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