/* $OpenBSD: msdosfs_fat.c,v 1.35 2023/04/30 17:16:36 sf Exp $ */ /* $NetBSD: msdosfs_fat.c,v 1.26 1997/10/17 11:24:02 ws Exp $ */ /*- * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank. * Copyright (C) 1994, 1995, 1997 TooLs GmbH. * All rights reserved. * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below). * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. 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. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by TooLs GmbH. * 4. The name of TooLs GmbH may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``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 TOOLS GMBH 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. */ /* * Written by Paul Popelka (paulp@uts.amdahl.com) * * You can do anything you want with this software, just don't say you wrote * it, and don't remove this notice. * * This software is provided "as is". * * The author supplies this software to be publicly redistributed on the * understanding that the author is not responsible for the correct * functioning of this software in any circumstances and is not liable for * any damages caused by this software. * * October 1992 */ /* * kernel include files. */ #include #include #include #include #include /* to define statfs structure */ #include /* to define vattr structure */ #include #include #include /* * msdosfs include files. */ #include #include #include #include #include /* * Fat cache stats. */ int fc_fileextends; /* # of file extends */ int fc_lfcempty; /* # of time last file cluster cache entry * was empty */ int fc_bmapcalls; /* # of times pcbmap was called */ #define LMMAX 20 int fc_lmdistance[LMMAX]; /* counters for how far off the last * cluster mapped entry was. */ int fc_largedistance; /* off by more than LMMAX */ static void fatblock(struct msdosfsmount *, uint32_t, uint32_t *, uint32_t *, uint32_t *); void updatefats(struct msdosfsmount *, struct buf *, uint32_t); static __inline void usemap_free(struct msdosfsmount *, uint32_t); static __inline void usemap_alloc(struct msdosfsmount *, uint32_t); static int fatchain(struct msdosfsmount *, uint32_t, uint32_t, uint32_t); int chainlength(struct msdosfsmount *, uint32_t, uint32_t); int chainalloc(struct msdosfsmount *, uint32_t, uint32_t, uint32_t, uint32_t *, uint32_t *); static void fatblock(struct msdosfsmount *pmp, uint32_t ofs, uint32_t *bnp, uint32_t *sizep, uint32_t *bop) { uint32_t bn, size; bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) * DEV_BSIZE; bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; if (bnp) *bnp = bn; if (sizep) *sizep = size; if (bop) *bop = ofs % pmp->pm_fatblocksize; } /* * Map the logical cluster number of a file into a physical disk sector * that is filesystem relative. * * dep - address of denode representing the file of interest * findcn - file relative cluster whose filesystem relative cluster number * and/or block number are/is to be found * bnp - address of where to place the file system relative block number. * If this pointer is null then don't return this quantity. * cnp - address of where to place the file system relative cluster number. * If this pointer is null then don't return this quantity. * sp - address of where to place the block size for the file/dir * If this pointer is null then don't return this quantity. * * NOTE: Either bnp or cnp must be non-null. * This function has one side effect. If the requested file relative cluster * is beyond the end of file, then the actual number of clusters in the file * is returned in *cnp. This is useful for determining how long a directory is. * If cnp is null, nothing is returned. */ int pcbmap(struct denode *dep, uint32_t findcn, daddr_t *bnp, uint32_t *cnp, int *sp) { int error; uint32_t i; uint32_t cn; uint32_t prevcn = 0; /* XXX: prevcn could be used uninitialized */ uint32_t byteoffset; uint32_t bn; uint32_t bo; struct buf *bp = NULL; uint32_t bp_bn = -1; struct msdosfsmount *pmp = dep->de_pmp; uint32_t bsize; fc_bmapcalls++; /* * If they don't give us someplace to return a value then don't * bother doing anything. */ if (bnp == NULL && cnp == NULL && sp == NULL) return (0); cn = dep->de_StartCluster; /* * The "file" that makes up the root directory is contiguous, * permanently allocated, of fixed size, and is not made up of * clusters. If the cluster number is beyond the end of the root * directory, then return the number of clusters in the file. */ if (cn == MSDOSFSROOT) { if (dep->de_Attributes & ATTR_DIRECTORY) { if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { if (cnp) *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); return (E2BIG); } if (bnp) *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); if (cnp) *cnp = MSDOSFSROOT; if (sp) *sp = min(pmp->pm_bpcluster, dep->de_FileSize - de_cn2off(pmp, findcn)); return (0); } else { /* just an empty file */ if (cnp) *cnp = 0; return (E2BIG); } } /* * All other files do I/O in cluster sized blocks */ if (sp) *sp = pmp->pm_bpcluster; /* * Rummage around in the fat cache, maybe we can avoid tromping * thru every fat entry for the file. And, keep track of how far * off the cache was from where we wanted to be. */ i = 0; fc_lookup(dep, findcn, &i, &cn); if ((bn = findcn - i) >= LMMAX) fc_largedistance++; else fc_lmdistance[bn]++; /* * Handle all other files or directories the normal way. */ for (; i < findcn; i++) { /* * Stop with all reserved clusters, not just with EOF. */ if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) goto hiteof; byteoffset = FATOFS(pmp, cn); fatblock(pmp, byteoffset, &bn, &bsize, &bo); if (bn != bp_bn) { if (bp) brelse(bp); error = bread(pmp->pm_devvp, bn, bsize, &bp); if (error) { brelse(bp); return (error); } bp_bn = bn; } prevcn = cn; if (bo >= bsize) { if (bp) brelse(bp); return (EIO); } if (FAT32(pmp)) cn = getulong(&bp->b_data[bo]); else cn = getushort(&bp->b_data[bo]); if (FAT12(pmp) && (prevcn & 1)) cn >>= 4; cn &= pmp->pm_fatmask; /* * Force the special cluster numbers * to be the same for all cluster sizes * to let the rest of msdosfs handle * all cases the same. */ if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) cn |= ~pmp->pm_fatmask; } if (!MSDOSFSEOF(pmp, cn)) { if (bp) brelse(bp); if (bnp) *bnp = cntobn(pmp, cn); if (cnp) *cnp = cn; fc_setcache(dep, FC_LASTMAP, i, cn); return (0); } hiteof: if (cnp) *cnp = i; if (bp) brelse(bp); /* update last file cluster entry in the fat cache */ fc_setcache(dep, FC_LASTFC, i - 1, prevcn); return (E2BIG); } /* * Find the closest entry in the fat cache to the cluster we are looking * for. */ void fc_lookup(struct denode *dep, uint32_t findcn, uint32_t *frcnp, uint32_t *fsrcnp) { int i; uint32_t cn; struct fatcache *closest = 0; for (i = 0; i < FC_SIZE; i++) { cn = dep->de_fc[i].fc_frcn; if (cn != FCE_EMPTY && cn <= findcn) { if (closest == 0 || cn > closest->fc_frcn) closest = &dep->de_fc[i]; } } if (closest) { *frcnp = closest->fc_frcn; *fsrcnp = closest->fc_fsrcn; } } /* * Purge the fat cache in denode dep of all entries relating to file * relative cluster frcn and beyond. */ void fc_purge(struct denode *dep, u_int frcn) { int i; struct fatcache *fcp; fcp = dep->de_fc; for (i = 0; i < FC_SIZE; i++, fcp++) { if (fcp->fc_frcn >= frcn) fcp->fc_frcn = FCE_EMPTY; } } /* * Update the fat. * If mirroring the fat, update all copies, with the first copy as last. * Else update only the current fat (ignoring the others). * * pmp - msdosfsmount structure for filesystem to update * bp - addr of modified fat block * fatbn - block number relative to begin of filesystem of the modified fat block. */ void updatefats(struct msdosfsmount *pmp, struct buf *bp, uint32_t fatbn) { int i; struct buf *bpn; #ifdef MSDOSFS_DEBUG printf("updatefats(pmp %p, buf %p, fatbn %d)\n", pmp, bp, fatbn); #endif /* * If we have an FSInfo block, update it. */ if (pmp->pm_fsinfo) { if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), &bpn) != 0) { /* * Ignore the error, but turn off FSInfo update for the future. */ pmp->pm_fsinfo = 0; brelse(bpn); } else { struct fsinfo *fp = (struct fsinfo *)bpn->b_data; putulong(fp->fsinfree, pmp->pm_freeclustercount); if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) bwrite(bpn); else bdwrite(bpn); } } if (pmp->pm_flags & MSDOSFS_FATMIRROR) { /* * Now copy the block(s) of the modified fat to the other copies of * the fat and write them out. This is faster than reading in the * other fats and then writing them back out. This could tie up * the fat for quite a while. Preventing others from accessing it. * To prevent us from going after the fat quite so much we use * delayed writes, unless they specified "synchronous" when the * filesystem was mounted. If synch is asked for then use * bwrite()'s and really slow things down. */ for (i = 1; i < pmp->pm_FATs; i++) { fatbn += pmp->pm_FATsecs; /* getblk() never fails */ bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, INFSLP); bcopy(bp->b_data, bpn->b_data, bp->b_bcount); if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) bwrite(bpn); else bdwrite(bpn); } } /* * Write out the first (or current) fat last. */ if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) bwrite(bp); else bdwrite(bp); /* * Maybe update fsinfo sector here? */ } /* * Updating entries in 12 bit fats is a pain in the butt. * * The following picture shows where nibbles go when moving from a 12 bit * cluster number into the appropriate bytes in the FAT. * * byte m byte m+1 byte m+2 * +----+----+ +----+----+ +----+----+ * | 0 1 | | 2 3 | | 4 5 | FAT bytes * +----+----+ +----+----+ +----+----+ * * +----+----+----+ +----+----+----+ * | 3 0 1 | | 4 5 2 | * +----+----+----+ +----+----+----+ * cluster n cluster n+1 * * Where n is even. m = n + (n >> 2) * */ static __inline void usemap_alloc(struct msdosfsmount *pmp, uint32_t cn) { KASSERT(cn <= pmp->pm_maxcluster); pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); pmp->pm_freeclustercount--; } static __inline void usemap_free(struct msdosfsmount *pmp, uint32_t cn) { KASSERT(cn <= pmp->pm_maxcluster); pmp->pm_freeclustercount++; pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); } int clusterfree(struct msdosfsmount *pmp, uint32_t cluster, uint32_t *oldcnp) { int error; uint32_t oldcn; usemap_free(pmp, cluster); error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); if (error) { usemap_alloc(pmp, cluster); return (error); } /* * If the cluster was successfully marked free, then update * the count of free clusters, and turn off the "allocated" * bit in the "in use" cluster bit map. */ if (oldcnp) *oldcnp = oldcn; return (0); } /* * Get or Set or 'Get and Set' the cluster'th entry in the fat. * * function - whether to get or set a fat entry * pmp - address of the msdosfsmount structure for the filesystem * whose fat is to be manipulated. * cn - which cluster is of interest * oldcontents - address of a word that is to receive the contents of the * cluster'th entry if this is a get function * newcontents - the new value to be written into the cluster'th element of * the fat if this is a set function. * * This function can also be used to free a cluster by setting the fat entry * for a cluster to 0. * * All copies of the fat are updated if this is a set function. NOTE: If * fatentry() marks a cluster as free it does not update the inusemap in * the msdosfsmount structure. This is left to the caller. */ int fatentry(int function, struct msdosfsmount *pmp, uint32_t cn, uint32_t *oldcontents, uint32_t newcontents) { int error; uint32_t readcn; uint32_t bn, bo, bsize, byteoffset; struct buf *bp; #ifdef MSDOSFS_DEBUG printf("fatentry(func %d, pmp %p, clust %d, oldcon %p, " "newcon %d)\n", function, pmp, cn, oldcontents, newcontents); #endif #ifdef DIAGNOSTIC /* * Be sure they asked us to do something. */ if ((function & (FAT_SET | FAT_GET)) == 0) { printf("fatentry(): function code doesn't specify get or set\n"); return (EINVAL); } /* * If they asked us to return a cluster number but didn't tell us * where to put it, give them an error. */ if ((function & FAT_GET) && oldcontents == NULL) { printf("fatentry(): get function with no place to put result\n"); return (EINVAL); } #endif /* * Be sure the requested cluster is in the filesystem. */ if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) return (EINVAL); byteoffset = FATOFS(pmp, cn); fatblock(pmp, byteoffset, &bn, &bsize, &bo); if ((error = bread(pmp->pm_devvp, bn, bsize, &bp)) != 0) { brelse(bp); return (error); } if (function & FAT_GET) { if (FAT32(pmp)) readcn = getulong(&bp->b_data[bo]); else readcn = getushort(&bp->b_data[bo]); if (FAT12(pmp) && (cn & 1)) readcn >>= 4; readcn &= pmp->pm_fatmask; /* map reserved fat entries to same values for all fats */ if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) readcn |= ~pmp->pm_fatmask; *oldcontents = readcn; } if (function & FAT_SET) { switch (pmp->pm_fatmask) { case FAT12_MASK: readcn = getushort(&bp->b_data[bo]); if (cn & 1) { readcn &= 0x000f; readcn |= newcontents << 4; } else { readcn &= 0xf000; readcn |= newcontents & 0xfff; } putushort(&bp->b_data[bo], readcn); break; case FAT16_MASK: putushort(&bp->b_data[bo], newcontents); break; case FAT32_MASK: /* * According to spec we have to retain the * high order bits of the fat entry. */ readcn = getulong(&bp->b_data[bo]); readcn &= ~FAT32_MASK; readcn |= newcontents & FAT32_MASK; putulong(&bp->b_data[bo], readcn); break; } updatefats(pmp, bp, bn); bp = NULL; pmp->pm_fmod = 1; } if (bp) brelse(bp); return (0); } /* * Update a contiguous cluster chain * * pmp - mount point * start - first cluster of chain * count - number of clusters in chain * fillwith - what to write into fat entry of last cluster */ static int fatchain(struct msdosfsmount *pmp, uint32_t start, uint32_t count, uint32_t fillwith) { int error; uint32_t bn, bo, bsize, byteoffset, readcn, newc; struct buf *bp; #ifdef MSDOSFS_DEBUG printf("fatchain(pmp %p, start %d, count %d, fillwith %d)\n", pmp, start, count, fillwith); #endif /* * Be sure the clusters are in the filesystem. */ if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) return (EINVAL); while (count > 0) { byteoffset = FATOFS(pmp, start); fatblock(pmp, byteoffset, &bn, &bsize, &bo); error = bread(pmp->pm_devvp, bn, bsize, &bp); if (error) { brelse(bp); return (error); } while (count > 0) { start++; newc = --count > 0 ? start : fillwith; switch (pmp->pm_fatmask) { case FAT12_MASK: readcn = getushort(&bp->b_data[bo]); if (start & 1) { readcn &= 0xf000; readcn |= newc & 0xfff; } else { readcn &= 0x000f; readcn |= newc << 4; } putushort(&bp->b_data[bo], readcn); bo++; if (!(start & 1)) bo++; break; case FAT16_MASK: putushort(&bp->b_data[bo], newc); bo += 2; break; case FAT32_MASK: readcn = getulong(&bp->b_data[bo]); readcn &= ~pmp->pm_fatmask; readcn |= newc & pmp->pm_fatmask; putulong(&bp->b_data[bo], readcn); bo += 4; break; } if (bo >= bsize) break; } updatefats(pmp, bp, bn); } pmp->pm_fmod = 1; return (0); } /* * Check the length of a free cluster chain starting at start. * * pmp - mount point * start - start of chain * count - maximum interesting length */ int chainlength(struct msdosfsmount *pmp, uint32_t start, uint32_t count) { uint32_t idx, max_idx; u_int map; uint32_t len; if (start > pmp->pm_maxcluster) return (0); max_idx = pmp->pm_maxcluster / N_INUSEBITS; idx = start / N_INUSEBITS; start %= N_INUSEBITS; map = pmp->pm_inusemap[idx]; map &= ~((1 << start) - 1); if (map) { len = ffs(map) - 1 - start; len = MIN(len, count); len = MIN(len, pmp->pm_maxcluster - start + 1); return (len); } len = N_INUSEBITS - start; if (len >= count) { len = MIN(count, pmp->pm_maxcluster - start + 1); return (len); } while (++idx <= max_idx) { if (len >= count) break; if ((map = pmp->pm_inusemap[idx]) != 0) { len += ffs(map) - 1; break; } len += N_INUSEBITS; } len = MIN(len, count); len = MIN(len, pmp->pm_maxcluster - start + 1); return (len); } /* * Allocate contiguous free clusters. * * pmp - mount point. * start - start of cluster chain. * count - number of clusters to allocate. * fillwith - put this value into the fat entry for the * last allocated cluster. * retcluster - put the first allocated cluster's number here. * got - how many clusters were actually allocated. */ int chainalloc(struct msdosfsmount *pmp, uint32_t start, uint32_t count, uint32_t fillwith, uint32_t *retcluster, uint32_t *got) { int error; uint32_t cl, n; for (cl = start, n = count; n-- > 0;) usemap_alloc(pmp, cl++); if ((error = fatchain(pmp, start, count, fillwith)) != 0) return (error); #ifdef MSDOSFS_DEBUG printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n", start, count); #endif if (retcluster) *retcluster = start; if (got) *got = count; return (0); } /* * Allocate contiguous free clusters. * * pmp - mount point. * start - preferred start of cluster chain. * count - number of clusters requested. * fillwith - put this value into the fat entry for the * last allocated cluster. * retcluster - put the first allocated cluster's number here. * got - how many clusters were actually allocated. */ int clusteralloc(struct msdosfsmount *pmp, uint32_t start, uint32_t count, uint32_t *retcluster, uint32_t *got) { uint32_t idx; uint32_t len, newst, foundl, cn, l; uint32_t foundcn = 0; /* XXX: foundcn could be used uninitialized */ uint32_t fillwith = CLUST_EOFE; u_int map; #ifdef MSDOSFS_DEBUG printf("clusteralloc(): find %d clusters\n",count); #endif if (start) { if ((len = chainlength(pmp, start, count)) >= count) return (chainalloc(pmp, start, count, fillwith, retcluster, got)); } else { /* * This is a new file, initialize start */ struct timeval tv; microtime(&tv); start = (tv.tv_usec >> 10) | tv.tv_usec; len = 0; } /* * Start at a (pseudo) random place to maximize cluster runs * under multiple writers. */ newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); foundl = 0; for (cn = newst; cn <= pmp->pm_maxcluster;) { idx = cn / N_INUSEBITS; map = pmp->pm_inusemap[idx]; map |= (1 << (cn % N_INUSEBITS)) - 1; if (map != (u_int)-1) { cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; if ((l = chainlength(pmp, cn, count)) >= count) return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); if (l > foundl) { foundcn = cn; foundl = l; } cn += l + 1; continue; } cn += N_INUSEBITS - cn % N_INUSEBITS; } for (cn = 0; cn < newst;) { idx = cn / N_INUSEBITS; map = pmp->pm_inusemap[idx]; map |= (1 << (cn % N_INUSEBITS)) - 1; if (map != (u_int)-1) { cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; if ((l = chainlength(pmp, cn, count)) >= count) return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); if (l > foundl) { foundcn = cn; foundl = l; } cn += l + 1; continue; } cn += N_INUSEBITS - cn % N_INUSEBITS; } if (!foundl) return (ENOSPC); if (len) return (chainalloc(pmp, start, len, fillwith, retcluster, got)); else return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); } /* * Free a chain of clusters. * * pmp - address of the msdosfs mount structure for the filesystem * containing the cluster chain to be freed. * startcluster - number of the 1st cluster in the chain of clusters to be * freed. */ int freeclusterchain(struct msdosfsmount *pmp, uint32_t cluster) { int error; struct buf *bp = NULL; uint32_t bn, bo, bsize, byteoffset; uint32_t readcn, lbn = -1; while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { byteoffset = FATOFS(pmp, cluster); fatblock(pmp, byteoffset, &bn, &bsize, &bo); if (lbn != bn) { if (bp) updatefats(pmp, bp, lbn); error = bread(pmp->pm_devvp, bn, bsize, &bp); if (error) { brelse(bp); return (error); } lbn = bn; } usemap_free(pmp, cluster); switch (pmp->pm_fatmask) { case FAT12_MASK: readcn = getushort(&bp->b_data[bo]); if (cluster & 1) { cluster = readcn >> 4; readcn &= 0x000f; readcn |= MSDOSFSFREE << 4; } else { cluster = readcn; readcn &= 0xf000; readcn |= MSDOSFSFREE & 0xfff; } putushort(&bp->b_data[bo], readcn); break; case FAT16_MASK: cluster = getushort(&bp->b_data[bo]); putushort(&bp->b_data[bo], MSDOSFSFREE); break; case FAT32_MASK: cluster = getulong(&bp->b_data[bo]); putulong(&bp->b_data[bo], (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); break; } cluster &= pmp->pm_fatmask; if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) cluster |= pmp->pm_fatmask; } if (bp) updatefats(pmp, bp, bn); return (0); } /* * Read in fat blocks looking for free clusters. For every free cluster * found turn off its corresponding bit in the pm_inusemap. */ int fillinusemap(struct msdosfsmount *pmp) { struct buf *bp = NULL; uint32_t cn, readcn; int error; uint32_t bn, bo, bsize, byteoffset; /* * Mark all clusters in use, we mark the free ones in the fat scan * loop further down. */ for (cn = 0; cn < howmany(pmp->pm_maxcluster + 1, N_INUSEBITS); cn++) pmp->pm_inusemap[cn] = (u_int)-1; /* * Figure how many free clusters are in the filesystem by ripping * through the fat counting the number of entries whose content is * zero. These represent free clusters. */ pmp->pm_freeclustercount = 0; for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { byteoffset = FATOFS(pmp, cn); bo = byteoffset % pmp->pm_fatblocksize; if (!bo || !bp) { /* Read new FAT block */ if (bp) brelse(bp); fatblock(pmp, byteoffset, &bn, &bsize, NULL); error = bread(pmp->pm_devvp, bn, bsize, &bp); if (error) { brelse(bp); return (error); } } if (FAT32(pmp)) readcn = getulong(&bp->b_data[bo]); else readcn = getushort(&bp->b_data[bo]); if (FAT12(pmp) && (cn & 1)) readcn >>= 4; readcn &= pmp->pm_fatmask; if (readcn == 0) usemap_free(pmp, cn); } brelse(bp); return (0); } /* * Allocate a new cluster and chain it onto the end of the file. * * dep - the file to extend * count - number of clusters to allocate * bpp - where to return the address of the buf header for the first new * file block * ncp - where to put cluster number of the first newly allocated cluster * If this pointer is 0, do not return the cluster number. * flags - see fat.h * * NOTE: This function is not responsible for turning on the DE_UPDATE bit of * the de_flag field of the denode and it does not change the de_FileSize * field. This is left for the caller to do. */ int extendfile(struct denode *dep, uint32_t count, struct buf **bpp, uint32_t *ncp, int flags) { int error; uint32_t frcn; uint32_t cn, got; struct msdosfsmount *pmp = dep->de_pmp; struct buf *bp; /* * Don't try to extend the root directory */ if (dep->de_StartCluster == MSDOSFSROOT && (dep->de_Attributes & ATTR_DIRECTORY)) { printf("extendfile(): attempt to extend root directory\n"); return (ENOSPC); } /* * If the "file's last cluster" cache entry is empty, and the file * is not empty, then fill the cache entry by calling pcbmap(). */ fc_fileextends++; if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && dep->de_StartCluster != 0) { fc_lfcempty++; error = pcbmap(dep, CLUST_END, 0, &cn, 0); /* we expect it to return E2BIG */ if (error != E2BIG) return (error); } /* * Preserve value for the last cluster before extending the file * to speed up further lookups. */ fc_setcache(dep, FC_OLASTFC, dep->de_fc[FC_LASTFC].fc_frcn, dep->de_fc[FC_LASTFC].fc_fsrcn); while (count > 0) { /* * Allocate a new cluster chain and cat onto the end of the * file. * If the file is empty we make de_StartCluster point * to the new block. Note that de_StartCluster being 0 is * sufficient to be sure the file is empty since we exclude * attempts to extend the root directory above, and the root * dir is the only file with a startcluster of 0 that has * blocks allocated (sort of). */ if (dep->de_StartCluster == 0) cn = 0; else cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; error = clusteralloc(pmp, cn, count, &cn, &got); if (error) return (error); count -= got; /* * Give them the filesystem relative cluster number if they want * it. */ if (ncp) { *ncp = cn; ncp = NULL; } if (dep->de_StartCluster == 0) { dep->de_StartCluster = cn; frcn = 0; } else { error = fatentry(FAT_SET, pmp, dep->de_fc[FC_LASTFC].fc_fsrcn, 0, cn); if (error) { clusterfree(pmp, cn, NULL); return (error); } frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; } /* * Update the "last cluster of the file" entry in the denode's fat * cache. */ fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); if (flags & DE_CLEAR) { while (got-- > 0) { /* * Get the buf header for the new block of the file. */ if (dep->de_Attributes & ATTR_DIRECTORY) bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), pmp->pm_bpcluster, 0, INFSLP); else { bp = getblk(DETOV(dep), frcn++, pmp->pm_bpcluster, 0, INFSLP); /* * Do the bmap now, as in msdosfs_write */ if (pcbmap(dep, bp->b_lblkno, &bp->b_blkno, 0, 0)) bp->b_blkno = -1; if (bp->b_blkno == -1) panic("extendfile: pcbmap"); } clrbuf(bp); if (bpp) { *bpp = bp; bpp = NULL; } else bdwrite(bp); } } } return (0); }