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671e39d7 MJ |
1 | /* |
2 | * Copyright (C) 2023 Michael Jeanson <mjeanson@efficios.com> | |
3 | * | |
4 | * SPDX-License-Identifier: LGPL-2.1-only | |
5 | * | |
6 | */ | |
7 | ||
8 | #include <common/error.hpp> | |
9 | #include <common/io-hint.hpp> | |
10 | #include <common/scope-exit.hpp> | |
11 | ||
12 | #include <cinttypes> | |
13 | #include <fcntl.h> | |
14 | #include <sys/mman.h> | |
15 | #include <unistd.h> | |
16 | ||
17 | /* | |
18 | * Use sync_file_range when available. | |
19 | */ | |
20 | #ifdef HAVE_SYNC_FILE_RANGE | |
21 | ||
22 | #include <fcntl.h> | |
23 | ||
24 | namespace { | |
25 | int flush_range(int fd, off_t offset, off_t nbytes, unsigned int flags) | |
26 | { | |
27 | int ret; | |
28 | ||
29 | ret = sync_file_range(fd, offset, nbytes, flags); | |
30 | if (ret) { | |
31 | PERROR("Failed to sync file range: fd=%i, offset=%" PRIu64 ", nbytes=%" PRIu64 | |
32 | ", flags=%i", | |
33 | fd, | |
34 | static_cast<uint64_t>(offset), | |
35 | static_cast<uint64_t>(nbytes), | |
36 | flags); | |
37 | } | |
38 | ||
39 | return ret; | |
40 | } | |
41 | ||
42 | int flush_range_sync(int fd, off_t offset, off_t nbytes) | |
43 | { | |
44 | return flush_range(fd, | |
45 | offset, | |
46 | nbytes, | |
47 | SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE | | |
48 | SYNC_FILE_RANGE_WAIT_AFTER); | |
49 | } | |
50 | ||
51 | int flush_range_async(int fd, off_t offset, off_t nbytes) | |
52 | { | |
53 | return flush_range(fd, offset, nbytes, SYNC_FILE_RANGE_WRITE); | |
54 | } | |
55 | } /* namespace */ | |
56 | ||
e8955cc6 | 57 | #else /* HAVE_SYNC_FILE_RANGE */ |
671e39d7 MJ |
58 | |
59 | namespace { | |
60 | /* | |
61 | * Use a memory mapping with msync() to emulate sync_file_range(). | |
62 | */ | |
63 | int flush_range(int fd, off_t offset, off_t nbytes, int flags) | |
64 | { | |
65 | void *mapped_region = mmap(NULL, nbytes, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset); | |
66 | if (mapped_region == MAP_FAILED) { | |
67 | PERROR("Failed to mmap region to flush range: fd=%i, offset=%" PRIu64 | |
68 | ", nbytes=%" PRIu64 ", flags=%i", | |
69 | fd, | |
70 | static_cast<uint64_t>(offset), | |
71 | static_cast<uint64_t>(nbytes), | |
72 | flags); | |
73 | return -1; | |
74 | } | |
75 | ||
76 | const auto munmap_on_exit = lttng::make_scope_exit([&]() noexcept { | |
77 | const auto munmap_ret = munmap(mapped_region, nbytes); | |
78 | if (munmap_ret) { | |
79 | PERROR("Failed to munmap region while flushing range: fd=%i, offset=%" PRIu64 | |
80 | ", nbytes=%" PRIu64 ", flags=%i", | |
81 | fd, | |
82 | static_cast<uint64_t>(offset), | |
83 | static_cast<uint64_t>(nbytes), | |
84 | flags); | |
85 | } | |
86 | }); | |
87 | ||
88 | const auto msync_ret = msync(mapped_region, nbytes, flags); | |
89 | if (msync_ret) { | |
90 | PERROR("Failed to msync region while flushing range: fd=%i, offset=%" PRIu64 | |
91 | ", nbytes=%" PRIu64 ", flags=%i", | |
92 | fd, | |
93 | static_cast<uint64_t>(offset), | |
94 | static_cast<uint64_t>(nbytes), | |
95 | flags); | |
96 | return -1; | |
97 | } | |
98 | ||
99 | return 0; | |
100 | } | |
101 | ||
102 | int flush_range_sync(int fd, off_t offset, off_t nbytes) | |
103 | { | |
104 | return flush_range(fd, offset, nbytes, MS_SYNC); | |
105 | } | |
106 | ||
107 | int flush_range_async(int fd, off_t offset, off_t nbytes) | |
108 | { | |
109 | return flush_range(fd, offset, nbytes, MS_ASYNC); | |
110 | } | |
111 | } /* namespace */ | |
e8955cc6 MJ |
112 | #endif /* !HAVE_SYNC_FILE_RANGE */ |
113 | ||
114 | /* | |
115 | * Use posix_fadvise when available. | |
116 | */ | |
117 | #ifdef HAVE_POSIX_FADVISE | |
118 | namespace { | |
119 | int hint_dont_need(int fd, off_t offset, off_t nbytes) | |
120 | { | |
121 | const int ret = posix_fadvise(fd, offset, nbytes, POSIX_FADV_DONTNEED); | |
122 | if (ret && ret != -ENOSYS) { | |
123 | PERROR("Failed to mark region as DONTNEED with posix_fadvise: fd=%i, offset=%" PRIu64 | |
124 | ", nbytes=%" PRIu64, | |
125 | fd, | |
126 | static_cast<uint64_t>(offset), | |
127 | static_cast<uint64_t>(nbytes)); | |
128 | errno = ret; | |
129 | } | |
130 | ||
131 | return ret; | |
132 | } | |
133 | } /* namespace */ | |
134 | ||
135 | #else /* HAVE_POSIX_FADVISE */ | |
136 | ||
137 | /* | |
138 | * Generic noop compat for platforms wihtout posix_fadvise, this is acceptable | |
139 | * since we are only giving a hint to the kernel. | |
140 | */ | |
141 | namespace { | |
142 | int hint_dont_need(int fd __attribute__((unused)), | |
143 | off_t offset __attribute__((unused)), | |
144 | off_t nbytes __attribute__((unused))) | |
145 | { | |
146 | return 0; | |
147 | } | |
148 | } /* namespace */ | |
149 | #endif /* !HAVE_POSIX_FADVISE */ | |
671e39d7 MJ |
150 | |
151 | /* | |
152 | * Give a hint to the kernel that we won't need the data at the specified range | |
153 | * so it can be dropped from the page cache and wait for it to be flushed to | |
154 | * disk. | |
155 | */ | |
156 | void lttng::io::hint_flush_range_dont_need_sync(int fd, off_t offset, off_t nbytes) | |
157 | { | |
158 | /* Waited for the page writeback to complete. */ | |
159 | flush_range_sync(fd, offset, nbytes); | |
160 | ||
161 | /* | |
162 | * Give hints to the kernel about how we access the file: | |
163 | * POSIX_FADV_DONTNEED : we won't re-access data in a near future after | |
164 | * we write it. | |
165 | * | |
166 | * We need to call fadvise again after the file grows because the | |
167 | * kernel does not seem to apply fadvise to non-existing parts of the | |
168 | * file. | |
169 | * | |
170 | * Call fadvise _after_ having waited for the page writeback to | |
171 | * complete because the dirty page writeback semantic is not well | |
172 | * defined. So it can be expected to lead to lower throughput in | |
173 | * streaming. | |
174 | */ | |
e8955cc6 | 175 | hint_dont_need(fd, offset, nbytes); |
671e39d7 MJ |
176 | } |
177 | ||
178 | /* | |
179 | * Give a hint to the kernel that the data at the specified range should be | |
180 | * flushed to disk and wait for it to complete. | |
181 | */ | |
182 | void lttng::io::hint_flush_range_sync(int fd, off_t offset, off_t nbytes) | |
183 | { | |
184 | flush_range_sync(fd, offset, nbytes); | |
185 | } | |
186 | ||
187 | /* | |
188 | * Give a hint to the kernel that the data at the specified range should be | |
189 | * flushed to disk and return immediatly. | |
190 | */ | |
191 | void lttng::io::hint_flush_range_async(int fd, off_t offset, off_t nbytes) | |
192 | { | |
193 | flush_range_async(fd, offset, nbytes); | |
194 | } |