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2698 jermar 1
/*
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 * Copyright (c) 2008 Jakub Jermar
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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/** @addtogroup fs
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 * @{
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 */
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/**
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 * @file    vfs_lookup.c
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 * @brief
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 */
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2753 jermar 38
#include "vfs.h"
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#include <ipc/ipc.h>
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#include <async.h>
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#include <errno.h>
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#include <string.h>
2763 jermar 43
#include <stdarg.h>
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#include <bool.h>
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#include <futex.h>
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#include <libadt/list.h>
2753 jermar 47
#include <vfs/canonify.h>
2698 jermar 48
 
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#define min(a, b)   ((a) < (b) ? (a) : (b))
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2766 jermar 51
futex_t plb_futex = FUTEX_INITIALIZER;
2698 jermar 52
link_t plb_head;    /**< PLB entry ring buffer. */
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uint8_t *plb = NULL;
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/** Perform a path lookup.
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 *
2752 jermar 57
 * @param path      Path to be resolved; it must be a NULL-terminated
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 *          string.
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 * @param lflag     Flags to be used during lookup.
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 * @param result    Empty structure where the lookup result will be stored.
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 *          Can be NULL.
2698 jermar 62
 * @param altroot   If non-empty, will be used instead of rootfs as the root
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 *          of the whole VFS tree.
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 *
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 * @return      EOK on success or an error code from errno.h.
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 */
2752 jermar 67
int vfs_lookup_internal(char *path, int lflag, vfs_lookup_res_t *result,
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    vfs_pair_t *altroot, ...)
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{
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    vfs_pair_t *root;
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    if (altroot)
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        root = altroot;
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    else
3109 jermar 75
        root = &rootfs;
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    if (!root->fs_handle)
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        return ENOENT;
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2752 jermar 80
    size_t len;
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    path = canonify(path, &len);
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    if (!path)
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        return EINVAL;
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2770 jermar 85
    fs_index_t index = 0;
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    if (lflag & L_LINK) {
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        va_list ap;
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        va_start(ap, altroot);
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        index = va_arg(ap, fs_index_t);
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        va_end(ap);
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    }
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2698 jermar 94
    futex_down(&plb_futex);
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    plb_entry_t entry;
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    link_initialize(&entry.plb_link);
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    entry.len = len;
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    off_t first;    /* the first free index */
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    off_t last; /* the last free index */
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    if (list_empty(&plb_head)) {
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        first = 0;
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        last = PLB_SIZE - 1;
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    } else {
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        plb_entry_t *oldest = list_get_instance(plb_head.next,
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            plb_entry_t, plb_link);
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        plb_entry_t *newest = list_get_instance(plb_head.prev,
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            plb_entry_t, plb_link);
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        first = (newest->index + newest->len) % PLB_SIZE;
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        last = (oldest->index - 1) % PLB_SIZE;
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    }
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    if (first <= last) {
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        if ((last - first) + 1 < len) {
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            /*
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             * The buffer cannot absorb the path.
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             */
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            futex_up(&plb_futex);
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            return ELIMIT;
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        }
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    } else {
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        if (PLB_SIZE - ((first - last) + 1) < len) {
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            /*
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             * The buffer cannot absorb the path.
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             */
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            futex_up(&plb_futex);
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            return ELIMIT;
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        }
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    }
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    /*
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     * We know the first free index in PLB and we also know that there is
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     * enough space in the buffer to hold our path.
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     */
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    entry.index = first;
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    entry.len = len;
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    /*
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     * Claim PLB space by inserting the entry into the PLB entry ring
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     * buffer.
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     */
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    list_append(&entry.plb_link, &plb_head);
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    futex_up(&plb_futex);
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    /*
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     * Copy the path into PLB.
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     */
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    size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
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    size_t cnt2 = len - cnt1;
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    memcpy(&plb[first], path, cnt1);
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    memcpy(plb, &path[cnt1], cnt2);
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    ipc_call_t answer;
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    int phone = vfs_grab_phone(root->fs_handle);
2763 jermar 161
    aid_t req = async_send_5(phone, VFS_LOOKUP, (ipcarg_t) first,
2698 jermar 162
        (ipcarg_t) (first + len - 1) % PLB_SIZE,
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        (ipcarg_t) root->dev_handle, (ipcarg_t) lflag, (ipcarg_t) index,
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        &answer);
2698 jermar 165
    vfs_release_phone(phone);
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    ipcarg_t rc;
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    async_wait_for(req, &rc);
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    futex_down(&plb_futex);
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    list_remove(&entry.plb_link);
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    /*
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     * Erasing the path from PLB will come handy for debugging purposes.
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     */
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    memset(&plb[first], 0, cnt1);
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    memset(plb, 0, cnt2);
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    futex_up(&plb_futex);
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2707 jermar 179
    if ((rc == EOK) && result) {
2770 jermar 180
        result->triplet.fs_handle = (fs_handle_t) IPC_GET_ARG1(answer);
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        result->triplet.dev_handle = (dev_handle_t) IPC_GET_ARG2(answer);
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        result->triplet.index = (fs_index_t) IPC_GET_ARG3(answer);
2698 jermar 183
        result->size = (size_t) IPC_GET_ARG4(answer);
2730 jermar 184
        result->lnkcnt = (unsigned) IPC_GET_ARG5(answer);
2698 jermar 185
    }
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    return rc;
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}
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/**
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 * @}
2751 jermar 192
 */