| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #ifndef FS_CEPH_FRAG_H |
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| 3 | #define FS_CEPH_FRAG_H |
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| 4 | |
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| 5 | /* |
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| 6 | * "Frags" are a way to describe a subset of a 32-bit number space, |
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| 7 | * using a mask and a value to match against that mask. Any given frag |
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| 8 | * (subset of the number space) can be partitioned into 2^n sub-frags. |
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| 9 | * |
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| 10 | * Frags are encoded into a 32-bit word: |
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| 11 | * 8 upper bits = "bits" |
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| 12 | * 24 lower bits = "value" |
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| 13 | * (We could go to 5+27 bits, but who cares.) |
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| 14 | * |
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| 15 | * We use the _most_ significant bits of the 24 bit value. This makes |
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| 16 | * values logically sort. |
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| 17 | * |
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| 18 | * Unfortunately, because the "bits" field is still in the high bits, we |
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| 19 | * can't sort encoded frags numerically. However, it does allow you |
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| 20 | * to feed encoded frags as values into frag_contains_value. |
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| 21 | */ |
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| 22 | static inline __u32 ceph_frag_make(__u32 b, __u32 v) |
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| 23 | { |
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| 24 | return (b << 24) | |
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| 25 | (v & (0xffffffu << (24-b)) & 0xffffffu); |
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| 26 | } |
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| 27 | static inline __u32 ceph_frag_bits(__u32 f) |
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| 28 | { |
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| 29 | return f >> 24; |
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| 30 | } |
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| 31 | static inline __u32 ceph_frag_value(__u32 f) |
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| 32 | { |
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| 33 | return f & 0xffffffu; |
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| 34 | } |
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| 35 | static inline __u32 ceph_frag_mask(__u32 f) |
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| 36 | { |
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| 37 | return (0xffffffu << (24-ceph_frag_bits(f))) & 0xffffffu; |
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| 38 | } |
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| 39 | static inline __u32 ceph_frag_mask_shift(__u32 f) |
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| 40 | { |
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| 41 | return 24 - ceph_frag_bits(f); |
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| 42 | } |
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| 43 | |
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| 44 | static inline bool ceph_frag_contains_value(__u32 f, __u32 v) |
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| 45 | { |
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| 46 | return (v & ceph_frag_mask(f)) == ceph_frag_value(f); |
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| 47 | } |
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| 48 | |
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| 49 | static inline __u32 ceph_frag_make_child(__u32 f, int by, int i) |
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| 50 | { |
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| 51 | int newbits = ceph_frag_bits(f) + by; |
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| 52 | return ceph_frag_make(b: newbits, |
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| 53 | v: ceph_frag_value(f) | (i << (24 - newbits))); |
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| 54 | } |
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| 55 | static inline bool ceph_frag_is_leftmost(__u32 f) |
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| 56 | { |
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| 57 | return ceph_frag_value(f) == 0; |
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| 58 | } |
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| 59 | static inline bool ceph_frag_is_rightmost(__u32 f) |
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| 60 | { |
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| 61 | return ceph_frag_value(f) == ceph_frag_mask(f); |
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| 62 | } |
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| 63 | static inline __u32 ceph_frag_next(__u32 f) |
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| 64 | { |
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| 65 | return ceph_frag_make(b: ceph_frag_bits(f), |
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| 66 | v: ceph_frag_value(f) + (0x1000000 >> ceph_frag_bits(f))); |
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| 67 | } |
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| 68 | |
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| 69 | /* |
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| 70 | * comparator to sort frags logically, as when traversing the |
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| 71 | * number space in ascending order... |
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| 72 | */ |
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| 73 | int ceph_frag_compare(__u32 a, __u32 b); |
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| 74 | |
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| 75 | #endif |
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| 76 | |
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