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33 * @(#)ffs_subr.c 8.5 (Berkeley) 3/21/95
34 * $FreeBSD: src/sys/ufs/ffs/ffs_subr.c,v 1.25 1999/12/29 04:55:04 peter Exp $
35 * $DragonFly: src/sys/vfs/ufs/ffs_subr.c,v 1.12 2006/04/27 23:28:37 dillon Exp $
38 #include <sys/param.h>
46 #include <sys/systm.h>
48 #include <sys/vnode.h>
50 #include <sys/ucred.h>
55 #include "ffs_extern.h"
58 * Return buffer with the contents of block "offset" from the beginning of
59 * directory "ip". If "res" is non-zero, fill it in with a pointer to the
60 * remaining space in the directory.
63 ffs_blkatoff(struct vnode *vp, off_t offset, char **res, struct buf **bpp)
73 lbn = lblkno(fs, offset);
74 bsize = blksize(fs, ip, lbn);
77 error = bread(vp, lblktodoff(fs, lbn), bsize, &bp);
83 *res = (char *)bp->b_data + blkoff(fs, offset);
90 * Update the frsum fields to reflect addition or deletion
94 ffs_fragacct(struct fs *fs, int fragmap, int32_t fraglist[], int cnt)
101 * inblk represents a bitmap of fragment sizes which may be
102 * contained in the data 'fragmap'. e.g. if a fragment of size
103 * 1 is available, bit 0 would be set. inblk is shifted left
104 * by one so we do not have to calculate (1 << (siz - 1)).
106 * fragment represents the data pattern we are trying to decipher,
107 * we shift it left by one to align it with the 'around' and 'inside'
110 * around represents the bits around the subfield and is a mask.
111 * inside represents what we must match within the mask, it is
112 * basically the mask with the first and last bit set to 0, allowing
113 * us to represent a whole fragment.
115 * When we find a match we bump our position by the size of the
116 * matching fragment, then bump the position again:
118 * 010101010 fragmap (shifted left by 1)
121 * 111 (shifted by siz)
123 * 111 (shifted again)
126 inblk = (int)(fragtbl[fs->fs_frag][fragmap]) << 1;
128 for (siz = 1; siz < fs->fs_frag; siz++) {
129 if ((inblk & (1 << (siz + (fs->fs_frag % NBBY)))) == 0)
132 subfield = inside[siz];
133 for (pos = siz; pos <= fs->fs_frag; pos++) {
134 if ((fragmap & field) == subfield) {
135 fraglist[siz] += cnt;
149 * check if a block is available
152 ffs_isblock(struct fs *fs, unsigned char *cp, ufs_daddr_t h)
156 switch ((int)fs->fs_frag) {
158 return (cp[h] == 0xff);
160 mask = 0x0f << ((h & 0x1) << 2);
161 return ((cp[h >> 1] & mask) == mask);
163 mask = 0x03 << ((h & 0x3) << 1);
164 return ((cp[h >> 2] & mask) == mask);
166 mask = 0x01 << (h & 0x7);
167 return ((cp[h >> 3] & mask) == mask);
169 panic("ffs_isblock");
174 * check if a block is free
177 ffs_isfreeblock(struct fs *fs, unsigned char *cp, ufs_daddr_t h)
179 switch ((int)fs->fs_frag) {
183 return ((cp[h >> 1] & (0x0f << ((h & 0x1) << 2))) == 0);
185 return ((cp[h >> 2] & (0x03 << ((h & 0x3) << 1))) == 0);
187 return ((cp[h >> 3] & (0x01 << (h & 0x7))) == 0);
189 panic("ffs_isfreeblock");
194 * take a block out of the map
197 ffs_clrblock(struct fs *fs, u_char *cp, ufs_daddr_t h)
199 switch ((int)fs->fs_frag) {
204 cp[h >> 1] &= ~(0x0f << ((h & 0x1) << 2));
207 cp[h >> 2] &= ~(0x03 << ((h & 0x3) << 1));
210 cp[h >> 3] &= ~(0x01 << (h & 0x7));
213 panic("ffs_clrblock");
218 * put a block into the map
221 ffs_setblock(struct fs *fs, unsigned char *cp, ufs_daddr_t h)
223 switch ((int)fs->fs_frag) {
228 cp[h >> 1] |= (0x0f << ((h & 0x1) << 2));
231 cp[h >> 2] |= (0x03 << ((h & 0x3) << 1));
234 cp[h >> 3] |= (0x01 << (h & 0x7));
237 panic("ffs_setblock");