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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. #define FAT_NODE(node)  ((node) ? (fat_node_t *) (node)->data : NULL)
  59. #define FS_NODE(node)   ((node) ? (node)->bp : NULL)
  60.  
  61. /** Futex protecting the list of cached free FAT nodes. */
  62. static futex_t ffn_futex = FUTEX_INITIALIZER;
  63.  
  64. /** List of cached free FAT nodes. */
  65. static LIST_INITIALIZE(ffn_head);
  66.  
  67. static void fat_node_initialize(fat_node_t *node)
  68. {
  69.     futex_initialize(&node->lock, 1);
  70.     node->bp = NULL;
  71.     node->idx = NULL;
  72.     node->type = 0;
  73.     link_initialize(&node->ffn_link);
  74.     node->size = 0;
  75.     node->lnkcnt = 0;
  76.     node->refcnt = 0;
  77.     node->dirty = false;
  78. }
  79.  
  80. static void fat_node_sync(fat_node_t *node)
  81. {
  82.     block_t *b;
  83.     fat_bs_t *bs;
  84.     fat_dentry_t *d;
  85.     uint16_t bps;
  86.     unsigned dps;
  87.    
  88.     assert(node->dirty);
  89.  
  90.     bs = block_bb_get(node->idx->dev_handle);
  91.     bps = uint16_t_le2host(bs->bps);
  92.     dps = bps / sizeof(fat_dentry_t);
  93.    
  94.     /* Read the block that contains the dentry of interest. */
  95.     b = _fat_block_get(bs, node->idx->dev_handle, node->idx->pfc,
  96.         (node->idx->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);
  97.  
  98.     d = ((fat_dentry_t *)b->data) + (node->idx->pdi % dps);
  99.  
  100.     d->firstc = host2uint16_t_le(node->firstc);
  101.     if (node->type == FAT_FILE) {
  102.         d->size = host2uint32_t_le(node->size);
  103.     } else if (node->type == FAT_DIRECTORY) {
  104.         d->attr = FAT_ATTR_SUBDIR;
  105.     }
  106.    
  107.     /* TODO: update other fields? (e.g time fields) */
  108.    
  109.     b->dirty = true;        /* need to sync block */
  110.     block_put(b);
  111. }
  112.  
  113. static fat_node_t *fat_node_get_new(void)
  114. {
  115.     fs_node_t *fn;
  116.     fat_node_t *nodep;
  117.  
  118.     futex_down(&ffn_futex);
  119.     if (!list_empty(&ffn_head)) {
  120.         /* Try to use a cached free node structure. */
  121.         fat_idx_t *idxp_tmp;
  122.         nodep = list_get_instance(ffn_head.next, fat_node_t, ffn_link);
  123.         if (futex_trydown(&nodep->lock) == ESYNCH_WOULD_BLOCK)
  124.             goto skip_cache;
  125.         idxp_tmp = nodep->idx;
  126.         if (futex_trydown(&idxp_tmp->lock) == ESYNCH_WOULD_BLOCK) {
  127.             futex_up(&nodep->lock);
  128.             goto skip_cache;
  129.         }
  130.         list_remove(&nodep->ffn_link);
  131.         futex_up(&ffn_futex);
  132.         if (nodep->dirty)
  133.             fat_node_sync(nodep);
  134.         idxp_tmp->nodep = NULL;
  135.         futex_up(&nodep->lock);
  136.         futex_up(&idxp_tmp->lock);
  137.         fn = FS_NODE(nodep);
  138.     } else {
  139. skip_cache:
  140.         /* Try to allocate a new node structure. */
  141.         futex_up(&ffn_futex);
  142.         fn = (fs_node_t *)malloc(sizeof(fs_node_t));
  143.         if (!fn)
  144.             return NULL;
  145.         nodep = (fat_node_t *)malloc(sizeof(fat_node_t));
  146.         if (!nodep) {
  147.             free(fn);
  148.             return NULL;
  149.         }
  150.     }
  151.     fat_node_initialize(nodep);
  152.     fn->data = nodep;
  153.     nodep->bp = fn;
  154.    
  155.     return nodep;
  156. }
  157.  
  158. /** Internal version of fat_node_get().
  159.  *
  160.  * @param idxp      Locked index structure.
  161.  */
  162. static fat_node_t *fat_node_get_core(fat_idx_t *idxp)
  163. {
  164.     block_t *b;
  165.     fat_bs_t *bs;
  166.     fat_dentry_t *d;
  167.     fat_node_t *nodep = NULL;
  168.     unsigned bps;
  169.     unsigned spc;
  170.     unsigned dps;
  171.  
  172.     if (idxp->nodep) {
  173.         /*
  174.          * We are lucky.
  175.          * The node is already instantiated in memory.
  176.          */
  177.         futex_down(&idxp->nodep->lock);
  178.         if (!idxp->nodep->refcnt++)
  179.             list_remove(&idxp->nodep->ffn_link);
  180.         futex_up(&idxp->nodep->lock);
  181.         return idxp->nodep;
  182.     }
  183.  
  184.     /*
  185.      * We must instantiate the node from the file system.
  186.      */
  187.    
  188.     assert(idxp->pfc);
  189.  
  190.     nodep = fat_node_get_new();
  191.     if (!nodep)
  192.         return NULL;
  193.  
  194.     bs = block_bb_get(idxp->dev_handle);
  195.     bps = uint16_t_le2host(bs->bps);
  196.     spc = bs->spc;
  197.     dps = bps / sizeof(fat_dentry_t);
  198.  
  199.     /* Read the block that contains the dentry of interest. */
  200.     b = _fat_block_get(bs, idxp->dev_handle, idxp->pfc,
  201.         (idxp->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);
  202.     assert(b);
  203.  
  204.     d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);
  205.     if (d->attr & FAT_ATTR_SUBDIR) {
  206.         /*
  207.          * The only directory which does not have this bit set is the
  208.          * root directory itself. The root directory node is handled
  209.          * and initialized elsewhere.
  210.          */
  211.         nodep->type = FAT_DIRECTORY;
  212.         /*
  213.          * Unfortunately, the 'size' field of the FAT dentry is not
  214.          * defined for the directory entry type. We must determine the
  215.          * size of the directory by walking the FAT.
  216.          */
  217.         nodep->size = bps * spc * fat_clusters_get(bs, idxp->dev_handle,
  218.             uint16_t_le2host(d->firstc));
  219.     } else {
  220.         nodep->type = FAT_FILE;
  221.         nodep->size = uint32_t_le2host(d->size);
  222.     }
  223.     nodep->firstc = uint16_t_le2host(d->firstc);
  224.     nodep->lnkcnt = 1;
  225.     nodep->refcnt = 1;
  226.  
  227.     block_put(b);
  228.  
  229.     /* Link the idx structure with the node structure. */
  230.     nodep->idx = idxp;
  231.     idxp->nodep = nodep;
  232.  
  233.     return nodep;
  234. }
  235.  
  236. /*
  237.  * Forward declarations of FAT libfs operations.
  238.  */
  239. static fs_node_t *fat_node_get(dev_handle_t, fs_index_t);
  240. static void fat_node_put(fs_node_t *);
  241. static fs_node_t *fat_create_node(dev_handle_t, int);
  242. static int fat_destroy_node(fs_node_t *);
  243. static int fat_link(fs_node_t *, fs_node_t *, const char *);
  244. static int fat_unlink(fs_node_t *, fs_node_t *);
  245. static fs_node_t *fat_match(fs_node_t *, const char *);
  246. static fs_index_t fat_index_get(fs_node_t *);
  247. static size_t fat_size_get(fs_node_t *);
  248. static unsigned fat_lnkcnt_get(fs_node_t *);
  249. static bool fat_has_children(fs_node_t *);
  250. static fs_node_t *fat_root_get(dev_handle_t);
  251. static char fat_plb_get_char(unsigned);
  252. static bool fat_is_directory(fs_node_t *);
  253. static bool fat_is_file(fs_node_t *node);
  254.  
  255. /*
  256.  * FAT libfs operations.
  257.  */
  258.  
  259. /** Instantiate a FAT in-core node. */
  260. fs_node_t *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
  261. {
  262.     fat_node_t *nodep;
  263.     fat_idx_t *idxp;
  264.  
  265.     idxp = fat_idx_get_by_index(dev_handle, index);
  266.     if (!idxp)
  267.         return NULL;
  268.     /* idxp->lock held */
  269.     nodep = fat_node_get_core(idxp);
  270.     futex_up(&idxp->lock);
  271.     return FS_NODE(nodep);
  272. }
  273.  
  274. void fat_node_put(fs_node_t *fn)
  275. {
  276.     fat_node_t *nodep = FAT_NODE(fn);
  277.     bool destroy = false;
  278.  
  279.     futex_down(&nodep->lock);
  280.     if (!--nodep->refcnt) {
  281.         if (nodep->idx) {
  282.             futex_down(&ffn_futex);
  283.             list_append(&nodep->ffn_link, &ffn_head);
  284.             futex_up(&ffn_futex);
  285.         } else {
  286.             /*
  287.              * The node does not have any index structure associated
  288.              * with itself. This can only mean that we are releasing
  289.              * the node after a failed attempt to allocate the index
  290.              * structure for it.
  291.              */
  292.             destroy = true;
  293.         }
  294.     }
  295.     futex_up(&nodep->lock);
  296.     if (destroy) {
  297.         free(nodep->bp);
  298.         free(nodep);
  299.     }
  300. }
  301.  
  302. fs_node_t *fat_create_node(dev_handle_t dev_handle, int flags)
  303. {
  304.     fat_idx_t *idxp;
  305.     fat_node_t *nodep;
  306.     fat_bs_t *bs;
  307.     fat_cluster_t mcl, lcl;
  308.     uint16_t bps;
  309.     int rc;
  310.  
  311.     bs = block_bb_get(dev_handle);
  312.     bps = uint16_t_le2host(bs->bps);
  313.     if (flags & L_DIRECTORY) {
  314.         /* allocate a cluster */
  315.         rc = fat_alloc_clusters(bs, dev_handle, 1, &mcl, &lcl);
  316.         if (rc != EOK)
  317.             return NULL;
  318.     }
  319.  
  320.     nodep = fat_node_get_new();
  321.     if (!nodep) {
  322.         fat_free_clusters(bs, dev_handle, mcl);
  323.         return NULL;
  324.     }
  325.     idxp = fat_idx_get_new(dev_handle);
  326.     if (!idxp) {
  327.         fat_free_clusters(bs, dev_handle, mcl);
  328.         fat_node_put(FS_NODE(nodep));
  329.         return NULL;
  330.     }
  331.     /* idxp->lock held */
  332.     if (flags & L_DIRECTORY) {
  333.         int i;
  334.         block_t *b;
  335.  
  336.         /*
  337.          * Populate the new cluster with unused dentries.
  338.          */
  339.         for (i = 0; i < bs->spc; i++) {
  340.             b = _fat_block_get(bs, dev_handle, mcl, i,
  341.                 BLOCK_FLAGS_NOREAD);
  342.             /* mark all dentries as never-used */
  343.             memset(b->data, 0, bps);
  344.             b->dirty = false;
  345.             block_put(b);
  346.         }
  347.         nodep->type = FAT_DIRECTORY;
  348.         nodep->firstc = mcl;
  349.         nodep->size = bps * bs->spc;
  350.     } else {
  351.         nodep->type = FAT_FILE;
  352.         nodep->firstc = FAT_CLST_RES0;
  353.         nodep->size = 0;
  354.     }
  355.     nodep->lnkcnt = 0;  /* not linked anywhere */
  356.     nodep->refcnt = 1;
  357.     nodep->dirty = true;
  358.  
  359.     nodep->idx = idxp;
  360.     idxp->nodep = nodep;
  361.  
  362.     futex_up(&idxp->lock);
  363.     return FS_NODE(nodep);
  364. }
  365.  
  366. int fat_destroy_node(fs_node_t *fn)
  367. {
  368.     fat_node_t *nodep = FAT_NODE(fn);
  369.     fat_bs_t *bs;
  370.  
  371.     /*
  372.      * The node is not reachable from the file system. This means that the
  373.      * link count should be zero and that the index structure cannot be
  374.      * found in the position hash. Obviously, we don't need to lock the node
  375.      * nor its index structure.
  376.      */
  377.     assert(nodep->lnkcnt == 0);
  378.  
  379.     /*
  380.      * The node may not have any children.
  381.      */
  382.     assert(fat_has_children(fn) == false);
  383.  
  384.     bs = block_bb_get(nodep->idx->dev_handle);
  385.     if (nodep->firstc != FAT_CLST_RES0) {
  386.         assert(nodep->size);
  387.         /* Free all clusters allocated to the node. */
  388.         fat_free_clusters(bs, nodep->idx->dev_handle, nodep->firstc);
  389.     }
  390.  
  391.     fat_idx_destroy(nodep->idx);
  392.     free(nodep->bp);
  393.     free(nodep);
  394.     return EOK;
  395. }
  396.  
  397. int fat_link(fs_node_t *pfn, fs_node_t *cfn, const char *name)
  398. {
  399.     fat_node_t *parentp = FAT_NODE(pfn);
  400.     fat_node_t *childp = FAT_NODE(cfn);
  401.     fat_dentry_t *d;
  402.     fat_bs_t *bs;
  403.     block_t *b;
  404.     int i, j;
  405.     uint16_t bps;
  406.     unsigned dps;
  407.     unsigned blocks;
  408.     fat_cluster_t mcl, lcl;
  409.     int rc;
  410.  
  411.     futex_down(&childp->lock);
  412.     if (childp->lnkcnt == 1) {
  413.         /*
  414.          * On FAT, we don't support multiple hard links.
  415.          */
  416.         futex_up(&childp->lock);
  417.         return EMLINK;
  418.     }
  419.     assert(childp->lnkcnt == 0);
  420.     futex_up(&childp->lock);
  421.  
  422.     if (!fat_dentry_name_verify(name)) {
  423.         /*
  424.          * Attempt to create unsupported name.
  425.          */
  426.         return ENOTSUP;
  427.     }
  428.  
  429.     /*
  430.      * Get us an unused parent node's dentry or grow the parent and allocate
  431.      * a new one.
  432.      */
  433.    
  434.     futex_down(&parentp->idx->lock);
  435.     bs = block_bb_get(parentp->idx->dev_handle);
  436.     bps = uint16_t_le2host(bs->bps);
  437.     dps = bps / sizeof(fat_dentry_t);
  438.  
  439.     blocks = parentp->size / bps;
  440.  
  441.     for (i = 0; i < blocks; i++) {
  442.         b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);
  443.         for (j = 0; j < dps; j++) {
  444.             d = ((fat_dentry_t *)b->data) + j;
  445.             switch (fat_classify_dentry(d)) {
  446.             case FAT_DENTRY_SKIP:
  447.             case FAT_DENTRY_VALID:
  448.                 /* skipping used and meta entries */
  449.                 continue;
  450.             case FAT_DENTRY_FREE:
  451.             case FAT_DENTRY_LAST:
  452.                 /* found an empty slot */
  453.                 goto hit;
  454.             }
  455.         }
  456.         block_put(b);
  457.     }
  458.     j = 0;
  459.    
  460.     /*
  461.      * We need to grow the parent in order to create a new unused dentry.
  462.      */
  463.     if (parentp->idx->pfc == FAT_CLST_ROOT) {
  464.         /* Can't grow the root directory. */
  465.         futex_up(&parentp->idx->lock);
  466.         return ENOSPC;
  467.     }
  468.     rc = fat_alloc_clusters(bs, parentp->idx->dev_handle, 1, &mcl, &lcl);
  469.     if (rc != EOK) {
  470.         futex_up(&parentp->idx->lock);
  471.         return rc;
  472.     }
  473.     fat_append_clusters(bs, parentp, mcl);
  474.     b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NOREAD);
  475.     d = (fat_dentry_t *)b->data;
  476.     /*
  477.      * Clear all dentries in the block except for the first one (the first
  478.      * dentry will be cleared in the next step).
  479.      */
  480.     memset(d + 1, 0, bps - sizeof(fat_dentry_t));
  481.  
  482. hit:
  483.     /*
  484.      * At this point we only establish the link between the parent and the
  485.      * child.  The dentry, except of the name and the extension, will remain
  486.      * uninitialized until the corresponding node is synced. Thus the valid
  487.      * dentry data is kept in the child node structure.
  488.      */
  489.     memset(d, 0, sizeof(fat_dentry_t));
  490.     fat_dentry_name_set(d, name);
  491.     b->dirty = true;        /* need to sync block */
  492.     block_put(b);
  493.     futex_up(&parentp->idx->lock);
  494.  
  495.     futex_down(&childp->idx->lock);
  496.    
  497.     /*
  498.      * If possible, create the Sub-directory Identifier Entry and the
  499.      * Sub-directory Parent Pointer Entry (i.e. "." and ".."). These entries
  500.      * are not mandatory according to Standard ECMA-107 and HelenOS VFS does
  501.      * not use them anyway, so this is rather a sign of our good will.
  502.      */
  503.     b = fat_block_get(bs, childp, 0, BLOCK_FLAGS_NONE);
  504.     d = (fat_dentry_t *)b->data;
  505.     if (fat_classify_dentry(d) == FAT_DENTRY_LAST ||
  506.         str_cmp(d->name, FAT_NAME_DOT) == 0) {
  507.         memset(d, 0, sizeof(fat_dentry_t));
  508.         str_cpy(d->name, 8, FAT_NAME_DOT);
  509.         str_cpy(d->ext, 3, FAT_EXT_PAD);
  510.         d->attr = FAT_ATTR_SUBDIR;
  511.         d->firstc = host2uint16_t_le(childp->firstc);
  512.         /* TODO: initialize also the date/time members. */
  513.     }
  514.     d++;
  515.     if (fat_classify_dentry(d) == FAT_DENTRY_LAST ||
  516.         str_cmp(d->name, FAT_NAME_DOT_DOT) == 0) {
  517.         memset(d, 0, sizeof(fat_dentry_t));
  518.         str_cpy(d->name, 8, FAT_NAME_DOT_DOT);
  519.         str_cpy(d->ext, 3, FAT_EXT_PAD);
  520.         d->attr = FAT_ATTR_SUBDIR;
  521.         d->firstc = (parentp->firstc == FAT_CLST_ROOT) ?
  522.             host2uint16_t_le(FAT_CLST_RES0) :
  523.             host2uint16_t_le(parentp->firstc);
  524.         /* TODO: initialize also the date/time members. */
  525.     }
  526.     b->dirty = true;        /* need to sync block */
  527.     block_put(b);
  528.  
  529.     childp->idx->pfc = parentp->firstc;
  530.     childp->idx->pdi = i * dps + j;
  531.     futex_up(&childp->idx->lock);
  532.  
  533.     futex_down(&childp->lock);
  534.     childp->lnkcnt = 1;
  535.     childp->dirty = true;       /* need to sync node */
  536.     futex_up(&childp->lock);
  537.  
  538.     /*
  539.      * Hash in the index structure into the position hash.
  540.      */
  541.     fat_idx_hashin(childp->idx);
  542.  
  543.     return EOK;
  544. }
  545.  
  546. int fat_unlink(fs_node_t *pfn, fs_node_t *cfn)
  547. {
  548.     fat_node_t *parentp = FAT_NODE(pfn);
  549.     fat_node_t *childp = FAT_NODE(cfn);
  550.     fat_bs_t *bs;
  551.     fat_dentry_t *d;
  552.     uint16_t bps;
  553.     block_t *b;
  554.  
  555.     futex_down(&parentp->lock);
  556.     futex_down(&childp->lock);
  557.     assert(childp->lnkcnt == 1);
  558.     futex_down(&childp->idx->lock);
  559.     bs = block_bb_get(childp->idx->dev_handle);
  560.     bps = uint16_t_le2host(bs->bps);
  561.  
  562.     b = _fat_block_get(bs, childp->idx->dev_handle, childp->idx->pfc,
  563.         (childp->idx->pdi * sizeof(fat_dentry_t)) / bps,
  564.         BLOCK_FLAGS_NONE);
  565.     d = (fat_dentry_t *)b->data +
  566.         (childp->idx->pdi % (bps / sizeof(fat_dentry_t)));
  567.     /* mark the dentry as not-currently-used */
  568.     d->name[0] = FAT_DENTRY_ERASED;
  569.     b->dirty = true;        /* need to sync block */
  570.     block_put(b);
  571.  
  572.     /* remove the index structure from the position hash */
  573.     fat_idx_hashout(childp->idx);
  574.     /* clear position information */
  575.     childp->idx->pfc = FAT_CLST_RES0;
  576.     childp->idx->pdi = 0;
  577.     futex_up(&childp->idx->lock);
  578.     childp->lnkcnt = 0;
  579.     childp->dirty = true;
  580.     futex_up(&childp->lock);
  581.     futex_up(&parentp->lock);
  582.  
  583.     return EOK;
  584. }
  585.  
  586. fs_node_t *fat_match(fs_node_t *pfn, const char *component)
  587. {
  588.     fat_bs_t *bs;
  589.     fat_node_t *parentp = FAT_NODE(pfn);
  590.     char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  591.     unsigned i, j;
  592.     unsigned bps;       /* bytes per sector */
  593.     unsigned dps;       /* dentries per sector */
  594.     unsigned blocks;
  595.     fat_dentry_t *d;
  596.     block_t *b;
  597.  
  598.     futex_down(&parentp->idx->lock);
  599.     bs = block_bb_get(parentp->idx->dev_handle);
  600.     bps = uint16_t_le2host(bs->bps);
  601.     dps = bps / sizeof(fat_dentry_t);
  602.     blocks = parentp->size / bps;
  603.     for (i = 0; i < blocks; i++) {
  604.         b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);
  605.         for (j = 0; j < dps; j++) {
  606.             d = ((fat_dentry_t *)b->data) + j;
  607.             switch (fat_classify_dentry(d)) {
  608.             case FAT_DENTRY_SKIP:
  609.             case FAT_DENTRY_FREE:
  610.                 continue;
  611.             case FAT_DENTRY_LAST:
  612.                 block_put(b);
  613.                 futex_up(&parentp->idx->lock);
  614.                 return NULL;
  615.             default:
  616.             case FAT_DENTRY_VALID:
  617.                 fat_dentry_name_get(d, name);
  618.                 break;
  619.             }
  620.             if (fat_dentry_namecmp(name, component) == 0) {
  621.                 /* hit */
  622.                 fat_node_t *nodep;
  623.                 /*
  624.                  * Assume tree hierarchy for locking.  We
  625.                  * already have the parent and now we are going
  626.                  * to lock the child.  Never lock in the oposite
  627.                  * order.
  628.                  */
  629.                 fat_idx_t *idx = fat_idx_get_by_pos(
  630.                     parentp->idx->dev_handle, parentp->firstc,
  631.                     i * dps + j);
  632.                 futex_up(&parentp->idx->lock);
  633.                 if (!idx) {
  634.                     /*
  635.                      * Can happen if memory is low or if we
  636.                      * run out of 32-bit indices.
  637.                      */
  638.                     block_put(b);
  639.                     return NULL;
  640.                 }
  641.                 nodep = fat_node_get_core(idx);
  642.                 futex_up(&idx->lock);
  643.                 block_put(b);
  644.                 return FS_NODE(nodep);
  645.             }
  646.         }
  647.         block_put(b);
  648.     }
  649.  
  650.     futex_up(&parentp->idx->lock);
  651.     return NULL;
  652. }
  653.  
  654. fs_index_t fat_index_get(fs_node_t *fn)
  655. {
  656.     return FAT_NODE(fn)->idx->index;
  657. }
  658.  
  659. size_t fat_size_get(fs_node_t *fn)
  660. {
  661.     return FAT_NODE(fn)->size;
  662. }
  663.  
  664. unsigned fat_lnkcnt_get(fs_node_t *fn)
  665. {
  666.     return FAT_NODE(fn)->lnkcnt;
  667. }
  668.  
  669. bool fat_has_children(fs_node_t *fn)
  670. {
  671.     fat_bs_t *bs;
  672.     fat_node_t *nodep = FAT_NODE(fn);
  673.     unsigned bps;
  674.     unsigned dps;
  675.     unsigned blocks;
  676.     block_t *b;
  677.     unsigned i, j;
  678.  
  679.     if (nodep->type != FAT_DIRECTORY)
  680.         return false;
  681.    
  682.     futex_down(&nodep->idx->lock);
  683.     bs = block_bb_get(nodep->idx->dev_handle);
  684.     bps = uint16_t_le2host(bs->bps);
  685.     dps = bps / sizeof(fat_dentry_t);
  686.  
  687.     blocks = nodep->size / bps;
  688.  
  689.     for (i = 0; i < blocks; i++) {
  690.         fat_dentry_t *d;
  691.    
  692.         b = fat_block_get(bs, nodep, i, BLOCK_FLAGS_NONE);
  693.         for (j = 0; j < dps; j++) {
  694.             d = ((fat_dentry_t *)b->data) + j;
  695.             switch (fat_classify_dentry(d)) {
  696.             case FAT_DENTRY_SKIP:
  697.             case FAT_DENTRY_FREE:
  698.                 continue;
  699.             case FAT_DENTRY_LAST:
  700.                 block_put(b);
  701.                 futex_up(&nodep->idx->lock);
  702.                 return false;
  703.             default:
  704.             case FAT_DENTRY_VALID:
  705.                 block_put(b);
  706.                 futex_up(&nodep->idx->lock);
  707.                 return true;
  708.             }
  709.             block_put(b);
  710.             futex_up(&nodep->idx->lock);
  711.             return true;
  712.         }
  713.         block_put(b);
  714.     }
  715.  
  716.     futex_up(&nodep->idx->lock);
  717.     return false;
  718. }
  719.  
  720. fs_node_t *fat_root_get(dev_handle_t dev_handle)
  721. {
  722.     return fat_node_get(dev_handle, 0);
  723. }
  724.  
  725. char fat_plb_get_char(unsigned pos)
  726. {
  727.     return fat_reg.plb_ro[pos % PLB_SIZE];
  728. }
  729.  
  730. bool fat_is_directory(fs_node_t *fn)
  731. {
  732.     return FAT_NODE(fn)->type == FAT_DIRECTORY;
  733. }
  734.  
  735. bool fat_is_file(fs_node_t *fn)
  736. {
  737.     return FAT_NODE(fn)->type == FAT_FILE;
  738. }
  739.  
  740. /** libfs operations */
  741. libfs_ops_t fat_libfs_ops = {
  742.     .match = fat_match,
  743.     .node_get = fat_node_get,
  744.     .node_put = fat_node_put,
  745.     .create = fat_create_node,
  746.     .destroy = fat_destroy_node,
  747.     .link = fat_link,
  748.     .unlink = fat_unlink,
  749.     .index_get = fat_index_get,
  750.     .size_get = fat_size_get,
  751.     .lnkcnt_get = fat_lnkcnt_get,
  752.     .has_children = fat_has_children,
  753.     .root_get = fat_root_get,
  754.     .plb_get_char = fat_plb_get_char,
  755.     .is_directory = fat_is_directory,
  756.     .is_file = fat_is_file
  757. };
  758.  
  759. /*
  760.  * VFS operations.
  761.  */
  762.  
  763. void fat_mounted(ipc_callid_t rid, ipc_call_t *request)
  764. {
  765.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  766.     fat_bs_t *bs;
  767.     uint16_t bps;
  768.     uint16_t rde;
  769.     int rc;
  770.  
  771.     /* accept the mount options */
  772.     ipc_callid_t callid;
  773.     size_t size;
  774.     if (!ipc_data_write_receive(&callid, &size)) {
  775.         ipc_answer_0(callid, EINVAL);
  776.         ipc_answer_0(rid, EINVAL);
  777.         return;
  778.     }
  779.     char *opts = malloc(size + 1);
  780.     if (!opts) {
  781.         ipc_answer_0(callid, ENOMEM);
  782.         ipc_answer_0(rid, ENOMEM);
  783.         return;
  784.     }
  785.     ipcarg_t retval = ipc_data_write_finalize(callid, opts, size);
  786.     if (retval != EOK) {
  787.         ipc_answer_0(rid, retval);
  788.         free(opts);
  789.         return;
  790.     }
  791.     opts[size] = '\0';
  792.  
  793.     /* initialize libblock */
  794.     rc = block_init(dev_handle, BS_SIZE);
  795.     if (rc != EOK) {
  796.         ipc_answer_0(rid, rc);
  797.         return;
  798.     }
  799.  
  800.     /* prepare the boot block */
  801.     rc = block_bb_read(dev_handle, BS_BLOCK * BS_SIZE, BS_SIZE);
  802.     if (rc != EOK) {
  803.         block_fini(dev_handle);
  804.         ipc_answer_0(rid, rc);
  805.         return;
  806.     }
  807.  
  808.     /* get the buffer with the boot sector */
  809.     bs = block_bb_get(dev_handle);
  810.    
  811.     /* Read the number of root directory entries. */
  812.     bps = uint16_t_le2host(bs->bps);
  813.     rde = uint16_t_le2host(bs->root_ent_max);
  814.  
  815.     if (bps != BS_SIZE) {
  816.         block_fini(dev_handle);
  817.         ipc_answer_0(rid, ENOTSUP);
  818.         return;
  819.     }
  820.  
  821.     /* Initialize the block cache */
  822.     rc = block_cache_init(dev_handle, bps, 0 /* XXX */);
  823.     if (rc != EOK) {
  824.         block_fini(dev_handle);
  825.         ipc_answer_0(rid, rc);
  826.         return;
  827.     }
  828.  
  829.     rc = fat_idx_init_by_dev_handle(dev_handle);
  830.     if (rc != EOK) {
  831.         block_fini(dev_handle);
  832.         ipc_answer_0(rid, rc);
  833.         return;
  834.     }
  835.  
  836.     /* Initialize the root node. */
  837.     fs_node_t *rfn = (fs_node_t *)malloc(sizeof(fs_node_t));
  838.     if (!rfn) {
  839.         block_fini(dev_handle);
  840.         fat_idx_fini_by_dev_handle(dev_handle);
  841.         ipc_answer_0(rid, ENOMEM);
  842.         return;
  843.     }
  844.     fat_node_t *rootp = (fat_node_t *)malloc(sizeof(fat_node_t));
  845.     if (!rootp) {
  846.         free(rfn);
  847.         block_fini(dev_handle);
  848.         fat_idx_fini_by_dev_handle(dev_handle);
  849.         ipc_answer_0(rid, ENOMEM);
  850.         return;
  851.     }
  852.     fat_node_initialize(rootp);
  853.  
  854.     fat_idx_t *ridxp = fat_idx_get_by_pos(dev_handle, FAT_CLST_ROOTPAR, 0);
  855.     if (!ridxp) {
  856.         free(rfn);
  857.         free(rootp);
  858.         block_fini(dev_handle);
  859.         fat_idx_fini_by_dev_handle(dev_handle);
  860.         ipc_answer_0(rid, ENOMEM);
  861.         return;
  862.     }
  863.     assert(ridxp->index == 0);
  864.     /* ridxp->lock held */
  865.  
  866.     rootp->type = FAT_DIRECTORY;
  867.     rootp->firstc = FAT_CLST_ROOT;
  868.     rootp->refcnt = 1;
  869.     rootp->lnkcnt = 0;  /* FS root is not linked */
  870.     rootp->size = rde * sizeof(fat_dentry_t);
  871.     rootp->idx = ridxp;
  872.     ridxp->nodep = rootp;
  873.     rootp->bp = rfn;
  874.     rfn->data = rootp;
  875.    
  876.     futex_up(&ridxp->lock);
  877.  
  878.     ipc_answer_3(rid, EOK, ridxp->index, rootp->size, rootp->lnkcnt);
  879. }
  880.  
  881. void fat_mount(ipc_callid_t rid, ipc_call_t *request)
  882. {
  883.     ipc_answer_0(rid, ENOTSUP);
  884. }
  885.  
  886. void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
  887. {
  888.     libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  889. }
  890.  
  891. void fat_read(ipc_callid_t rid, ipc_call_t *request)
  892. {
  893.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  894.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  895.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  896.     fs_node_t *fn = fat_node_get(dev_handle, index);
  897.     fat_node_t *nodep;
  898.     fat_bs_t *bs;
  899.     uint16_t bps;
  900.     size_t bytes;
  901.     block_t *b;
  902.  
  903.     if (!fn) {
  904.         ipc_answer_0(rid, ENOENT);
  905.         return;
  906.     }
  907.     nodep = FAT_NODE(fn);
  908.  
  909.     ipc_callid_t callid;
  910.     size_t len;
  911.     if (!ipc_data_read_receive(&callid, &len)) {
  912.         fat_node_put(fn);
  913.         ipc_answer_0(callid, EINVAL);
  914.         ipc_answer_0(rid, EINVAL);
  915.         return;
  916.     }
  917.  
  918.     bs = block_bb_get(dev_handle);
  919.     bps = uint16_t_le2host(bs->bps);
  920.  
  921.     if (nodep->type == FAT_FILE) {
  922.         /*
  923.          * Our strategy for regular file reads is to read one block at
  924.          * most and make use of the possibility to return less data than
  925.          * requested. This keeps the code very simple.
  926.          */
  927.         if (pos >= nodep->size) {
  928.             /* reading beyond the EOF */
  929.             bytes = 0;
  930.             (void) ipc_data_read_finalize(callid, NULL, 0);
  931.         } else {
  932.             bytes = min(len, bps - pos % bps);
  933.             bytes = min(bytes, nodep->size - pos);
  934.             b = fat_block_get(bs, nodep, pos / bps,
  935.                 BLOCK_FLAGS_NONE);
  936.             (void) ipc_data_read_finalize(callid, b->data + pos % bps,
  937.                 bytes);
  938.             block_put(b);
  939.         }
  940.     } else {
  941.         unsigned bnum;
  942.         off_t spos = pos;
  943.         char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  944.         fat_dentry_t *d;
  945.  
  946.         assert(nodep->type == FAT_DIRECTORY);
  947.         assert(nodep->size % bps == 0);
  948.         assert(bps % sizeof(fat_dentry_t) == 0);
  949.  
  950.         /*
  951.          * Our strategy for readdir() is to use the position pointer as
  952.          * an index into the array of all dentries. On entry, it points
  953.          * to the first unread dentry. If we skip any dentries, we bump
  954.          * the position pointer accordingly.
  955.          */
  956.         bnum = (pos * sizeof(fat_dentry_t)) / bps;
  957.         while (bnum < nodep->size / bps) {
  958.             off_t o;
  959.  
  960.             b = fat_block_get(bs, nodep, bnum, BLOCK_FLAGS_NONE);
  961.             for (o = pos % (bps / sizeof(fat_dentry_t));
  962.                 o < bps / sizeof(fat_dentry_t);
  963.                 o++, pos++) {
  964.                 d = ((fat_dentry_t *)b->data) + o;
  965.                 switch (fat_classify_dentry(d)) {
  966.                 case FAT_DENTRY_SKIP:
  967.                 case FAT_DENTRY_FREE:
  968.                     continue;
  969.                 case FAT_DENTRY_LAST:
  970.                     block_put(b);
  971.                     goto miss;
  972.                 default:
  973.                 case FAT_DENTRY_VALID:
  974.                     fat_dentry_name_get(d, name);
  975.                     block_put(b);
  976.                     goto hit;
  977.                 }
  978.             }
  979.             block_put(b);
  980.             bnum++;
  981.         }
  982. miss:
  983.         fat_node_put(fn);
  984.         ipc_answer_0(callid, ENOENT);
  985.         ipc_answer_1(rid, ENOENT, 0);
  986.         return;
  987. hit:
  988.         (void) ipc_data_read_finalize(callid, name, str_size(name) + 1);
  989.         bytes = (pos - spos) + 1;
  990.     }
  991.  
  992.     fat_node_put(fn);
  993.     ipc_answer_1(rid, EOK, (ipcarg_t)bytes);
  994. }
  995.  
  996. void fat_write(ipc_callid_t rid, ipc_call_t *request)
  997. {
  998.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  999.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  1000.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  1001.     fs_node_t *fn = fat_node_get(dev_handle, index);
  1002.     fat_node_t *nodep;
  1003.     fat_bs_t *bs;
  1004.     size_t bytes;
  1005.     block_t *b;
  1006.     uint16_t bps;
  1007.     unsigned spc;
  1008.     unsigned bpc;       /* bytes per cluster */
  1009.     off_t boundary;
  1010.     int flags = BLOCK_FLAGS_NONE;
  1011.    
  1012.     if (!fn) {
  1013.         ipc_answer_0(rid, ENOENT);
  1014.         return;
  1015.     }
  1016.     nodep = FAT_NODE(fn);
  1017.    
  1018.     ipc_callid_t callid;
  1019.     size_t len;
  1020.     if (!ipc_data_write_receive(&callid, &len)) {
  1021.         fat_node_put(fn);
  1022.         ipc_answer_0(callid, EINVAL);
  1023.         ipc_answer_0(rid, EINVAL);
  1024.         return;
  1025.     }
  1026.  
  1027.     bs = block_bb_get(dev_handle);
  1028.     bps = uint16_t_le2host(bs->bps);
  1029.     spc = bs->spc;
  1030.     bpc = bps * spc;
  1031.  
  1032.     /*
  1033.      * In all scenarios, we will attempt to write out only one block worth
  1034.      * of data at maximum. There might be some more efficient approaches,
  1035.      * but this one greatly simplifies fat_write(). Note that we can afford
  1036.      * to do this because the client must be ready to handle the return
  1037.      * value signalizing a smaller number of bytes written.
  1038.      */
  1039.     bytes = min(len, bps - pos % bps);
  1040.     if (bytes == bps)
  1041.         flags |= BLOCK_FLAGS_NOREAD;
  1042.    
  1043.     boundary = ROUND_UP(nodep->size, bpc);
  1044.     if (pos < boundary) {
  1045.         /*
  1046.          * This is the easier case - we are either overwriting already
  1047.          * existing contents or writing behind the EOF, but still within
  1048.          * the limits of the last cluster. The node size may grow to the
  1049.          * next block size boundary.
  1050.          */
  1051.         fat_fill_gap(bs, nodep, FAT_CLST_RES0, pos);
  1052.         b = fat_block_get(bs, nodep, pos / bps, flags);
  1053.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  1054.             bytes);
  1055.         b->dirty = true;        /* need to sync block */
  1056.         block_put(b);
  1057.         if (pos + bytes > nodep->size) {
  1058.             nodep->size = pos + bytes;
  1059.             nodep->dirty = true;    /* need to sync node */
  1060.         }
  1061.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  1062.         fat_node_put(fn);
  1063.         return;
  1064.     } else {
  1065.         /*
  1066.          * This is the more difficult case. We must allocate new
  1067.          * clusters for the node and zero them out.
  1068.          */
  1069.         int status;
  1070.         unsigned nclsts;
  1071.         fat_cluster_t mcl, lcl;
  1072.  
  1073.         nclsts = (ROUND_UP(pos + bytes, bpc) - boundary) / bpc;
  1074.         /* create an independent chain of nclsts clusters in all FATs */
  1075.         status = fat_alloc_clusters(bs, dev_handle, nclsts, &mcl, &lcl);
  1076.         if (status != EOK) {
  1077.             /* could not allocate a chain of nclsts clusters */
  1078.             fat_node_put(fn);
  1079.             ipc_answer_0(callid, status);
  1080.             ipc_answer_0(rid, status);
  1081.             return;
  1082.         }
  1083.         /* zero fill any gaps */
  1084.         fat_fill_gap(bs, nodep, mcl, pos);
  1085.         b = _fat_block_get(bs, dev_handle, lcl, (pos / bps) % spc,
  1086.             flags);
  1087.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  1088.             bytes);
  1089.         b->dirty = true;        /* need to sync block */
  1090.         block_put(b);
  1091.         /*
  1092.          * Append the cluster chain starting in mcl to the end of the
  1093.          * node's cluster chain.
  1094.          */
  1095.         fat_append_clusters(bs, nodep, mcl);
  1096.         nodep->size = pos + bytes;
  1097.         nodep->dirty = true;        /* need to sync node */
  1098.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  1099.         fat_node_put(fn);
  1100.         return;
  1101.     }
  1102. }
  1103.  
  1104. void fat_truncate(ipc_callid_t rid, ipc_call_t *request)
  1105. {
  1106.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  1107.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  1108.     size_t size = (off_t)IPC_GET_ARG3(*request);
  1109.     fs_node_t *fn = fat_node_get(dev_handle, index);
  1110.     fat_node_t *nodep;
  1111.     fat_bs_t *bs;
  1112.     uint16_t bps;
  1113.     uint8_t spc;
  1114.     unsigned bpc;   /* bytes per cluster */
  1115.     int rc;
  1116.  
  1117.     if (!fn) {
  1118.         ipc_answer_0(rid, ENOENT);
  1119.         return;
  1120.     }
  1121.     nodep = FAT_NODE(fn);
  1122.  
  1123.     bs = block_bb_get(dev_handle);
  1124.     bps = uint16_t_le2host(bs->bps);
  1125.     spc = bs->spc;
  1126.     bpc = bps * spc;
  1127.  
  1128.     if (nodep->size == size) {
  1129.         rc = EOK;
  1130.     } else if (nodep->size < size) {
  1131.         /*
  1132.          * The standard says we have the freedom to grow the node.
  1133.          * For now, we simply return an error.
  1134.          */
  1135.         rc = EINVAL;
  1136.     } else if (ROUND_UP(nodep->size, bpc) == ROUND_UP(size, bpc)) {
  1137.         /*
  1138.          * The node will be shrunk, but no clusters will be deallocated.
  1139.          */
  1140.         nodep->size = size;
  1141.         nodep->dirty = true;        /* need to sync node */
  1142.         rc = EOK;  
  1143.     } else {
  1144.         /*
  1145.          * The node will be shrunk, clusters will be deallocated.
  1146.          */
  1147.         if (size == 0) {
  1148.             fat_chop_clusters(bs, nodep, FAT_CLST_RES0);
  1149.         } else {
  1150.             fat_cluster_t lastc;
  1151.             (void) fat_cluster_walk(bs, dev_handle, nodep->firstc,
  1152.                 &lastc, (size - 1) / bpc);
  1153.             fat_chop_clusters(bs, nodep, lastc);
  1154.         }
  1155.         nodep->size = size;
  1156.         nodep->dirty = true;        /* need to sync node */
  1157.         rc = EOK;  
  1158.     }
  1159.     fat_node_put(fn);
  1160.     ipc_answer_0(rid, rc);
  1161.     return;
  1162. }
  1163.  
  1164. void fat_destroy(ipc_callid_t rid, ipc_call_t *request)
  1165. {
  1166.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  1167.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  1168.     int rc;
  1169.  
  1170.     fs_node_t *fn = fat_node_get(dev_handle, index);
  1171.     if (!fn) {
  1172.         ipc_answer_0(rid, ENOENT);
  1173.         return;
  1174.     }
  1175.  
  1176.     rc = fat_destroy_node(fn);
  1177.     ipc_answer_0(rid, rc);
  1178. }
  1179.  
  1180. /**
  1181.  * @}
  1182.  */
  1183.