source: mainline/uspace/srv/fs/tmpfs/tmpfs_ops.c@ ae78b530

/*
 * 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 <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

/*
 * 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);

        /*
         * This is only for debugging. Once we can create files and directories
         * using VFS, we can get rid of this.
         */
        tmpfs_dentry_t *d;
        d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));
        if (!d) {
                free(root);
                root = NULL;
                return false;
        }
        tmpfs_dentry_initialize(d);
        d->index = tmpfs_next_index++;
        root->child = d;
        d->parent = root;
        d->type = TMPFS_DIRECTORY;
        d->name = "dir1";
        hash_table_insert(&dentries, &d->index, &d->dh_link);

        d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));
        if (!d) {
                free(root->child);
                free(root);
                root = NULL;
                return false;
        }
        tmpfs_dentry_initialize(d);
        d->index = tmpfs_next_index++;
        root->child->sibling = d;
        d->parent = root;
        d->type = TMPFS_DIRECTORY;
        d->name = "dir2";
        hash_table_insert(&dentries, &d->index, &d->dh_link);
        
        d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));
        if (!d) {
                free(root->child->sibling);
                free(root->child);
                free(root);
                root = NULL;
                return false;
        }
        tmpfs_dentry_initialize(d);
        d->index = tmpfs_next_index++;
        root->child->child = d;
        d->parent = root->child;
        d->type = TMPFS_FILE;
        d->name = "file1";
        d->data = "This is the contents of /dir1/file1.\n";
        d->size = strlen(d->data);
        hash_table_insert(&dentries, &d->index, &d->dh_link);

        d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));
        if (!d) {
                free(root->child->sibling);
                free(root->child->child);
                free(root->child);
                free(root);
                root = NULL;
                return false;
        }
        tmpfs_dentry_initialize(d);
        d->index = tmpfs_next_index++;
        root->child->sibling->child = d;
        d->parent = root->child->sibling;
        d->type = TMPFS_FILE;
        d->name = "file2";
        d->data = "This is the contents of /dir2/file2.\n";
        d->size = strlen(d->data);
        hash_table_insert(&dentries, &d->index, &d->dh_link);

        return true;
}

/** Compare one component of path to a directory entry.
 *
 * @param dentry        Directory entry to compare the path component with.
 * @param start         Index into PLB where the path component starts.
 * @param last          Index of the last character of the path in PLB.
 *
 * @return              Zero on failure or delta such that (index + delta) %
 *                      PLB_SIZE points to the first unprocessed character in
 *                      PLB which comprises the path.
 */
static unsigned match_path_component(tmpfs_dentry_t *dentry, unsigned start,
    unsigned last)
{
        int i, j;
        size_t namelen;

        namelen = strlen(dentry->name);

        if (last < start)
                last += PLB_SIZE;

        for (i = 0, j = start; i < namelen && j <= last; i++, j++) {
                if (dentry->name[i] != PLB_GET_CHAR(j))
                        return 0;
        }
        
        if (i != namelen)
                return 0;
        if (j < last && PLB_GET_CHAR(j) != '/')
                return 0;
        if (j == last)
                return 0;
        
        return (j - start);
}

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;

        if (!root && !tmpfs_init()) {
                ipc_answer_0(rid, ENOMEM);
                return;
        }

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

        bool hit = true;
        
        if (PLB_GET_CHAR(next) == '/')
                next++;         /* eat slash */
        
        while (next <= last) {
                unsigned delta;
                hit = false;
                do {
                        delta = match_path_component(dtmp, next, last);
                        if (!delta) {
                                dtmp = dtmp->sibling;
                        } else {
                                hit = true;
                                next += delta;
                                next++;         /* eat slash */
                                dcur = dtmp;
                                dtmp = dtmp->child;
                        }       
                } while (delta == 0 && dtmp);
                if (!hit) {
                        ipc_answer_3(rid, ENOENT, tmpfs_reg.fs_handle,
                            dev_handle, dcur->index);
                        return;
                }
        }

        ipc_answer_4(rid, EOK, tmpfs_reg.fs_handle, dev_handle, dcur->index,
            dcur->size);
}

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_1(rid, EOK, len);
                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_1(rid, EOK, 0);
                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);
}

/**
 * @}
 */