0,0 → 1,454 |
/* |
* 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, BLOCK_FLAGS_NONE); |
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. |
* @param flags Flags passed to libblock. |
* |
* @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, int flags) |
{ |
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, flags); |
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, flags); |
|
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; o < pos && o < boundary; |
o = ALIGN_DOWN(o + bps, bps)) { |
int flags = (o % bps == 0) ? |
BLOCK_FLAGS_NOREAD : BLOCK_FLAGS_NONE; |
b = fat_block_get(bs, nodep, o / bps, flags); |
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, BLOCK_FLAGS_NOREAD); |
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, |
BLOCK_FLAGS_NONE); |
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, BLOCK_FLAGS_NONE); |
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 all copies of FAT. |
* |
* This function will attempt to allocate the requested number of clusters in |
* all instances of the FAT. 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; b++) { |
blk = block_get(dev_handle, rscnt + b, BLOCK_FLAGS_NONE); |
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) { |
assert(firstc >= FAT_CLST_FIRST && firstc < FAT_CLST_BAD); |
nextc = fat_get_cluster(bs, dev_handle, firstc); |
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 = 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); |
} |
} |
|
/** |
* @} |
*/ |