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  1. /*
  2.  * Copyright (c) 2008 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup fs
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    fat_ops.c
  35.  * @brief   Implementation of VFS operations for the FAT file system server.
  36.  */
  37.  
  38. #include "fat.h"
  39. #include "fat_dentry.h"
  40. #include "fat_fat.h"
  41. #include "../../vfs/vfs.h"
  42. #include <libfs.h>
  43. #include <libblock.h>
  44. #include <ipc/ipc.h>
  45. #include <ipc/services.h>
  46. #include <ipc/devmap.h>
  47. #include <async.h>
  48. #include <errno.h>
  49. #include <string.h>
  50. #include <byteorder.h>
  51. #include <libadt/hash_table.h>
  52. #include <libadt/list.h>
  53. #include <assert.h>
  54. #include <futex.h>
  55. #include <sys/mman.h>
  56. #include <align.h>
  57.  
  58. /** Futex protecting the list of cached free FAT nodes. */
  59. static futex_t ffn_futex = FUTEX_INITIALIZER;
  60.  
  61. /** List of cached free FAT nodes. */
  62. static LIST_INITIALIZE(ffn_head);
  63.  
  64. static void fat_node_initialize(fat_node_t *node)
  65. {
  66.     futex_initialize(&node->lock, 1);
  67.     node->idx = NULL;
  68.     node->type = 0;
  69.     link_initialize(&node->ffn_link);
  70.     node->size = 0;
  71.     node->lnkcnt = 0;
  72.     node->refcnt = 0;
  73.     node->dirty = false;
  74. }
  75.  
  76. static void fat_node_sync(fat_node_t *node)
  77. {
  78.     block_t *b;
  79.     fat_bs_t *bs;
  80.     fat_dentry_t *d;
  81.     uint16_t bps;
  82.     unsigned dps;
  83.    
  84.     assert(node->dirty);
  85.  
  86.     bs = block_bb_get(node->idx->dev_handle);
  87.     bps = uint16_t_le2host(bs->bps);
  88.     dps = bps / sizeof(fat_dentry_t);
  89.    
  90.     /* Read the block that contains the dentry of interest. */
  91.     b = _fat_block_get(bs, node->idx->dev_handle, node->idx->pfc,
  92.         (node->idx->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);
  93.  
  94.     d = ((fat_dentry_t *)b->data) + (node->idx->pdi % dps);
  95.  
  96.     d->firstc = host2uint16_t_le(node->firstc);
  97.     if (node->type == FAT_FILE)
  98.         d->size = host2uint32_t_le(node->size);
  99.     /* TODO: update other fields? (e.g time fields, attr field) */
  100.    
  101.     b->dirty = true;        /* need to sync block */
  102.     block_put(b);
  103. }
  104.  
  105. static fat_node_t *fat_node_get_new(void)
  106. {
  107.     fat_node_t *nodep;
  108.  
  109.     futex_down(&ffn_futex);
  110.     if (!list_empty(&ffn_head)) {
  111.         /* Try to use a cached free node structure. */
  112.         fat_idx_t *idxp_tmp;
  113.         nodep = list_get_instance(ffn_head.next, fat_node_t, ffn_link);
  114.         if (futex_trydown(&nodep->lock) == ESYNCH_WOULD_BLOCK)
  115.             goto skip_cache;
  116.         idxp_tmp = nodep->idx;
  117.         if (futex_trydown(&idxp_tmp->lock) == ESYNCH_WOULD_BLOCK) {
  118.             futex_up(&nodep->lock);
  119.             goto skip_cache;
  120.         }
  121.         list_remove(&nodep->ffn_link);
  122.         futex_up(&ffn_futex);
  123.         if (nodep->dirty)
  124.             fat_node_sync(nodep);
  125.         idxp_tmp->nodep = NULL;
  126.         futex_up(&nodep->lock);
  127.         futex_up(&idxp_tmp->lock);
  128.     } else {
  129. skip_cache:
  130.         /* Try to allocate a new node structure. */
  131.         futex_up(&ffn_futex);
  132.         nodep = (fat_node_t *)malloc(sizeof(fat_node_t));
  133.         if (!nodep)
  134.             return NULL;
  135.     }
  136.     fat_node_initialize(nodep);
  137.    
  138.     return nodep;
  139. }
  140.  
  141. /** Internal version of fat_node_get().
  142.  *
  143.  * @param idxp      Locked index structure.
  144.  */
  145. static void *fat_node_get_core(fat_idx_t *idxp)
  146. {
  147.     block_t *b;
  148.     fat_bs_t *bs;
  149.     fat_dentry_t *d;
  150.     fat_node_t *nodep = NULL;
  151.     unsigned bps;
  152.     unsigned spc;
  153.     unsigned dps;
  154.  
  155.     if (idxp->nodep) {
  156.         /*
  157.          * We are lucky.
  158.          * The node is already instantiated in memory.
  159.          */
  160.         futex_down(&idxp->nodep->lock);
  161.         if (!idxp->nodep->refcnt++)
  162.             list_remove(&idxp->nodep->ffn_link);
  163.         futex_up(&idxp->nodep->lock);
  164.         return idxp->nodep;
  165.     }
  166.  
  167.     /*
  168.      * We must instantiate the node from the file system.
  169.      */
  170.    
  171.     assert(idxp->pfc);
  172.  
  173.     nodep = fat_node_get_new();
  174.     if (!nodep)
  175.         return NULL;
  176.  
  177.     bs = block_bb_get(idxp->dev_handle);
  178.     bps = uint16_t_le2host(bs->bps);
  179.     spc = bs->spc;
  180.     dps = bps / sizeof(fat_dentry_t);
  181.  
  182.     /* Read the block that contains the dentry of interest. */
  183.     b = _fat_block_get(bs, idxp->dev_handle, idxp->pfc,
  184.         (idxp->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);
  185.     assert(b);
  186.  
  187.     d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);
  188.     if (d->attr & FAT_ATTR_SUBDIR) {
  189.         /*
  190.          * The only directory which does not have this bit set is the
  191.          * root directory itself. The root directory node is handled
  192.          * and initialized elsewhere.
  193.          */
  194.         nodep->type = FAT_DIRECTORY;
  195.         /*
  196.          * Unfortunately, the 'size' field of the FAT dentry is not
  197.          * defined for the directory entry type. We must determine the
  198.          * size of the directory by walking the FAT.
  199.          */
  200.         nodep->size = bps * spc * fat_clusters_get(bs, idxp->dev_handle,
  201.             uint16_t_le2host(d->firstc));
  202.     } else {
  203.         nodep->type = FAT_FILE;
  204.         nodep->size = uint32_t_le2host(d->size);
  205.     }
  206.     nodep->firstc = uint16_t_le2host(d->firstc);
  207.     nodep->lnkcnt = 1;
  208.     nodep->refcnt = 1;
  209.  
  210.     block_put(b);
  211.  
  212.     /* Link the idx structure with the node structure. */
  213.     nodep->idx = idxp;
  214.     idxp->nodep = nodep;
  215.  
  216.     return nodep;
  217. }
  218.  
  219. /** Instantiate a FAT in-core node. */
  220. static void *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
  221. {
  222.     void *node;
  223.     fat_idx_t *idxp;
  224.  
  225.     idxp = fat_idx_get_by_index(dev_handle, index);
  226.     if (!idxp)
  227.         return NULL;
  228.     /* idxp->lock held */
  229.     node = fat_node_get_core(idxp);
  230.     futex_up(&idxp->lock);
  231.     return node;
  232. }
  233.  
  234. static void fat_node_put(void *node)
  235. {
  236.     fat_node_t *nodep = (fat_node_t *)node;
  237.     bool destroy = false;
  238.  
  239.     futex_down(&nodep->lock);
  240.     if (!--nodep->refcnt) {
  241.         if (nodep->idx) {
  242.             futex_down(&ffn_futex);
  243.             list_append(&nodep->ffn_link, &ffn_head);
  244.             futex_up(&ffn_futex);
  245.         } else {
  246.             /*
  247.              * The node does not have any index structure associated
  248.              * with itself. This can only mean that we are releasing
  249.              * the node after a failed attempt to allocate the index
  250.              * structure for it.
  251.              */
  252.             destroy = true;
  253.         }
  254.     }
  255.     futex_up(&nodep->lock);
  256.     if (destroy)
  257.         free(node);
  258. }
  259.  
  260. static void *fat_create_node(dev_handle_t dev_handle, int flags)
  261. {
  262.     fat_idx_t *idxp;
  263.     fat_node_t *nodep;
  264.  
  265.     nodep = fat_node_get_new();
  266.     if (!nodep)
  267.         return NULL;
  268.     idxp = fat_idx_get_new(dev_handle);
  269.     if (!idxp) {
  270.         fat_node_put(nodep);
  271.         return NULL;
  272.     }
  273.     /* idxp->lock held */
  274.     if (flags & L_DIRECTORY) {
  275.         nodep->type = FAT_DIRECTORY;
  276.     } else {
  277.         nodep->type = FAT_FILE;
  278.     }
  279.     nodep->size = 0;
  280.     nodep->firstc = FAT_CLST_RES0;
  281.     nodep->lnkcnt = 0;  /* not linked anywhere */
  282.     nodep->refcnt = 1;
  283.  
  284.     nodep->idx = idxp;
  285.     idxp->nodep = nodep;
  286.  
  287.     futex_up(&idxp->lock);
  288.     return nodep;
  289. }
  290.  
  291. static int fat_destroy_node(void *node)
  292. {
  293.     return ENOTSUP; /* not supported at the moment */
  294. }
  295.  
  296. static bool fat_link(void *prnt, void *chld, const char *name)
  297. {
  298.     return false;   /* not supported at the moment */
  299. }
  300.  
  301. static int fat_unlink(void *prnt, void *chld)
  302. {
  303.     return ENOTSUP; /* not supported at the moment */
  304. }
  305.  
  306. static void *fat_match(void *prnt, const char *component)
  307. {
  308.     fat_bs_t *bs;
  309.     fat_node_t *parentp = (fat_node_t *)prnt;
  310.     char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  311.     unsigned i, j;
  312.     unsigned bps;       /* bytes per sector */
  313.     unsigned dps;       /* dentries per sector */
  314.     unsigned blocks;
  315.     fat_dentry_t *d;
  316.     block_t *b;
  317.  
  318.     futex_down(&parentp->idx->lock);
  319.     bs = block_bb_get(parentp->idx->dev_handle);
  320.     bps = uint16_t_le2host(bs->bps);
  321.     dps = bps / sizeof(fat_dentry_t);
  322.     blocks = parentp->size / bps;
  323.     for (i = 0; i < blocks; i++) {
  324.         b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);
  325.         for (j = 0; j < dps; j++) {
  326.             d = ((fat_dentry_t *)b->data) + j;
  327.             switch (fat_classify_dentry(d)) {
  328.             case FAT_DENTRY_SKIP:
  329.                 continue;
  330.             case FAT_DENTRY_LAST:
  331.                 block_put(b);
  332.                 futex_up(&parentp->idx->lock);
  333.                 return NULL;
  334.             default:
  335.             case FAT_DENTRY_VALID:
  336.                 dentry_name_canonify(d, name);
  337.                 break;
  338.             }
  339.             if (stricmp(name, component) == 0) {
  340.                 /* hit */
  341.                 void *node;
  342.                 /*
  343.                  * Assume tree hierarchy for locking.  We
  344.                  * already have the parent and now we are going
  345.                  * to lock the child.  Never lock in the oposite
  346.                  * order.
  347.                  */
  348.                 fat_idx_t *idx = fat_idx_get_by_pos(
  349.                     parentp->idx->dev_handle, parentp->firstc,
  350.                     i * dps + j);
  351.                 futex_up(&parentp->idx->lock);
  352.                 if (!idx) {
  353.                     /*
  354.                      * Can happen if memory is low or if we
  355.                      * run out of 32-bit indices.
  356.                      */
  357.                     block_put(b);
  358.                     return NULL;
  359.                 }
  360.                 node = fat_node_get_core(idx);
  361.                 futex_up(&idx->lock);
  362.                 block_put(b);
  363.                 return node;
  364.             }
  365.         }
  366.         block_put(b);
  367.     }
  368.  
  369.     futex_up(&parentp->idx->lock);
  370.     return NULL;
  371. }
  372.  
  373. static fs_index_t fat_index_get(void *node)
  374. {
  375.     fat_node_t *fnodep = (fat_node_t *)node;
  376.     if (!fnodep)
  377.         return 0;
  378.     return fnodep->idx->index;
  379. }
  380.  
  381. static size_t fat_size_get(void *node)
  382. {
  383.     return ((fat_node_t *)node)->size;
  384. }
  385.  
  386. static unsigned fat_lnkcnt_get(void *node)
  387. {
  388.     return ((fat_node_t *)node)->lnkcnt;
  389. }
  390.  
  391. static bool fat_has_children(void *node)
  392. {
  393.     fat_bs_t *bs;
  394.     fat_node_t *nodep = (fat_node_t *)node;
  395.     unsigned bps;
  396.     unsigned dps;
  397.     unsigned blocks;
  398.     block_t *b;
  399.     unsigned i, j;
  400.  
  401.     if (nodep->type != FAT_DIRECTORY)
  402.         return false;
  403.    
  404.     futex_down(&nodep->idx->lock);
  405.     bs = block_bb_get(nodep->idx->dev_handle);
  406.     bps = uint16_t_le2host(bs->bps);
  407.     dps = bps / sizeof(fat_dentry_t);
  408.  
  409.     blocks = nodep->size / bps;
  410.  
  411.     for (i = 0; i < blocks; i++) {
  412.         fat_dentry_t *d;
  413.    
  414.         b = fat_block_get(bs, nodep, i, BLOCK_FLAGS_NONE);
  415.         for (j = 0; j < dps; j++) {
  416.             d = ((fat_dentry_t *)b->data) + j;
  417.             switch (fat_classify_dentry(d)) {
  418.             case FAT_DENTRY_SKIP:
  419.                 continue;
  420.             case FAT_DENTRY_LAST:
  421.                 block_put(b);
  422.                 futex_up(&nodep->idx->lock);
  423.                 return false;
  424.             default:
  425.             case FAT_DENTRY_VALID:
  426.                 block_put(b);
  427.                 futex_up(&nodep->idx->lock);
  428.                 return true;
  429.             }
  430.             block_put(b);
  431.             futex_up(&nodep->idx->lock);
  432.             return true;
  433.         }
  434.         block_put(b);
  435.     }
  436.  
  437.     futex_up(&nodep->idx->lock);
  438.     return false;
  439. }
  440.  
  441. static void *fat_root_get(dev_handle_t dev_handle)
  442. {
  443.     return fat_node_get(dev_handle, 0);
  444. }
  445.  
  446. static char fat_plb_get_char(unsigned pos)
  447. {
  448.     return fat_reg.plb_ro[pos % PLB_SIZE];
  449. }
  450.  
  451. static bool fat_is_directory(void *node)
  452. {
  453.     return ((fat_node_t *)node)->type == FAT_DIRECTORY;
  454. }
  455.  
  456. static bool fat_is_file(void *node)
  457. {
  458.     return ((fat_node_t *)node)->type == FAT_FILE;
  459. }
  460.  
  461. /** libfs operations */
  462. libfs_ops_t fat_libfs_ops = {
  463.     .match = fat_match,
  464.     .node_get = fat_node_get,
  465.     .node_put = fat_node_put,
  466.     .create = fat_create_node,
  467.     .destroy = fat_destroy_node,
  468.     .link = fat_link,
  469.     .unlink = fat_unlink,
  470.     .index_get = fat_index_get,
  471.     .size_get = fat_size_get,
  472.     .lnkcnt_get = fat_lnkcnt_get,
  473.     .has_children = fat_has_children,
  474.     .root_get = fat_root_get,
  475.     .plb_get_char = fat_plb_get_char,
  476.     .is_directory = fat_is_directory,
  477.     .is_file = fat_is_file
  478. };
  479.  
  480. void fat_mounted(ipc_callid_t rid, ipc_call_t *request)
  481. {
  482.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  483.     fat_bs_t *bs;
  484.     uint16_t bps;
  485.     uint16_t rde;
  486.     int rc;
  487.  
  488.     /* initialize libblock */
  489.     rc = block_init(dev_handle, BS_SIZE);
  490.     if (rc != EOK) {
  491.         ipc_answer_0(rid, rc);
  492.         return;
  493.     }
  494.  
  495.     /* prepare the boot block */
  496.     rc = block_bb_read(dev_handle, BS_BLOCK * BS_SIZE, BS_SIZE);
  497.     if (rc != EOK) {
  498.         block_fini(dev_handle);
  499.         ipc_answer_0(rid, rc);
  500.         return;
  501.     }
  502.  
  503.     /* get the buffer with the boot sector */
  504.     bs = block_bb_get(dev_handle);
  505.    
  506.     /* Read the number of root directory entries. */
  507.     bps = uint16_t_le2host(bs->bps);
  508.     rde = uint16_t_le2host(bs->root_ent_max);
  509.  
  510.     if (bps != BS_SIZE) {
  511.         block_fini(dev_handle);
  512.         ipc_answer_0(rid, ENOTSUP);
  513.         return;
  514.     }
  515.  
  516.     /* Initialize the block cache */
  517.     rc = block_cache_init(dev_handle, bps, 0 /* XXX */);
  518.     if (rc != EOK) {
  519.         block_fini(dev_handle);
  520.         ipc_answer_0(rid, rc);
  521.         return;
  522.     }
  523.  
  524.     rc = fat_idx_init_by_dev_handle(dev_handle);
  525.     if (rc != EOK) {
  526.         block_fini(dev_handle);
  527.         ipc_answer_0(rid, rc);
  528.         return;
  529.     }
  530.  
  531.     /* Initialize the root node. */
  532.     fat_node_t *rootp = (fat_node_t *)malloc(sizeof(fat_node_t));
  533.     if (!rootp) {
  534.         block_fini(dev_handle);
  535.         fat_idx_fini_by_dev_handle(dev_handle);
  536.         ipc_answer_0(rid, ENOMEM);
  537.         return;
  538.     }
  539.     fat_node_initialize(rootp);
  540.  
  541.     fat_idx_t *ridxp = fat_idx_get_by_pos(dev_handle, FAT_CLST_ROOTPAR, 0);
  542.     if (!ridxp) {
  543.         block_fini(dev_handle);
  544.         free(rootp);
  545.         fat_idx_fini_by_dev_handle(dev_handle);
  546.         ipc_answer_0(rid, ENOMEM);
  547.         return;
  548.     }
  549.     assert(ridxp->index == 0);
  550.     /* ridxp->lock held */
  551.  
  552.     rootp->type = FAT_DIRECTORY;
  553.     rootp->firstc = FAT_CLST_ROOT;
  554.     rootp->refcnt = 1;
  555.     rootp->lnkcnt = 0;  /* FS root is not linked */
  556.     rootp->size = rde * sizeof(fat_dentry_t);
  557.     rootp->idx = ridxp;
  558.     ridxp->nodep = rootp;
  559.    
  560.     futex_up(&ridxp->lock);
  561.  
  562.     ipc_answer_3(rid, EOK, ridxp->index, rootp->size, rootp->lnkcnt);
  563. }
  564.  
  565. void fat_mount(ipc_callid_t rid, ipc_call_t *request)
  566. {
  567.     ipc_answer_0(rid, ENOTSUP);
  568. }
  569.  
  570. void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
  571. {
  572.     libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  573. }
  574.  
  575. void fat_read(ipc_callid_t rid, ipc_call_t *request)
  576. {
  577.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  578.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  579.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  580.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  581.     fat_bs_t *bs;
  582.     uint16_t bps;
  583.     size_t bytes;
  584.     block_t *b;
  585.  
  586.     if (!nodep) {
  587.         ipc_answer_0(rid, ENOENT);
  588.         return;
  589.     }
  590.  
  591.     ipc_callid_t callid;
  592.     size_t len;
  593.     if (!ipc_data_read_receive(&callid, &len)) {
  594.         fat_node_put(nodep);
  595.         ipc_answer_0(callid, EINVAL);
  596.         ipc_answer_0(rid, EINVAL);
  597.         return;
  598.     }
  599.  
  600.     bs = block_bb_get(dev_handle);
  601.     bps = uint16_t_le2host(bs->bps);
  602.  
  603.     if (nodep->type == FAT_FILE) {
  604.         /*
  605.          * Our strategy for regular file reads is to read one block at
  606.          * most and make use of the possibility to return less data than
  607.          * requested. This keeps the code very simple.
  608.          */
  609.         if (pos >= nodep->size) {
  610.             /* reading beyond the EOF */
  611.             bytes = 0;
  612.             (void) ipc_data_read_finalize(callid, NULL, 0);
  613.         } else {
  614.             bytes = min(len, bps - pos % bps);
  615.             bytes = min(bytes, nodep->size - pos);
  616.             b = fat_block_get(bs, nodep, pos / bps,
  617.                 BLOCK_FLAGS_NONE);
  618.             (void) ipc_data_read_finalize(callid, b->data + pos % bps,
  619.                 bytes);
  620.             block_put(b);
  621.         }
  622.     } else {
  623.         unsigned bnum;
  624.         off_t spos = pos;
  625.         char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  626.         fat_dentry_t *d;
  627.  
  628.         assert(nodep->type == FAT_DIRECTORY);
  629.         assert(nodep->size % bps == 0);
  630.         assert(bps % sizeof(fat_dentry_t) == 0);
  631.  
  632.         /*
  633.          * Our strategy for readdir() is to use the position pointer as
  634.          * an index into the array of all dentries. On entry, it points
  635.          * to the first unread dentry. If we skip any dentries, we bump
  636.          * the position pointer accordingly.
  637.          */
  638.         bnum = (pos * sizeof(fat_dentry_t)) / bps;
  639.         while (bnum < nodep->size / bps) {
  640.             off_t o;
  641.  
  642.             b = fat_block_get(bs, nodep, bnum, BLOCK_FLAGS_NONE);
  643.             for (o = pos % (bps / sizeof(fat_dentry_t));
  644.                 o < bps / sizeof(fat_dentry_t);
  645.                 o++, pos++) {
  646.                 d = ((fat_dentry_t *)b->data) + o;
  647.                 switch (fat_classify_dentry(d)) {
  648.                 case FAT_DENTRY_SKIP:
  649.                     continue;
  650.                 case FAT_DENTRY_LAST:
  651.                     block_put(b);
  652.                     goto miss;
  653.                 default:
  654.                 case FAT_DENTRY_VALID:
  655.                     dentry_name_canonify(d, name);
  656.                     block_put(b);
  657.                     goto hit;
  658.                 }
  659.             }
  660.             block_put(b);
  661.             bnum++;
  662.         }
  663. miss:
  664.         fat_node_put(nodep);
  665.         ipc_answer_0(callid, ENOENT);
  666.         ipc_answer_1(rid, ENOENT, 0);
  667.         return;
  668. hit:
  669.         (void) ipc_data_read_finalize(callid, name, strlen(name) + 1);
  670.         bytes = (pos - spos) + 1;
  671.     }
  672.  
  673.     fat_node_put(nodep);
  674.     ipc_answer_1(rid, EOK, (ipcarg_t)bytes);
  675. }
  676.  
  677. void fat_write(ipc_callid_t rid, ipc_call_t *request)
  678. {
  679.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  680.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  681.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  682.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  683.     fat_bs_t *bs;
  684.     size_t bytes;
  685.     block_t *b;
  686.     uint16_t bps;
  687.     unsigned spc;
  688.     unsigned bpc;       /* bytes per cluster */
  689.     off_t boundary;
  690.     int flags = BLOCK_FLAGS_NONE;
  691.    
  692.     if (!nodep) {
  693.         ipc_answer_0(rid, ENOENT);
  694.         return;
  695.     }
  696.    
  697.     ipc_callid_t callid;
  698.     size_t len;
  699.     if (!ipc_data_write_receive(&callid, &len)) {
  700.         fat_node_put(nodep);
  701.         ipc_answer_0(callid, EINVAL);
  702.         ipc_answer_0(rid, EINVAL);
  703.         return;
  704.     }
  705.  
  706.     bs = block_bb_get(dev_handle);
  707.     bps = uint16_t_le2host(bs->bps);
  708.     spc = bs->spc;
  709.     bpc = bps * spc;
  710.  
  711.     /*
  712.      * In all scenarios, we will attempt to write out only one block worth
  713.      * of data at maximum. There might be some more efficient approaches,
  714.      * but this one greatly simplifies fat_write(). Note that we can afford
  715.      * to do this because the client must be ready to handle the return
  716.      * value signalizing a smaller number of bytes written.
  717.      */
  718.     bytes = min(len, bps - pos % bps);
  719.     if (bytes == bps)
  720.         flags |= BLOCK_FLAGS_NOREAD;
  721.    
  722.     boundary = ROUND_UP(nodep->size, bpc);
  723.     if (pos < boundary) {
  724.         /*
  725.          * This is the easier case - we are either overwriting already
  726.          * existing contents or writing behind the EOF, but still within
  727.          * the limits of the last cluster. The node size may grow to the
  728.          * next block size boundary.
  729.          */
  730.         fat_fill_gap(bs, nodep, FAT_CLST_RES0, pos);
  731.         b = fat_block_get(bs, nodep, pos / bps, flags);
  732.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  733.             bytes);
  734.         b->dirty = true;        /* need to sync block */
  735.         block_put(b);
  736.         if (pos + bytes > nodep->size) {
  737.             nodep->size = pos + bytes;
  738.             nodep->dirty = true;    /* need to sync node */
  739.         }
  740.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  741.         fat_node_put(nodep);
  742.         return;
  743.     } else {
  744.         /*
  745.          * This is the more difficult case. We must allocate new
  746.          * clusters for the node and zero them out.
  747.          */
  748.         int status;
  749.         unsigned nclsts;
  750.         fat_cluster_t mcl, lcl;
  751.  
  752.         nclsts = (ROUND_UP(pos + bytes, bpc) - boundary) / bpc;
  753.         /* create an independent chain of nclsts clusters in all FATs */
  754.         status = fat_alloc_clusters(bs, dev_handle, nclsts, &mcl, &lcl);
  755.         if (status != EOK) {
  756.             /* could not allocate a chain of nclsts clusters */
  757.             fat_node_put(nodep);
  758.             ipc_answer_0(callid, status);
  759.             ipc_answer_0(rid, status);
  760.             return;
  761.         }
  762.         /* zero fill any gaps */
  763.         fat_fill_gap(bs, nodep, mcl, pos);
  764.         b = _fat_block_get(bs, dev_handle, lcl, (pos / bps) % spc,
  765.             flags);
  766.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  767.             bytes);
  768.         b->dirty = true;        /* need to sync block */
  769.         block_put(b);
  770.         /*
  771.          * Append the cluster chain starting in mcl to the end of the
  772.          * node's cluster chain.
  773.          */
  774.         fat_append_clusters(bs, nodep, mcl);
  775.         nodep->size = pos + bytes;
  776.         nodep->dirty = true;        /* need to sync node */
  777.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  778.         fat_node_put(nodep);
  779.         return;
  780.     }
  781. }
  782.  
  783. void fat_truncate(ipc_callid_t rid, ipc_call_t *request)
  784. {
  785.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  786.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  787.     size_t size = (off_t)IPC_GET_ARG3(*request);
  788.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  789.     fat_bs_t *bs;
  790.     uint16_t bps;
  791.     uint8_t spc;
  792.     unsigned bpc;   /* bytes per cluster */
  793.     int rc;
  794.  
  795.     if (!nodep) {
  796.         ipc_answer_0(rid, ENOENT);
  797.         return;
  798.     }
  799.  
  800.     bs = block_bb_get(dev_handle);
  801.     bps = uint16_t_le2host(bs->bps);
  802.     spc = bs->spc;
  803.     bpc = bps * spc;
  804.  
  805.     if (nodep->size == size) {
  806.         rc = EOK;
  807.     } else if (nodep->size < size) {
  808.         /*
  809.          * The standard says we have the freedom to grow the node.
  810.          * For now, we simply return an error.
  811.          */
  812.         rc = EINVAL;
  813.     } else if (ROUND_UP(nodep->size, bpc) == ROUND_UP(size, bpc)) {
  814.         /*
  815.          * The node will be shrunk, but no clusters will be deallocated.
  816.          */
  817.         nodep->size = size;
  818.         nodep->dirty = true;        /* need to sync node */
  819.         rc = EOK;  
  820.     } else {
  821.         /*
  822.          * The node will be shrunk, clusters will be deallocated.
  823.          */
  824.         if (size == 0) {
  825.             fat_chop_clusters(bs, nodep, FAT_CLST_RES0);
  826.         } else {
  827.             fat_cluster_t lastc;
  828.             (void) fat_cluster_walk(bs, dev_handle, nodep->firstc,
  829.                 &lastc, (size - 1) / bpc);
  830.             fat_chop_clusters(bs, nodep, lastc);
  831.         }
  832.         nodep->size = size;
  833.         nodep->dirty = true;        /* need to sync node */
  834.         rc = EOK;  
  835.     }
  836.     fat_node_put(nodep);
  837.     ipc_answer_0(rid, rc);
  838.     return;
  839. }
  840.  
  841. /**
  842.  * @}
  843.  */
  844.