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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 <ipc/ipc.h>
  44. #include <ipc/services.h>
  45. #include <ipc/devmap.h>
  46. #include <async.h>
  47. #include <errno.h>
  48. #include <string.h>
  49. #include <byteorder.h>
  50. #include <libadt/hash_table.h>
  51. #include <libadt/list.h>
  52. #include <assert.h>
  53. #include <futex.h>
  54. #include <sys/mman.h>
  55. #include <align.h>
  56.  
  57. /** Futex protecting the list of cached free FAT nodes. */
  58. static futex_t ffn_futex = FUTEX_INITIALIZER;
  59.  
  60. /** List of cached free FAT nodes. */
  61. static LIST_INITIALIZE(ffn_head);
  62.  
  63. static int dev_phone = -1;      /* FIXME */
  64. static void *dev_buffer = NULL;     /* FIXME */
  65.  
  66. block_t *block_get(dev_handle_t dev_handle, off_t offset, size_t bs)
  67. {
  68.     /* FIXME */
  69.     block_t *b;
  70.     off_t bufpos = 0;
  71.     size_t buflen = 0;
  72.     off_t pos = offset * bs;
  73.  
  74.     assert(dev_phone != -1);
  75.     assert(dev_buffer);
  76.  
  77.     b = malloc(sizeof(block_t));
  78.     if (!b)
  79.         return NULL;
  80.    
  81.     b->data = malloc(bs);
  82.     if (!b->data) {
  83.         free(b);
  84.         return NULL;
  85.     }
  86.     b->size = bs;
  87.  
  88.     if (!libfs_blockread(dev_phone, dev_buffer, &bufpos, &buflen, &pos,
  89.         b->data, bs, bs)) {
  90.         free(b->data);
  91.         free(b);
  92.         return NULL;
  93.     }
  94.  
  95.     return b;
  96. }
  97.  
  98. void block_put(block_t *block)
  99. {
  100.     /* FIXME */
  101.     free(block->data);
  102.     free(block);
  103. }
  104.  
  105. static void fat_node_initialize(fat_node_t *node)
  106. {
  107.     futex_initialize(&node->lock, 1);
  108.     node->idx = NULL;
  109.     node->type = 0;
  110.     link_initialize(&node->ffn_link);
  111.     node->size = 0;
  112.     node->lnkcnt = 0;
  113.     node->refcnt = 0;
  114.     node->dirty = false;
  115. }
  116.  
  117. static void fat_node_sync(fat_node_t *node)
  118. {
  119.     /* TODO */
  120. }
  121.  
  122. /** Internal version of fat_node_get().
  123.  *
  124.  * @param idxp      Locked index structure.
  125.  */
  126. static void *fat_node_get_core(fat_idx_t *idxp)
  127. {
  128.     block_t *bb, *b;
  129.     fat_dentry_t *d;
  130.     fat_node_t *nodep = NULL;
  131.     unsigned bps;
  132.     unsigned dps;
  133.  
  134.     if (idxp->nodep) {
  135.         /*
  136.          * We are lucky.
  137.          * The node is already instantiated in memory.
  138.          */
  139.         futex_down(&idxp->nodep->lock);
  140.         if (!idxp->nodep->refcnt++)
  141.             list_remove(&idxp->nodep->ffn_link);
  142.         futex_up(&idxp->nodep->lock);
  143.         return idxp->nodep;
  144.     }
  145.  
  146.     /*
  147.      * We must instantiate the node from the file system.
  148.      */
  149.    
  150.     assert(idxp->pfc);
  151.  
  152.     futex_down(&ffn_futex);
  153.     if (!list_empty(&ffn_head)) {
  154.         /* Try to use a cached free node structure. */
  155.         fat_idx_t *idxp_tmp;
  156.         nodep = list_get_instance(ffn_head.next, fat_node_t, ffn_link);
  157.         if (futex_trydown(&nodep->lock) == ESYNCH_WOULD_BLOCK)
  158.             goto skip_cache;
  159.         idxp_tmp = nodep->idx;
  160.         if (futex_trydown(&idxp_tmp->lock) == ESYNCH_WOULD_BLOCK) {
  161.             futex_up(&nodep->lock);
  162.             goto skip_cache;
  163.         }
  164.         list_remove(&nodep->ffn_link);
  165.         futex_up(&ffn_futex);
  166.         if (nodep->dirty)
  167.             fat_node_sync(nodep);
  168.         idxp_tmp->nodep = NULL;
  169.         futex_up(&nodep->lock);
  170.         futex_up(&idxp_tmp->lock);
  171.     } else {
  172. skip_cache:
  173.         /* Try to allocate a new node structure. */
  174.         futex_up(&ffn_futex);
  175.         nodep = (fat_node_t *)malloc(sizeof(fat_node_t));
  176.         if (!nodep)
  177.             return NULL;
  178.     }
  179.     fat_node_initialize(nodep);
  180.  
  181.     bb = block_get(idxp->dev_handle, BS_BLOCK, BS_SIZE);
  182.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  183.     dps = bps / sizeof(fat_dentry_t);
  184.  
  185.     /* Read the block that contains the dentry of interest. */
  186.     b = _fat_block_get(bb->data, idxp->dev_handle, idxp->pfc,
  187.         (idxp->pdi * sizeof(fat_dentry_t)) / bps);
  188.     assert(b);
  189.  
  190.     d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);
  191.     if (d->attr & FAT_ATTR_SUBDIR) {
  192.         /*
  193.          * The only directory which does not have this bit set is the
  194.          * root directory itself. The root directory node is handled
  195.          * and initialized elsewhere.
  196.          */
  197.         nodep->type = FAT_DIRECTORY;
  198.         /*
  199.          * Unfortunately, the 'size' field of the FAT dentry is not
  200.          * defined for the directory entry type. We must determine the
  201.          * size of the directory by walking the FAT.
  202.          */
  203.         nodep->size = bps * _fat_blcks_get(bb->data, idxp->dev_handle,
  204.             uint16_t_le2host(d->firstc), NULL);
  205.     } else {
  206.         nodep->type = FAT_FILE;
  207.         nodep->size = uint32_t_le2host(d->size);
  208.     }
  209.     nodep->firstc = uint16_t_le2host(d->firstc);
  210.     nodep->lnkcnt = 1;
  211.     nodep->refcnt = 1;
  212.  
  213.     block_put(b);
  214.     block_put(bb);
  215.  
  216.     /* Link the idx structure with the node structure. */
  217.     nodep->idx = idxp;
  218.     idxp->nodep = nodep;
  219.  
  220.     return nodep;
  221. }
  222.  
  223. /** Instantiate a FAT in-core node. */
  224. static void *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
  225. {
  226.     void *node;
  227.     fat_idx_t *idxp;
  228.  
  229.     idxp = fat_idx_get_by_index(dev_handle, index);
  230.     if (!idxp)
  231.         return NULL;
  232.     /* idxp->lock held */
  233.     node = fat_node_get_core(idxp);
  234.     futex_up(&idxp->lock);
  235.     return node;
  236. }
  237.  
  238. static void fat_node_put(void *node)
  239. {
  240.     fat_node_t *nodep = (fat_node_t *)node;
  241.  
  242.     futex_down(&nodep->lock);
  243.     if (!--nodep->refcnt) {
  244.         futex_down(&ffn_futex);
  245.         list_append(&nodep->ffn_link, &ffn_head);
  246.         futex_up(&ffn_futex);
  247.     }
  248.     futex_up(&nodep->lock);
  249. }
  250.  
  251. static void *fat_create(int flags)
  252. {
  253.     return NULL;    /* not supported at the moment */
  254. }
  255.  
  256. static int fat_destroy(void *node)
  257. {
  258.     return ENOTSUP; /* not supported at the moment */
  259. }
  260.  
  261. static bool fat_link(void *prnt, void *chld, const char *name)
  262. {
  263.     return false;   /* not supported at the moment */
  264. }
  265.  
  266. static int fat_unlink(void *prnt, void *chld)
  267. {
  268.     return ENOTSUP; /* not supported at the moment */
  269. }
  270.  
  271. static void *fat_match(void *prnt, const char *component)
  272. {
  273.     fat_node_t *parentp = (fat_node_t *)prnt;
  274.     char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  275.     unsigned i, j;
  276.     unsigned bps;       /* bytes per sector */
  277.     unsigned dps;       /* dentries per sector */
  278.     unsigned blocks;
  279.     fat_dentry_t *d;
  280.     block_t *bb, *b;
  281.  
  282.     futex_down(&parentp->idx->lock);
  283.     bb = block_get(parentp->idx->dev_handle, BS_BLOCK, BS_SIZE);
  284.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  285.     dps = bps / sizeof(fat_dentry_t);
  286.     blocks = parentp->size / bps + (parentp->size % bps != 0);
  287.     for (i = 0; i < blocks; i++) {
  288.         unsigned dentries;
  289.        
  290.         b = fat_block_get(bb->data, parentp, i);
  291.         dentries = (i == blocks - 1) ?
  292.             parentp->size % sizeof(fat_dentry_t) :
  293.             dps;
  294.         for (j = 0; j < dentries; j++) {
  295.             d = ((fat_dentry_t *)b->data) + j;
  296.             switch (fat_classify_dentry(d)) {
  297.             case FAT_DENTRY_SKIP:
  298.                 continue;
  299.             case FAT_DENTRY_LAST:
  300.                 block_put(b);
  301.                 block_put(bb);
  302.                 futex_up(&parentp->idx->lock);
  303.                 return NULL;
  304.             default:
  305.             case FAT_DENTRY_VALID:
  306.                 dentry_name_canonify(d, name);
  307.                 break;
  308.             }
  309.             if (stricmp(name, component) == 0) {
  310.                 /* hit */
  311.                 void *node;
  312.                 /*
  313.                  * Assume tree hierarchy for locking.  We
  314.                  * already have the parent and now we are going
  315.                  * to lock the child.  Never lock in the oposite
  316.                  * order.
  317.                  */
  318.                 fat_idx_t *idx = fat_idx_get_by_pos(
  319.                     parentp->idx->dev_handle, parentp->firstc,
  320.                     i * dps + j);
  321.                 futex_up(&parentp->idx->lock);
  322.                 if (!idx) {
  323.                     /*
  324.                      * Can happen if memory is low or if we
  325.                      * run out of 32-bit indices.
  326.                      */
  327.                     block_put(b);
  328.                     block_put(bb);
  329.                     return NULL;
  330.                 }
  331.                 node = fat_node_get_core(idx);
  332.                 futex_up(&idx->lock);
  333.                 block_put(b);
  334.                 block_put(bb);
  335.                 return node;
  336.             }
  337.         }
  338.         block_put(b);
  339.     }
  340.     block_put(bb);
  341.  
  342.     futex_up(&parentp->idx->lock);
  343.     return NULL;
  344. }
  345.  
  346. static fs_index_t fat_index_get(void *node)
  347. {
  348.     fat_node_t *fnodep = (fat_node_t *)node;
  349.     if (!fnodep)
  350.         return 0;
  351.     return fnodep->idx->index;
  352. }
  353.  
  354. static size_t fat_size_get(void *node)
  355. {
  356.     return ((fat_node_t *)node)->size;
  357. }
  358.  
  359. static unsigned fat_lnkcnt_get(void *node)
  360. {
  361.     return ((fat_node_t *)node)->lnkcnt;
  362. }
  363.  
  364. static bool fat_has_children(void *node)
  365. {
  366.     fat_node_t *nodep = (fat_node_t *)node;
  367.     unsigned bps;
  368.     unsigned dps;
  369.     unsigned blocks;
  370.     block_t *bb, *b;
  371.     unsigned i, j;
  372.  
  373.     if (nodep->type != FAT_DIRECTORY)
  374.         return false;
  375.  
  376.     futex_down(&nodep->idx->lock);
  377.     bb = block_get(nodep->idx->dev_handle, BS_BLOCK, BS_SIZE);
  378.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  379.     dps = bps / sizeof(fat_dentry_t);
  380.  
  381.     blocks = nodep->size / bps + (nodep->size % bps != 0);
  382.  
  383.     for (i = 0; i < blocks; i++) {
  384.         unsigned dentries;
  385.         fat_dentry_t *d;
  386.    
  387.         b = fat_block_get(bb->data, nodep, i);
  388.         dentries = (i == blocks - 1) ?
  389.             nodep->size % sizeof(fat_dentry_t) :
  390.             dps;
  391.         for (j = 0; j < dentries; j++) {
  392.             d = ((fat_dentry_t *)b->data) + j;
  393.             switch (fat_classify_dentry(d)) {
  394.             case FAT_DENTRY_SKIP:
  395.                 continue;
  396.             case FAT_DENTRY_LAST:
  397.                 block_put(b);
  398.                 block_put(bb);
  399.                 futex_up(&nodep->idx->lock);
  400.                 return false;
  401.             default:
  402.             case FAT_DENTRY_VALID:
  403.                 block_put(b);
  404.                 block_put(bb);
  405.                 futex_up(&nodep->idx->lock);
  406.                 return true;
  407.             }
  408.             block_put(b);
  409.             block_put(bb);
  410.             futex_up(&nodep->idx->lock);
  411.             return true;
  412.         }
  413.         block_put(b);
  414.     }
  415.     block_put(bb);
  416.  
  417.     futex_up(&nodep->idx->lock);
  418.     return false;
  419. }
  420.  
  421. static void *fat_root_get(dev_handle_t dev_handle)
  422. {
  423.     return fat_node_get(dev_handle, 0);
  424. }
  425.  
  426. static char fat_plb_get_char(unsigned pos)
  427. {
  428.     return fat_reg.plb_ro[pos % PLB_SIZE];
  429. }
  430.  
  431. static bool fat_is_directory(void *node)
  432. {
  433.     return ((fat_node_t *)node)->type == FAT_DIRECTORY;
  434. }
  435.  
  436. static bool fat_is_file(void *node)
  437. {
  438.     return ((fat_node_t *)node)->type == FAT_FILE;
  439. }
  440.  
  441. /** libfs operations */
  442. libfs_ops_t fat_libfs_ops = {
  443.     .match = fat_match,
  444.     .node_get = fat_node_get,
  445.     .node_put = fat_node_put,
  446.     .create = fat_create,
  447.     .destroy = fat_destroy,
  448.     .link = fat_link,
  449.     .unlink = fat_unlink,
  450.     .index_get = fat_index_get,
  451.     .size_get = fat_size_get,
  452.     .lnkcnt_get = fat_lnkcnt_get,
  453.     .has_children = fat_has_children,
  454.     .root_get = fat_root_get,
  455.     .plb_get_char = fat_plb_get_char,
  456.     .is_directory = fat_is_directory,
  457.     .is_file = fat_is_file
  458. };
  459.  
  460. void fat_mounted(ipc_callid_t rid, ipc_call_t *request)
  461. {
  462.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  463.     block_t *bb;
  464.     uint16_t bps;
  465.     uint16_t rde;
  466.     int rc;
  467.  
  468.     /*
  469.      * For now, we don't bother to remember dev_handle, dev_phone or
  470.      * dev_buffer in some data structure. We use global variables because we
  471.      * know there will be at most one mount on this file system.
  472.      * Of course, this is a huge TODO item.
  473.      */
  474.     dev_buffer = mmap(NULL, BS_SIZE, PROTO_READ | PROTO_WRITE,
  475.         MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
  476.    
  477.     if (!dev_buffer) {
  478.         ipc_answer_0(rid, ENOMEM);
  479.         return;
  480.     }
  481.  
  482.     dev_phone = ipc_connect_me_to(PHONE_NS, SERVICE_DEVMAP,
  483.         DEVMAP_CONNECT_TO_DEVICE, dev_handle);
  484.  
  485.     if (dev_phone < 0) {
  486.         munmap(dev_buffer, BS_SIZE);
  487.         ipc_answer_0(rid, dev_phone);
  488.         return;
  489.     }
  490.  
  491.     rc = ipc_share_out_start(dev_phone, dev_buffer,
  492.         AS_AREA_READ | AS_AREA_WRITE);
  493.     if (rc != EOK) {
  494.             munmap(dev_buffer, BS_SIZE);
  495.         ipc_answer_0(rid, rc);
  496.         return;
  497.     }
  498.  
  499.     /* Read the number of root directory entries. */
  500.     bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
  501.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  502.     rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);
  503.     block_put(bb);
  504.  
  505.     if (bps != BS_SIZE) {
  506.         munmap(dev_buffer, BS_SIZE);
  507.         ipc_answer_0(rid, ENOTSUP);
  508.         return;
  509.     }
  510.  
  511.     rc = fat_idx_init_by_dev_handle(dev_handle);
  512.     if (rc != EOK) {
  513.             munmap(dev_buffer, BS_SIZE);
  514.         ipc_answer_0(rid, rc);
  515.         return;
  516.     }
  517.  
  518.     /* Initialize the root node. */
  519.     fat_node_t *rootp = (fat_node_t *)malloc(sizeof(fat_node_t));
  520.     if (!rootp) {
  521.             munmap(dev_buffer, BS_SIZE);
  522.         fat_idx_fini_by_dev_handle(dev_handle);
  523.         ipc_answer_0(rid, ENOMEM);
  524.         return;
  525.     }
  526.     fat_node_initialize(rootp);
  527.  
  528.     fat_idx_t *ridxp = fat_idx_get_by_pos(dev_handle, FAT_CLST_ROOTPAR, 0);
  529.     if (!ridxp) {
  530.             munmap(dev_buffer, BS_SIZE);
  531.         free(rootp);
  532.         fat_idx_fini_by_dev_handle(dev_handle);
  533.         ipc_answer_0(rid, ENOMEM);
  534.         return;
  535.     }
  536.     assert(ridxp->index == 0);
  537.     /* ridxp->lock held */
  538.  
  539.     rootp->type = FAT_DIRECTORY;
  540.     rootp->firstc = FAT_CLST_ROOT;
  541.     rootp->refcnt = 1;
  542.     rootp->lnkcnt = 0;  /* FS root is not linked */
  543.     rootp->size = rde * sizeof(fat_dentry_t);
  544.     rootp->idx = ridxp;
  545.     ridxp->nodep = rootp;
  546.    
  547.     futex_up(&ridxp->lock);
  548.  
  549.     ipc_answer_3(rid, EOK, ridxp->index, rootp->size, rootp->lnkcnt);
  550. }
  551.  
  552. void fat_mount(ipc_callid_t rid, ipc_call_t *request)
  553. {
  554.     ipc_answer_0(rid, ENOTSUP);
  555. }
  556.  
  557. void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
  558. {
  559.     libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  560. }
  561.  
  562. void fat_read(ipc_callid_t rid, ipc_call_t *request)
  563. {
  564.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  565.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  566.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  567.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  568.     uint16_t bps;
  569.     size_t bytes;
  570.     block_t *bb, *b;
  571.  
  572.     if (!nodep) {
  573.         ipc_answer_0(rid, ENOENT);
  574.         return;
  575.     }
  576.  
  577.     ipc_callid_t callid;
  578.     size_t len;
  579.     if (!ipc_data_read_receive(&callid, &len)) {
  580.         fat_node_put(nodep);
  581.         ipc_answer_0(callid, EINVAL);
  582.         ipc_answer_0(rid, EINVAL);
  583.         return;
  584.     }
  585.  
  586.     bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
  587.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  588.  
  589.     if (nodep->type == FAT_FILE) {
  590.         /*
  591.          * Our strategy for regular file reads is to read one block at
  592.          * most and make use of the possibility to return less data than
  593.          * requested. This keeps the code very simple.
  594.          */
  595.         bytes = min(len, bps - pos % bps);
  596.         b = fat_block_get(bb->data, nodep, pos / bps);
  597.         (void) ipc_data_read_finalize(callid, b->data + pos % bps,
  598.             bytes);
  599.         block_put(b);
  600.     } else {
  601.         unsigned bnum;
  602.         off_t spos = pos;
  603.         char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  604.         fat_dentry_t *d;
  605.  
  606.         assert(nodep->type == FAT_DIRECTORY);
  607.         assert(nodep->size % bps == 0);
  608.         assert(bps % sizeof(fat_dentry_t) == 0);
  609.  
  610.         /*
  611.          * Our strategy for readdir() is to use the position pointer as
  612.          * an index into the array of all dentries. On entry, it points
  613.          * to the first unread dentry. If we skip any dentries, we bump
  614.          * the position pointer accordingly.
  615.          */
  616.         bnum = (pos * sizeof(fat_dentry_t)) / bps;
  617.         while (bnum < nodep->size / bps) {
  618.             off_t o;
  619.  
  620.             b = fat_block_get(bb->data, nodep, bnum);
  621.             for (o = pos % (bps / sizeof(fat_dentry_t));
  622.                 o < bps / sizeof(fat_dentry_t);
  623.                 o++, pos++) {
  624.                 d = ((fat_dentry_t *)b->data) + o;
  625.                 switch (fat_classify_dentry(d)) {
  626.                 case FAT_DENTRY_SKIP:
  627.                     continue;
  628.                 case FAT_DENTRY_LAST:
  629.                     block_put(b);
  630.                     goto miss;
  631.                 default:
  632.                 case FAT_DENTRY_VALID:
  633.                     dentry_name_canonify(d, name);
  634.                     block_put(b);
  635.                     goto hit;
  636.                 }
  637.             }
  638.             block_put(b);
  639.             bnum++;
  640.         }
  641. miss:
  642.         fat_node_put(nodep);
  643.         block_put(bb);
  644.         ipc_answer_0(callid, ENOENT);
  645.         ipc_answer_1(rid, ENOENT, 0);
  646.         return;
  647. hit:
  648.         (void) ipc_data_read_finalize(callid, name, strlen(name) + 1);
  649.         bytes = (pos - spos) + 1;
  650.     }
  651.  
  652.     fat_node_put(nodep);
  653.     block_put(bb);
  654.     ipc_answer_1(rid, EOK, (ipcarg_t)bytes);
  655. }
  656.  
  657. void fat_write(ipc_callid_t rid, ipc_call_t *request)
  658. {
  659.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  660.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  661.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  662.     fat_node_t *nodep = (fat_node_t *)fat_node_get(dev_handle, index);
  663.     size_t bytes;
  664.     block_t *b, *bb;
  665.     uint16_t bps;
  666.     unsigned spc;
  667.     off_t boundary;
  668.    
  669.     if (!nodep) {
  670.         ipc_answer_0(rid, ENOENT);
  671.         return;
  672.     }
  673.    
  674.     /* XXX remove me when you are ready */
  675.     {
  676.         ipc_answer_0(rid, ENOTSUP);
  677.         fat_node_put(nodep);
  678.         return;
  679.     }
  680.  
  681.     ipc_callid_t callid;
  682.     size_t len;
  683.     if (!ipc_data_write_receive(&callid, &len)) {
  684.         fat_node_put(nodep);
  685.         ipc_answer_0(callid, EINVAL);
  686.         ipc_answer_0(rid, EINVAL);
  687.         return;
  688.     }
  689.  
  690.     /*
  691.      * In all scenarios, we will attempt to write out only one block worth
  692.      * of data at maximum. There might be some more efficient approaches,
  693.      * but this one greatly simplifies fat_write(). Note that we can afford
  694.      * to do this because the client must be ready to handle the return
  695.      * value signalizing a smaller number of bytes written.
  696.      */
  697.     bytes = min(len, bps - pos % bps);
  698.  
  699.     bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
  700.     bps = uint16_t_le2host(FAT_BS(bb)->bps);
  701.     spc = FAT_BS(bb)->spc;
  702.    
  703.     boundary = ROUND_UP(nodep->size, bps * spc);
  704.     if (pos < boundary) {
  705.         /*
  706.          * This is the easier case - we are either overwriting already
  707.          * existing contents or writing behind the EOF, but still within
  708.          * the limits of the last cluster. The node size may grow to the
  709.          * next block size boundary.
  710.          */
  711.         fat_fill_gap(bb->data, nodep, FAT_CLST_RES0, pos);
  712.         b = fat_block_get(bb->data, nodep, pos / bps);
  713.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  714.             bytes);
  715.         b->dirty = true;        /* need to sync block */
  716.         block_put(b);
  717.         if (pos + bytes > nodep->size) {
  718.             nodep->size = pos + bytes;
  719.             nodep->dirty = true;    /* need to sync node */
  720.         }
  721.         fat_node_put(nodep);
  722.         block_put(bb);
  723.         ipc_answer_1(rid, EOK, bytes); 
  724.         return;
  725.     } else {
  726.         /*
  727.          * This is the more difficult case. We must allocate new
  728.          * clusters for the node and zero them out.
  729.          */
  730.         int status;
  731.         unsigned nclsts;
  732.         fat_cluster_t mcl, lcl;
  733.    
  734.         nclsts = (ROUND_UP(pos + bytes, bps * spc) - boundary) /
  735.             bps * spc;
  736.         /* create an independent chain of nclsts clusters in all FATs */
  737.         status = fat_alloc_clusters(bb->data, dev_handle, nclsts, &mcl,
  738.             &lcl);
  739.         if (status != EOK) {
  740.             /* could not allocate a chain of nclsts clusters */
  741.             fat_node_put(nodep);
  742.             block_put(bb);
  743.             ipc_answer_0(callid, status);
  744.             ipc_answer_0(rid, status);
  745.             return;
  746.         }
  747.         /* zero fill any gaps */
  748.         fat_fill_gap(bb->data, nodep, mcl, pos);
  749.         b = _fat_block_get(bb->data, dev_handle, lcl,
  750.             (pos / bps) % spc);
  751.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  752.             bytes);
  753.         b->dirty = true;        /* need to sync block */
  754.         block_put(b);
  755.         /*
  756.          * Append the cluster chain starting in mcl to the end of the
  757.          * node's cluster chain.
  758.          */
  759.         fat_append_clusters(bb->data, nodep, mcl);
  760.         nodep->size = pos + bytes;
  761.         nodep->dirty = true;        /* need to sync node */
  762.         fat_node_put(nodep);
  763.         block_put(bb);
  764.         ipc_answer_1(rid, EOK, bytes);
  765.         return;
  766.     }
  767. }
  768.  
  769. /**
  770.  * @}
  771.  */
  772.