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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_fat.c
  35.  * @brief   Functions that manipulate the File Allocation Tables.
  36.  */
  37.  
  38. #include "fat_fat.h"
  39. #include "fat_dentry.h"
  40. #include "fat.h"
  41. #include "../../vfs/vfs.h"
  42. #include <libfs.h>
  43. #include <libblock.h>
  44. #include <errno.h>
  45. #include <byteorder.h>
  46. #include <align.h>
  47. #include <assert.h>
  48. #include <futex.h>
  49.  
  50. /**
  51.  * The fat_alloc_lock futex protects all copies of the File Allocation Table
  52.  * during allocation of clusters. The lock does not have to be held durring
  53.  * deallocation of clusters.
  54.  */  
  55. static futex_t fat_alloc_lock = FUTEX_INITIALIZER;
  56.  
  57. /** Walk the cluster chain.
  58.  *
  59.  * @param bs        Buffer holding the boot sector for the file.
  60.  * @param dev_handle    Device handle of the device with the file.
  61.  * @param firstc    First cluster to start the walk with.
  62.  * @param lastc     If non-NULL, output argument hodling the last cluster number visited.
  63.  * @param max_clusters  Maximum number of clusters to visit.   
  64.  *
  65.  * @return      Number of clusters seen during the walk.
  66.  */
  67. uint16_t
  68. fat_cluster_walk(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  69.     fat_cluster_t *lastc, uint16_t max_clusters)
  70. {
  71.     block_t *b;
  72.     unsigned bps;
  73.     unsigned rscnt;     /* block address of the first FAT */
  74.     uint16_t clusters = 0;
  75.     fat_cluster_t clst = firstc;
  76.  
  77.     bps = uint16_t_le2host(bs->bps);
  78.     rscnt = uint16_t_le2host(bs->rscnt);
  79.  
  80.     if (firstc == FAT_CLST_RES0) {
  81.         /* No space allocated to the file. */
  82.         if (lastc)
  83.             *lastc = firstc;
  84.         return 0;
  85.     }
  86.  
  87.     while (clst < FAT_CLST_LAST1 && clusters < max_clusters) {
  88.         bn_t fsec;  /* sector offset relative to FAT1 */
  89.         unsigned fidx;  /* FAT1 entry index */
  90.  
  91.         assert(clst >= FAT_CLST_FIRST);
  92.         if (lastc)
  93.             *lastc = clst;  /* remember the last cluster number */
  94.         fsec = (clst * sizeof(fat_cluster_t)) / bps;
  95.         fidx = clst % (bps / sizeof(fat_cluster_t));
  96.         /* read FAT1 */
  97.         b = block_get(dev_handle, rscnt + fsec);
  98.         clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
  99.         assert(clst != FAT_CLST_BAD);
  100.         block_put(b);
  101.         clusters++;
  102.     }
  103.  
  104.     if (lastc && clst < FAT_CLST_LAST1)
  105.         *lastc = clst;
  106.  
  107.     return clusters;
  108. }
  109.  
  110. /** Read block from file located on a FAT file system.
  111.  *
  112.  * @param bs        Buffer holding the boot sector of the file system.
  113.  * @param dev_handle    Device handle of the file system.
  114.  * @param firstc    First cluster used by the file. Can be zero if the file
  115.  *          is empty.
  116.  * @param bn        Block number.
  117.  *
  118.  * @return      Block structure holding the requested block.
  119.  */
  120. block_t *
  121. _fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  122.     bn_t bn)
  123. {
  124.     block_t *b;
  125.     unsigned bps;
  126.     unsigned rscnt;     /* block address of the first FAT */
  127.     unsigned rde;
  128.     unsigned rds;       /* root directory size */
  129.     unsigned sf;
  130.     unsigned ssa;       /* size of the system area */
  131.     unsigned clusters, max_clusters;
  132.     fat_cluster_t lastc;
  133.  
  134.     bps = uint16_t_le2host(bs->bps);
  135.     rscnt = uint16_t_le2host(bs->rscnt);
  136.     rde = uint16_t_le2host(bs->root_ent_max);
  137.     sf = uint16_t_le2host(bs->sec_per_fat);
  138.  
  139.     rds = (sizeof(fat_dentry_t) * rde) / bps;
  140.     rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
  141.     ssa = rscnt + bs->fatcnt * sf + rds;
  142.  
  143.     if (firstc == FAT_CLST_ROOT) {
  144.         /* root directory special case */
  145.         assert(bn < rds);
  146.         b = block_get(dev_handle, rscnt + bs->fatcnt * sf + bn);
  147.         return b;
  148.     }
  149.  
  150.     max_clusters = bn / bs->spc;
  151.     clusters = fat_cluster_walk(bs, dev_handle, firstc, &lastc,
  152.         max_clusters);
  153.     assert(clusters == max_clusters);
  154.  
  155.     b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
  156.         bn % bs->spc);
  157.  
  158.     return b;
  159. }
  160.  
  161. /** Fill the gap between EOF and a new file position.
  162.  *
  163.  * @param bs        Buffer holding the boot sector for nodep.
  164.  * @param nodep     FAT node with the gap.
  165.  * @param mcl       First cluster in an independent cluster chain that will
  166.  *          be later appended to the end of the node's own cluster
  167.  *          chain. If pos is still in the last allocated cluster,
  168.  *          this argument is ignored.
  169.  * @param pos       Position in the last node block.
  170.  */
  171. void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
  172. {
  173.     uint16_t bps;
  174.     unsigned spc;
  175.     block_t *b;
  176.     off_t o, boundary;
  177.  
  178.     bps = uint16_t_le2host(bs->bps);
  179.     spc = bs->spc;
  180.    
  181.     boundary = ROUND_UP(nodep->size, bps * spc);
  182.  
  183.     /* zero out already allocated space */
  184.     for (o = nodep->size - 1; o < pos && o < boundary;
  185.         o = ALIGN_DOWN(o + bps, bps)) {
  186.         b = fat_block_get(bs, nodep, o / bps);
  187.         memset(b->data + o % bps, 0, bps - o % bps);
  188.         b->dirty = true;        /* need to sync node */
  189.         block_put(b);
  190.     }
  191.    
  192.     if (o >= pos)
  193.         return;
  194.    
  195.     /* zero out the initial part of the new cluster chain */
  196.     for (o = boundary; o < pos; o += bps) {
  197.         b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
  198.             (o - boundary) / bps);
  199.         memset(b->data, 0, min(bps, pos - o));
  200.         b->dirty = true;        /* need to sync node */
  201.         block_put(b);
  202.     }
  203. }
  204.  
  205. /** Get cluster from the first FAT.
  206.  *
  207.  * @param bs        Buffer holding the boot sector for the file system.
  208.  * @param dev_handle    Device handle for the file system.
  209.  * @param clst      Cluster which to get.
  210.  *
  211.  * @return      Value found in the cluster.
  212.  */
  213. fat_cluster_t
  214. fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst)
  215. {
  216.     block_t *b;
  217.     uint16_t bps;
  218.     uint16_t rscnt;
  219.     fat_cluster_t *cp, value;
  220.  
  221.     bps = uint16_t_le2host(bs->bps);
  222.     rscnt = uint16_t_le2host(bs->rscnt);
  223.  
  224.     b = block_get(dev_handle, rscnt + (clst * sizeof(fat_cluster_t)) / bps);
  225.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  226.     value = uint16_t_le2host(*cp);
  227.     block_put(b);
  228.    
  229.     return value;
  230. }
  231.  
  232. /** Set cluster in one instance of FAT.
  233.  *
  234.  * @param bs        Buffer holding the boot sector for the file system.
  235.  * @param dev_handle    Device handle for the file system.
  236.  * @param fatno     Number of the FAT instance where to make the change.
  237.  * @param clst      Cluster which is to be set.
  238.  * @param value     Value to set the cluster with.
  239.  */
  240. void
  241. fat_set_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
  242.     fat_cluster_t clst, fat_cluster_t value)
  243. {
  244.     block_t *b;
  245.     uint16_t bps;
  246.     uint16_t rscnt;
  247.     uint16_t sf;
  248.     fat_cluster_t *cp;
  249.  
  250.     bps = uint16_t_le2host(bs->bps);
  251.     rscnt = uint16_t_le2host(bs->rscnt);
  252.     sf = uint16_t_le2host(bs->sec_per_fat);
  253.  
  254.     assert(fatno < bs->fatcnt);
  255.     b = block_get(dev_handle, rscnt + sf * fatno +
  256.         (clst * sizeof(fat_cluster_t)) / bps);
  257.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  258.     *cp = host2uint16_t_le(value);
  259.     b->dirty = true;        /* need to sync block */
  260.     block_put(b);
  261. }
  262.  
  263. /** Replay the allocatoin of clusters in all shadow instances of FAT.
  264.  *
  265.  * @param bs        Buffer holding the boot sector of the file system.
  266.  * @param dev_handle    Device handle of the file system.
  267.  * @param lifo      Chain of allocated clusters.
  268.  * @param nclsts    Number of clusters in the lifo chain.
  269.  */
  270. void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle,
  271.     fat_cluster_t *lifo, unsigned nclsts)
  272. {
  273.     uint8_t fatno;
  274.     unsigned c;
  275.  
  276.     for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
  277.         for (c = 0; c < nclsts; c++) {
  278.             fat_set_cluster(bs, dev_handle, fatno, lifo[c],
  279.                 c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
  280.         }
  281.     }
  282. }
  283.  
  284. /** Allocate clusters in FAT1.
  285.  *
  286.  * This function will attempt to allocate the requested number of clusters in
  287.  * the first FAT instance.  The FAT will be altered so that the allocated
  288.  * clusters form an independent chain (i.e. a chain which does not belong to any
  289.  * file yet).
  290.  *
  291.  * @param bs        Buffer holding the boot sector of the file system.
  292.  * @param dev_handle    Device handle of the file system.
  293.  * @param nclsts    Number of clusters to allocate.
  294.  * @param mcl       Output parameter where the first cluster in the chain
  295.  *          will be returned.
  296.  * @param lcl       Output parameter where the last cluster in the chain
  297.  *          will be returned.
  298.  *
  299.  * @return      EOK on success, a negative error code otherwise.
  300.  */
  301. int
  302. fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts,
  303.     fat_cluster_t *mcl, fat_cluster_t *lcl)
  304. {
  305.     uint16_t bps;
  306.     uint16_t rscnt;
  307.     uint16_t sf;
  308.     block_t *blk;
  309.     fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
  310.     unsigned found = 0; /* top of the free cluster number stack */
  311.     unsigned b, c, cl;
  312.  
  313.     lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
  314.     if (lifo)
  315.         return ENOMEM;
  316.    
  317.     bps = uint16_t_le2host(bs->bps);
  318.     rscnt = uint16_t_le2host(bs->rscnt);
  319.     sf = uint16_t_le2host(bs->sec_per_fat);
  320.    
  321.     /*
  322.      * Search FAT1 for unused clusters.
  323.      */
  324.     futex_down(&fat_alloc_lock);
  325.     for (b = 0, cl = 0; b < sf; blk++) {
  326.         blk = block_get(dev_handle, rscnt + b);
  327.         for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
  328.             fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
  329.             if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
  330.                 /*
  331.                  * The cluster is free. Put it into our stack
  332.                  * of found clusters and mark it as non-free.
  333.                  */
  334.                 lifo[found] = cl;
  335.                 *clst = (found == 0) ?
  336.                     host2uint16_t_le(FAT_CLST_LAST1) :
  337.                     host2uint16_t_le(lifo[found - 1]);
  338.                 blk->dirty = true;  /* need to sync block */
  339.                 if (++found == nclsts) {
  340.                     /* we are almost done */
  341.                     block_put(blk);
  342.                     /* update the shadow copies of FAT */
  343.                     fat_alloc_shadow_clusters(bs,
  344.                         dev_handle, lifo, nclsts);
  345.                     *mcl = lifo[found - 1];
  346.                     *lcl = lifo[0];
  347.                     free(lifo);
  348.                     futex_up(&fat_alloc_lock);
  349.                     return EOK;
  350.                 }
  351.             }
  352.         }
  353.         block_put(blk);
  354.     }
  355.     futex_up(&fat_alloc_lock);
  356.  
  357.     /*
  358.      * We could not find enough clusters. Now we need to free the clusters
  359.      * we have allocated so far.
  360.      */
  361.     while (found--) {
  362.         fat_set_cluster(bs, dev_handle, FAT1, lifo[found],
  363.             FAT_CLST_RES0);
  364.     }
  365.    
  366.     free(lifo);
  367.     return ENOSPC;
  368. }
  369.  
  370. /** Free clusters forming a cluster chain in all copies of FAT.
  371.  *
  372.  * @param bs        Buffer hodling the boot sector of the file system.
  373.  * @param dev_handle    Device handle of the file system.
  374.  * @param firstc    First cluster in the chain which is to be freed.
  375.  */
  376. void
  377. fat_free_clusters(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc)
  378. {
  379.     unsigned fatno;
  380.     fat_cluster_t nextc;
  381.  
  382.     /* Mark all clusters in the chain as free in all copies of FAT. */
  383.     while (firstc < FAT_CLST_LAST1) {
  384.         nextc = fat_get_cluster(bs, dev_handle, firstc);
  385.         assert(nextc >= FAT_CLST_FIRST && nextc < FAT_CLST_BAD);
  386.         for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  387.             fat_set_cluster(bs, dev_handle, fatno, firstc,
  388.                 FAT_CLST_RES0);
  389.         firstc = nextc;
  390.     }
  391. }
  392.  
  393. /** Append a cluster chain to the last file cluster in all FATs.
  394.  *
  395.  * @param bs        Buffer holding the boot sector of the file system.
  396.  * @param nodep     Node representing the file.
  397.  * @param mcl       First cluster of the cluster chain to append.
  398.  */
  399. void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
  400. {
  401.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  402.     fat_cluster_t lcl;
  403.     uint8_t fatno;
  404.  
  405.     if (fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl,
  406.         (uint16_t) -1) == 0) {
  407.         /* No clusters allocated to the node yet. */
  408.         nodep->firstc = host2uint16_t_le(mcl);
  409.         nodep->dirty = true;        /* need to sync node */
  410.         return;
  411.     }
  412.  
  413.     for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  414.         fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
  415. }
  416.  
  417. /** Chop off node clusters in all copies of FAT.
  418.  *
  419.  * @param bs        Buffer holding the boot sector of the file system.
  420.  * @param nodep     FAT node where the chopping will take place.
  421.  * @param lastc     Last cluster which will remain in the node. If this
  422.  *          argument is FAT_CLST_RES0, then all clusters will
  423.  *          be chopped off.
  424.  */
  425. void fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc)
  426. {
  427.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  428.     if (lastc == FAT_CLST_RES0) {
  429.         /* The node will have zero size and no clusters allocated. */
  430.         fat_free_clusters(bs, dev_handle, nodep->firstc);
  431.         nodep->firstc = FAT_CLST_RES0;
  432.         nodep->dirty = true;        /* need to sync node */
  433.     } else {
  434.         fat_cluster_t nextc;
  435.         unsigned fatno;
  436.  
  437.         nextc = fat_get_cluster(bs, dev_handle, lastc);
  438.  
  439.         /* Terminate the cluster chain in all copies of FAT. */
  440.         for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  441.             fat_set_cluster(bs, dev_handle, fatno, lastc, FAT_CLST_LAST1);
  442.  
  443.         /* Free all following clusters. */
  444.         fat_free_clusters(bs, dev_handle, nextc);
  445.     }
  446. }
  447.  
  448. /**
  449.  * @}
  450.  */
  451.