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.
2700	jermar	58	* @param lflag Flags to be used during lookup.
2698	jermar	59	* @param result Empty structure where the lookup result will be stored.
		60	* @param altroot If non-empty, will be used instead of rootfs as the root
		61	* of the whole VFS tree.
		62	*
		63	* @return EOK on success or an error code from errno.h.
		64	*/
2700	jermar	65	int vfs_lookup_internal(char *path, size_t len, int lflag,
		66	vfs_lookup_res_t result, vfs_pair_t altroot)
2698	jermar	67	{
		68	vfs_pair_t *root;
		69
		70	if (!len)
		71	return EINVAL;
		72
		73	if (altroot)
		74	root = altroot;
		75	else
		76	root = (vfs_pair_t *) &rootfs;
		77
		78	if (!root->fs_handle)
		79	return ENOENT;
		80
		81	futex_down(&plb_futex);
		82
		83	plb_entry_t entry;
		84	link_initialize(&entry.plb_link);
		85	entry.len = len;
		86
		87	off_t first; /* the first free index */
		88	off_t last; /* the last free index */
		89
		90	if (list_empty(&plb_head)) {
		91	first = 0;
		92	last = PLB_SIZE - 1;
		93	} else {
		94	plb_entry_t *oldest = list_get_instance(plb_head.next,
		95	plb_entry_t, plb_link);
		96	plb_entry_t *newest = list_get_instance(plb_head.prev,
		97	plb_entry_t, plb_link);
		98
		99	first = (newest->index + newest->len) % PLB_SIZE;
		100	last = (oldest->index - 1) % PLB_SIZE;
		101	}
		102
		103	if (first <= last) {
		104	if ((last - first) + 1 < len) {
		105	/*
		106	* The buffer cannot absorb the path.
		107	*/
		108	futex_up(&plb_futex);
		109	return ELIMIT;
		110	}
		111	} else {
		112	if (PLB_SIZE - ((first - last) + 1) < len) {
		113	/*
		114	* The buffer cannot absorb the path.
		115	*/
		116	futex_up(&plb_futex);
		117	return ELIMIT;
		118	}
		119	}
		120
		121	/*
		122	* We know the first free index in PLB and we also know that there is
		123	* enough space in the buffer to hold our path.
		124	*/
		125
		126	entry.index = first;
		127	entry.len = len;
		128
		129	/*
		130	* Claim PLB space by inserting the entry into the PLB entry ring
		131	* buffer.
		132	*/
		133	list_append(&entry.plb_link, &plb_head);
		134
		135	futex_up(&plb_futex);
		136
		137	/*
		138	* Copy the path into PLB.
		139	*/
		140	size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
		141	size_t cnt2 = len - cnt1;
		142
		143	memcpy(&plb[first], path, cnt1);
		144	memcpy(plb, &path[cnt1], cnt2);
		145
		146	ipc_call_t answer;
		147	int phone = vfs_grab_phone(root->fs_handle);
2700	jermar	148	aid_t req = async_send_4(phone, VFS_LOOKUP, (ipcarg_t) first,
2698	jermar	149	(ipcarg_t) (first + len - 1) % PLB_SIZE,
2700	jermar	150	(ipcarg_t) root->dev_handle, (ipcarg_t) lflag, &answer);
2698	jermar	151	vfs_release_phone(phone);
		152
		153	ipcarg_t rc;
		154	async_wait_for(req, &rc);
		155
		156	futex_down(&plb_futex);
		157	list_remove(&entry.plb_link);
		158	/*
		159	* Erasing the path from PLB will come handy for debugging purposes.
		160	*/
		161	memset(&plb[first], 0, cnt1);
		162	memset(plb, 0, cnt2);
		163	futex_up(&plb_futex);
		164
		165	if (rc == EOK) {
		166	result->triplet.fs_handle = (int) IPC_GET_ARG1(answer);
		167	result->triplet.dev_handle = (int) IPC_GET_ARG2(answer);
		168	result->triplet.index = (int) IPC_GET_ARG3(answer);
		169	result->size = (size_t) IPC_GET_ARG4(answer);
		170	}
		171
		172	return rc;
		173	}
		174
		175	/**
		176	* @}
		177	*/

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