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52212483 BJ |
1 | /* lfs_balloc.c 5.1 82/07/15 */ |
2 | ||
3 | #include "../h/param.h" | |
4 | #include "../h/systm.h" | |
5 | #include "../h/conf.h" | |
6 | #include "../h/inode.h" | |
7 | #include "../h/dir.h" | |
8 | #include "../h/user.h" | |
9 | #include "../h/buf.h" | |
10 | #include "../h/proc.h" | |
11 | #include "../h/fs.h" | |
12 | ||
13 | /* | |
14 | * Bmap defines the structure of file system storage | |
15 | * by returning the physical block number on a device given the | |
16 | * inode and the logical block number in a file. | |
17 | * When convenient, it also leaves the physical | |
18 | * block number of the next block of the file in rablock | |
19 | * for use in read-ahead. | |
20 | */ | |
21 | /*VARARGS3*/ | |
22 | daddr_t | |
23 | bmap(ip, bn, rwflg, size) | |
24 | register struct inode *ip; | |
25 | daddr_t bn; | |
26 | int rwflg; | |
27 | int size; /* supplied only when rwflg == B_WRITE */ | |
28 | { | |
29 | register int i; | |
30 | int osize, nsize; | |
31 | struct buf *bp, *nbp; | |
32 | struct fs *fs; | |
33 | int j, sh; | |
34 | daddr_t nb, *bap, pref, blkpref(); | |
35 | ||
36 | if (bn < 0) { | |
37 | u.u_error = EFBIG; | |
38 | return ((daddr_t)0); | |
39 | } | |
40 | fs = ip->i_fs; | |
41 | rablock = 0; | |
42 | rasize = 0; /* conservative */ | |
43 | ||
44 | /* | |
45 | * If the next write will extend the file into a new block, | |
46 | * and the file is currently composed of a fragment | |
47 | * this fragment has to be extended to be a full block. | |
48 | */ | |
49 | nb = lblkno(fs, ip->i_size); | |
50 | if (rwflg == B_WRITE && nb < NDADDR && nb < bn) { | |
51 | osize = blksize(fs, ip, nb); | |
52 | if (osize < fs->fs_bsize && osize > 0) { | |
53 | bp = realloccg(ip, ip->i_db[nb], | |
54 | nb == 0 ? 0 : ip->i_db[nb - 1] + fs->fs_frag, | |
55 | osize, fs->fs_bsize); | |
56 | ip->i_size = (nb + 1) * fs->fs_bsize; | |
57 | ip->i_db[nb] = dbtofsb(fs, bp->b_blkno); | |
58 | ip->i_flag |= IUPD|ICHG; | |
59 | bdwrite(bp); | |
60 | } | |
61 | } | |
62 | /* | |
63 | * The first NDADDR blocks are direct blocks | |
64 | */ | |
65 | if (bn < NDADDR) { | |
66 | i = bn; | |
67 | nb = ip->i_db[i]; | |
68 | if (rwflg == B_READ) { | |
69 | if (nb == 0) | |
70 | return ((daddr_t)-1); | |
71 | goto gotit; | |
72 | } | |
73 | if (nb == 0 || ip->i_size < (i + 1) * fs->fs_bsize) { | |
74 | if (nb != 0) { | |
75 | /* consider need to reallocate a frag */ | |
76 | osize = fragroundup(fs, blkoff(fs, ip->i_size)); | |
77 | nsize = fragroundup(fs, size); | |
78 | if (nsize <= osize) | |
79 | goto gotit; | |
80 | bp = realloccg(ip, nb, i == 0 ? | |
81 | 0 : ip->i_db[i - 1] + fs->fs_frag, | |
82 | osize, nsize); | |
83 | } else { | |
84 | if (ip->i_size < (i + 1) * fs->fs_bsize) | |
85 | nsize = fragroundup(fs, size); | |
86 | else | |
87 | nsize = fs->fs_bsize; | |
88 | bp = alloc(ip, i > 0 ? | |
89 | ip->i_db[i - 1] + fs->fs_frag : 0, | |
90 | nsize); | |
91 | } | |
92 | if (bp == NULL) | |
93 | return ((daddr_t)-1); | |
94 | nb = dbtofsb(fs, bp->b_blkno); | |
95 | if ((ip->i_mode&IFMT) == IFDIR) | |
96 | /* | |
97 | * Write directory blocks synchronously | |
98 | * so they never appear with garbage in | |
99 | * them on the disk. | |
100 | */ | |
101 | bwrite(bp); | |
102 | else | |
103 | bdwrite(bp); | |
104 | ip->i_db[i] = nb; | |
105 | ip->i_flag |= IUPD|ICHG; | |
106 | } | |
107 | gotit: | |
108 | if (i < NDADDR - 1) { | |
109 | rablock = fsbtodb(fs, ip->i_db[i+1]); | |
110 | rasize = blksize(fs, ip, i+1); | |
111 | } | |
112 | return (nb); | |
113 | } | |
114 | ||
115 | /* | |
116 | * Determine how many levels of indirection. | |
117 | */ | |
118 | sh = 1; | |
119 | bn -= NDADDR; | |
120 | for (j = NIADDR; j>0; j--) { | |
121 | sh *= NINDIR(fs); | |
122 | if (bn < sh) | |
123 | break; | |
124 | bn -= sh; | |
125 | } | |
126 | if (j == 0) { | |
127 | u.u_error = EFBIG; | |
128 | return ((daddr_t)0); | |
129 | } | |
130 | ||
131 | /* | |
132 | * fetch the first indirect block | |
133 | */ | |
134 | nb = ip->i_ib[NIADDR - j]; | |
135 | if (nb == 0) { | |
136 | if (rwflg==B_READ || | |
137 | (bp = alloc(ip, (daddr_t)0, fs->fs_bsize)) == NULL) | |
138 | return ((daddr_t)-1); | |
139 | nb = dbtofsb(fs, bp->b_blkno); | |
140 | /* | |
141 | * Write synchronously so that indirect blocks | |
142 | * never point at garbage. | |
143 | */ | |
144 | bwrite(bp); | |
145 | ip->i_ib[NIADDR - j] = nb; | |
146 | ip->i_flag |= IUPD|ICHG; | |
147 | } | |
148 | ||
149 | /* | |
150 | * fetch through the indirect blocks | |
151 | */ | |
152 | for (; j <= NIADDR; j++) { | |
153 | bp = bread(ip->i_dev, fsbtodb(fs, nb), fs->fs_bsize); | |
154 | if (bp->b_flags & B_ERROR) { | |
155 | brelse(bp); | |
156 | return ((daddr_t)0); | |
157 | } | |
158 | bap = bp->b_un.b_daddr; | |
159 | sh /= NINDIR(fs); | |
160 | i = (bn / sh) % NINDIR(fs); | |
161 | nb = bap[i]; | |
162 | if (nb == 0) { | |
163 | if (rwflg==B_READ) { | |
164 | brelse(bp); | |
165 | return ((daddr_t)-1); | |
166 | } | |
167 | if (i % (fs->fs_fsize / sizeof(daddr_t)) == 0 || | |
168 | bap[i - 1] == 0) | |
169 | pref = blkpref(ip->i_fs); | |
170 | else | |
171 | pref = bap[i - 1] + fs->fs_frag; | |
172 | nbp = alloc(ip, pref, fs->fs_bsize); | |
173 | if (nbp == NULL) { | |
174 | brelse(bp); | |
175 | return ((daddr_t)-1); | |
176 | } | |
177 | nb = dbtofsb(fs, nbp->b_blkno); | |
178 | if (j < NIADDR || (ip->i_mode&IFMT) == IFDIR) | |
179 | /* | |
180 | * Write synchronously so indirect blocks | |
181 | * never point at garbage and blocks | |
182 | * in directories never contain garbage. | |
183 | */ | |
184 | bwrite(nbp); | |
185 | else | |
186 | bdwrite(nbp); | |
187 | bap[i] = nb; | |
188 | bdwrite(bp); | |
189 | } else | |
190 | brelse(bp); | |
191 | } | |
192 | ||
193 | /* | |
194 | * calculate read-ahead. | |
195 | */ | |
196 | if (i < NINDIR(fs) - 1) { | |
197 | rablock = fsbtodb(fs, bap[i+1]); | |
198 | rasize = fs->fs_bsize; | |
199 | } | |
200 | return (nb); | |
201 | } |