156	list_remove(&entry.plb_link);
		157	/*
		158	* Erasing the path from PLB will come handy for debugging purposes.
		159	*/
		160	memset(&plb[first], 0, cnt1);
		161	memset(plb, 0, cnt2);
		162	futex_up(&plb_futex);
		163
		164	if (rc == EOK) {
		165	result->triplet.fs_handle = (int) IPC_GET_ARG1(answer);
		166	result->triplet.dev_handle = (int) IPC_GET_ARG2(answer);
		167	result->triplet.index = (int) IPC_GET_ARG3(answer);
		168	result->size = (size_t) IPC_GET_ARG4(answer);
		169	}
		170
		171	return rc;
		172	}
		173
		174	/**
		175	* @}
		176	*/

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