LXR linux/include/linux/ceph/ceph

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