msdosfs_fileno.c revision 263670
1/*- 2 * Copyright (c) 2003-2004 Tim J. Robbins. 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 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26/* 27 * Compress 64-bit file numbers into temporary, unique 32-bit file numbers. 28 * This is needed because the algorithm we use to calculate these numbers 29 * generates 64-bit quantities, but struct dirent's d_fileno member and 30 * struct vnodeattr's va_fileid member only have space for 32 bits. 31 * 32 * 32-bit file numbers are generated sequentially, and stored in a 33 * red-black tree, indexed on 64-bit file number. The mappings do not 34 * persist across reboots (or unmounts); anything that relies on this 35 * (e.g. NFS) will not work correctly. This scheme consumes 32 bytes 36 * of kernel memory per file (on i386), and it may be possible for a user 37 * to cause a panic by creating millions of tiny files. 38 * 39 * As an optimization, we split the file number space between statically 40 * allocated and dynamically allocated. File numbers less than 41 * FILENO_FIRST_DYN are left unchanged and do not have any tree nodes 42 * allocated to them. 43 */ 44 45#include <sys/cdefs.h> 46__FBSDID("$FreeBSD: stable/10/sys/fs/msdosfs/msdosfs_fileno.c 263670 2014-03-23 19:48:30Z pfg $"); 47 48#include <sys/param.h> 49#include <sys/systm.h> 50#include <sys/kernel.h> 51#include <sys/lock.h> 52#include <sys/malloc.h> 53#include <sys/mount.h> 54 55#include <fs/msdosfs/bpb.h> 56#include <fs/msdosfs/direntry.h> 57#include <fs/msdosfs/msdosfsmount.h> 58 59static MALLOC_DEFINE(M_MSDOSFSFILENO, "msdosfs_fileno", "MSDOSFS fileno mapping node"); 60 61RB_PROTOTYPE(msdosfs_filenotree, msdosfs_fileno, mf_tree, 62 msdosfs_fileno_compare) 63 64static int msdosfs_fileno_compare(struct msdosfs_fileno *, 65 struct msdosfs_fileno *); 66 67#define FILENO_FIRST_DYN 0xf0000000 68 69/* Initialize file number mapping structures. */ 70void 71msdosfs_fileno_init(mp) 72 struct mount *mp; 73{ 74 struct msdosfsmount *pmp = VFSTOMSDOSFS(mp); 75 76 RB_INIT(&pmp->pm_filenos); 77 pmp->pm_nfileno = FILENO_FIRST_DYN; 78 if (pmp->pm_HugeSectors > 0xffffffff / 79 (pmp->pm_BytesPerSec / sizeof(struct direntry)) + 1) 80 pmp->pm_flags |= MSDOSFS_LARGEFS; 81} 82 83/* Free 32-bit file number generation structures. */ 84void 85msdosfs_fileno_free(mp) 86 struct mount *mp; 87{ 88 struct msdosfsmount *pmp = VFSTOMSDOSFS(mp); 89 struct msdosfs_fileno *mf, *next; 90 91 for (mf = RB_MIN(msdosfs_filenotree, &pmp->pm_filenos); mf != NULL; 92 mf = next) { 93 next = RB_NEXT(msdosfs_filenotree, &pmp->pm_filenos, mf); 94 RB_REMOVE(msdosfs_filenotree, &pmp->pm_filenos, mf); 95 free(mf, M_MSDOSFSFILENO); 96 } 97} 98 99/* Map a 64-bit file number into a 32-bit one. */ 100uint32_t 101msdosfs_fileno_map(mp, fileno) 102 struct mount *mp; 103 uint64_t fileno; 104{ 105 struct msdosfsmount *pmp = VFSTOMSDOSFS(mp); 106 struct msdosfs_fileno key, *mf, *tmf; 107 uint32_t mapped; 108 109 if ((pmp->pm_flags & MSDOSFS_LARGEFS) == 0) { 110 KASSERT((uint32_t)fileno == fileno, 111 ("fileno >32 bits but not a large fs?")); 112 return ((uint32_t)fileno); 113 } 114 if (fileno < FILENO_FIRST_DYN) 115 return ((uint32_t)fileno); 116 MSDOSFS_LOCK_MP(pmp); 117 key.mf_fileno64 = fileno; 118 mf = RB_FIND(msdosfs_filenotree, &pmp->pm_filenos, &key); 119 if (mf != NULL) { 120 mapped = mf->mf_fileno32; 121 MSDOSFS_UNLOCK_MP(pmp); 122 return (mapped); 123 } 124 if (pmp->pm_nfileno < FILENO_FIRST_DYN) 125 panic("msdosfs_fileno_map: wraparound"); 126 MSDOSFS_UNLOCK_MP(pmp); 127 mf = malloc(sizeof(*mf), M_MSDOSFSFILENO, M_WAITOK); 128 MSDOSFS_LOCK_MP(pmp); 129 tmf = RB_FIND(msdosfs_filenotree, &pmp->pm_filenos, &key); 130 if (tmf != NULL) { 131 mapped = tmf->mf_fileno32; 132 MSDOSFS_UNLOCK_MP(pmp); 133 free(mf, M_MSDOSFSFILENO); 134 return (mapped); 135 } 136 mf->mf_fileno64 = fileno; 137 mapped = mf->mf_fileno32 = pmp->pm_nfileno++; 138 RB_INSERT(msdosfs_filenotree, &pmp->pm_filenos, mf); 139 MSDOSFS_UNLOCK_MP(pmp); 140 return (mapped); 141} 142 143/* Compare by 64-bit file number. */ 144static int 145msdosfs_fileno_compare(fa, fb) 146 struct msdosfs_fileno *fa, *fb; 147{ 148 149 if (fa->mf_fileno64 > fb->mf_fileno64) 150 return (1); 151 else if (fa->mf_fileno64 < fb->mf_fileno64) 152 return (-1); 153 return (0); 154} 155 156RB_GENERATE(msdosfs_filenotree, msdosfs_fileno, mf_tree, 157 msdosfs_fileno_compare) 158