source: mainline/uspace/srv/vfs/vfs_lookup.c@ b7c62a9

/*
 * Copyright (c) 2008 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup fs
 * @{
 */

/**
 * @file vfs_lookup.c
 * @brief
 */

#include "vfs.h"
#include <macros.h>
#include <async.h>
#include <errno.h>
#include <str.h>
#include <stdarg.h>
#include <stdbool.h>
#include <fibril_synch.h>
#include <adt/list.h>
#include <vfs/canonify.h>
#include <dirent.h>
#include <assert.h>

#define DPRINTF(...)

#define min(a, b)  ((a) < (b) ? (a) : (b))

FIBRIL_MUTEX_INITIALIZE(plb_mutex);
LIST_INITIALIZE(plb_entries);   /**< PLB entry ring buffer. */
uint8_t *plb = NULL;

static int plb_insert_entry(plb_entry_t *entry, char *path, size_t *start, size_t len)
{
        fibril_mutex_lock(&plb_mutex);

        link_initialize(&entry->plb_link);
        entry->len = len;

        size_t first;   /* the first free index */
        size_t last;    /* the last free index */

        if (list_empty(&plb_entries)) {
                first = 0;
                last = PLB_SIZE - 1;
        } else {
                plb_entry_t *oldest = list_get_instance(
                    list_first(&plb_entries), plb_entry_t, plb_link);
                plb_entry_t *newest = list_get_instance(
                    list_last(&plb_entries), plb_entry_t, plb_link);

                first = (newest->index + newest->len) % PLB_SIZE;
                last = (oldest->index - 1) % PLB_SIZE;
        }

        if (first <= last) {
                if ((last - first) + 1 < len) {
                        /*
                         * The buffer cannot absorb the path.
                         */
                        fibril_mutex_unlock(&plb_mutex);
                        return ELIMIT;
                }
        } else {
                if (PLB_SIZE - ((first - last) + 1) < len) {
                        /*
                         * The buffer cannot absorb the path.
                         */
                        fibril_mutex_unlock(&plb_mutex);
                        return ELIMIT;
                }
        }

        /*
         * We know the first free index in PLB and we also know that there is
         * enough space in the buffer to hold our path.
         */

        entry->index = first;
        entry->len = len;

        /*
         * Claim PLB space by inserting the entry into the PLB entry ring
         * buffer.
         */
        list_append(&entry->plb_link, &plb_entries);
        
        fibril_mutex_unlock(&plb_mutex);

        /*
         * Copy the path into PLB.
         */
        size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
        size_t cnt2 = len - cnt1;
        
        memcpy(&plb[first], path, cnt1);
        memcpy(plb, &path[cnt1], cnt2);

        *start = first;
        return EOK;
}

static void plb_clear_entry(plb_entry_t *entry, size_t first, size_t len)
{
        fibril_mutex_lock(&plb_mutex);
        list_remove(&entry->plb_link);
        /*
         * Erasing the path from PLB will come handy for debugging purposes.
         */
        size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
        size_t cnt2 = len - cnt1;
        memset(&plb[first], 0, cnt1);
        memset(plb, 0, cnt2);
        fibril_mutex_unlock(&plb_mutex);
}

static char *_strrchr(char *path, int c)
{
        char *res = NULL;
        while (*path != 0) {
                if (*path == c) {
                        res = path;
                }
                path++;
        }
        return res;
}

int vfs_link_internal(vfs_triplet_t *base, char *path, vfs_triplet_t *child)
{
        assert(base != NULL);
        assert(child != NULL);
        assert(base->fs_handle);
        assert(child->fs_handle);
        assert(path != NULL);
        
        vfs_lookup_res_t res;
        char component[NAME_MAX + 1];
        int rc;
        
        size_t len;
        char *npath = canonify(path, &len);
        if (!npath) {
                rc = EINVAL;
                goto out;
        }
        path = npath;
        
        char *slash = _strrchr(path, '/');
        if (slash && slash != path) {
                if (slash[1] == 0) {
                        rc = EINVAL;
                        goto out;
                }
                
                memcpy(component, slash + 1, str_size(slash));
                *slash = 0;
                
                rc = vfs_lookup_internal(base, path, L_DIRECTORY, &res);
                if (rc != EOK) {
                        goto out;
                }
                base = &res.triplet;
                
                *slash = '/';
        } else {
                memcpy(component, path + 1, str_size(path));
        }
        
        if (base->fs_handle != child->fs_handle || base->service_id != child->service_id) {
                rc = EXDEV;
                goto out;
        }
        
        async_exch_t *exch = vfs_exchange_grab(base->fs_handle);
        aid_t req = async_send_3(exch, VFS_OUT_LINK, base->service_id, base->index, child->index, NULL);
        
        rc = async_data_write_start(exch, component, str_size(component) + 1);
        sysarg_t orig_rc;
        async_wait_for(req, &orig_rc);
        vfs_exchange_release(exch);
        if (orig_rc != EOK) {
                rc = orig_rc;
        }
        
out:
        DPRINTF("vfs_link_internal() with path '%s' returns %d\n", path, rc);
        return rc;
}

/** Perform a path lookup.
 *
 * @param base    The file from which to perform the lookup.
 * @param path    Path to be resolved; it must be a NULL-terminated
 *                string.
 * @param lflag   Flags to be used during lookup.
 * @param result  Empty structure where the lookup result will be stored.
 *                Can be NULL.
 *
 * @return EOK on success or an error code from errno.h.
 *
 */
int vfs_lookup_internal(vfs_triplet_t *base, char *path, int lflag, vfs_lookup_res_t *result)
{
        assert(base != NULL);
        assert(path != NULL);
        
        sysarg_t rc;
        
        if (!base->fs_handle) {
                rc = ENOENT;
                goto out;
        }
        
        size_t len;
        char *npath = canonify(path, &len);
        if (!npath) {
                rc = EINVAL;
                goto out;
        }
        path = npath;
        
        assert(path[0] == '/');
        
        size_t first;
        
        plb_entry_t entry;
        rc = plb_insert_entry(&entry, path, &first, len);
        if (rc != EOK) {
                goto out;
        }
        
        ipc_call_t answer;
        async_exch_t *exch = vfs_exchange_grab(base->fs_handle);
        aid_t req = async_send_5(exch, VFS_OUT_LOOKUP, (sysarg_t) first, (sysarg_t) len,
            (sysarg_t) base->service_id, (sysarg_t) base->index, (sysarg_t) lflag, &answer);
        async_wait_for(req, &rc);
        vfs_exchange_release(exch);
        
        plb_clear_entry(&entry, first, len);
        
        if ((int) rc < 0) {
                goto out;
        }
        
        if (!result) {
                rc = EOK;
                goto out;
        }
        
        result->triplet.fs_handle = (fs_handle_t) rc;
        result->triplet.service_id = (service_id_t) IPC_GET_ARG1(answer);
        result->triplet.index = (fs_index_t) IPC_GET_ARG2(answer);
        result->size =
            (aoff64_t) MERGE_LOUP32(IPC_GET_ARG3(answer), IPC_GET_ARG4(answer));
        result->type = IPC_GET_ARG5(answer);
        rc = EOK;

out:
        DPRINTF("vfs_lookup_internal() with path '%s' returns %d\n", path, rc);
        return rc;
}

/**
 * @}
 */