source: mainline/uspace/srv/fs/tmpfs/tmpfs_ops.c@ b5553a2

/*
 * 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        tmpfs_ops.c
 * @brief       Implementation of VFS operations for the TMPFS file system
 *              server.
 */

#include "tmpfs.h"
#include "../../vfs/vfs.h"
#include <ipc/ipc.h>
#include <async.h>
#include <errno.h>
#include <atomic.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <dirent.h>
#include <assert.h>
#include <sys/types.h>
#include <libadt/hash_table.h>
#include <as.h>

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

#define PLB_GET_CHAR(i)         (tmpfs_reg.plb_ro[(i) % PLB_SIZE])

#define DENTRIES_BUCKETS        256

#define TMPFS_GET_INDEX(x)      (((tmpfs_dentry_t *)(x))->index)
#define TMPFS_GET_LNKCNT(x)     1

/*
 * Hash table of all directory entries.
 */
hash_table_t dentries;

static hash_index_t dentries_hash(unsigned long *key)
{
        return *key % DENTRIES_BUCKETS;
}

static int dentries_compare(unsigned long *key, hash_count_t keys,
    link_t *item)
{
        tmpfs_dentry_t *dentry = hash_table_get_instance(item, tmpfs_dentry_t,
            dh_link);
        return dentry->index == *key;
}

static void dentries_remove_callback(link_t *item)
{
}

/** TMPFS dentries hash table operations. */
hash_table_operations_t dentries_ops = {
        .hash = dentries_hash,
        .compare = dentries_compare,
        .remove_callback = dentries_remove_callback
};

unsigned tmpfs_next_index = 1;

static void tmpfs_dentry_initialize(tmpfs_dentry_t *dentry)
{
        dentry->index = 0;
        dentry->parent = NULL;
        dentry->sibling = NULL;
        dentry->child = NULL;
        dentry->name = NULL;
        dentry->type = TMPFS_NONE;
        dentry->size = 0;
        dentry->data = NULL;
        link_initialize(&dentry->dh_link);
}

/*
 * For now, we don't distinguish between different dev_handles/instances. All
 * requests resolve to the only instance, rooted in the following variable.
 */
static tmpfs_dentry_t *root;

static bool tmpfs_init(void)
{
        if (!hash_table_create(&dentries, DENTRIES_BUCKETS, 1, &dentries_ops))
                return false;

        root = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));
        if (!root)
                return false;
        tmpfs_dentry_initialize(root);
        root->index = tmpfs_next_index++;
        root->name = "";
        root->type = TMPFS_DIRECTORY;
        hash_table_insert(&dentries, &root->index, &root->dh_link);

        return true;
}

/** Compare one component of path to a directory entry.
 *
 * @param nodep         Node to compare the path component with.
 * @param component     Array of characters holding component name.
 *
 * @return              True on match, false otherwise.
 */
static bool match_component(void *nodep, const char *component)
{
        tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) nodep;

        return !strcmp(dentry->name, component);
}

static void *create_node(void *nodep,
    const char *component, int lflag)
{
        tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) nodep;

        assert(dentry->type == TMPFS_DIRECTORY);
        assert((lflag & L_FILE) ^ (lflag & L_DIRECTORY));

        tmpfs_dentry_t *node = malloc(sizeof(tmpfs_dentry_t));
        if (!node)
                return NULL;
        size_t len = strlen(component);
        char *name = malloc(len + 1);
        if (!name) {
                free(node);
                return NULL;
        }
        strcpy(name, component);

        tmpfs_dentry_initialize(node);
        node->index = tmpfs_next_index++;
        node->name = name;
        node->parent = dentry;
        if (lflag & L_DIRECTORY) 
                node->type = TMPFS_DIRECTORY;
        else 
                node->type = TMPFS_FILE;

        /* Insert the new node into the namespace. */
        if (dentry->child) {
                tmpfs_dentry_t *tmp = dentry->child;
                while (tmp->sibling)
                        tmp = tmp->sibling;
                tmp->sibling = node;
        } else {
                dentry->child = node;
        }

        /* Insert the new node into the dentry hash table. */
        hash_table_insert(&dentries, &node->index, &node->dh_link);
        return (void *) node;
}

static int destroy_component(void *nodeptr)
{
        return EPERM;
}

void tmpfs_lookup(ipc_callid_t rid, ipc_call_t *request)
{
        unsigned next = IPC_GET_ARG1(*request);
        unsigned last = IPC_GET_ARG2(*request);
        int dev_handle = IPC_GET_ARG3(*request);
        int lflag = IPC_GET_ARG4(*request);

        if (last < next)
                last += PLB_SIZE;

        /*
         * Initialize TMPFS.
         */
        if (!root && !tmpfs_init()) {
                ipc_answer_0(rid, ENOMEM);
                return;
        }

        tmpfs_dentry_t *dtmp = root->child; 
        tmpfs_dentry_t *dcur = root;

        if (PLB_GET_CHAR(next) == '/')
                next++;         /* eat slash */
        
        char component[NAME_MAX + 1];
        int len = 0;
        while (dtmp && next <= last) {

                /* collect the component */
                if (PLB_GET_CHAR(next) != '/') {
                        if (len + 1 == NAME_MAX) {
                                /* comopnent length overflow */
                                ipc_answer_0(rid, ENAMETOOLONG);
                                return;
                        }
                        component[len++] = PLB_GET_CHAR(next);
                        next++; /* process next character */
                        if (next <= last) 
                                continue;
                }

                assert(len);
                component[len] = '\0';
                next++;         /* eat slash */
                len = 0;

                /* match the component */
                while (dtmp && !match_component(dtmp, component))
                        dtmp = dtmp->sibling;

                /* handle miss: match amongst siblings */
                if (!dtmp) {
                        if ((next > last) && (lflag & L_CREATE)) {
                                /* no components left and L_CREATE specified */
                                if (dcur->type != TMPFS_DIRECTORY) {
                                        ipc_answer_0(rid, ENOTDIR);
                                        return;
                                } 
                                void *nodep = create_node(dcur,
                                    component, lflag);
                                if (nodep) {
                                        ipc_answer_5(rid, EOK,
                                            tmpfs_reg.fs_handle, dev_handle,
                                            TMPFS_GET_INDEX(nodep), 0,
                                            TMPFS_GET_LNKCNT(nodep));
                                } else {
                                        ipc_answer_0(rid, ENOSPC);
                                }
                                return;
                        }
                        ipc_answer_0(rid, ENOENT);
                        return;
                }

                /* descend one level */
                dcur = dtmp;
                dtmp = dtmp->child;
        }

        /* handle miss: excessive components */
        if (!dtmp && next <= last) {
                if (lflag & L_CREATE) {
                        if (dcur->type != TMPFS_DIRECTORY) {
                                ipc_answer_0(rid, ENOTDIR);
                                return;
                        }

                        /* collect next component */
                        while (next <= last) {
                                if (PLB_GET_CHAR(next) == '/') {
                                        /* more than one component */
                                        ipc_answer_0(rid, ENOENT);
                                        return;
                                }
                                if (len + 1 == NAME_MAX) {
                                        /* component length overflow */
                                        ipc_answer_0(rid, ENAMETOOLONG);
                                        return;
                                }
                                component[len++] = PLB_GET_CHAR(next);
                                next++; /* process next character */
                        }
                        assert(len);
                        component[len] = '\0';
                        len = 0;
                                
                        void *nodep = create_node(dcur, component, lflag);
                        if (nodep) {
                                ipc_answer_5(rid, EOK, tmpfs_reg.fs_handle,
                                    dev_handle, TMPFS_GET_INDEX(nodep), 0,
                                    TMPFS_GET_LNKCNT(nodep));
                        } else {
                                ipc_answer_0(rid, ENOSPC);
                        }
                        return;
                }
                ipc_answer_0(rid, ENOENT);
                return;
        }

        /* handle hit */
        if (lflag & L_DESTROY) {
                int res = destroy_component(dcur);
                ipc_answer_0(rid, res);
                return;
        }
        if ((lflag & (L_CREATE | L_EXCLUSIVE)) == (L_CREATE | L_EXCLUSIVE)) {
                ipc_answer_0(rid, EEXIST);
                return;
        }
        if ((lflag & L_FILE) && (dcur->type != TMPFS_FILE)) {
                ipc_answer_0(rid, EISDIR);
                return;
        }
        if ((lflag & L_DIRECTORY) && (dcur->type != TMPFS_DIRECTORY)) {
                ipc_answer_0(rid, ENOTDIR);
                return;
        }

        ipc_answer_5(rid, EOK, tmpfs_reg.fs_handle, dev_handle, dcur->index,
            dcur->size, TMPFS_GET_LNKCNT(dcur));
}

void tmpfs_read(ipc_callid_t rid, ipc_call_t *request)
{
        int dev_handle = IPC_GET_ARG1(*request);
        unsigned long index = IPC_GET_ARG2(*request);
        off_t pos = IPC_GET_ARG3(*request);

        /*
         * Lookup the respective dentry.
         */
        link_t *hlp;
        hlp = hash_table_find(&dentries, &index);
        if (!hlp) {
                ipc_answer_0(rid, ENOENT);
                return;
        }
        tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,
            dh_link);

        /*
         * Receive the read request.
         */
        ipc_callid_t callid;
        size_t len;
        if (!ipc_data_read_receive(&callid, &len)) {
                ipc_answer_0(callid, EINVAL);   
                ipc_answer_0(rid, EINVAL);
                return;
        }

        size_t bytes;
        if (dentry->type == TMPFS_FILE) {
                bytes = max(0, min(dentry->size - pos, len));
                (void) ipc_data_read_finalize(callid, dentry->data + pos,
                    bytes);
        } else {
                int i;
                tmpfs_dentry_t *cur = dentry->child;
                
                assert(dentry->type == TMPFS_DIRECTORY);
                
                /*
                 * Yes, we really use O(n) algorithm here.
                 * If it bothers someone, it could be fixed by introducing a
                 * hash table.
                 */
                for (i = 0, cur = dentry->child; i < pos && cur; i++,
                    cur = cur->sibling)
                        ;

                if (!cur) {
                        ipc_answer_0(callid, ENOENT);
                        ipc_answer_1(rid, ENOENT, 0);
                        return;
                }

                (void) ipc_data_read_finalize(callid, cur->name,
                    strlen(cur->name) + 1);
                bytes = 1;
        }

        /*
         * Answer the VFS_READ call.
         */
        ipc_answer_1(rid, EOK, bytes);
}

void tmpfs_write(ipc_callid_t rid, ipc_call_t *request)
{
        int dev_handle = IPC_GET_ARG1(*request);
        unsigned long index = IPC_GET_ARG2(*request);
        off_t pos = IPC_GET_ARG3(*request);

        /*
         * Lookup the respective dentry.
         */
        link_t *hlp;
        hlp = hash_table_find(&dentries, &index);
        if (!hlp) {
                ipc_answer_0(rid, ENOENT);
                return;
        }
        tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,
            dh_link);

        /*
         * Receive the write request.
         */
        ipc_callid_t callid;
        size_t len;
        if (!ipc_data_write_receive(&callid, &len)) {
                ipc_answer_0(callid, EINVAL);   
                ipc_answer_0(rid, EINVAL);
                return;
        }

        /*
         * Check whether the file needs to grow.
         */
        if (pos + len <= dentry->size) {
                /* The file size is not changing. */
                (void) ipc_data_write_finalize(callid, dentry->data + pos, len);
                ipc_answer_2(rid, EOK, len, dentry->size);
                return;
        }
        size_t delta = (pos + len) - dentry->size;
        /*
         * At this point, we are deliberately extremely straightforward and
         * simply realloc the contents of the file on every write that grows the
         * file. In the end, the situation might not be as bad as it may look:
         * our heap allocator can save us and just grow the block whenever
         * possible.
         */
        void *newdata = realloc(dentry->data, dentry->size + delta);
        if (!newdata) {
                ipc_answer_0(callid, ENOMEM);
                ipc_answer_2(rid, EOK, 0, dentry->size);
                return;
        }
        /* Clear any newly allocated memory in order to emulate gaps. */
        memset(newdata + dentry->size, 0, delta);
        dentry->size += delta;
        dentry->data = newdata;
        (void) ipc_data_write_finalize(callid, dentry->data + pos, len);
        ipc_answer_2(rid, EOK, len, dentry->size);
}

void tmpfs_truncate(ipc_callid_t rid, ipc_call_t *request)
{
        int dev_handle = IPC_GET_ARG1(*request);
        unsigned long index = IPC_GET_ARG2(*request);
        size_t size = IPC_GET_ARG3(*request);

        /*
         * Lookup the respective dentry.
         */
        link_t *hlp;
        hlp = hash_table_find(&dentries, &index);
        if (!hlp) {
                ipc_answer_0(rid, ENOENT);
                return;
        }
        tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,
            dh_link);

        if (size == dentry->size) {
                ipc_answer_0(rid, EOK);
                return;
        }

        void *newdata = realloc(dentry->data, size);
        if (!newdata) {
                ipc_answer_0(rid, ENOMEM);
                return;
        }
        if (size > dentry->size) {
                size_t delta = size - dentry->size;
                memset(newdata + dentry->size, 0, delta);
        }
        dentry->size = size;
        dentry->data = newdata;
        ipc_answer_0(rid, EOK);
}

/**
 * @}
 */