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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 penult    If non-NULL, output argument hodling the
  63.  *          the penultimate cluster visited.
  64.  * @param ult       If non-NULL, output argument holding the
  65.  *          ultimate cluster visited.
  66.  * @param max_clusters  Maximum number of clusters to visit.   
  67.  *
  68.  * @return      Number of clusters seen during the walk.
  69.  */
  70. uint16_t
  71. fat_cluster_walk(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  72.     fat_cluster_t *penult, fat_cluster_t *ult, uint16_t max_clusters)
  73. {
  74.     block_t *b;
  75.     unsigned bps;
  76.     unsigned rscnt;     /* block address of the first FAT */
  77.     uint16_t clusters = 0;
  78.     fat_cluster_t clst = firstc;
  79.  
  80.     bps = uint16_t_le2host(bs->bps);
  81.     rscnt = uint16_t_le2host(bs->rscnt);
  82.  
  83.     if (firstc == FAT_CLST_RES0) {
  84.         /* No space allocated to the file. */
  85.         if (ult)
  86.             *ult = firstc;
  87.         return 0;
  88.     }
  89.  
  90.     /* At this point, the meaning of penult is not well-defined. */
  91.     if (penult)
  92.         *penult = FAT_CLST_RES0;
  93.  
  94.     while (clst < FAT_CLST_LAST1 && clusters < max_clusters) {
  95.         unsigned fsec;  /* sector offset relative to FAT1 */
  96.         unsigned fidx;  /* FAT1 entry index */
  97.  
  98.         assert(clst >= FAT_CLST_FIRST);
  99.         if (penult)
  100.             *penult = clst; /* remember the penultimate cluster */
  101.         fsec = (clst * sizeof(fat_cluster_t)) / bps;
  102.         fidx = clst % (bps / sizeof(fat_cluster_t));
  103.         /* read FAT1 */
  104.         b = block_get(dev_handle, rscnt + fsec);
  105.         clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
  106.         assert(clst != FAT_CLST_BAD);
  107.         block_put(b);
  108.         clusters++;
  109.     }
  110.  
  111.     if (ult)
  112.         *ult = clst;
  113.  
  114.     return clusters;
  115. }
  116.  
  117. /** Read block from file located on a FAT file system.
  118.  *
  119.  * @param bs        Buffer holding the boot sector of the file system.
  120.  * @param dev_handle    Device handle of the file system.
  121.  * @param firstc    First cluster used by the file. Can be zero if the file
  122.  *          is empty.
  123.  * @param offset    Offset in blocks.
  124.  *
  125.  * @return      Block structure holding the requested block.
  126.  */
  127. block_t *
  128. _fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  129.     off_t offset)
  130. {
  131.     block_t *b;
  132.     unsigned bps;
  133.     unsigned rscnt;     /* block address of the first FAT */
  134.     unsigned rde;
  135.     unsigned rds;       /* root directory size */
  136.     unsigned sf;
  137.     unsigned ssa;       /* size of the system area */
  138.     unsigned clusters, max_clusters;
  139.     fat_cluster_t lastc, clst = firstc;
  140.  
  141.     bps = uint16_t_le2host(bs->bps);
  142.     rscnt = uint16_t_le2host(bs->rscnt);
  143.     rde = uint16_t_le2host(bs->root_ent_max);
  144.     sf = uint16_t_le2host(bs->sec_per_fat);
  145.  
  146.     rds = (sizeof(fat_dentry_t) * rde) / bps;
  147.     rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
  148.     ssa = rscnt + bs->fatcnt * sf + rds;
  149.  
  150.     if (firstc == FAT_CLST_ROOT) {
  151.         /* root directory special case */
  152.         assert(offset < rds);
  153.         b = block_get(dev_handle, rscnt + bs->fatcnt * sf + offset);
  154.         return b;
  155.     }
  156.  
  157.     max_clusters = offset / bs->spc;
  158.     clusters = fat_cluster_walk(bs, dev_handle, firstc, NULL, &lastc,
  159.         max_clusters);
  160.     assert(clusters == max_clusters);
  161.  
  162.     b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
  163.         offset % bs->spc);
  164.  
  165.     return b;
  166. }
  167.  
  168.  
  169. /** Fill the gap between EOF and a new file position.
  170.  *
  171.  * @param bs        Buffer holding the boot sector for nodep.
  172.  * @param nodep     FAT node with the gap.
  173.  * @param mcl       First cluster in an independent cluster chain that will
  174.  *          be later appended to the end of the node's own cluster
  175.  *          chain. If pos is still in the last allocated cluster,
  176.  *          this argument is ignored.
  177.  * @param pos       Position in the last node block.
  178.  */
  179. void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
  180. {
  181.     uint16_t bps;
  182.     unsigned spc;
  183.     block_t *b;
  184.     off_t o, boundary;
  185.  
  186.     bps = uint16_t_le2host(bs->bps);
  187.     spc = bs->spc;
  188.    
  189.     boundary = ROUND_UP(nodep->size, bps * spc);
  190.  
  191.     /* zero out already allocated space */
  192.     for (o = nodep->size - 1; o < pos && o < boundary;
  193.         o = ALIGN_DOWN(o + bps, bps)) {
  194.         b = fat_block_get(bs, nodep, o / bps);
  195.         memset(b->data + o % bps, 0, bps - o % bps);
  196.         b->dirty = true;        /* need to sync node */
  197.         block_put(b);
  198.     }
  199.    
  200.     if (o >= pos)
  201.         return;
  202.    
  203.     /* zero out the initial part of the new cluster chain */
  204.     for (o = boundary; o < pos; o += bps) {
  205.         b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
  206.             (o - boundary) / bps);
  207.         memset(b->data, 0, min(bps, pos - o));
  208.         b->dirty = true;        /* need to sync node */
  209.         block_put(b);
  210.     }
  211. }
  212.  
  213. /** Mark cluster in one instance of FAT.
  214.  *
  215.  * @param bs        Buffer holding the boot sector for the file system.
  216.  * @param dev_handle    Device handle for the file system.
  217.  * @param fatno     Number of the FAT instance where to make the change.
  218.  * @param clst      Cluster which is to be marked.
  219.  * @param value     Value mark the cluster with.
  220.  */
  221. void
  222. fat_mark_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
  223.     fat_cluster_t clst, fat_cluster_t value)
  224. {
  225.     block_t *b;
  226.     uint16_t bps;
  227.     uint16_t rscnt;
  228.     uint16_t sf;
  229.     fat_cluster_t *cp;
  230.  
  231.     bps = uint16_t_le2host(bs->bps);
  232.     rscnt = uint16_t_le2host(bs->rscnt);
  233.     sf = uint16_t_le2host(bs->sec_per_fat);
  234.  
  235.     assert(fatno < bs->fatcnt);
  236.     b = block_get(dev_handle, rscnt + sf * fatno +
  237.         (clst * sizeof(fat_cluster_t)) / bps);
  238.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  239.     *cp = host2uint16_t_le(value);
  240.     b->dirty = true;        /* need to sync block */
  241.     block_put(b);
  242. }
  243.  
  244. /** Replay the allocatoin of clusters in all shadow instances of FAT.
  245.  *
  246.  * @param bs        Buffer holding the boot sector of the file system.
  247.  * @param dev_handle    Device handle of the file system.
  248.  * @param lifo      Chain of allocated clusters.
  249.  * @param nclsts    Number of clusters in the lifo chain.
  250.  */
  251. void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle,
  252.     fat_cluster_t *lifo, unsigned nclsts)
  253. {
  254.     uint8_t fatno;
  255.     unsigned c;
  256.  
  257.     for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
  258.         for (c = 0; c < nclsts; c++) {
  259.             fat_mark_cluster(bs, dev_handle, fatno, lifo[c],
  260.                 c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
  261.         }
  262.     }
  263. }
  264.  
  265. /** Allocate clusters in FAT1.
  266.  *
  267.  * This function will attempt to allocate the requested number of clusters in
  268.  * the first FAT instance.  The FAT will be altered so that the allocated
  269.  * clusters form an independent chain (i.e. a chain which does not belong to any
  270.  * file yet).
  271.  *
  272.  * @param bs        Buffer holding the boot sector of the file system.
  273.  * @param dev_handle    Device handle of the file system.
  274.  * @param nclsts    Number of clusters to allocate.
  275.  * @param mcl       Output parameter where the first cluster in the chain
  276.  *          will be returned.
  277.  * @param lcl       Output parameter where the last cluster in the chain
  278.  *          will be returned.
  279.  *
  280.  * @return      EOK on success, a negative error code otherwise.
  281.  */
  282. int
  283. fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts,
  284.     fat_cluster_t *mcl, fat_cluster_t *lcl)
  285. {
  286.     uint16_t bps;
  287.     uint16_t rscnt;
  288.     uint16_t sf;
  289.     block_t *blk;
  290.     fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
  291.     unsigned found = 0; /* top of the free cluster number stack */
  292.     unsigned b, c, cl;
  293.  
  294.     lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
  295.     if (lifo)
  296.         return ENOMEM;
  297.    
  298.     bps = uint16_t_le2host(bs->bps);
  299.     rscnt = uint16_t_le2host(bs->rscnt);
  300.     sf = uint16_t_le2host(bs->sec_per_fat);
  301.    
  302.     /*
  303.      * Search FAT1 for unused clusters.
  304.      */
  305.     futex_down(&fat_alloc_lock);
  306.     for (b = 0, cl = 0; b < sf; blk++) {
  307.         blk = block_get(dev_handle, rscnt + b);
  308.         for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
  309.             fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
  310.             if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
  311.                 /*
  312.                  * The cluster is free. Put it into our stack
  313.                  * of found clusters and mark it as non-free.
  314.                  */
  315.                 lifo[found] = cl;
  316.                 *clst = (found == 0) ?
  317.                     host2uint16_t_le(FAT_CLST_LAST1) :
  318.                     host2uint16_t_le(lifo[found - 1]);
  319.                 blk->dirty = true;  /* need to sync block */
  320.                 if (++found == nclsts) {
  321.                     /* we are almost done */
  322.                     block_put(blk);
  323.                     /* update the shadow copies of FAT */
  324.                     fat_alloc_shadow_clusters(bs,
  325.                         dev_handle, lifo, nclsts);
  326.                     *mcl = lifo[found - 1];
  327.                     *lcl = lifo[0];
  328.                     free(lifo);
  329.                     futex_up(&fat_alloc_lock);
  330.                     return EOK;
  331.                 }
  332.             }
  333.         }
  334.         block_put(blk);
  335.     }
  336.     futex_up(&fat_alloc_lock);
  337.  
  338.     /*
  339.      * We could not find enough clusters. Now we need to free the clusters
  340.      * we have allocated so far.
  341.      */
  342.     while (found--) {
  343.         fat_mark_cluster(bs, dev_handle, FAT1, lifo[found],
  344.             FAT_CLST_RES0);
  345.     }
  346.    
  347.     free(lifo);
  348.     return ENOSPC;
  349. }
  350.  
  351. /** Append a cluster chain to the last file cluster in all FATs.
  352.  *
  353.  * @param bs        Buffer holding boot sector of the file system.
  354.  * @param nodep     Node representing the file.
  355.  * @param mcl       First cluster of the cluster chain to append.
  356.  */
  357. void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
  358. {
  359.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  360.     fat_cluster_t lcl;
  361.     uint8_t fatno;
  362.  
  363.     if (fat_cluster_walk(bs, nodep->idx->dev_handle, nodep->firstc, &lcl,
  364.         NULL, (uint16_t) -1) == 0) {
  365.         /* No clusters allocated to the node yet. */
  366.         nodep->firstc = host2uint16_t_le(mcl);
  367.         nodep->dirty = true;        /* need to sync node */
  368.         return;
  369.     }
  370.  
  371.     for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  372.         fat_mark_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
  373. }
  374.  
  375. /**
  376.  * @}
  377.  */
  378.