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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 <adt/hash_table.h>
  52. #include <adt/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.     fs_node_initialize(fn);
  153.     fn->data = nodep;
  154.     nodep->bp = fn;
  155.    
  156.     return nodep;
  157. }
  158.  
  159. /** Internal version of fat_node_get().
  160.  *
  161.  * @param idxp      Locked index structure.
  162.  */
  163. static fat_node_t *fat_node_get_core(fat_idx_t *idxp)
  164. {
  165.     block_t *b;
  166.     fat_bs_t *bs;
  167.     fat_dentry_t *d;
  168.     fat_node_t *nodep = NULL;
  169.     unsigned bps;
  170.     unsigned spc;
  171.     unsigned dps;
  172.  
  173.     if (idxp->nodep) {
  174.         /*
  175.          * We are lucky.
  176.          * The node is already instantiated in memory.
  177.          */
  178.         futex_down(&idxp->nodep->lock);
  179.         if (!idxp->nodep->refcnt++)
  180.             list_remove(&idxp->nodep->ffn_link);
  181.         futex_up(&idxp->nodep->lock);
  182.         return idxp->nodep;
  183.     }
  184.  
  185.     /*
  186.      * We must instantiate the node from the file system.
  187.      */
  188.    
  189.     assert(idxp->pfc);
  190.  
  191.     nodep = fat_node_get_new();
  192.     if (!nodep)
  193.         return NULL;
  194.  
  195.     bs = block_bb_get(idxp->dev_handle);
  196.     bps = uint16_t_le2host(bs->bps);
  197.     spc = bs->spc;
  198.     dps = bps / sizeof(fat_dentry_t);
  199.  
  200.     /* Read the block that contains the dentry of interest. */
  201.     b = _fat_block_get(bs, idxp->dev_handle, idxp->pfc,
  202.         (idxp->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);
  203.     assert(b);
  204.  
  205.     d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);
  206.     if (d->attr & FAT_ATTR_SUBDIR) {
  207.         /*
  208.          * The only directory which does not have this bit set is the
  209.          * root directory itself. The root directory node is handled
  210.          * and initialized elsewhere.
  211.          */
  212.         nodep->type = FAT_DIRECTORY;
  213.         /*
  214.          * Unfortunately, the 'size' field of the FAT dentry is not
  215.          * defined for the directory entry type. We must determine the
  216.          * size of the directory by walking the FAT.
  217.          */
  218.         nodep->size = bps * spc * fat_clusters_get(bs, idxp->dev_handle,
  219.             uint16_t_le2host(d->firstc));
  220.     } else {
  221.         nodep->type = FAT_FILE;
  222.         nodep->size = uint32_t_le2host(d->size);
  223.     }
  224.     nodep->firstc = uint16_t_le2host(d->firstc);
  225.     nodep->lnkcnt = 1;
  226.     nodep->refcnt = 1;
  227.  
  228.     block_put(b);
  229.  
  230.     /* Link the idx structure with the node structure. */
  231.     nodep->idx = idxp;
  232.     idxp->nodep = nodep;
  233.  
  234.     return nodep;
  235. }
  236.  
  237. /*
  238.  * Forward declarations of FAT libfs operations.
  239.  */
  240. static fs_node_t *fat_node_get(dev_handle_t, fs_index_t);
  241. static void fat_node_put(fs_node_t *);
  242. static fs_node_t *fat_create_node(dev_handle_t, int);
  243. static int fat_destroy_node(fs_node_t *);
  244. static int fat_link(fs_node_t *, fs_node_t *, const char *);
  245. static int fat_unlink(fs_node_t *, fs_node_t *, const char *);
  246. static fs_node_t *fat_match(fs_node_t *, const char *);
  247. static fs_index_t fat_index_get(fs_node_t *);
  248. static size_t fat_size_get(fs_node_t *);
  249. static unsigned fat_lnkcnt_get(fs_node_t *);
  250. static bool fat_has_children(fs_node_t *);
  251. static fs_node_t *fat_root_get(dev_handle_t);
  252. static char fat_plb_get_char(unsigned);
  253. static bool fat_is_directory(fs_node_t *);
  254. static bool fat_is_file(fs_node_t *node);
  255.  
  256. /*
  257.  * FAT libfs operations.
  258.  */
  259.  
  260. /** Instantiate a FAT in-core node. */
  261. fs_node_t *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
  262. {
  263.     fat_node_t *nodep;
  264.     fat_idx_t *idxp;
  265.  
  266.     idxp = fat_idx_get_by_index(dev_handle, index);
  267.     if (!idxp)
  268.         return NULL;
  269.     /* idxp->lock held */
  270.     nodep = fat_node_get_core(idxp);
  271.     futex_up(&idxp->lock);
  272.     return FS_NODE(nodep);
  273. }
  274.  
  275. void fat_node_put(fs_node_t *fn)
  276. {
  277.     fat_node_t *nodep = FAT_NODE(fn);
  278.     bool destroy = false;
  279.  
  280.     futex_down(&nodep->lock);
  281.     if (!--nodep->refcnt) {
  282.         if (nodep->idx) {
  283.             futex_down(&ffn_futex);
  284.             list_append(&nodep->ffn_link, &ffn_head);
  285.             futex_up(&ffn_futex);
  286.         } else {
  287.             /*
  288.              * The node does not have any index structure associated
  289.              * with itself. This can only mean that we are releasing
  290.              * the node after a failed attempt to allocate the index
  291.              * structure for it.
  292.              */
  293.             destroy = true;
  294.         }
  295.     }
  296.     futex_up(&nodep->lock);
  297.     if (destroy) {
  298.         free(nodep->bp);
  299.         free(nodep);
  300.     }
  301. }
  302.  
  303. fs_node_t *fat_create_node(dev_handle_t dev_handle, int flags)
  304. {
  305.     fat_idx_t *idxp;
  306.     fat_node_t *nodep;
  307.     fat_bs_t *bs;
  308.     fat_cluster_t mcl, lcl;
  309.     uint16_t bps;
  310.     int rc;
  311.  
  312.     bs = block_bb_get(dev_handle);
  313.     bps = uint16_t_le2host(bs->bps);
  314.     if (flags & L_DIRECTORY) {
  315.         /* allocate a cluster */
  316.         rc = fat_alloc_clusters(bs, dev_handle, 1, &mcl, &lcl);
  317.         if (rc != EOK)
  318.             return NULL;
  319.     }
  320.  
  321.     nodep = fat_node_get_new();
  322.     if (!nodep) {
  323.         fat_free_clusters(bs, dev_handle, mcl);
  324.         return NULL;
  325.     }
  326.     idxp = fat_idx_get_new(dev_handle);
  327.     if (!idxp) {
  328.         fat_free_clusters(bs, dev_handle, mcl);
  329.         fat_node_put(FS_NODE(nodep));
  330.         return NULL;
  331.     }
  332.     /* idxp->lock held */
  333.     if (flags & L_DIRECTORY) {
  334.         int i;
  335.         block_t *b;
  336.  
  337.         /*
  338.          * Populate the new cluster with unused dentries.
  339.          */
  340.         for (i = 0; i < bs->spc; i++) {
  341.             b = _fat_block_get(bs, dev_handle, mcl, i,
  342.                 BLOCK_FLAGS_NOREAD);
  343.             /* mark all dentries as never-used */
  344.             memset(b->data, 0, bps);
  345.             b->dirty = false;
  346.             block_put(b);
  347.         }
  348.         nodep->type = FAT_DIRECTORY;
  349.         nodep->firstc = mcl;
  350.         nodep->size = bps * bs->spc;
  351.     } else {
  352.         nodep->type = FAT_FILE;
  353.         nodep->firstc = FAT_CLST_RES0;
  354.         nodep->size = 0;
  355.     }
  356.     nodep->lnkcnt = 0;  /* not linked anywhere */
  357.     nodep->refcnt = 1;
  358.     nodep->dirty = true;
  359.  
  360.     nodep->idx = idxp;
  361.     idxp->nodep = nodep;
  362.  
  363.     futex_up(&idxp->lock);
  364.     return FS_NODE(nodep);
  365. }
  366.  
  367. int fat_destroy_node(fs_node_t *fn)
  368. {
  369.     fat_node_t *nodep = FAT_NODE(fn);
  370.     fat_bs_t *bs;
  371.  
  372.     /*
  373.      * The node is not reachable from the file system. This means that the
  374.      * link count should be zero and that the index structure cannot be
  375.      * found in the position hash. Obviously, we don't need to lock the node
  376.      * nor its index structure.
  377.      */
  378.     assert(nodep->lnkcnt == 0);
  379.  
  380.     /*
  381.      * The node may not have any children.
  382.      */
  383.     assert(fat_has_children(fn) == false);
  384.  
  385.     bs = block_bb_get(nodep->idx->dev_handle);
  386.     if (nodep->firstc != FAT_CLST_RES0) {
  387.         assert(nodep->size);
  388.         /* Free all clusters allocated to the node. */
  389.         fat_free_clusters(bs, nodep->idx->dev_handle, nodep->firstc);
  390.     }
  391.  
  392.     fat_idx_destroy(nodep->idx);
  393.     free(nodep->bp);
  394.     free(nodep);
  395.     return EOK;
  396. }
  397.  
  398. int fat_link(fs_node_t *pfn, fs_node_t *cfn, const char *name)
  399. {
  400.     fat_node_t *parentp = FAT_NODE(pfn);
  401.     fat_node_t *childp = FAT_NODE(cfn);
  402.     fat_dentry_t *d;
  403.     fat_bs_t *bs;
  404.     block_t *b;
  405.     int i, j;
  406.     uint16_t bps;
  407.     unsigned dps;
  408.     unsigned blocks;
  409.     fat_cluster_t mcl, lcl;
  410.     int rc;
  411.  
  412.     futex_down(&childp->lock);
  413.     if (childp->lnkcnt == 1) {
  414.         /*
  415.          * On FAT, we don't support multiple hard links.
  416.          */
  417.         futex_up(&childp->lock);
  418.         return EMLINK;
  419.     }
  420.     assert(childp->lnkcnt == 0);
  421.     futex_up(&childp->lock);
  422.  
  423.     if (!fat_dentry_name_verify(name)) {
  424.         /*
  425.          * Attempt to create unsupported name.
  426.          */
  427.         return ENOTSUP;
  428.     }
  429.  
  430.     /*
  431.      * Get us an unused parent node's dentry or grow the parent and allocate
  432.      * a new one.
  433.      */
  434.    
  435.     futex_down(&parentp->idx->lock);
  436.     bs = block_bb_get(parentp->idx->dev_handle);
  437.     bps = uint16_t_le2host(bs->bps);
  438.     dps = bps / sizeof(fat_dentry_t);
  439.  
  440.     blocks = parentp->size / bps;
  441.  
  442.     for (i = 0; i < blocks; i++) {
  443.         b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);
  444.         for (j = 0; j < dps; j++) {
  445.             d = ((fat_dentry_t *)b->data) + j;
  446.             switch (fat_classify_dentry(d)) {
  447.             case FAT_DENTRY_SKIP:
  448.             case FAT_DENTRY_VALID:
  449.                 /* skipping used and meta entries */
  450.                 continue;
  451.             case FAT_DENTRY_FREE:
  452.             case FAT_DENTRY_LAST:
  453.                 /* found an empty slot */
  454.                 goto hit;
  455.             }
  456.         }
  457.         block_put(b);
  458.     }
  459.     j = 0;
  460.    
  461.     /*
  462.      * We need to grow the parent in order to create a new unused dentry.
  463.      */
  464.     if (parentp->idx->pfc == FAT_CLST_ROOT) {
  465.         /* Can't grow the root directory. */
  466.         futex_up(&parentp->idx->lock);
  467.         return ENOSPC;
  468.     }
  469.     rc = fat_alloc_clusters(bs, parentp->idx->dev_handle, 1, &mcl, &lcl);
  470.     if (rc != EOK) {
  471.         futex_up(&parentp->idx->lock);
  472.         return rc;
  473.     }
  474.     fat_append_clusters(bs, parentp, mcl);
  475.     b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NOREAD);
  476.     d = (fat_dentry_t *)b->data;
  477.     /*
  478.      * Clear all dentries in the block except for the first one (the first
  479.      * dentry will be cleared in the next step).
  480.      */
  481.     memset(d + 1, 0, bps - sizeof(fat_dentry_t));
  482.  
  483. hit:
  484.     /*
  485.      * At this point we only establish the link between the parent and the
  486.      * child.  The dentry, except of the name and the extension, will remain
  487.      * uninitialized until the corresponding node is synced. Thus the valid
  488.      * dentry data is kept in the child node structure.
  489.      */
  490.     memset(d, 0, sizeof(fat_dentry_t));
  491.     fat_dentry_name_set(d, name);
  492.     b->dirty = true;        /* need to sync block */
  493.     block_put(b);
  494.     futex_up(&parentp->idx->lock);
  495.  
  496.     futex_down(&childp->idx->lock);
  497.    
  498.     /*
  499.      * If possible, create the Sub-directory Identifier Entry and the
  500.      * Sub-directory Parent Pointer Entry (i.e. "." and ".."). These entries
  501.      * are not mandatory according to Standard ECMA-107 and HelenOS VFS does
  502.      * not use them anyway, so this is rather a sign of our good will.
  503.      */
  504.     b = fat_block_get(bs, childp, 0, BLOCK_FLAGS_NONE);
  505.     d = (fat_dentry_t *)b->data;
  506.     if (fat_classify_dentry(d) == FAT_DENTRY_LAST ||
  507.         str_cmp(d->name, FAT_NAME_DOT) == 0) {
  508.         memset(d, 0, sizeof(fat_dentry_t));
  509.         str_cpy(d->name, 8, FAT_NAME_DOT);
  510.         str_cpy(d->ext, 3, FAT_EXT_PAD);
  511.         d->attr = FAT_ATTR_SUBDIR;
  512.         d->firstc = host2uint16_t_le(childp->firstc);
  513.         /* TODO: initialize also the date/time members. */
  514.     }
  515.     d++;
  516.     if (fat_classify_dentry(d) == FAT_DENTRY_LAST ||
  517.         str_cmp(d->name, FAT_NAME_DOT_DOT) == 0) {
  518.         memset(d, 0, sizeof(fat_dentry_t));
  519.         str_cpy(d->name, 8, FAT_NAME_DOT_DOT);
  520.         str_cpy(d->ext, 3, FAT_EXT_PAD);
  521.         d->attr = FAT_ATTR_SUBDIR;
  522.         d->firstc = (parentp->firstc == FAT_CLST_ROOT) ?
  523.             host2uint16_t_le(FAT_CLST_RES0) :
  524.             host2uint16_t_le(parentp->firstc);
  525.         /* TODO: initialize also the date/time members. */
  526.     }
  527.     b->dirty = true;        /* need to sync block */
  528.     block_put(b);
  529.  
  530.     childp->idx->pfc = parentp->firstc;
  531.     childp->idx->pdi = i * dps + j;
  532.     futex_up(&childp->idx->lock);
  533.  
  534.     futex_down(&childp->lock);
  535.     childp->lnkcnt = 1;
  536.     childp->dirty = true;       /* need to sync node */
  537.     futex_up(&childp->lock);
  538.  
  539.     /*
  540.      * Hash in the index structure into the position hash.
  541.      */
  542.     fat_idx_hashin(childp->idx);
  543.  
  544.     return EOK;
  545. }
  546.  
  547. int fat_unlink(fs_node_t *pfn, fs_node_t *cfn, const char *nm)
  548. {
  549.     fat_node_t *parentp = FAT_NODE(pfn);
  550.     fat_node_t *childp = FAT_NODE(cfn);
  551.     fat_bs_t *bs;
  552.     fat_dentry_t *d;
  553.     uint16_t bps;
  554.     block_t *b;
  555.  
  556.     if (!parentp)
  557.         return EBUSY;
  558.    
  559.     if (fat_has_children(cfn))
  560.         return ENOTEMPTY;
  561.  
  562.     futex_down(&parentp->lock);
  563.     futex_down(&childp->lock);
  564.     assert(childp->lnkcnt == 1);
  565.     futex_down(&childp->idx->lock);
  566.     bs = block_bb_get(childp->idx->dev_handle);
  567.     bps = uint16_t_le2host(bs->bps);
  568.  
  569.     b = _fat_block_get(bs, childp->idx->dev_handle, childp->idx->pfc,
  570.         (childp->idx->pdi * sizeof(fat_dentry_t)) / bps,
  571.         BLOCK_FLAGS_NONE);
  572.     d = (fat_dentry_t *)b->data +
  573.         (childp->idx->pdi % (bps / sizeof(fat_dentry_t)));
  574.     /* mark the dentry as not-currently-used */
  575.     d->name[0] = FAT_DENTRY_ERASED;
  576.     b->dirty = true;        /* need to sync block */
  577.     block_put(b);
  578.  
  579.     /* remove the index structure from the position hash */
  580.     fat_idx_hashout(childp->idx);
  581.     /* clear position information */
  582.     childp->idx->pfc = FAT_CLST_RES0;
  583.     childp->idx->pdi = 0;
  584.     futex_up(&childp->idx->lock);
  585.     childp->lnkcnt = 0;
  586.     childp->dirty = true;
  587.     futex_up(&childp->lock);
  588.     futex_up(&parentp->lock);
  589.  
  590.     return EOK;
  591. }
  592.  
  593. fs_node_t *fat_match(fs_node_t *pfn, const char *component)
  594. {
  595.     fat_bs_t *bs;
  596.     fat_node_t *parentp = FAT_NODE(pfn);
  597.     char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  598.     unsigned i, j;
  599.     unsigned bps;       /* bytes per sector */
  600.     unsigned dps;       /* dentries per sector */
  601.     unsigned blocks;
  602.     fat_dentry_t *d;
  603.     block_t *b;
  604.  
  605.     futex_down(&parentp->idx->lock);
  606.     bs = block_bb_get(parentp->idx->dev_handle);
  607.     bps = uint16_t_le2host(bs->bps);
  608.     dps = bps / sizeof(fat_dentry_t);
  609.     blocks = parentp->size / bps;
  610.     for (i = 0; i < blocks; i++) {
  611.         b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);
  612.         for (j = 0; j < dps; j++) {
  613.             d = ((fat_dentry_t *)b->data) + j;
  614.             switch (fat_classify_dentry(d)) {
  615.             case FAT_DENTRY_SKIP:
  616.             case FAT_DENTRY_FREE:
  617.                 continue;
  618.             case FAT_DENTRY_LAST:
  619.                 block_put(b);
  620.                 futex_up(&parentp->idx->lock);
  621.                 return NULL;
  622.             default:
  623.             case FAT_DENTRY_VALID:
  624.                 fat_dentry_name_get(d, name);
  625.                 break;
  626.             }
  627.             if (fat_dentry_namecmp(name, component) == 0) {
  628.                 /* hit */
  629.                 fat_node_t *nodep;
  630.                 /*
  631.                  * Assume tree hierarchy for locking.  We
  632.                  * already have the parent and now we are going
  633.                  * to lock the child.  Never lock in the oposite
  634.                  * order.
  635.                  */
  636.                 fat_idx_t *idx = fat_idx_get_by_pos(
  637.                     parentp->idx->dev_handle, parentp->firstc,
  638.                     i * dps + j);
  639.                 futex_up(&parentp->idx->lock);
  640.                 if (!idx) {
  641.                     /*
  642.                      * Can happen if memory is low or if we
  643.                      * run out of 32-bit indices.
  644.                      */
  645.                     block_put(b);
  646.                     return NULL;
  647.                 }
  648.                 nodep = fat_node_get_core(idx);
  649.                 futex_up(&idx->lock);
  650.                 block_put(b);
  651.                 return FS_NODE(nodep);
  652.             }
  653.         }
  654.         block_put(b);
  655.     }
  656.  
  657.     futex_up(&parentp->idx->lock);
  658.     return NULL;
  659. }
  660.  
  661. fs_index_t fat_index_get(fs_node_t *fn)
  662. {
  663.     return FAT_NODE(fn)->idx->index;
  664. }
  665.  
  666. size_t fat_size_get(fs_node_t *fn)
  667. {
  668.     return FAT_NODE(fn)->size;
  669. }
  670.  
  671. unsigned fat_lnkcnt_get(fs_node_t *fn)
  672. {
  673.     return FAT_NODE(fn)->lnkcnt;
  674. }
  675.  
  676. bool fat_has_children(fs_node_t *fn)
  677. {
  678.     fat_bs_t *bs;
  679.     fat_node_t *nodep = FAT_NODE(fn);
  680.     unsigned bps;
  681.     unsigned dps;
  682.     unsigned blocks;
  683.     block_t *b;
  684.     unsigned i, j;
  685.  
  686.     if (nodep->type != FAT_DIRECTORY)
  687.         return false;
  688.    
  689.     futex_down(&nodep->idx->lock);
  690.     bs = block_bb_get(nodep->idx->dev_handle);
  691.     bps = uint16_t_le2host(bs->bps);
  692.     dps = bps / sizeof(fat_dentry_t);
  693.  
  694.     blocks = nodep->size / bps;
  695.  
  696.     for (i = 0; i < blocks; i++) {
  697.         fat_dentry_t *d;
  698.    
  699.         b = fat_block_get(bs, nodep, i, BLOCK_FLAGS_NONE);
  700.         for (j = 0; j < dps; j++) {
  701.             d = ((fat_dentry_t *)b->data) + j;
  702.             switch (fat_classify_dentry(d)) {
  703.             case FAT_DENTRY_SKIP:
  704.             case FAT_DENTRY_FREE:
  705.                 continue;
  706.             case FAT_DENTRY_LAST:
  707.                 block_put(b);
  708.                 futex_up(&nodep->idx->lock);
  709.                 return false;
  710.             default:
  711.             case FAT_DENTRY_VALID:
  712.                 block_put(b);
  713.                 futex_up(&nodep->idx->lock);
  714.                 return true;
  715.             }
  716.             block_put(b);
  717.             futex_up(&nodep->idx->lock);
  718.             return true;
  719.         }
  720.         block_put(b);
  721.     }
  722.  
  723.     futex_up(&nodep->idx->lock);
  724.     return false;
  725. }
  726.  
  727. fs_node_t *fat_root_get(dev_handle_t dev_handle)
  728. {
  729.     return fat_node_get(dev_handle, 0);
  730. }
  731.  
  732. char fat_plb_get_char(unsigned pos)
  733. {
  734.     return fat_reg.plb_ro[pos % PLB_SIZE];
  735. }
  736.  
  737. bool fat_is_directory(fs_node_t *fn)
  738. {
  739.     return FAT_NODE(fn)->type == FAT_DIRECTORY;
  740. }
  741.  
  742. bool fat_is_file(fs_node_t *fn)
  743. {
  744.     return FAT_NODE(fn)->type == FAT_FILE;
  745. }
  746.  
  747. /** libfs operations */
  748. libfs_ops_t fat_libfs_ops = {
  749.     .match = fat_match,
  750.     .node_get = fat_node_get,
  751.     .node_put = fat_node_put,
  752.     .create = fat_create_node,
  753.     .destroy = fat_destroy_node,
  754.     .link = fat_link,
  755.     .unlink = fat_unlink,
  756.     .index_get = fat_index_get,
  757.     .size_get = fat_size_get,
  758.     .lnkcnt_get = fat_lnkcnt_get,
  759.     .has_children = fat_has_children,
  760.     .root_get = fat_root_get,
  761.     .plb_get_char = fat_plb_get_char,
  762.     .is_directory = fat_is_directory,
  763.     .is_file = fat_is_file
  764. };
  765.  
  766. /*
  767.  * VFS operations.
  768.  */
  769.  
  770. void fat_mounted(ipc_callid_t rid, ipc_call_t *request)
  771. {
  772.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  773.     fat_bs_t *bs;
  774.     uint16_t bps;
  775.     uint16_t rde;
  776.     int rc;
  777.  
  778.     /* accept the mount options */
  779.     ipc_callid_t callid;
  780.     size_t size;
  781.     if (!ipc_data_write_receive(&callid, &size)) {
  782.         ipc_answer_0(callid, EINVAL);
  783.         ipc_answer_0(rid, EINVAL);
  784.         return;
  785.     }
  786.     char *opts = malloc(size + 1);
  787.     if (!opts) {
  788.         ipc_answer_0(callid, ENOMEM);
  789.         ipc_answer_0(rid, ENOMEM);
  790.         return;
  791.     }
  792.     ipcarg_t retval = ipc_data_write_finalize(callid, opts, size);
  793.     if (retval != EOK) {
  794.         ipc_answer_0(rid, retval);
  795.         free(opts);
  796.         return;
  797.     }
  798.     opts[size] = '\0';
  799.  
  800.     /* initialize libblock */
  801.     rc = block_init(dev_handle, BS_SIZE);
  802.     if (rc != EOK) {
  803.         ipc_answer_0(rid, rc);
  804.         return;
  805.     }
  806.  
  807.     /* prepare the boot block */
  808.     rc = block_bb_read(dev_handle, BS_BLOCK * BS_SIZE, BS_SIZE);
  809.     if (rc != EOK) {
  810.         block_fini(dev_handle);
  811.         ipc_answer_0(rid, rc);
  812.         return;
  813.     }
  814.  
  815.     /* get the buffer with the boot sector */
  816.     bs = block_bb_get(dev_handle);
  817.    
  818.     /* Read the number of root directory entries. */
  819.     bps = uint16_t_le2host(bs->bps);
  820.     rde = uint16_t_le2host(bs->root_ent_max);
  821.  
  822.     if (bps != BS_SIZE) {
  823.         block_fini(dev_handle);
  824.         ipc_answer_0(rid, ENOTSUP);
  825.         return;
  826.     }
  827.  
  828.     /* Initialize the block cache */
  829.     rc = block_cache_init(dev_handle, bps, 0 /* XXX */);
  830.     if (rc != EOK) {
  831.         block_fini(dev_handle);
  832.         ipc_answer_0(rid, rc);
  833.         return;
  834.     }
  835.  
  836.     rc = fat_idx_init_by_dev_handle(dev_handle);
  837.     if (rc != EOK) {
  838.         block_fini(dev_handle);
  839.         ipc_answer_0(rid, rc);
  840.         return;
  841.     }
  842.  
  843.     /* Initialize the root node. */
  844.     fs_node_t *rfn = (fs_node_t *)malloc(sizeof(fs_node_t));
  845.     if (!rfn) {
  846.         block_fini(dev_handle);
  847.         fat_idx_fini_by_dev_handle(dev_handle);
  848.         ipc_answer_0(rid, ENOMEM);
  849.         return;
  850.     }
  851.     fs_node_initialize(rfn);
  852.     fat_node_t *rootp = (fat_node_t *)malloc(sizeof(fat_node_t));
  853.     if (!rootp) {
  854.         free(rfn);
  855.         block_fini(dev_handle);
  856.         fat_idx_fini_by_dev_handle(dev_handle);
  857.         ipc_answer_0(rid, ENOMEM);
  858.         return;
  859.     }
  860.     fat_node_initialize(rootp);
  861.  
  862.     fat_idx_t *ridxp = fat_idx_get_by_pos(dev_handle, FAT_CLST_ROOTPAR, 0);
  863.     if (!ridxp) {
  864.         free(rfn);
  865.         free(rootp);
  866.         block_fini(dev_handle);
  867.         fat_idx_fini_by_dev_handle(dev_handle);
  868.         ipc_answer_0(rid, ENOMEM);
  869.         return;
  870.     }
  871.     assert(ridxp->index == 0);
  872.     /* ridxp->lock held */
  873.  
  874.     rootp->type = FAT_DIRECTORY;
  875.     rootp->firstc = FAT_CLST_ROOT;
  876.     rootp->refcnt = 1;
  877.     rootp->lnkcnt = 0;  /* FS root is not linked */
  878.     rootp->size = rde * sizeof(fat_dentry_t);
  879.     rootp->idx = ridxp;
  880.     ridxp->nodep = rootp;
  881.     rootp->bp = rfn;
  882.     rfn->data = rootp;
  883.    
  884.     futex_up(&ridxp->lock);
  885.  
  886.     ipc_answer_3(rid, EOK, ridxp->index, rootp->size, rootp->lnkcnt);
  887. }
  888.  
  889. void fat_mount(ipc_callid_t rid, ipc_call_t *request)
  890. {
  891.     libfs_mount(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  892. }
  893.  
  894. void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
  895. {
  896.     libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  897. }
  898.  
  899. void fat_read(ipc_callid_t rid, ipc_call_t *request)
  900. {
  901.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  902.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  903.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  904.     fs_node_t *fn = fat_node_get(dev_handle, index);
  905.     fat_node_t *nodep;
  906.     fat_bs_t *bs;
  907.     uint16_t bps;
  908.     size_t bytes;
  909.     block_t *b;
  910.  
  911.     if (!fn) {
  912.         ipc_answer_0(rid, ENOENT);
  913.         return;
  914.     }
  915.     nodep = FAT_NODE(fn);
  916.  
  917.     ipc_callid_t callid;
  918.     size_t len;
  919.     if (!ipc_data_read_receive(&callid, &len)) {
  920.         fat_node_put(fn);
  921.         ipc_answer_0(callid, EINVAL);
  922.         ipc_answer_0(rid, EINVAL);
  923.         return;
  924.     }
  925.  
  926.     bs = block_bb_get(dev_handle);
  927.     bps = uint16_t_le2host(bs->bps);
  928.  
  929.     if (nodep->type == FAT_FILE) {
  930.         /*
  931.          * Our strategy for regular file reads is to read one block at
  932.          * most and make use of the possibility to return less data than
  933.          * requested. This keeps the code very simple.
  934.          */
  935.         if (pos >= nodep->size) {
  936.             /* reading beyond the EOF */
  937.             bytes = 0;
  938.             (void) ipc_data_read_finalize(callid, NULL, 0);
  939.         } else {
  940.             bytes = min(len, bps - pos % bps);
  941.             bytes = min(bytes, nodep->size - pos);
  942.             b = fat_block_get(bs, nodep, pos / bps,
  943.                 BLOCK_FLAGS_NONE);
  944.             (void) ipc_data_read_finalize(callid, b->data + pos % bps,
  945.                 bytes);
  946.             block_put(b);
  947.         }
  948.     } else {
  949.         unsigned bnum;
  950.         off_t spos = pos;
  951.         char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];
  952.         fat_dentry_t *d;
  953.  
  954.         assert(nodep->type == FAT_DIRECTORY);
  955.         assert(nodep->size % bps == 0);
  956.         assert(bps % sizeof(fat_dentry_t) == 0);
  957.  
  958.         /*
  959.          * Our strategy for readdir() is to use the position pointer as
  960.          * an index into the array of all dentries. On entry, it points
  961.          * to the first unread dentry. If we skip any dentries, we bump
  962.          * the position pointer accordingly.
  963.          */
  964.         bnum = (pos * sizeof(fat_dentry_t)) / bps;
  965.         while (bnum < nodep->size / bps) {
  966.             off_t o;
  967.  
  968.             b = fat_block_get(bs, nodep, bnum, BLOCK_FLAGS_NONE);
  969.             for (o = pos % (bps / sizeof(fat_dentry_t));
  970.                 o < bps / sizeof(fat_dentry_t);
  971.                 o++, pos++) {
  972.                 d = ((fat_dentry_t *)b->data) + o;
  973.                 switch (fat_classify_dentry(d)) {
  974.                 case FAT_DENTRY_SKIP:
  975.                 case FAT_DENTRY_FREE:
  976.                     continue;
  977.                 case FAT_DENTRY_LAST:
  978.                     block_put(b);
  979.                     goto miss;
  980.                 default:
  981.                 case FAT_DENTRY_VALID:
  982.                     fat_dentry_name_get(d, name);
  983.                     block_put(b);
  984.                     goto hit;
  985.                 }
  986.             }
  987.             block_put(b);
  988.             bnum++;
  989.         }
  990. miss:
  991.         fat_node_put(fn);
  992.         ipc_answer_0(callid, ENOENT);
  993.         ipc_answer_1(rid, ENOENT, 0);
  994.         return;
  995. hit:
  996.         (void) ipc_data_read_finalize(callid, name, str_size(name) + 1);
  997.         bytes = (pos - spos) + 1;
  998.     }
  999.  
  1000.     fat_node_put(fn);
  1001.     ipc_answer_1(rid, EOK, (ipcarg_t)bytes);
  1002. }
  1003.  
  1004. void fat_write(ipc_callid_t rid, ipc_call_t *request)
  1005. {
  1006.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  1007.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  1008.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  1009.     fs_node_t *fn = fat_node_get(dev_handle, index);
  1010.     fat_node_t *nodep;
  1011.     fat_bs_t *bs;
  1012.     size_t bytes;
  1013.     block_t *b;
  1014.     uint16_t bps;
  1015.     unsigned spc;
  1016.     unsigned bpc;       /* bytes per cluster */
  1017.     off_t boundary;
  1018.     int flags = BLOCK_FLAGS_NONE;
  1019.    
  1020.     if (!fn) {
  1021.         ipc_answer_0(rid, ENOENT);
  1022.         return;
  1023.     }
  1024.     nodep = FAT_NODE(fn);
  1025.    
  1026.     ipc_callid_t callid;
  1027.     size_t len;
  1028.     if (!ipc_data_write_receive(&callid, &len)) {
  1029.         fat_node_put(fn);
  1030.         ipc_answer_0(callid, EINVAL);
  1031.         ipc_answer_0(rid, EINVAL);
  1032.         return;
  1033.     }
  1034.  
  1035.     bs = block_bb_get(dev_handle);
  1036.     bps = uint16_t_le2host(bs->bps);
  1037.     spc = bs->spc;
  1038.     bpc = bps * spc;
  1039.  
  1040.     /*
  1041.      * In all scenarios, we will attempt to write out only one block worth
  1042.      * of data at maximum. There might be some more efficient approaches,
  1043.      * but this one greatly simplifies fat_write(). Note that we can afford
  1044.      * to do this because the client must be ready to handle the return
  1045.      * value signalizing a smaller number of bytes written.
  1046.      */
  1047.     bytes = min(len, bps - pos % bps);
  1048.     if (bytes == bps)
  1049.         flags |= BLOCK_FLAGS_NOREAD;
  1050.    
  1051.     boundary = ROUND_UP(nodep->size, bpc);
  1052.     if (pos < boundary) {
  1053.         /*
  1054.          * This is the easier case - we are either overwriting already
  1055.          * existing contents or writing behind the EOF, but still within
  1056.          * the limits of the last cluster. The node size may grow to the
  1057.          * next block size boundary.
  1058.          */
  1059.         fat_fill_gap(bs, nodep, FAT_CLST_RES0, pos);
  1060.         b = fat_block_get(bs, nodep, pos / bps, flags);
  1061.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  1062.             bytes);
  1063.         b->dirty = true;        /* need to sync block */
  1064.         block_put(b);
  1065.         if (pos + bytes > nodep->size) {
  1066.             nodep->size = pos + bytes;
  1067.             nodep->dirty = true;    /* need to sync node */
  1068.         }
  1069.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  1070.         fat_node_put(fn);
  1071.         return;
  1072.     } else {
  1073.         /*
  1074.          * This is the more difficult case. We must allocate new
  1075.          * clusters for the node and zero them out.
  1076.          */
  1077.         int status;
  1078.         unsigned nclsts;
  1079.         fat_cluster_t mcl, lcl;
  1080.  
  1081.         nclsts = (ROUND_UP(pos + bytes, bpc) - boundary) / bpc;
  1082.         /* create an independent chain of nclsts clusters in all FATs */
  1083.         status = fat_alloc_clusters(bs, dev_handle, nclsts, &mcl, &lcl);
  1084.         if (status != EOK) {
  1085.             /* could not allocate a chain of nclsts clusters */
  1086.             fat_node_put(fn);
  1087.             ipc_answer_0(callid, status);
  1088.             ipc_answer_0(rid, status);
  1089.             return;
  1090.         }
  1091.         /* zero fill any gaps */
  1092.         fat_fill_gap(bs, nodep, mcl, pos);
  1093.         b = _fat_block_get(bs, dev_handle, lcl, (pos / bps) % spc,
  1094.             flags);
  1095.         (void) ipc_data_write_finalize(callid, b->data + pos % bps,
  1096.             bytes);
  1097.         b->dirty = true;        /* need to sync block */
  1098.         block_put(b);
  1099.         /*
  1100.          * Append the cluster chain starting in mcl to the end of the
  1101.          * node's cluster chain.
  1102.          */
  1103.         fat_append_clusters(bs, nodep, mcl);
  1104.         nodep->size = pos + bytes;
  1105.         nodep->dirty = true;        /* need to sync node */
  1106.         ipc_answer_2(rid, EOK, bytes, nodep->size);
  1107.         fat_node_put(fn);
  1108.         return;
  1109.     }
  1110. }
  1111.  
  1112. void fat_truncate(ipc_callid_t rid, ipc_call_t *request)
  1113. {
  1114.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  1115.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  1116.     size_t size = (off_t)IPC_GET_ARG3(*request);
  1117.     fs_node_t *fn = fat_node_get(dev_handle, index);
  1118.     fat_node_t *nodep;
  1119.     fat_bs_t *bs;
  1120.     uint16_t bps;
  1121.     uint8_t spc;
  1122.     unsigned bpc;   /* bytes per cluster */
  1123.     int rc;
  1124.  
  1125.     if (!fn) {
  1126.         ipc_answer_0(rid, ENOENT);
  1127.         return;
  1128.     }
  1129.     nodep = FAT_NODE(fn);
  1130.  
  1131.     bs = block_bb_get(dev_handle);
  1132.     bps = uint16_t_le2host(bs->bps);
  1133.     spc = bs->spc;
  1134.     bpc = bps * spc;
  1135.  
  1136.     if (nodep->size == size) {
  1137.         rc = EOK;
  1138.     } else if (nodep->size < size) {
  1139.         /*
  1140.          * The standard says we have the freedom to grow the node.
  1141.          * For now, we simply return an error.
  1142.          */
  1143.         rc = EINVAL;
  1144.     } else if (ROUND_UP(nodep->size, bpc) == ROUND_UP(size, bpc)) {
  1145.         /*
  1146.          * The node will be shrunk, but no clusters will be deallocated.
  1147.          */
  1148.         nodep->size = size;
  1149.         nodep->dirty = true;        /* need to sync node */
  1150.         rc = EOK;  
  1151.     } else {
  1152.         /*
  1153.          * The node will be shrunk, clusters will be deallocated.
  1154.          */
  1155.         if (size == 0) {
  1156.             fat_chop_clusters(bs, nodep, FAT_CLST_RES0);
  1157.         } else {
  1158.             fat_cluster_t lastc;
  1159.             (void) fat_cluster_walk(bs, dev_handle, nodep->firstc,
  1160.                 &lastc, (size - 1) / bpc);
  1161.             fat_chop_clusters(bs, nodep, lastc);
  1162.         }
  1163.         nodep->size = size;
  1164.         nodep->dirty = true;        /* need to sync node */
  1165.         rc = EOK;  
  1166.     }
  1167.     fat_node_put(fn);
  1168.     ipc_answer_0(rid, rc);
  1169.     return;
  1170. }
  1171.  
  1172. void fat_close(ipc_callid_t rid, ipc_call_t *request)
  1173. {
  1174.     ipc_answer_0(rid, EOK);
  1175. }
  1176.  
  1177. void fat_destroy(ipc_callid_t rid, ipc_call_t *request)
  1178. {
  1179.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  1180.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  1181.     int rc;
  1182.  
  1183.     fs_node_t *fn = fat_node_get(dev_handle, index);
  1184.     if (!fn) {
  1185.         ipc_answer_0(rid, ENOENT);
  1186.         return;
  1187.     }
  1188.  
  1189.     rc = fat_destroy_node(fn);
  1190.     ipc_answer_0(rid, rc);
  1191. }
  1192.  
  1193. void fat_open_node(ipc_callid_t rid, ipc_call_t *request)
  1194. {
  1195.     libfs_open_node(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
  1196. }
  1197.  
  1198. void fat_device(ipc_callid_t rid, ipc_call_t *request)
  1199. {
  1200.     ipc_answer_0(rid, ENOTSUP);
  1201. }
  1202.  
  1203. void fat_sync(ipc_callid_t rid, ipc_call_t *request)
  1204. {
  1205.     /* Dummy implementation */
  1206.     ipc_answer_0(rid, EOK);
  1207. }
  1208.  
  1209. /**
  1210.  * @}
  1211.  */
  1212.