| 0,0 → 1,450 |
|---|
| /* |
| * Copyright (c) 2008 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| /** @addtogroup fs |
| * @{ |
| */ |
| |
| /** |
| * @file fat_fat.c |
| * @brief Functions that manipulate the File Allocation Tables. |
| */ |
| |
| #include "fat_fat.h" |
| #include "fat_dentry.h" |
| #include "fat.h" |
| #include "../../vfs/vfs.h" |
| #include <libfs.h> |
| #include <libblock.h> |
| #include <errno.h> |
| #include <byteorder.h> |
| #include <align.h> |
| #include <assert.h> |
| #include <futex.h> |
| |
| /** |
| * The fat_alloc_lock futex protects all copies of the File Allocation Table |
| * during allocation of clusters. The lock does not have to be held durring |
| * deallocation of clusters. |
| */ |
| static futex_t fat_alloc_lock = FUTEX_INITIALIZER; |
| |
| /** Walk the cluster chain. |
| * |
| * @param bs Buffer holding the boot sector for the file. |
| * @param dev_handle Device handle of the device with the file. |
| * @param firstc First cluster to start the walk with. |
| * @param lastc If non-NULL, output argument hodling the last cluster number visited. |
| * @param max_clusters Maximum number of clusters to visit. |
| * |
| * @return Number of clusters seen during the walk. |
| */ |
| uint16_t |
| fat_cluster_walk(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc, |
| fat_cluster_t *lastc, uint16_t max_clusters) |
| { |
| block_t *b; |
| unsigned bps; |
| unsigned rscnt; /* block address of the first FAT */ |
| uint16_t clusters = 0; |
| fat_cluster_t clst = firstc; |
| |
| bps = uint16_t_le2host(bs->bps); |
| rscnt = uint16_t_le2host(bs->rscnt); |
| |
| if (firstc == FAT_CLST_RES0) { |
| /* No space allocated to the file. */ |
| if (lastc) |
| *lastc = firstc; |
| return 0; |
| } |
| |
| while (clst < FAT_CLST_LAST1 && clusters < max_clusters) { |
| bn_t fsec; /* sector offset relative to FAT1 */ |
| unsigned fidx; /* FAT1 entry index */ |
| |
| assert(clst >= FAT_CLST_FIRST); |
| if (lastc) |
| *lastc = clst; /* remember the last cluster number */ |
| fsec = (clst * sizeof(fat_cluster_t)) / bps; |
| fidx = clst % (bps / sizeof(fat_cluster_t)); |
| /* read FAT1 */ |
| b = block_get(dev_handle, rscnt + fsec); |
| clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]); |
| assert(clst != FAT_CLST_BAD); |
| block_put(b); |
| clusters++; |
| } |
| |
| if (lastc && clst < FAT_CLST_LAST1) |
| *lastc = clst; |
| |
| return clusters; |
| } |
| |
| /** Read block from file located on a FAT file system. |
| * |
| * @param bs Buffer holding the boot sector of the file system. |
| * @param dev_handle Device handle of the file system. |
| * @param firstc First cluster used by the file. Can be zero if the file |
| * is empty. |
| * @param bn Block number. |
| * |
| * @return Block structure holding the requested block. |
| */ |
| block_t * |
| _fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc, |
| bn_t bn) |
| { |
| block_t *b; |
| unsigned bps; |
| unsigned rscnt; /* block address of the first FAT */ |
| unsigned rde; |
| unsigned rds; /* root directory size */ |
| unsigned sf; |
| unsigned ssa; /* size of the system area */ |
| unsigned clusters, max_clusters; |
| fat_cluster_t lastc; |
| |
| bps = uint16_t_le2host(bs->bps); |
| rscnt = uint16_t_le2host(bs->rscnt); |
| rde = uint16_t_le2host(bs->root_ent_max); |
| sf = uint16_t_le2host(bs->sec_per_fat); |
| |
| rds = (sizeof(fat_dentry_t) * rde) / bps; |
| rds += ((sizeof(fat_dentry_t) * rde) % bps != 0); |
| ssa = rscnt + bs->fatcnt * sf + rds; |
| |
| if (firstc == FAT_CLST_ROOT) { |
| /* root directory special case */ |
| assert(bn < rds); |
| b = block_get(dev_handle, rscnt + bs->fatcnt * sf + bn); |
| return b; |
| } |
| |
| max_clusters = bn / bs->spc; |
| clusters = fat_cluster_walk(bs, dev_handle, firstc, &lastc, |
| max_clusters); |
| assert(clusters == max_clusters); |
| |
| b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc + |
| bn % bs->spc); |
| |
| return b; |
| } |
| |
| /** Fill the gap between EOF and a new file position. |
| * |
| * @param bs Buffer holding the boot sector for nodep. |
| * @param nodep FAT node with the gap. |
| * @param mcl First cluster in an independent cluster chain that will |
| * be later appended to the end of the node's own cluster |
| * chain. If pos is still in the last allocated cluster, |
| * this argument is ignored. |
| * @param pos Position in the last node block. |
| */ |
| void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos) |
| { |
| uint16_t bps; |
| unsigned spc; |
| block_t *b; |
| off_t o, boundary; |
| |
| bps = uint16_t_le2host(bs->bps); |
| spc = bs->spc; |
| |
| boundary = ROUND_UP(nodep->size, bps * spc); |
| |
| /* zero out already allocated space */ |
| for (o = nodep->size - 1; o < pos && o < boundary; |
| o = ALIGN_DOWN(o + bps, bps)) { |
| b = fat_block_get(bs, nodep, o / bps); |
| memset(b->data + o % bps, 0, bps - o % bps); |
| b->dirty = true; /* need to sync node */ |
| block_put(b); |
| } |
| |
| if (o >= pos) |
| return; |
| |
| /* zero out the initial part of the new cluster chain */ |
| for (o = boundary; o < pos; o += bps) { |
| b = _fat_block_get(bs, nodep->idx->dev_handle, mcl, |
| (o - boundary) / bps); |
| memset(b->data, 0, min(bps, pos - o)); |
| b->dirty = true; /* need to sync node */ |
| block_put(b); |
| } |
| } |
| |
| /** Get cluster from the first FAT. |
| * |
| * @param bs Buffer holding the boot sector for the file system. |
| * @param dev_handle Device handle for the file system. |
| * @param clst Cluster which to get. |
| * |
| * @return Value found in the cluster. |
| */ |
| fat_cluster_t |
| fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst) |
| { |
| block_t *b; |
| uint16_t bps; |
| uint16_t rscnt; |
| fat_cluster_t *cp, value; |
| |
| bps = uint16_t_le2host(bs->bps); |
| rscnt = uint16_t_le2host(bs->rscnt); |
| |
| b = block_get(dev_handle, rscnt + (clst * sizeof(fat_cluster_t)) / bps); |
| cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t)); |
| value = uint16_t_le2host(*cp); |
| block_put(b); |
| |
| return value; |
| } |
| |
| /** Set cluster in one instance of FAT. |
| * |
| * @param bs Buffer holding the boot sector for the file system. |
| * @param dev_handle Device handle for the file system. |
| * @param fatno Number of the FAT instance where to make the change. |
| * @param clst Cluster which is to be set. |
| * @param value Value to set the cluster with. |
| */ |
| void |
| fat_set_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno, |
| fat_cluster_t clst, fat_cluster_t value) |
| { |
| block_t *b; |
| uint16_t bps; |
| uint16_t rscnt; |
| uint16_t sf; |
| fat_cluster_t *cp; |
| |
| bps = uint16_t_le2host(bs->bps); |
| rscnt = uint16_t_le2host(bs->rscnt); |
| sf = uint16_t_le2host(bs->sec_per_fat); |
| |
| assert(fatno < bs->fatcnt); |
| b = block_get(dev_handle, rscnt + sf * fatno + |
| (clst * sizeof(fat_cluster_t)) / bps); |
| cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t)); |
| *cp = host2uint16_t_le(value); |
| b->dirty = true; /* need to sync block */ |
| block_put(b); |
| } |
| |
| /** Replay the allocatoin of clusters in all shadow instances of FAT. |
| * |
| * @param bs Buffer holding the boot sector of the file system. |
| * @param dev_handle Device handle of the file system. |
| * @param lifo Chain of allocated clusters. |
| * @param nclsts Number of clusters in the lifo chain. |
| */ |
| void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle, |
| fat_cluster_t *lifo, unsigned nclsts) |
| { |
| uint8_t fatno; |
| unsigned c; |
| |
| for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) { |
| for (c = 0; c < nclsts; c++) { |
| fat_set_cluster(bs, dev_handle, fatno, lifo[c], |
| c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]); |
| } |
| } |
| } |
| |
| /** Allocate clusters in FAT1. |
| * |
| * This function will attempt to allocate the requested number of clusters in |
| * the first FAT instance. The FAT will be altered so that the allocated |
| * clusters form an independent chain (i.e. a chain which does not belong to any |
| * file yet). |
| * |
| * @param bs Buffer holding the boot sector of the file system. |
| * @param dev_handle Device handle of the file system. |
| * @param nclsts Number of clusters to allocate. |
| * @param mcl Output parameter where the first cluster in the chain |
| * will be returned. |
| * @param lcl Output parameter where the last cluster in the chain |
| * will be returned. |
| * |
| * @return EOK on success, a negative error code otherwise. |
| */ |
| int |
| fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts, |
| fat_cluster_t *mcl, fat_cluster_t *lcl) |
| { |
| uint16_t bps; |
| uint16_t rscnt; |
| uint16_t sf; |
| block_t *blk; |
| fat_cluster_t *lifo; /* stack for storing free cluster numbers */ |
| unsigned found = 0; /* top of the free cluster number stack */ |
| unsigned b, c, cl; |
| |
| lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t)); |
| if (lifo) |
| return ENOMEM; |
| |
| bps = uint16_t_le2host(bs->bps); |
| rscnt = uint16_t_le2host(bs->rscnt); |
| sf = uint16_t_le2host(bs->sec_per_fat); |
| |
| /* |
| * Search FAT1 for unused clusters. |
| */ |
| futex_down(&fat_alloc_lock); |
| for (b = 0, cl = 0; b < sf; blk++) { |
| blk = block_get(dev_handle, rscnt + b); |
| for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) { |
| fat_cluster_t *clst = (fat_cluster_t *)blk->data + c; |
| if (uint16_t_le2host(*clst) == FAT_CLST_RES0) { |
| /* |
| * The cluster is free. Put it into our stack |
| * of found clusters and mark it as non-free. |
| */ |
| lifo[found] = cl; |
| *clst = (found == 0) ? |
| host2uint16_t_le(FAT_CLST_LAST1) : |
| host2uint16_t_le(lifo[found - 1]); |
| blk->dirty = true; /* need to sync block */ |
| if (++found == nclsts) { |
| /* we are almost done */ |
| block_put(blk); |
| /* update the shadow copies of FAT */ |
| fat_alloc_shadow_clusters(bs, |
| dev_handle, lifo, nclsts); |
| *mcl = lifo[found - 1]; |
| *lcl = lifo[0]; |
| free(lifo); |
| futex_up(&fat_alloc_lock); |
| return EOK; |
| } |
| } |
| } |
| block_put(blk); |
| } |
| futex_up(&fat_alloc_lock); |
| |
| /* |
| * We could not find enough clusters. Now we need to free the clusters |
| * we have allocated so far. |
| */ |
| while (found--) { |
| fat_set_cluster(bs, dev_handle, FAT1, lifo[found], |
| FAT_CLST_RES0); |
| } |
| |
| free(lifo); |
| return ENOSPC; |
| } |
| |
| /** Free clusters forming a cluster chain in all copies of FAT. |
| * |
| * @param bs Buffer hodling the boot sector of the file system. |
| * @param dev_handle Device handle of the file system. |
| * @param firstc First cluster in the chain which is to be freed. |
| */ |
| void |
| fat_free_clusters(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc) |
| { |
| unsigned fatno; |
| fat_cluster_t nextc; |
| |
| /* Mark all clusters in the chain as free in all copies of FAT. */ |
| while (firstc < FAT_CLST_LAST1) { |
| nextc = fat_get_cluster(bs, dev_handle, firstc); |
| assert(nextc >= FAT_CLST_FIRST && nextc < FAT_CLST_BAD); |
| for (fatno = FAT1; fatno < bs->fatcnt; fatno++) |
| fat_set_cluster(bs, dev_handle, fatno, firstc, |
| FAT_CLST_RES0); |
| firstc = nextc; |
| } |
| } |
| |
| /** Append a cluster chain to the last file cluster in all FATs. |
| * |
| * @param bs Buffer holding the boot sector of the file system. |
| * @param nodep Node representing the file. |
| * @param mcl First cluster of the cluster chain to append. |
| */ |
| void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl) |
| { |
| dev_handle_t dev_handle = nodep->idx->dev_handle; |
| fat_cluster_t lcl; |
| uint8_t fatno; |
| |
| if (fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl, |
| (uint16_t) -1) == 0) { |
| /* No clusters allocated to the node yet. */ |
| nodep->firstc = host2uint16_t_le(mcl); |
| nodep->dirty = true; /* need to sync node */ |
| return; |
| } |
| |
| for (fatno = FAT1; fatno < bs->fatcnt; fatno++) |
| fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl); |
| } |
| |
| /** Chop off node clusters in all copies of FAT. |
| * |
| * @param bs Buffer holding the boot sector of the file system. |
| * @param nodep FAT node where the chopping will take place. |
| * @param lastc Last cluster which will remain in the node. If this |
| * argument is FAT_CLST_RES0, then all clusters will |
| * be chopped off. |
| */ |
| void fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc) |
| { |
| dev_handle_t dev_handle = nodep->idx->dev_handle; |
| if (lastc == FAT_CLST_RES0) { |
| /* The node will have zero size and no clusters allocated. */ |
| fat_free_clusters(bs, dev_handle, nodep->firstc); |
| nodep->firstc = FAT_CLST_RES0; |
| nodep->dirty = true; /* need to sync node */ |
| } else { |
| fat_cluster_t nextc; |
| unsigned fatno; |
| |
| nextc = fat_get_cluster(bs, dev_handle, lastc); |
| |
| /* Terminate the cluster chain in all copies of FAT. */ |
| for (fatno = FAT1; fatno < bs->fatcnt; fatno++) |
| fat_set_cluster(bs, dev_handle, fatno, lastc, FAT_CLST_LAST1); |
| |
| /* Free all following clusters. */ |
| fat_free_clusters(bs, dev_handle, nextc); |
| } |
| } |
| |
| /** |
| * @} |
| */ |