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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 <fibril_sync.h>
  49. #include <mem.h>
  50.  
  51. /**
  52.  * The fat_alloc_lock mutex protects all copies of the File Allocation Table
  53.  * during allocation of clusters. The lock does not have to be held durring
  54.  * deallocation of clusters.
  55.  */  
  56. static FIBRIL_MUTEX_INITIALIZE(fat_alloc_lock);
  57.  
  58. /** Walk the cluster chain.
  59.  *
  60.  * @param bs        Buffer holding the boot sector for the file.
  61.  * @param dev_handle    Device handle of the device with the file.
  62.  * @param firstc    First cluster to start the walk with.
  63.  * @param lastc     If non-NULL, output argument hodling the last cluster number visited.
  64.  * @param max_clusters  Maximum number of clusters to visit.   
  65.  *
  66.  * @return      Number of clusters seen during the walk.
  67.  */
  68. uint16_t
  69. fat_cluster_walk(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  70.     fat_cluster_t *lastc, uint16_t max_clusters)
  71. {
  72.     block_t *b;
  73.     unsigned bps;
  74.     unsigned rscnt;     /* block address of the first FAT */
  75.     uint16_t clusters = 0;
  76.     fat_cluster_t clst = firstc;
  77.  
  78.     bps = uint16_t_le2host(bs->bps);
  79.     rscnt = uint16_t_le2host(bs->rscnt);
  80.  
  81.     if (firstc == FAT_CLST_RES0) {
  82.         /* No space allocated to the file. */
  83.         if (lastc)
  84.             *lastc = firstc;
  85.         return 0;
  86.     }
  87.  
  88.     while (clst < FAT_CLST_LAST1 && clusters < max_clusters) {
  89.         bn_t fsec;  /* sector offset relative to FAT1 */
  90.         unsigned fidx;  /* FAT1 entry index */
  91.  
  92.         assert(clst >= FAT_CLST_FIRST);
  93.         if (lastc)
  94.             *lastc = clst;  /* remember the last cluster number */
  95.         fsec = (clst * sizeof(fat_cluster_t)) / bps;
  96.         fidx = clst % (bps / sizeof(fat_cluster_t));
  97.         /* read FAT1 */
  98.         b = block_get(dev_handle, rscnt + fsec, BLOCK_FLAGS_NONE);
  99.         clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
  100.         assert(clst != FAT_CLST_BAD);
  101.         block_put(b);
  102.         clusters++;
  103.     }
  104.  
  105.     if (lastc && clst < FAT_CLST_LAST1)
  106.         *lastc = clst;
  107.  
  108.     return clusters;
  109. }
  110.  
  111. /** Read block from file located on a FAT file system.
  112.  *
  113.  * @param bs        Buffer holding the boot sector of the file system.
  114.  * @param dev_handle    Device handle of the file system.
  115.  * @param firstc    First cluster used by the file. Can be zero if the file
  116.  *          is empty.
  117.  * @param bn        Block number.
  118.  * @param flags     Flags passed to libblock.
  119.  *
  120.  * @return      Block structure holding the requested block.
  121.  */
  122. block_t *
  123. _fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
  124.     bn_t bn, int flags)
  125. {
  126.     block_t *b;
  127.     unsigned bps;
  128.     unsigned rscnt;     /* block address of the first FAT */
  129.     unsigned rde;
  130.     unsigned rds;       /* root directory size */
  131.     unsigned sf;
  132.     unsigned ssa;       /* size of the system area */
  133.     unsigned clusters, max_clusters;
  134.     fat_cluster_t lastc;
  135.  
  136.     bps = uint16_t_le2host(bs->bps);
  137.     rscnt = uint16_t_le2host(bs->rscnt);
  138.     rde = uint16_t_le2host(bs->root_ent_max);
  139.     sf = uint16_t_le2host(bs->sec_per_fat);
  140.  
  141.     rds = (sizeof(fat_dentry_t) * rde) / bps;
  142.     rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
  143.     ssa = rscnt + bs->fatcnt * sf + rds;
  144.  
  145.     if (firstc == FAT_CLST_ROOT) {
  146.         /* root directory special case */
  147.         assert(bn < rds);
  148.         b = block_get(dev_handle, rscnt + bs->fatcnt * sf + bn, flags);
  149.         return b;
  150.     }
  151.  
  152.     max_clusters = bn / bs->spc;
  153.     clusters = fat_cluster_walk(bs, dev_handle, firstc, &lastc,
  154.         max_clusters);
  155.     assert(clusters == max_clusters);
  156.  
  157.     b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
  158.         bn % bs->spc, flags);
  159.  
  160.     return b;
  161. }
  162.  
  163. /** Fill the gap between EOF and a new file position.
  164.  *
  165.  * @param bs        Buffer holding the boot sector for nodep.
  166.  * @param nodep     FAT node with the gap.
  167.  * @param mcl       First cluster in an independent cluster chain that will
  168.  *          be later appended to the end of the node's own cluster
  169.  *          chain. If pos is still in the last allocated cluster,
  170.  *          this argument is ignored.
  171.  * @param pos       Position in the last node block.
  172.  */
  173. void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
  174. {
  175.     uint16_t bps;
  176.     unsigned spc;
  177.     block_t *b;
  178.     off_t o, boundary;
  179.  
  180.     bps = uint16_t_le2host(bs->bps);
  181.     spc = bs->spc;
  182.    
  183.     boundary = ROUND_UP(nodep->size, bps * spc);
  184.  
  185.     /* zero out already allocated space */
  186.     for (o = nodep->size; o < pos && o < boundary;
  187.         o = ALIGN_DOWN(o + bps, bps)) {
  188.             int flags = (o % bps == 0) ?
  189.             BLOCK_FLAGS_NOREAD : BLOCK_FLAGS_NONE;
  190.         b = fat_block_get(bs, nodep, o / bps, flags);
  191.         memset(b->data + o % bps, 0, bps - o % bps);
  192.         b->dirty = true;        /* need to sync node */
  193.         block_put(b);
  194.     }
  195.    
  196.     if (o >= pos)
  197.         return;
  198.    
  199.     /* zero out the initial part of the new cluster chain */
  200.     for (o = boundary; o < pos; o += bps) {
  201.         b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
  202.             (o - boundary) / bps, BLOCK_FLAGS_NOREAD);
  203.         memset(b->data, 0, min(bps, pos - o));
  204.         b->dirty = true;        /* need to sync node */
  205.         block_put(b);
  206.     }
  207. }
  208.  
  209. /** Get cluster from the first FAT.
  210.  *
  211.  * @param bs        Buffer holding the boot sector for the file system.
  212.  * @param dev_handle    Device handle for the file system.
  213.  * @param clst      Cluster which to get.
  214.  *
  215.  * @return      Value found in the cluster.
  216.  */
  217. fat_cluster_t
  218. fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst)
  219. {
  220.     block_t *b;
  221.     uint16_t bps;
  222.     uint16_t rscnt;
  223.     fat_cluster_t *cp, value;
  224.  
  225.     bps = uint16_t_le2host(bs->bps);
  226.     rscnt = uint16_t_le2host(bs->rscnt);
  227.  
  228.     b = block_get(dev_handle, rscnt + (clst * sizeof(fat_cluster_t)) / bps,
  229.         BLOCK_FLAGS_NONE);
  230.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  231.     value = uint16_t_le2host(*cp);
  232.     block_put(b);
  233.    
  234.     return value;
  235. }
  236.  
  237. /** Set cluster in one instance of FAT.
  238.  *
  239.  * @param bs        Buffer holding the boot sector for the file system.
  240.  * @param dev_handle    Device handle for the file system.
  241.  * @param fatno     Number of the FAT instance where to make the change.
  242.  * @param clst      Cluster which is to be set.
  243.  * @param value     Value to set the cluster with.
  244.  */
  245. void
  246. fat_set_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
  247.     fat_cluster_t clst, fat_cluster_t value)
  248. {
  249.     block_t *b;
  250.     uint16_t bps;
  251.     uint16_t rscnt;
  252.     uint16_t sf;
  253.     fat_cluster_t *cp;
  254.  
  255.     bps = uint16_t_le2host(bs->bps);
  256.     rscnt = uint16_t_le2host(bs->rscnt);
  257.     sf = uint16_t_le2host(bs->sec_per_fat);
  258.  
  259.     assert(fatno < bs->fatcnt);
  260.     b = block_get(dev_handle, rscnt + sf * fatno +
  261.         (clst * sizeof(fat_cluster_t)) / bps, BLOCK_FLAGS_NONE);
  262.     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
  263.     *cp = host2uint16_t_le(value);
  264.     b->dirty = true;        /* need to sync block */
  265.     block_put(b);
  266. }
  267.  
  268. /** Replay the allocatoin of clusters in all shadow instances of FAT.
  269.  *
  270.  * @param bs        Buffer holding the boot sector of the file system.
  271.  * @param dev_handle    Device handle of the file system.
  272.  * @param lifo      Chain of allocated clusters.
  273.  * @param nclsts    Number of clusters in the lifo chain.
  274.  */
  275. void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle,
  276.     fat_cluster_t *lifo, unsigned nclsts)
  277. {
  278.     uint8_t fatno;
  279.     unsigned c;
  280.  
  281.     for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
  282.         for (c = 0; c < nclsts; c++) {
  283.             fat_set_cluster(bs, dev_handle, fatno, lifo[c],
  284.                 c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
  285.         }
  286.     }
  287. }
  288.  
  289. /** Allocate clusters in all copies of FAT.
  290.  *
  291.  * This function will attempt to allocate the requested number of clusters in
  292.  * all instances of the FAT.  The FAT will be altered so that the allocated
  293.  * clusters form an independent chain (i.e. a chain which does not belong to any
  294.  * file yet).
  295.  *
  296.  * @param bs        Buffer holding the boot sector of the file system.
  297.  * @param dev_handle    Device handle of the file system.
  298.  * @param nclsts    Number of clusters to allocate.
  299.  * @param mcl       Output parameter where the first cluster in the chain
  300.  *          will be returned.
  301.  * @param lcl       Output parameter where the last cluster in the chain
  302.  *          will be returned.
  303.  *
  304.  * @return      EOK on success, a negative error code otherwise.
  305.  */
  306. int
  307. fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts,
  308.     fat_cluster_t *mcl, fat_cluster_t *lcl)
  309. {
  310.     uint16_t bps;
  311.     uint16_t rscnt;
  312.     uint16_t sf;
  313.     block_t *blk;
  314.     fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
  315.     unsigned found = 0; /* top of the free cluster number stack */
  316.     unsigned b, c, cl;
  317.  
  318.     lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
  319.     if (!lifo)
  320.         return ENOMEM;
  321.    
  322.     bps = uint16_t_le2host(bs->bps);
  323.     rscnt = uint16_t_le2host(bs->rscnt);
  324.     sf = uint16_t_le2host(bs->sec_per_fat);
  325.    
  326.     /*
  327.      * Search FAT1 for unused clusters.
  328.      */
  329.     fibril_mutex_lock(&fat_alloc_lock);
  330.     for (b = 0, cl = 0; b < sf; b++) {
  331.         blk = block_get(dev_handle, rscnt + b, BLOCK_FLAGS_NONE);
  332.         for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
  333.             fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
  334.             if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
  335.                 /*
  336.                  * The cluster is free. Put it into our stack
  337.                  * of found clusters and mark it as non-free.
  338.                  */
  339.                 lifo[found] = cl;
  340.                 *clst = (found == 0) ?
  341.                     host2uint16_t_le(FAT_CLST_LAST1) :
  342.                     host2uint16_t_le(lifo[found - 1]);
  343.                 blk->dirty = true;  /* need to sync block */
  344.                 if (++found == nclsts) {
  345.                     /* we are almost done */
  346.                     block_put(blk);
  347.                     /* update the shadow copies of FAT */
  348.                     fat_alloc_shadow_clusters(bs,
  349.                         dev_handle, lifo, nclsts);
  350.                     *mcl = lifo[found - 1];
  351.                     *lcl = lifo[0];
  352.                     free(lifo);
  353.                     fibril_mutex_unlock(&fat_alloc_lock);
  354.                     return EOK;
  355.                 }
  356.             }
  357.         }
  358.         block_put(blk);
  359.     }
  360.     fibril_mutex_unlock(&fat_alloc_lock);
  361.  
  362.     /*
  363.      * We could not find enough clusters. Now we need to free the clusters
  364.      * we have allocated so far.
  365.      */
  366.     while (found--) {
  367.         fat_set_cluster(bs, dev_handle, FAT1, lifo[found],
  368.             FAT_CLST_RES0);
  369.     }
  370.    
  371.     free(lifo);
  372.     return ENOSPC;
  373. }
  374.  
  375. /** Free clusters forming a cluster chain in all copies of FAT.
  376.  *
  377.  * @param bs        Buffer hodling the boot sector of the file system.
  378.  * @param dev_handle    Device handle of the file system.
  379.  * @param firstc    First cluster in the chain which is to be freed.
  380.  */
  381. void
  382. fat_free_clusters(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc)
  383. {
  384.     unsigned fatno;
  385.     fat_cluster_t nextc;
  386.  
  387.     /* Mark all clusters in the chain as free in all copies of FAT. */
  388.     while (firstc < FAT_CLST_LAST1) {
  389.         assert(firstc >= FAT_CLST_FIRST && firstc < FAT_CLST_BAD);
  390.         nextc = fat_get_cluster(bs, dev_handle, firstc);
  391.         for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  392.             fat_set_cluster(bs, dev_handle, fatno, firstc,
  393.                 FAT_CLST_RES0);
  394.         firstc = nextc;
  395.     }
  396. }
  397.  
  398. /** Append a cluster chain to the last file cluster in all FATs.
  399.  *
  400.  * @param bs        Buffer holding the boot sector of the file system.
  401.  * @param nodep     Node representing the file.
  402.  * @param mcl       First cluster of the cluster chain to append.
  403.  */
  404. void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
  405. {
  406.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  407.     fat_cluster_t lcl;
  408.     uint8_t fatno;
  409.  
  410.     if (fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl,
  411.         (uint16_t) -1) == 0) {
  412.         /* No clusters allocated to the node yet. */
  413.         nodep->firstc = mcl;
  414.         nodep->dirty = true;        /* need to sync node */
  415.         return;
  416.     }
  417.  
  418.     for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  419.         fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
  420. }
  421.  
  422. /** Chop off node clusters in all copies of FAT.
  423.  *
  424.  * @param bs        Buffer holding the boot sector of the file system.
  425.  * @param nodep     FAT node where the chopping will take place.
  426.  * @param lastc     Last cluster which will remain in the node. If this
  427.  *          argument is FAT_CLST_RES0, then all clusters will
  428.  *          be chopped off.
  429.  */
  430. void fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc)
  431. {
  432.     dev_handle_t dev_handle = nodep->idx->dev_handle;
  433.     if (lastc == FAT_CLST_RES0) {
  434.         /* The node will have zero size and no clusters allocated. */
  435.         fat_free_clusters(bs, dev_handle, nodep->firstc);
  436.         nodep->firstc = FAT_CLST_RES0;
  437.         nodep->dirty = true;        /* need to sync node */
  438.     } else {
  439.         fat_cluster_t nextc;
  440.         unsigned fatno;
  441.  
  442.         nextc = fat_get_cluster(bs, dev_handle, lastc);
  443.  
  444.         /* Terminate the cluster chain in all copies of FAT. */
  445.         for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
  446.             fat_set_cluster(bs, dev_handle, fatno, lastc, FAT_CLST_LAST1);
  447.  
  448.         /* Free all following clusters. */
  449.         fat_free_clusters(bs, dev_handle, nextc);
  450.     }
  451. }
  452.  
  453. /**
  454.  * @}
  455.  */
  456.