source: mainline/uspace/srv/fs/fat/fat_ops.c@ add5835

/*
 * 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        fat_ops.c
 * @brief       Implementation of VFS operations for the FAT file system server.
 */

#include "fat.h"
#include "../../vfs/vfs.h"
#include <libfs.h>
#include <ipc/ipc.h>
#include <async.h>
#include <errno.h>
#include <string.h>
#include <byteorder.h>
#include <libadt/hash_table.h>
#include <libadt/list.h>
#include <assert.h>
#include <futex.h>

#define BS_BLOCK                0

/** Futex protecting the list of cached free FAT nodes. */
static futex_t ffn_futex = FUTEX_INITIALIZER;

/** List of cached free FAT nodes. */
static LIST_INITIALIZE(ffn_head);

#define FAT_NAME_LEN            8
#define FAT_EXT_LEN             3

#define FAT_PAD                 ' ' 

#define FAT_DENTRY_UNUSED       0x00
#define FAT_DENTRY_E5_ESC       0x05
#define FAT_DENTRY_DOT          0x2e
#define FAT_DENTRY_ERASED       0xe5

static void dentry_name_canonify(fat_dentry_t *d, char *buf)
{
        int i;

        for (i = 0; i < FAT_NAME_LEN; i++) {
                if (d->name[i] == FAT_PAD) {
                        buf++;
                        break;
                }
                if (d->name[i] == FAT_DENTRY_E5_ESC)
                        *buf++ = 0xe5;
                else
                        *buf++ = d->name[i];
        }
        if (d->ext[0] != FAT_PAD)
                *buf++ = '.';
        for (i = 0; i < FAT_EXT_LEN; i++) {
                if (d->ext[i] == FAT_PAD) {
                        *buf = '\0';
                        return;
                }
                if (d->ext[i] == FAT_DENTRY_E5_ESC)
                        *buf++ = 0xe5;
                else
                        *buf++ = d->ext[i];
        }
}

/* TODO move somewhere else */
typedef struct {
        void *data;
} block_t;

static block_t *block_get(dev_handle_t dev_handle, off_t offset)
{
        return NULL;    /* TODO */
}

static void block_put(block_t *block)
{
        /* TODO */
}

#define FAT_BS(b)               ((fat_bs_t *)((b)->data))

#define FAT_CLST_RES0   0x0000
#define FAT_CLST_RES1   0x0001  /* internally used to mark root directory */
#define FAT_CLST_FIRST  0x0002
#define FAT_CLST_BAD    0xfff7
#define FAT_CLST_LAST1  0xfff8
#define FAT_CLST_LAST8  0xffff

#define fat_block_get(np, off) \
    _fat_block_get((np)->idx->dev_handle, (np)->firstc, (off))

static block_t *
_fat_block_get(dev_handle_t dev_handle, fat_cluster_t firstc, off_t offset)
{
        block_t *bb;
        block_t *b;
        unsigned bps;
        unsigned spc;
        unsigned rscnt;         /* block address of the first FAT */
        unsigned fatcnt;
        unsigned rde;
        unsigned rds;           /* root directory size */
        unsigned sf;
        unsigned ssa;           /* size of the system area */
        unsigned clusters;
        fat_cluster_t clst = firstc;
        unsigned i;

        bb = block_get(dev_handle, BS_BLOCK);
        bps = uint16_t_le2host(FAT_BS(bb)->bps);
        spc = FAT_BS(bb)->spc;
        rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);
        fatcnt = FAT_BS(bb)->fatcnt;
        rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);
        sf = uint16_t_le2host(FAT_BS(bb)->sec_per_fat);
        block_put(bb);

        rds = (sizeof(fat_dentry_t) * rde) / bps;
        rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
        ssa = rscnt + fatcnt * sf + rds;

        if (firstc == FAT_CLST_RES1) {
                /* root directory special case */
                assert(offset < rds);
                b = block_get(dev_handle, rscnt + fatcnt * sf + offset);
                return b;
        }

        clusters = offset / spc; 
        for (i = 0; i < clusters; i++) {
                unsigned fsec;  /* sector offset relative to FAT1 */
                unsigned fidx;  /* FAT1 entry index */

                assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);
                fsec = (clst * sizeof(fat_cluster_t)) / bps;
                fidx = clst % (bps / sizeof(fat_cluster_t));
                /* read FAT1 */
                b = block_get(dev_handle, rscnt + fsec);
                clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
                assert(clst != FAT_CLST_BAD);
                assert(clst < FAT_CLST_LAST1);
                block_put(b);
        }

        b = block_get(dev_handle, ssa + (clst - FAT_CLST_FIRST) * spc +
            offset % spc);

        return b;
}

static void fat_node_initialize(fat_node_t *node)
{
        futex_initialize(&node->lock, 1);
        node->idx = NULL;
        node->type = 0;
        link_initialize(&node->ffn_link);
        node->size = 0;
        node->lnkcnt = 0;
        node->refcnt = 0;
        node->dirty = false;
}

static uint16_t fat_bps_get(dev_handle_t dev_handle)
{
        block_t *bb;
        uint16_t bps;
        
        bb = block_get(dev_handle, BS_BLOCK);
        assert(bb != NULL);
        bps = uint16_t_le2host(FAT_BS(bb)->bps);
        block_put(bb);

        return bps;
}

typedef enum {
        FAT_DENTRY_SKIP,
        FAT_DENTRY_LAST,
        FAT_DENTRY_VALID
} fat_dentry_clsf_t;

static fat_dentry_clsf_t fat_classify_dentry(fat_dentry_t *d)
{
        if (d->attr & FAT_ATTR_VOLLABEL) {
                /* volume label entry */
                return FAT_DENTRY_SKIP;
        }
        if (d->name[0] == FAT_DENTRY_ERASED) {
                /* not-currently-used entry */
                return FAT_DENTRY_SKIP;
        }
        if (d->name[0] == FAT_DENTRY_UNUSED) {
                /* never used entry */
                return FAT_DENTRY_LAST;
        }
        if (d->name[0] == FAT_DENTRY_DOT) {
                /*
                 * Most likely '.' or '..'.
                 * It cannot occur in a regular file name.
                 */
                return FAT_DENTRY_SKIP;
        }
        return FAT_DENTRY_VALID;
}

static void fat_node_sync(fat_node_t *node)
{
        /* TODO */
}

/** Internal version of fat_node_get().
 *
 * @param idxp          Locked index structure.
 */
static void *fat_node_get_core(fat_idx_t *idxp)
{
        block_t *b;
        fat_dentry_t *d;
        fat_node_t *nodep;
        unsigned bps;
        unsigned dps;

        if (idxp->nodep) {
                /*
                 * We are lucky.
                 * The node is already instantiated in memory.
                 */
                futex_down(&idxp->nodep->lock);
                if (!idxp->nodep->refcnt++)
                        list_remove(&nodep->ffn_link);
                futex_up(&idxp->nodep->lock);
                return idxp->nodep;
        }

        /*
         * We must instantiate the node from the file system.
         */
        
        assert(idxp->pfc);

        futex_down(&ffn_futex);
        if (!list_empty(&ffn_head)) {
                /* Try to use a cached free node structure. */
                fat_idx_t *idxp_tmp;
                nodep = list_get_instance(ffn_head.next, fat_node_t, ffn_link);
                if (futex_trydown(&nodep->lock) == ESYNCH_WOULD_BLOCK)
                        goto skip_cache;
                idxp_tmp = nodep->idx;
                if (futex_trydown(&idxp_tmp->lock) == ESYNCH_WOULD_BLOCK) {
                        futex_up(&nodep->lock);
                        goto skip_cache;
                }
                list_remove(&nodep->ffn_link);
                futex_up(&ffn_futex);
                if (nodep->dirty)
                        fat_node_sync(nodep);
                idxp_tmp->nodep = NULL;
                futex_up(&nodep->lock);
                futex_up(&idxp_tmp->lock);
        } else {
skip_cache:
                /* Try to allocate a new node structure. */
                futex_up(&ffn_futex);
                nodep = (fat_node_t *)malloc(sizeof(fat_node_t));
                if (!nodep)
                        return NULL;
        }
        fat_node_initialize(nodep);

        bps = fat_bps_get(idxp->dev_handle);
        dps = bps / sizeof(fat_dentry_t);

        /* Read the block that contains the dentry of interest. */
        b = _fat_block_get(idxp->dev_handle, idxp->pfc,
            (idxp->pdi * sizeof(fat_dentry_t)) / bps);
        assert(b);

        d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);
        if (d->attr & FAT_ATTR_SUBDIR) {
                /* 
                 * The only directory which does not have this bit set is the
                 * root directory itself. The root directory node is handled
                 * and initialized elsewhere.
                 */
                nodep->type = FAT_DIRECTORY;
        } else {
                nodep->type = FAT_FILE;
        }
        nodep->firstc = uint16_t_le2host(d->firstc);
        nodep->size = uint32_t_le2host(d->size);
        nodep->lnkcnt = 1;
        nodep->refcnt = 1;

        block_put(b);

        /* Link the idx structure with the node structure. */
        nodep->idx = idxp;
        idxp->nodep = nodep;

        return nodep;
}

/** Instantiate a FAT in-core node. */
static void *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
{
        void *node;
        fat_idx_t *idxp;

        idxp = fat_idx_get_by_index(dev_handle, index);
        if (!idxp)
                return NULL;
        /* idxp->lock held */
        node = fat_node_get_core(idxp);
        futex_up(&idxp->lock);
        return node;
}

static void fat_node_put(void *node)
{
        fat_node_t *nodep = (fat_node_t *)node;

        futex_down(&nodep->lock);
        if (!--nodep->refcnt) {
                futex_down(&ffn_futex);
                list_append(&nodep->ffn_link, &ffn_head);
                futex_up(&ffn_futex);
        }
        futex_up(&nodep->lock);
}

static void *fat_create(int flags)
{
        return NULL;    /* not supported at the moment */
}

static int fat_destroy(void *node)
{
        return ENOTSUP; /* not supported at the moment */
}

static bool fat_link(void *prnt, void *chld, const char *name)
{
        return false;   /* not supported at the moment */
}

static int fat_unlink(void *prnt, void *chld)
{
        return ENOTSUP; /* not supported at the moment */
}

static void *fat_match(void *prnt, const char *component)
{
        fat_node_t *parentp = (fat_node_t *)prnt;
        char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
        unsigned i, j;
        unsigned bps;           /* bytes per sector */
        unsigned dps;           /* dentries per sector */
        unsigned blocks;
        fat_dentry_t *d;
        block_t *b;

        bps = fat_bps_get(parentp->idx->dev_handle);
        dps = bps / sizeof(fat_dentry_t);
        blocks = parentp->size / bps + (parentp->size % bps != 0);
        for (i = 0; i < blocks; i++) {
                unsigned dentries;
                
                b = fat_block_get(parentp, i);
                dentries = (i == blocks - 1) ?
                    parentp->size % sizeof(fat_dentry_t) :
                    dps;
                for (j = 0; j < dentries; j++) { 
                        d = ((fat_dentry_t *)b->data) + j;
                        switch (fat_classify_dentry(d)) {
                        case FAT_DENTRY_SKIP:
                                continue;
                        case FAT_DENTRY_LAST:
                                block_put(b);
                                return NULL;
                        default:
                        case FAT_DENTRY_VALID:
                                dentry_name_canonify(d, name);
                                break;
                        }
                        if (strcmp(name, component) == 0) {
                                /* hit */
                                void *node;
                                fat_idx_t *idx = fat_idx_get_by_pos(
                                    parentp->idx->dev_handle, parentp->firstc,
                                    i * dps + j);
                                if (!idx) {
                                        /*
                                         * Can happen if memory is low or if we
                                         * run out of 32-bit indices.
                                         */
                                        block_put(b);
                                        return NULL;
                                }
                                node = fat_node_get_core(idx);
                                futex_up(&idx->lock);
                                block_put(b);
                                return node;
                        }
                }
                block_put(b);
        }

        return NULL;
}

static fs_index_t fat_index_get(void *node)
{
        fat_node_t *fnodep = (fat_node_t *)node;
        if (!fnodep)
                return 0;
        return fnodep->idx->index;
}

static size_t fat_size_get(void *node)
{
        return ((fat_node_t *)node)->size;
}

static unsigned fat_lnkcnt_get(void *node)
{
        return ((fat_node_t *)node)->lnkcnt;
}

static bool fat_has_children(void *node)
{
        fat_node_t *nodep = (fat_node_t *)node;
        unsigned bps;
        unsigned dps;
        unsigned blocks;
        block_t *b;
        unsigned i, j;

        if (nodep->type != FAT_DIRECTORY)
                return false;

        futex_down(&nodep->idx->lock);
        bps = fat_bps_get(nodep->idx->dev_handle);
        dps = bps / sizeof(fat_dentry_t);

        blocks = nodep->size / bps + (nodep->size % bps != 0);

        for (i = 0; i < blocks; i++) {
                unsigned dentries;
                fat_dentry_t *d;
        
                b = fat_block_get(nodep, i);
                dentries = (i == blocks - 1) ?
                    nodep->size % sizeof(fat_dentry_t) :
                    dps;
                for (j = 0; j < dentries; j++) {
                        d = ((fat_dentry_t *)b->data) + j;
                        switch (fat_classify_dentry(d)) {
                        case FAT_DENTRY_SKIP:
                                continue;
                        case FAT_DENTRY_LAST:
                                block_put(b);
                                futex_up(&nodep->idx->lock);
                                return false;
                        default:
                        case FAT_DENTRY_VALID:
                                block_put(b);
                                futex_up(&nodep->idx->lock);
                                return true;
                        }
                        block_put(b);
                        futex_up(&nodep->idx->lock);
                        return true;
                }
                block_put(b);
        }

        futex_up(&nodep->idx->lock);
        return false;
}

static void *fat_root_get(dev_handle_t dev_handle)
{
        return NULL;    /* TODO */
}

static char fat_plb_get_char(unsigned pos)
{
        return fat_reg.plb_ro[pos % PLB_SIZE];
}

static bool fat_is_directory(void *node)
{
        return ((fat_node_t *)node)->type == FAT_DIRECTORY;
}

static bool fat_is_file(void *node)
{
        return ((fat_node_t *)node)->type == FAT_FILE;
}

/** libfs operations */
libfs_ops_t fat_libfs_ops = {
        .match = fat_match,
        .node_get = fat_node_get,
        .node_put = fat_node_put,
        .create = fat_create,
        .destroy = fat_destroy,
        .link = fat_link,
        .unlink = fat_unlink,
        .index_get = fat_index_get,
        .size_get = fat_size_get,
        .lnkcnt_get = fat_lnkcnt_get,
        .has_children = fat_has_children,
        .root_get = fat_root_get,
        .plb_get_char = fat_plb_get_char,
        .is_directory = fat_is_directory,
        .is_file = fat_is_file
};

void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
{
        libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
}

/**
 * @}
 */