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
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(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. */
83void
84msdosfs_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. */
98uint32_t
99msdosfs_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. */
140static int
141msdosfs_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
151RB_GENERATE(msdosfs_filenotree, msdosfs_fileno, mf_tree,
152    msdosfs_fileno_compare)
153