/*
* 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 penult If non-NULL, output argument hodling the
* the penultimate cluster visited.
* @param ult If non-NULL, output argument holding the
* ultimate cluster 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 *penult, fat_cluster_t *ult, 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 (ult)
*ult = firstc;
return 0;
}
/* At this point, the meaning of penult is not well-defined. */
if (penult)
*penult = FAT_CLST_RES0;
while (clst < FAT_CLST_LAST1 && clusters < max_clusters) {
unsigned fsec; /* sector offset relative to FAT1 */
unsigned fidx; /* FAT1 entry index */
assert(clst
>= FAT_CLST_FIRST
); if (penult)
*penult = clst; /* remember the penultimate cluster */
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]);
block_put(b);
clusters++;
}
if (ult)
*ult = 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 offset Offset in blocks.
*
* @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,
off_t offset)
{
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, clst = firstc;
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 */
b = block_get(dev_handle, rscnt + bs->fatcnt * sf + offset);
return b;
}
max_clusters = offset / bs->spc;
clusters = fat_cluster_walk(bs, dev_handle, firstc, NULL, &lastc,
max_clusters);
assert(clusters
== max_clusters
);
b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
offset % 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);
}
}
/** Mark 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 marked.
* @param value Value mark the cluster with.
*/
void
fat_mark_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);
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_mark_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];
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_mark_cluster(bs, dev_handle, FAT1, lifo[found],
FAT_CLST_RES0);
}
return ENOSPC;
}
/** Append a cluster chain to the last file cluster in all FATs.
*
* @param bs Buffer holding 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, nodep->idx->dev_handle, nodep->firstc, &lcl,
NULL, (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_mark_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
}
/**
* @}
*/