WebSVN – HelenOS – Blame – /branches/network/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.
2707	jermar	60	* Can be NULL.
2698	jermar	61	* @param altroot If non-empty, will be used instead of rootfs as the root
		62	* of the whole VFS tree.
		63	*
		64	* @return EOK on success or an error code from errno.h.
		65	*/
2700	jermar	66	int vfs_lookup_internal(char *path, size_t len, int lflag,
		67	vfs_lookup_res_t result, vfs_pair_t altroot)
2698	jermar	68	{
		69	vfs_pair_t *root;
		70
		71	if (!len)
		72	return EINVAL;
		73
		74	if (altroot)
		75	root = altroot;
		76	else
		77	root = (vfs_pair_t *) &rootfs;
		78
		79	if (!root->fs_handle)
		80	return ENOENT;
		81
		82	futex_down(&plb_futex);
		83
		84	plb_entry_t entry;
		85	link_initialize(&entry.plb_link);
		86	entry.len = len;
		87
		88	off_t first; /* the first free index */
		89	off_t last; /* the last free index */
		90
		91	if (list_empty(&plb_head)) {
		92	first = 0;
		93	last = PLB_SIZE - 1;
		94	} else {
		95	plb_entry_t *oldest = list_get_instance(plb_head.next,
		96	plb_entry_t, plb_link);
		97	plb_entry_t *newest = list_get_instance(plb_head.prev,
		98	plb_entry_t, plb_link);
		99
		100	first = (newest->index + newest->len) % PLB_SIZE;
		101	last = (oldest->index - 1) % PLB_SIZE;
		102	}
		103
		104	if (first <= last) {
		105	if ((last - first) + 1 < len) {
		106	/*
		107	* The buffer cannot absorb the path.
		108	*/
		109	futex_up(&plb_futex);
		110	return ELIMIT;
		111	}
		112	} else {
		113	if (PLB_SIZE - ((first - last) + 1) < len) {
		114	/*
		115	* The buffer cannot absorb the path.
		116	*/
		117	futex_up(&plb_futex);
		118	return ELIMIT;
		119	}
		120	}
		121
		122	/*
		123	* We know the first free index in PLB and we also know that there is
		124	* enough space in the buffer to hold our path.
		125	*/
		126
		127	entry.index = first;
		128	entry.len = len;
		129
		130	/*
		131	* Claim PLB space by inserting the entry into the PLB entry ring
		132	* buffer.
		133	*/
		134	list_append(&entry.plb_link, &plb_head);
		135
		136	futex_up(&plb_futex);
		137
		138	/*
		139	* Copy the path into PLB.
		140	*/
		141	size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
		142	size_t cnt2 = len - cnt1;
		143
		144	memcpy(&plb[first], path, cnt1);
		145	memcpy(plb, &path[cnt1], cnt2);
		146
		147	ipc_call_t answer;
		148	int phone = vfs_grab_phone(root->fs_handle);
2700	jermar	149	aid_t req = async_send_4(phone, VFS_LOOKUP, (ipcarg_t) first,
2698	jermar	150	(ipcarg_t) (first + len - 1) % PLB_SIZE,
2700	jermar	151	(ipcarg_t) root->dev_handle, (ipcarg_t) lflag, &answer);
2698	jermar	152	vfs_release_phone(phone);
		153
		154	ipcarg_t rc;
		155	async_wait_for(req, &rc);
		156
		157	futex_down(&plb_futex);
		158	list_remove(&entry.plb_link);
		159	/*
		160	* Erasing the path from PLB will come handy for debugging purposes.
		161	*/
		162	memset(&plb[first], 0, cnt1);
		163	memset(plb, 0, cnt2);
		164	futex_up(&plb_futex);
		165
2707	jermar	166	if ((rc == EOK) && result) {
2698	jermar	167	result->triplet.fs_handle = (int) IPC_GET_ARG1(answer);
		168	result->triplet.dev_handle = (int) IPC_GET_ARG2(answer);
		169	result->triplet.index = (int) IPC_GET_ARG3(answer);
		170	result->size = (size_t) IPC_GET_ARG4(answer);
		171	}
		172
		173	return rc;
		174	}
		175
		176	/**
		177	* @}
		178	*/

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