1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
#ifndef CEPH_LIBRBD_IO_BLOCK_GUARD_H
#define CEPH_LIBRBD_IO_BLOCK_GUARD_H
#include "include/int_types.h"
#include "common/dout.h"
#include "common/ceph_mutex.h"
#include <boost/intrusive/list.hpp>
#include <boost/intrusive/set.hpp>
#include <deque>
#include <list>
#include "include/ceph_assert.h"
#define dout_subsys ceph_subsys_rbd
#undef dout_prefix
#define dout_prefix *_dout << "librbd::BlockGuard: " << this << " " \
<< __func__ << ": "
namespace librbd {
struct BlockExtent {
// [block_start, block_end)
uint64_t block_start = 0;
uint64_t block_end = 0;
BlockExtent() {
}
BlockExtent(uint64_t block_start, uint64_t block_end)
: block_start(block_start), block_end(block_end) {
}
friend std::ostream& operator<< (std::ostream& os, const BlockExtent& block_extent) {
os << "[block_start=" << block_extent.block_start
<< ", block_end=" << block_extent.block_end << "]";
return os;
}
};
struct BlockGuardCell {
};
/**
* Helper class to restrict and order concurrent IO to the same block. The
* definition of a block is dependent upon the user of this class. It might
* represent a backing object, 512 byte sectors, etc.
*/
template <typename BlockOperation>
class BlockGuard {
private:
struct DetainedBlockExtent;
public:
typedef std::list<BlockOperation> BlockOperations;
BlockGuard(CephContext *cct)
: m_cct(cct) {
}
BlockGuard(const BlockGuard&) = delete;
BlockGuard &operator=(const BlockGuard&) = delete;
/**
* Detain future IO for a range of blocks. the guard will keep
* ownership of the provided operation if the operation is blocked.
* @return 0 upon success and IO can be issued
* >0 if the IO is blocked,
* <0 upon error
*/
int detain(const BlockExtent &block_extent, BlockOperation *block_operation,
BlockGuardCell **cell) {
std::lock_guard locker{m_lock};
ldout(m_cct, 20) << block_extent
<< ", free_slots="
<< m_free_detained_block_extents.size()
<< dendl;
DetainedBlockExtent *detained_block_extent;
auto it = m_detained_block_extents.find(block_extent);
if (it != m_detained_block_extents.end()) {
// request against an already detained block
detained_block_extent = &(*it);
if (block_operation != nullptr) {
detained_block_extent->block_operations.emplace_back(
std::move(*block_operation));
}
// alert the caller that the IO was detained
*cell = nullptr;
return detained_block_extent->block_operations.size();
} else {
if (!m_free_detained_block_extents.empty()) {
detained_block_extent = &m_free_detained_block_extents.front();
detained_block_extent->block_operations.clear();
m_free_detained_block_extents.pop_front();
} else {
ldout(m_cct, 20) << "no free detained block cells" << dendl;
m_detained_block_extent_pool.emplace_back();
detained_block_extent = &m_detained_block_extent_pool.back();
}
detained_block_extent->block_extent = block_extent;
m_detained_block_extents.insert(*detained_block_extent);
*cell = reinterpret_cast<BlockGuardCell*>(detained_block_extent);
return 0;
}
}
/**
* Release any detained IO operations from the provided cell.
*/
void release(BlockGuardCell *cell, BlockOperations *block_operations) {
std::lock_guard locker{m_lock};
ceph_assert(cell != nullptr);
auto &detained_block_extent = reinterpret_cast<DetainedBlockExtent &>(
*cell);
ldout(m_cct, 20) << detained_block_extent.block_extent
<< ", pending_ops="
<< detained_block_extent.block_operations.size()
<< dendl;
*block_operations = std::move(detained_block_extent.block_operations);
m_detained_block_extents.erase(detained_block_extent.block_extent);
m_free_detained_block_extents.push_back(detained_block_extent);
}
private:
struct DetainedBlockExtent : public boost::intrusive::list_base_hook<>,
public boost::intrusive::set_base_hook<> {
BlockExtent block_extent;
BlockOperations block_operations;
};
struct DetainedBlockExtentKey {
typedef BlockExtent type;
const BlockExtent &operator()(const DetainedBlockExtent &value) {
return value.block_extent;
}
};
struct DetainedBlockExtentCompare {
bool operator()(const BlockExtent &lhs,
const BlockExtent &rhs) const {
// check for range overlap (lhs < rhs)
if (lhs.block_end <= rhs.block_start) {
return true;
}
return false;
}
};
typedef std::deque<DetainedBlockExtent> DetainedBlockExtentsPool;
typedef boost::intrusive::list<DetainedBlockExtent> DetainedBlockExtents;
typedef boost::intrusive::set<
DetainedBlockExtent,
boost::intrusive::compare<DetainedBlockExtentCompare>,
boost::intrusive::key_of_value<DetainedBlockExtentKey> >
BlockExtentToDetainedBlockExtents;
CephContext *m_cct;
ceph::mutex m_lock = ceph::make_mutex("librbd::BlockGuard::m_lock");
DetainedBlockExtentsPool m_detained_block_extent_pool;
DetainedBlockExtents m_free_detained_block_extents;
BlockExtentToDetainedBlockExtents m_detained_block_extents;
};
} // namespace librbd
#undef dout_subsys
#undef dout_prefix
#define dout_prefix *_dout
#endif // CEPH_LIBRBD_IO_BLOCK_GUARD_H
|
