1*4882a593Smuzhiyun /* SPDX-License-Identifier: GPL-2.0 */
2*4882a593Smuzhiyun #ifndef FS_CEPH_FRAG_H
3*4882a593Smuzhiyun #define FS_CEPH_FRAG_H
4*4882a593Smuzhiyun
5*4882a593Smuzhiyun /*
6*4882a593Smuzhiyun * "Frags" are a way to describe a subset of a 32-bit number space,
7*4882a593Smuzhiyun * using a mask and a value to match against that mask. Any given frag
8*4882a593Smuzhiyun * (subset of the number space) can be partitioned into 2^n sub-frags.
9*4882a593Smuzhiyun *
10*4882a593Smuzhiyun * Frags are encoded into a 32-bit word:
11*4882a593Smuzhiyun * 8 upper bits = "bits"
12*4882a593Smuzhiyun * 24 lower bits = "value"
13*4882a593Smuzhiyun * (We could go to 5+27 bits, but who cares.)
14*4882a593Smuzhiyun *
15*4882a593Smuzhiyun * We use the _most_ significant bits of the 24 bit value. This makes
16*4882a593Smuzhiyun * values logically sort.
17*4882a593Smuzhiyun *
18*4882a593Smuzhiyun * Unfortunately, because the "bits" field is still in the high bits, we
19*4882a593Smuzhiyun * can't sort encoded frags numerically. However, it does allow you
20*4882a593Smuzhiyun * to feed encoded frags as values into frag_contains_value.
21*4882a593Smuzhiyun */
ceph_frag_make(__u32 b,__u32 v)22*4882a593Smuzhiyun static inline __u32 ceph_frag_make(__u32 b, __u32 v)
23*4882a593Smuzhiyun {
24*4882a593Smuzhiyun return (b << 24) |
25*4882a593Smuzhiyun (v & (0xffffffu << (24-b)) & 0xffffffu);
26*4882a593Smuzhiyun }
ceph_frag_bits(__u32 f)27*4882a593Smuzhiyun static inline __u32 ceph_frag_bits(__u32 f)
28*4882a593Smuzhiyun {
29*4882a593Smuzhiyun return f >> 24;
30*4882a593Smuzhiyun }
ceph_frag_value(__u32 f)31*4882a593Smuzhiyun static inline __u32 ceph_frag_value(__u32 f)
32*4882a593Smuzhiyun {
33*4882a593Smuzhiyun return f & 0xffffffu;
34*4882a593Smuzhiyun }
ceph_frag_mask(__u32 f)35*4882a593Smuzhiyun static inline __u32 ceph_frag_mask(__u32 f)
36*4882a593Smuzhiyun {
37*4882a593Smuzhiyun return (0xffffffu << (24-ceph_frag_bits(f))) & 0xffffffu;
38*4882a593Smuzhiyun }
ceph_frag_mask_shift(__u32 f)39*4882a593Smuzhiyun static inline __u32 ceph_frag_mask_shift(__u32 f)
40*4882a593Smuzhiyun {
41*4882a593Smuzhiyun return 24 - ceph_frag_bits(f);
42*4882a593Smuzhiyun }
43*4882a593Smuzhiyun
ceph_frag_contains_value(__u32 f,__u32 v)44*4882a593Smuzhiyun static inline bool ceph_frag_contains_value(__u32 f, __u32 v)
45*4882a593Smuzhiyun {
46*4882a593Smuzhiyun return (v & ceph_frag_mask(f)) == ceph_frag_value(f);
47*4882a593Smuzhiyun }
48*4882a593Smuzhiyun
ceph_frag_make_child(__u32 f,int by,int i)49*4882a593Smuzhiyun static inline __u32 ceph_frag_make_child(__u32 f, int by, int i)
50*4882a593Smuzhiyun {
51*4882a593Smuzhiyun int newbits = ceph_frag_bits(f) + by;
52*4882a593Smuzhiyun return ceph_frag_make(newbits,
53*4882a593Smuzhiyun ceph_frag_value(f) | (i << (24 - newbits)));
54*4882a593Smuzhiyun }
ceph_frag_is_leftmost(__u32 f)55*4882a593Smuzhiyun static inline bool ceph_frag_is_leftmost(__u32 f)
56*4882a593Smuzhiyun {
57*4882a593Smuzhiyun return ceph_frag_value(f) == 0;
58*4882a593Smuzhiyun }
ceph_frag_is_rightmost(__u32 f)59*4882a593Smuzhiyun static inline bool ceph_frag_is_rightmost(__u32 f)
60*4882a593Smuzhiyun {
61*4882a593Smuzhiyun return ceph_frag_value(f) == ceph_frag_mask(f);
62*4882a593Smuzhiyun }
ceph_frag_next(__u32 f)63*4882a593Smuzhiyun static inline __u32 ceph_frag_next(__u32 f)
64*4882a593Smuzhiyun {
65*4882a593Smuzhiyun return ceph_frag_make(ceph_frag_bits(f),
66*4882a593Smuzhiyun ceph_frag_value(f) + (0x1000000 >> ceph_frag_bits(f)));
67*4882a593Smuzhiyun }
68*4882a593Smuzhiyun
69*4882a593Smuzhiyun /*
70*4882a593Smuzhiyun * comparator to sort frags logically, as when traversing the
71*4882a593Smuzhiyun * number space in ascending order...
72*4882a593Smuzhiyun */
73*4882a593Smuzhiyun int ceph_frag_compare(__u32 a, __u32 b);
74*4882a593Smuzhiyun
75*4882a593Smuzhiyun #endif
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