| Sage Weil | de57606 | 2009-10-06 11:31:07 -0700 | [diff] [blame] | 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 |