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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, BLOCK_FLAGS_NONE);
  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.  * @param flags     Flags passed to libblock.
  118.  *
  119.  * @return      Block structure holding the requested block.
  120.  */
  121. block_t *
  122. _fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  123.     bn_t bn, int flags)
  124. {
  125.     block_t *b;
  126.     unsigned bps;
  127.     unsigned rscnt;     /* block address of the first FAT */
  128.     unsigned rde;
  129.     unsigned rds;       /* root directory size */
  130.     unsigned sf;
  131.     unsigned ssa;       /* size of the system area */
  132.     unsigned clusters, max_clusters;
  133.     fat_cluster_t lastc;
  134.  
  135.     bps = uint16_t_le2host(bs->bps);
  136.     rscnt = uint16_t_le2host(bs->rscnt);
  137.     rde = uint16_t_le2host(bs->root_ent_max);
  138.     sf = uint16_t_le2host(bs->sec_per_fat);
  139.  
  140.     rds = (sizeof(fat_dentry_t) * rde) / bps;
  141.     rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
  142.     ssa = rscnt + bs->fatcnt * sf + rds;
  143.  
  144.     if (firstc == FAT_CLST_ROOT) {
  145.         /* root directory special case */
  146.         assert(bn < rds);
  147.         b = block_get(dev_handle, rscnt + bs->fatcnt * sf + bn, flags);
  148.         return b;
  149.     }
  150.  
  151.     max_clusters = bn / bs->spc;
  152.     clusters = fat_cluster_walk(bs, dev_handle, firstc, &lastc,
  153.         max_clusters);
  154.     assert(clusters == max_clusters);
  155.  
  156.     b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
  157.         bn % bs->spc, flags);
  158.  
  159.     return b;
  160. }
  161.  
  162. /** Fill the gap between EOF and a new file position.
  163.  *
  164.  * @param bs        Buffer holding the boot sector for nodep.
  165.  * @param nodep     FAT node with the gap.
  166.  * @param mcl       First cluster in an independent cluster chain that will
  167.  *          be later appended to the end of the node's own cluster
  168.  *          chain. If pos is still in the last allocated cluster,
  169.  *          this argument is ignored.
  170.  * @param pos       Position in the last node block.
  171.  */
  172. void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
  173. {
  174.     uint16_t bps;
  175.     unsigned spc;
  176.     block_t *b;
  177.     off_t o, boundary;
  178.  
  179.     bps = uint16_t_le2host(bs->bps);
  180.     spc = bs->spc;
  181.    
  182.     boundary = ROUND_UP(nodep->size, bps * spc);
  183.  
  184.     /* zero out already allocated space */
  185.     for (o = nodep->size - 1; o < pos && o < boundary;
  186.         o = ALIGN_DOWN(o + bps, bps)) {
  187.             int flags = (o % bps == 0) ?
  188.             BLOCK_FLAGS_NOREAD : BLOCK_FLAGS_NONE;
  189.         b = fat_block_get(bs, nodep, o / bps, flags);
  190.         memset(b->data + o % bps, 0, bps - o % bps);
  191.         b->dirty = true;        /* need to sync node */
  192.         block_put(b);
  193.     }
  194.    
  195.     if (o >= pos)
  196.         return;
  197.    
  198.     /* zero out the initial part of the new cluster chain */
  199.     for (o = boundary; o < pos; o += bps) {
  200.         b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
  201.             (o - boundary) / bps, BLOCK_FLAGS_NOREAD);
  202.         memset(b->data, 0, min(bps, pos - o));
  203.         b->dirty = true;        /* need to sync node */
  204.         block_put(b);
  205.     }
  206. }
  207.  
  208. /** Get cluster from the first FAT.
  209.  *
  210.  * @param bs        Buffer holding the boot sector for the file system.
  211.  * @param dev_handle    Device handle for the file system.
  212.  * @param clst      Cluster which to get.
  213.  *
  214.  * @return      Value found in the cluster.
  215.  */
  216. fat_cluster_t
  217. fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst)
  218. {
  219.     block_t *b;
  220.     uint16_t bps;
  221.     uint16_t rscnt;
  222.     fat_cluster_t *cp, value;
  223.  
  224.     bps = uint16_t_le2host(bs->bps);
  225.     rscnt = uint16_t_le2host(bs->rscnt);
  226.  
  227.     b = block_get(dev_handle, rscnt + (clst * sizeof(fat_cluster_t)) / bps,
  228.         BLOCK_FLAGS_NONE);
  229.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  230.     value = uint16_t_le2host(*cp);
  231.     block_put(b);
  232.    
  233.     return value;
  234. }
  235.  
  236. /** Set cluster in one instance of FAT.
  237.  *
  238.  * @param bs        Buffer holding the boot sector for the file system.
  239.  * @param dev_handle    Device handle for the file system.
  240.  * @param fatno     Number of the FAT instance where to make the change.
  241.  * @param clst      Cluster which is to be set.
  242.  * @param value     Value to set the cluster with.
  243.  */
  244. void
  245. fat_set_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
  246.     fat_cluster_t clst, fat_cluster_t value)
  247. {
  248.     block_t *b;
  249.     uint16_t bps;
  250.     uint16_t rscnt;
  251.     uint16_t sf;
  252.     fat_cluster_t *cp;
  253.  
  254.     bps = uint16_t_le2host(bs->bps);
  255.     rscnt = uint16_t_le2host(bs->rscnt);
  256.     sf = uint16_t_le2host(bs->sec_per_fat);
  257.  
  258.     assert(fatno < bs->fatcnt);
  259.     b = block_get(dev_handle, rscnt + sf * fatno +
  260.         (clst * sizeof(fat_cluster_t)) / bps, BLOCK_FLAGS_NONE);
  261.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  262.     *cp = host2uint16_t_le(value);
  263.     b->dirty = true;        /* need to sync block */
  264.     block_put(b);
  265. }
  266.  
  267. /** Replay the allocatoin of clusters in all shadow instances of FAT.
  268.  *
  269.  * @param bs        Buffer holding the boot sector of the file system.
  270.  * @param dev_handle    Device handle of the file system.
  271.  * @param lifo      Chain of allocated clusters.
  272.  * @param nclsts    Number of clusters in the lifo chain.
  273.  */
  274. void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle,
  275.     fat_cluster_t *lifo, unsigned nclsts)
  276. {
  277.     uint8_t fatno;
  278.     unsigned c;
  279.  
  280.     for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
  281.         for (c = 0; c < nclsts; c++) {
  282.             fat_set_cluster(bs, dev_handle, fatno, lifo[c],
  283.                 c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
  284.         }
  285.     }
  286. }
  287.  
  288. /** Allocate clusters in FAT1.
  289.  *
  290.  * This function will attempt to allocate the requested number of clusters in
  291.  * the first FAT instance.  The FAT will be altered so that the allocated
  292.  * clusters form an independent chain (i.e. a chain which does not belong to any
  293.  * file yet).
  294.  *
  295.  * @param bs        Buffer holding the boot sector of the file system.
  296.  * @param dev_handle    Device handle of the file system.
  297.  * @param nclsts    Number of clusters to allocate.
  298.  * @param mcl       Output parameter where the first cluster in the chain
  299.  *          will be returned.
  300.  * @param lcl       Output parameter where the last cluster in the chain
  301.  *          will be returned.
  302.  *
  303.  * @return      EOK on success, a negative error code otherwise.
  304.  */
  305. int
  306. fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts,
  307.     fat_cluster_t *mcl, fat_cluster_t *lcl)
  308. {
  309.     uint16_t bps;
  310.     uint16_t rscnt;
  311.     uint16_t sf;
  312.     block_t *blk;
  313.     fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
  314.     unsigned found = 0; /* top of the free cluster number stack */
  315.     unsigned b, c, cl;
  316.  
  317.     lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
  318.     if (lifo)
  319.         return ENOMEM;
  320.    
  321.     bps = uint16_t_le2host(bs->bps);
  322.     rscnt = uint16_t_le2host(bs->rscnt);
  323.     sf = uint16_t_le2host(bs->sec_per_fat);
  324.    
  325.     /*
  326.      * Search FAT1 for unused clusters.
  327.      */
  328.     futex_down(&fat_alloc_lock);
  329.     for (b = 0, cl = 0; b < sf; blk++) {
  330.         blk = block_get(dev_handle, rscnt + b, BLOCK_FLAGS_NOREAD);
  331.         for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
  332.             fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
  333.             if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
  334.                 /*
  335.                  * The cluster is free. Put it into our stack
  336.                  * of found clusters and mark it as non-free.
  337.                  */
  338.                 lifo[found] = cl;
  339.                 *clst = (found == 0) ?
  340.                     host2uint16_t_le(FAT_CLST_LAST1) :
  341.                     host2uint16_t_le(lifo[found - 1]);
  342.                 blk->dirty = true;  /* need to sync block */
  343.                 if (++found == nclsts) {
  344.                     /* we are almost done */
  345.                     block_put(blk);
  346.                     /* update the shadow copies of FAT */
  347.                     fat_alloc_shadow_clusters(bs,
  348.                         dev_handle, lifo, nclsts);
  349.                     *mcl = lifo[found - 1];
  350.                     *lcl = lifo[0];
  351.                     free(lifo);
  352.                     futex_up(&fat_alloc_lock);
  353.                     return EOK;
  354.                 }
  355.             }
  356.         }
  357.         block_put(blk);
  358.     }
  359.     futex_up(&fat_alloc_lock);
  360.  
  361.     /*
  362.      * We could not find enough clusters. Now we need to free the clusters
  363.      * we have allocated so far.
  364.      */
  365.     while (found--) {
  366.         fat_set_cluster(bs, dev_handle, FAT1, lifo[found],
  367.             FAT_CLST_RES0);
  368.     }
  369.    
  370.     free(lifo);
  371.     return ENOSPC;
  372. }
  373.  
  374. /** Free clusters forming a cluster chain in all copies of FAT.
  375.  *
  376.  * @param bs        Buffer hodling the boot sector of the file system.
  377.  * @param dev_handle    Device handle of the file system.
  378.  * @param firstc    First cluster in the chain which is to be freed.
  379.  */
  380. void
  381. fat_free_clusters(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc)
  382. {
  383.     unsigned fatno;
  384.     fat_cluster_t nextc;
  385.  
  386.     /* Mark all clusters in the chain as free in all copies of FAT. */
  387.     while (firstc < FAT_CLST_LAST1) {
  388.         nextc = fat_get_cluster(bs, dev_handle, firstc);
  389.         assert(nextc >= FAT_CLST_FIRST && nextc < FAT_CLST_BAD);
  390.         for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  391.             fat_set_cluster(bs, dev_handle, fatno, firstc,
  392.                 FAT_CLST_RES0);
  393.         firstc = nextc;
  394.     }
  395. }
  396.  
  397. /** Append a cluster chain to the last file cluster in all FATs.
  398.  *
  399.  * @param bs        Buffer holding the boot sector of the file system.
  400.  * @param nodep     Node representing the file.
  401.  * @param mcl       First cluster of the cluster chain to append.
  402.  */
  403. void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
  404. {
  405.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  406.     fat_cluster_t lcl;
  407.     uint8_t fatno;
  408.  
  409.     if (fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl,
  410.         (uint16_t) -1) == 0) {
  411.         /* No clusters allocated to the node yet. */
  412.         nodep->firstc = host2uint16_t_le(mcl);
  413.         nodep->dirty = true;        /* need to sync node */
  414.         return;
  415.     }
  416.  
  417.     for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  418.         fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
  419. }
  420.  
  421. /** Chop off node clusters in all copies of FAT.
  422.  *
  423.  * @param bs        Buffer holding the boot sector of the file system.
  424.  * @param nodep     FAT node where the chopping will take place.
  425.  * @param lastc     Last cluster which will remain in the node. If this
  426.  *          argument is FAT_CLST_RES0, then all clusters will
  427.  *          be chopped off.
  428.  */
  429. void fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc)
  430. {
  431.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  432.     if (lastc == FAT_CLST_RES0) {
  433.         /* The node will have zero size and no clusters allocated. */
  434.         fat_free_clusters(bs, dev_handle, nodep->firstc);
  435.         nodep->firstc = FAT_CLST_RES0;
  436.         nodep->dirty = true;        /* need to sync node */
  437.     } else {
  438.         fat_cluster_t nextc;
  439.         unsigned fatno;
  440.  
  441.         nextc = fat_get_cluster(bs, dev_handle, lastc);
  442.  
  443.         /* Terminate the cluster chain in all copies of FAT. */
  444.         for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  445.             fat_set_cluster(bs, dev_handle, fatno, lastc, FAT_CLST_LAST1);
  446.  
  447.         /* Free all following clusters. */
  448.         fat_free_clusters(bs, dev_handle, nextc);
  449.     }
  450. }
  451.  
  452. /**
  453.  * @}
  454.  */
  455.