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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. /** Read block from file located on a FAT file system.
  58.  *
  59.  * @param bs        Buffer holding the boot sector of the file system.
  60.  * @param dev_handle    Device handle of the file system.
  61.  * @param firstc    First cluster used by the file. Can be zero if the file
  62.  *          is empty.
  63.  * @param offset    Offset in blocks.
  64.  *
  65.  * @return      Block structure holding the requested block.
  66.  */
  67. block_t *
  68. _fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  69.     off_t offset)
  70. {
  71.     block_t *b;
  72.     unsigned bps;
  73.     unsigned spc;
  74.     unsigned rscnt;     /* block address of the first FAT */
  75.     unsigned fatcnt;
  76.     unsigned rde;
  77.     unsigned rds;       /* root directory size */
  78.     unsigned sf;
  79.     unsigned ssa;       /* size of the system area */
  80.     unsigned clusters;
  81.     fat_cluster_t clst = firstc;
  82.     unsigned i;
  83.  
  84.     bps = uint16_t_le2host(bs->bps);
  85.     spc = bs->spc;
  86.     rscnt = uint16_t_le2host(bs->rscnt);
  87.     fatcnt = bs->fatcnt;
  88.     rde = uint16_t_le2host(bs->root_ent_max);
  89.     sf = uint16_t_le2host(bs->sec_per_fat);
  90.  
  91.     rds = (sizeof(fat_dentry_t) * rde) / bps;
  92.     rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
  93.     ssa = rscnt + fatcnt * sf + rds;
  94.  
  95.     if (firstc == FAT_CLST_ROOT) {
  96.         /* root directory special case */
  97.         assert(offset < rds);
  98.         b = block_get(dev_handle, rscnt + fatcnt * sf + offset, bps);
  99.         return b;
  100.     }
  101.  
  102.     clusters = offset / spc;
  103.     for (i = 0; i < clusters; i++) {
  104.         unsigned fsec;  /* sector offset relative to FAT1 */
  105.         unsigned fidx;  /* FAT1 entry index */
  106.  
  107.         assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);
  108.         fsec = (clst * sizeof(fat_cluster_t)) / bps;
  109.         fidx = clst % (bps / sizeof(fat_cluster_t));
  110.         /* read FAT1 */
  111.         b = block_get(dev_handle, rscnt + fsec, bps);
  112.         clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
  113.         assert(clst != FAT_CLST_BAD);
  114.         assert(clst < FAT_CLST_LAST1);
  115.         block_put(b);
  116.     }
  117.  
  118.     b = block_get(dev_handle, ssa + (clst - FAT_CLST_FIRST) * spc +
  119.         offset % spc, bps);
  120.  
  121.     return b;
  122. }
  123.  
  124. /** Return number of blocks allocated to a file.
  125.  *
  126.  * @param bs        Buffer holding the boot sector for the file.
  127.  * @param dev_handle    Device handle of the device with the file.
  128.  * @param firstc    First cluster of the file.
  129.  * @param lastc     If non-NULL, output argument holding the
  130.  *          last cluster.
  131.  *
  132.  * @return      Number of blocks allocated to the file.
  133.  */
  134. uint16_t
  135. _fat_blcks_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  136.     fat_cluster_t *lastc)
  137. {
  138.     block_t *b;
  139.     unsigned bps;
  140.     unsigned spc;
  141.     unsigned rscnt;     /* block address of the first FAT */
  142.     unsigned clusters = 0;
  143.     fat_cluster_t clst = firstc;
  144.  
  145.     bps = uint16_t_le2host(bs->bps);
  146.     spc = bs->spc;
  147.     rscnt = uint16_t_le2host(bs->rscnt);
  148.  
  149.     if (firstc == FAT_CLST_RES0) {
  150.         /* No space allocated to the file. */
  151.         if (lastc)
  152.             *lastc = firstc;
  153.         return 0;
  154.     }
  155.  
  156.     while (clst < FAT_CLST_LAST1) {
  157.         unsigned fsec;  /* sector offset relative to FAT1 */
  158.         unsigned fidx;  /* FAT1 entry index */
  159.  
  160.         assert(clst >= FAT_CLST_FIRST);
  161.         if (lastc)
  162.             *lastc = clst;      /* remember the last cluster */
  163.         fsec = (clst * sizeof(fat_cluster_t)) / bps;
  164.         fidx = clst % (bps / sizeof(fat_cluster_t));
  165.         /* read FAT1 */
  166.         b = block_get(dev_handle, rscnt + fsec, bps);
  167.         clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
  168.         assert(clst != FAT_CLST_BAD);
  169.         block_put(b);
  170.         clusters++;
  171.     }
  172.  
  173.     if (lastc)
  174.         *lastc = clst;
  175.     return clusters * spc;
  176. }
  177.  
  178. /** Fill the gap between EOF and a new file position.
  179.  *
  180.  * @param bs        Buffer holding the boot sector for nodep.
  181.  * @param nodep     FAT node with the gap.
  182.  * @param mcl       First cluster in an independent cluster chain that will
  183.  *          be later appended to the end of the node's own cluster
  184.  *          chain. If pos is still in the last allocated cluster,
  185.  *          this argument is ignored.
  186.  * @param pos       Position in the last node block.
  187.  */
  188. void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
  189. {
  190.     uint16_t bps;
  191.     unsigned spc;
  192.     block_t *b;
  193.     off_t o, boundary;
  194.  
  195.     bps = uint16_t_le2host(bs->bps);
  196.     spc = bs->spc;
  197.    
  198.     boundary = ROUND_UP(nodep->size, bps * spc);
  199.  
  200.     /* zero out already allocated space */
  201.     for (o = nodep->size - 1; o < pos && o < boundary;
  202.         o = ALIGN_DOWN(o + bps, bps)) {
  203.         b = fat_block_get(bs, nodep, o / bps);
  204.         memset(b->data + o % bps, 0, bps - o % bps);
  205.         b->dirty = true;        /* need to sync node */
  206.         block_put(b);
  207.     }
  208.    
  209.     if (o >= pos)
  210.         return;
  211.    
  212.     /* zero out the initial part of the new cluster chain */
  213.     for (o = boundary; o < pos; o += bps) {
  214.         b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
  215.             (o - boundary) / bps);
  216.         memset(b->data, 0, min(bps, pos - o));
  217.         b->dirty = true;        /* need to sync node */
  218.         block_put(b);
  219.     }
  220. }
  221.  
  222. /** Mark cluster in one instance of FAT.
  223.  *
  224.  * @param bs        Buffer holding the boot sector for the file system.
  225.  * @param dev_handle    Device handle for the file system.
  226.  * @param fatno     Number of the FAT instance where to make the change.
  227.  * @param clst      Cluster which is to be marked.
  228.  * @param value     Value mark the cluster with.
  229.  */
  230. void
  231. fat_mark_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
  232.     fat_cluster_t clst, fat_cluster_t value)
  233. {
  234.     block_t *b;
  235.     uint16_t bps;
  236.     uint16_t rscnt;
  237.     uint16_t sf;
  238.     fat_cluster_t *cp;
  239.  
  240.     bps = uint16_t_le2host(bs->bps);
  241.     rscnt = uint16_t_le2host(bs->rscnt);
  242.     sf = uint16_t_le2host(bs->sec_per_fat);
  243.  
  244.     assert(fatno < bs->fatcnt);
  245.     b = block_get(dev_handle, rscnt + sf * fatno +
  246.         (clst * sizeof(fat_cluster_t)) / bps, bps);
  247.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  248.     *cp = host2uint16_t_le(value);
  249.     b->dirty = true;        /* need to sync block */
  250.     block_put(b);
  251. }
  252.  
  253. /** Replay the allocatoin of clusters in all shadow instances of FAT.
  254.  *
  255.  * @param bs        Buffer holding the boot sector of the file system.
  256.  * @param dev_handle    Device handle of the file system.
  257.  * @param lifo      Chain of allocated clusters.
  258.  * @param nclsts    Number of clusters in the lifo chain.
  259.  */
  260. void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle,
  261.     fat_cluster_t *lifo, unsigned nclsts)
  262. {
  263.     uint8_t fatno;
  264.     unsigned c;
  265.  
  266.     for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
  267.         for (c = 0; c < nclsts; c++) {
  268.             fat_mark_cluster(bs, dev_handle, fatno, lifo[c],
  269.                 c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
  270.         }
  271.     }
  272. }
  273.  
  274. /** Allocate clusters in FAT1.
  275.  *
  276.  * This function will attempt to allocate the requested number of clusters in
  277.  * the first FAT instance.  The FAT will be altered so that the allocated
  278.  * clusters form an independent chain (i.e. a chain which does not belong to any
  279.  * file yet).
  280.  *
  281.  * @param bs        Buffer holding the boot sector of the file system.
  282.  * @param dev_handle    Device handle of the file system.
  283.  * @param nclsts    Number of clusters to allocate.
  284.  * @param mcl       Output parameter where the first cluster in the chain
  285.  *          will be returned.
  286.  * @param lcl       Output parameter where the last cluster in the chain
  287.  *          will be returned.
  288.  *
  289.  * @return      EOK on success, a negative error code otherwise.
  290.  */
  291. int
  292. fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts,
  293.     fat_cluster_t *mcl, fat_cluster_t *lcl)
  294. {
  295.     uint16_t bps;
  296.     uint16_t rscnt;
  297.     uint16_t sf;
  298.     block_t *blk;
  299.     fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
  300.     unsigned found = 0; /* top of the free cluster number stack */
  301.     unsigned b, c, cl;
  302.  
  303.     lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
  304.     if (lifo)
  305.         return ENOMEM;
  306.    
  307.     bps = uint16_t_le2host(bs->bps);
  308.     rscnt = uint16_t_le2host(bs->rscnt);
  309.     sf = uint16_t_le2host(bs->sec_per_fat);
  310.    
  311.     /*
  312.      * Search FAT1 for unused clusters.
  313.      */
  314.     futex_down(&fat_alloc_lock);
  315.     for (b = 0, cl = 0; b < sf; blk++) {
  316.         blk = block_get(dev_handle, rscnt + b, bps);
  317.         for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
  318.             fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
  319.             if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
  320.                 /*
  321.                  * The cluster is free. Put it into our stack
  322.                  * of found clusters and mark it as non-free.
  323.                  */
  324.                 lifo[found] = cl;
  325.                 *clst = (found == 0) ?
  326.                     host2uint16_t_le(FAT_CLST_LAST1) :
  327.                     host2uint16_t_le(lifo[found - 1]);
  328.                 blk->dirty = true;  /* need to sync block */
  329.                 if (++found == nclsts) {
  330.                     /* we are almost done */
  331.                     block_put(blk);
  332.                     /* update the shadow copies of FAT */
  333.                     fat_alloc_shadow_clusters(bs,
  334.                         dev_handle, lifo, nclsts);
  335.                     *mcl = lifo[found - 1];
  336.                     *lcl = lifo[0];
  337.                     free(lifo);
  338.                     futex_up(&fat_alloc_lock);
  339.                     return EOK;
  340.                 }
  341.             }
  342.         }
  343.         block_put(blk);
  344.     }
  345.     futex_up(&fat_alloc_lock);
  346.  
  347.     /*
  348.      * We could not find enough clusters. Now we need to free the clusters
  349.      * we have allocated so far.
  350.      */
  351.     while (found--) {
  352.         fat_mark_cluster(bs, dev_handle, FAT1, lifo[found],
  353.             FAT_CLST_RES0);
  354.     }
  355.    
  356.     free(lifo);
  357.     return ENOSPC;
  358. }
  359.  
  360. /** Append a cluster chain to the last file cluster in all FATs.
  361.  *
  362.  * @param bs        Buffer holding boot sector of the file system.
  363.  * @param nodep     Node representing the file.
  364.  * @param mcl       First cluster of the cluster chain to append.
  365.  */
  366. void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
  367. {
  368.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  369.     fat_cluster_t lcl;
  370.     uint8_t fatno;
  371.  
  372.     if (_fat_blcks_get(bs, dev_handle, nodep->firstc, &lcl) == 0) {
  373.         nodep->firstc = host2uint16_t_le(mcl);
  374.         nodep->dirty = true;        /* need to sync node */
  375.         return;
  376.     }
  377.  
  378.     for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  379.         fat_mark_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
  380. }
  381.  
  382. /**
  383.  * @}
  384.  */
  385.