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 */ 21 static inline __u32 ceph_frag_make(__u32 b, __u32 v) 22 { 23 return (b << 24) | 24 (v & (0xffffffu << (24-b)) & 0xffffffu); 25 } 26 static inline __u32 ceph_frag_bits(__u32 f) 27 { 28 return f >> 24; 29 } 30 static inline __u32 ceph_frag_value(__u32 f) 31 { 32 return f & 0xffffffu; 33 } 34 static inline __u32 ceph_frag_mask(__u32 f) 35 { 36 return (0xffffffu << (24-ceph_frag_bits(f))) & 0xffffffu; 37 } 38 static inline __u32 ceph_frag_mask_shift(__u32 f) 39 { 40 return 24 - ceph_frag_bits(f); 41 } 42 43 static inline int ceph_frag_contains_value(__u32 f, __u32 v) 44 { 45 return (v & ceph_frag_mask(f)) == ceph_frag_value(f); 46 } 47 static inline int ceph_frag_contains_frag(__u32 f, __u32 sub) 48 { 49 /* is sub as specific as us, and contained by us? */ 50 return ceph_frag_bits(sub) >= ceph_frag_bits(f) && 51 (ceph_frag_value(sub) & ceph_frag_mask(f)) == ceph_frag_value(f); 52 } 53 54 static inline __u32 ceph_frag_parent(__u32 f) 55 { 56 return ceph_frag_make(ceph_frag_bits(f) - 1, 57 ceph_frag_value(f) & (ceph_frag_mask(f) << 1)); 58 } 59 static inline int ceph_frag_is_left_child(__u32 f) 60 { 61 return ceph_frag_bits(f) > 0 && 62 (ceph_frag_value(f) & (0x1000000 >> ceph_frag_bits(f))) == 0; 63 } 64 static inline int ceph_frag_is_right_child(__u32 f) 65 { 66 return ceph_frag_bits(f) > 0 && 67 (ceph_frag_value(f) & (0x1000000 >> ceph_frag_bits(f))) == 1; 68 } 69 static inline __u32 ceph_frag_sibling(__u32 f) 70 { 71 return ceph_frag_make(ceph_frag_bits(f), 72 ceph_frag_value(f) ^ (0x1000000 >> ceph_frag_bits(f))); 73 } 74 static inline __u32 ceph_frag_left_child(__u32 f) 75 { 76 return ceph_frag_make(ceph_frag_bits(f)+1, ceph_frag_value(f)); 77 } 78 static inline __u32 ceph_frag_right_child(__u32 f) 79 { 80 return ceph_frag_make(ceph_frag_bits(f)+1, 81 ceph_frag_value(f) | (0x1000000 >> (1+ceph_frag_bits(f)))); 82 } 83 static inline __u32 ceph_frag_make_child(__u32 f, int by, int i) 84 { 85 int newbits = ceph_frag_bits(f) + by; 86 return ceph_frag_make(newbits, 87 ceph_frag_value(f) | (i << (24 - newbits))); 88 } 89 static inline int ceph_frag_is_leftmost(__u32 f) 90 { 91 return ceph_frag_value(f) == 0; 92 } 93 static inline int ceph_frag_is_rightmost(__u32 f) 94 { 95 return ceph_frag_value(f) == ceph_frag_mask(f); 96 } 97 static inline __u32 ceph_frag_next(__u32 f) 98 { 99 return ceph_frag_make(ceph_frag_bits(f), 100 ceph_frag_value(f) + (0x1000000 >> ceph_frag_bits(f))); 101 } 102 103 /* 104 * comparator to sort frags logically, as when traversing the 105 * number space in ascending order... 106 */ 107 int ceph_frag_compare(__u32 a, __u32 b); 108 109 #endif 110