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("$FreeBSD$");
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
59 static MALLOC_DEFINE(M_MSDOSFSFILENO, "msdosfs_fileno", "MSDOSFS fileno mapping node");
60
61 RB_PROTOTYPE(msdosfs_filenotree, msdosfs_fileno, mf_tree,
62 msdosfs_fileno_compare)
63
64 static 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. */
70 void
msdosfs_fileno_init(struct mount * mp)71 msdosfs_fileno_init(struct mount *mp)
72 {
73 struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
74
75 RB_INIT(&pmp->pm_filenos);
76 pmp->pm_nfileno = FILENO_FIRST_DYN;
77 if (pmp->pm_HugeSectors > 0xffffffff /
78 (pmp->pm_BytesPerSec / sizeof(struct direntry)) + 1)
79 pmp->pm_flags |= MSDOSFS_LARGEFS;
80 }
81
82 /* Free 32-bit file number generation structures. */
83 void
msdosfs_fileno_free(struct mount * mp)84 msdosfs_fileno_free(struct mount *mp)
85 {
86 struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
87 struct msdosfs_fileno *mf, *next;
88
89 for (mf = RB_MIN(msdosfs_filenotree, &pmp->pm_filenos); mf != NULL;
90 mf = next) {
91 next = RB_NEXT(msdosfs_filenotree, &pmp->pm_filenos, mf);
92 RB_REMOVE(msdosfs_filenotree, &pmp->pm_filenos, mf);
93 free(mf, M_MSDOSFSFILENO);
94 }
95 }
96
97 /* Map a 64-bit file number into a 32-bit one. */
98 uint32_t
msdosfs_fileno_map(struct mount * mp,uint64_t fileno)99 msdosfs_fileno_map(struct mount *mp, uint64_t fileno)
100 {
101 struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
102 struct msdosfs_fileno key, *mf, *tmf;
103 uint32_t mapped;
104
105 if ((pmp->pm_flags & MSDOSFS_LARGEFS) == 0) {
106 KASSERT((uint32_t)fileno == fileno,
107 ("fileno >32 bits but not a large fs?"));
108 return ((uint32_t)fileno);
109 }
110 if (fileno < FILENO_FIRST_DYN)
111 return ((uint32_t)fileno);
112 MSDOSFS_LOCK_MP(pmp);
113 key.mf_fileno64 = fileno;
114 mf = RB_FIND(msdosfs_filenotree, &pmp->pm_filenos, &key);
115 if (mf != NULL) {
116 mapped = mf->mf_fileno32;
117 MSDOSFS_UNLOCK_MP(pmp);
118 return (mapped);
119 }
120 if (pmp->pm_nfileno < FILENO_FIRST_DYN)
121 panic("msdosfs_fileno_map: wraparound");
122 MSDOSFS_UNLOCK_MP(pmp);
123 mf = malloc(sizeof(*mf), M_MSDOSFSFILENO, M_WAITOK);
124 MSDOSFS_LOCK_MP(pmp);
125 tmf = RB_FIND(msdosfs_filenotree, &pmp->pm_filenos, &key);
126 if (tmf != NULL) {
127 mapped = tmf->mf_fileno32;
128 MSDOSFS_UNLOCK_MP(pmp);
129 free(mf, M_MSDOSFSFILENO);
130 return (mapped);
131 }
132 mf->mf_fileno64 = fileno;
133 mapped = mf->mf_fileno32 = pmp->pm_nfileno++;
134 RB_INSERT(msdosfs_filenotree, &pmp->pm_filenos, mf);
135 MSDOSFS_UNLOCK_MP(pmp);
136 return (mapped);
137 }
138
139 /* Compare by 64-bit file number. */
140 static int
msdosfs_fileno_compare(struct msdosfs_fileno * fa,struct msdosfs_fileno * fb)141 msdosfs_fileno_compare(struct msdosfs_fileno *fa, struct msdosfs_fileno *fb)
142 {
143
144 if (fa->mf_fileno64 > fb->mf_fileno64)
145 return (1);
146 else if (fa->mf_fileno64 < fb->mf_fileno64)
147 return (-1);
148 return (0);
149 }
150
151 RB_GENERATE(msdosfs_filenotree, msdosfs_fileno, mf_tree,
152 msdosfs_fileno_compare)
153