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
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
|
/* extent-scan.c -- core functions for scanning extents
Copyright (C) 2010-2012 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Written by Jie Liu (jeff.liu@oracle.com). */
#include <config.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/utsname.h>
#include <assert.h>
#include "system.h"
#include "extent-scan.h"
#include "fiemap.h"
#include "xstrtol.h"
/* Work around Linux kernel issues on BTRFS and EXT4 before 2.6.39.
FIXME: remove in 2013, or whenever we're pretty confident
that the offending, unpatched kernels are no longer in use. */
static bool
extent_need_sync (void)
{
/* For now always return true, to be on the safe side.
If/when FIEMAP semantics are well defined (before SEEK_HOLE support
is usable) and kernels implementing them are in use, we may relax
this once again. */
return true;
#if FIEMAP_BEHAVIOR_IS_DEFINED_AND_USABLE
static int need_sync = -1;
if (need_sync == -1)
{
struct utsname name;
need_sync = 0; /* No workaround by default. */
# ifdef __linux__
if (uname (&name) != -1 && STRNCMP_LIT (name.release, "2.6.") == 0)
{
unsigned long val;
if (xstrtoul (name.release + 4, NULL, 10, &val, NULL) == LONGINT_OK)
{
if (val < 39)
need_sync = 1;
}
}
# endif
}
return need_sync;
#endif
}
/* Allocate space for struct extent_scan, initialize the entries if
necessary and return it as the input argument of extent_scan_read(). */
extern void
extent_scan_init (int src_fd, struct extent_scan *scan)
{
scan->fd = src_fd;
scan->ei_count = 0;
scan->ext_info = NULL;
scan->scan_start = 0;
scan->initial_scan_failed = false;
scan->hit_final_extent = false;
scan->fm_flags = extent_need_sync () ? FIEMAP_FLAG_SYNC : 0;
}
#ifdef __linux__
# ifndef FS_IOC_FIEMAP
# define FS_IOC_FIEMAP _IOWR ('f', 11, struct fiemap)
# endif
/* Call ioctl(2) with FS_IOC_FIEMAP (available in linux 2.6.27) to
obtain a map of file extents excluding holes. */
extern bool
extent_scan_read (struct extent_scan *scan)
{
unsigned int si = 0;
struct extent_info *last_ei = scan->ext_info;
while (true)
{
union { struct fiemap f; char c[4096]; } fiemap_buf;
struct fiemap *fiemap = &fiemap_buf.f;
struct fiemap_extent *fm_extents = &fiemap->fm_extents[0];
enum { count = (sizeof fiemap_buf - sizeof *fiemap)/sizeof *fm_extents };
verify (count > 1);
/* This is required at least to initialize fiemap->fm_start,
but also serves (in mid 2010) to appease valgrind, which
appears not to know the semantics of the FIEMAP ioctl. */
memset (&fiemap_buf, 0, sizeof fiemap_buf);
fiemap->fm_start = scan->scan_start;
fiemap->fm_flags = scan->fm_flags;
fiemap->fm_extent_count = count;
fiemap->fm_length = FIEMAP_MAX_OFFSET - scan->scan_start;
/* Fall back to the standard copy if call ioctl(2) failed for
the first time. */
if (ioctl (scan->fd, FS_IOC_FIEMAP, fiemap) < 0)
{
if (scan->scan_start == 0)
scan->initial_scan_failed = true;
return false;
}
/* If 0 extents are returned, then no more scans are needed. */
if (fiemap->fm_mapped_extents == 0)
{
scan->hit_final_extent = true;
return scan->scan_start != 0;
}
assert (scan->ei_count <= SIZE_MAX - fiemap->fm_mapped_extents);
scan->ei_count += fiemap->fm_mapped_extents;
{
/* last_ei points into a buffer that may be freed via xnrealloc.
Record its offset and adjust after allocation. */
size_t prev_idx = last_ei - scan->ext_info;
scan->ext_info = xnrealloc (scan->ext_info, scan->ei_count,
sizeof (struct extent_info));
last_ei = scan->ext_info + prev_idx;
}
unsigned int i = 0;
for (i = 0; i < fiemap->fm_mapped_extents; i++)
{
assert (fm_extents[i].fe_logical
<= OFF_T_MAX - fm_extents[i].fe_length);
if (si && last_ei->ext_flags
== (fm_extents[i].fe_flags & ~FIEMAP_EXTENT_LAST)
&& (last_ei->ext_logical + last_ei->ext_length
== fm_extents[i].fe_logical))
{
/* Merge previous with last. */
last_ei->ext_length += fm_extents[i].fe_length;
/* Copy flags in case different. */
last_ei->ext_flags = fm_extents[i].fe_flags;
}
else if ((si == 0 && scan->scan_start > fm_extents[i].fe_logical)
|| (si && (last_ei->ext_logical + last_ei->ext_length
> fm_extents[i].fe_logical)))
{
/* BTRFS before 2.6.38 could return overlapping extents
for sparse files. We adjust the returned extents
rather than failing, as otherwise it would be inefficient
to detect this on the initial scan. */
uint64_t new_logical;
uint64_t length_adjust;
if (si == 0)
new_logical = scan->scan_start;
else
{
/* We could return here if scan->scan_start == 0
but don't so as to minimize special cases. */
new_logical = last_ei->ext_logical + last_ei->ext_length;
}
length_adjust = new_logical - fm_extents[i].fe_logical;
/* If an extent is contained within the previous one, fail. */
if (length_adjust < fm_extents[i].fe_length)
{
if (scan->scan_start == 0)
scan->initial_scan_failed = true;
return false;
}
fm_extents[i].fe_logical = new_logical;
fm_extents[i].fe_length -= length_adjust;
/* Process the adjusted extent again. */
i--;
continue;
}
else
{
last_ei = scan->ext_info + si;
last_ei->ext_logical = fm_extents[i].fe_logical;
last_ei->ext_length = fm_extents[i].fe_length;
last_ei->ext_flags = fm_extents[i].fe_flags;
si++;
}
}
if (last_ei->ext_flags & FIEMAP_EXTENT_LAST)
scan->hit_final_extent = true;
/* If we have enough extents, discard the last as it might
be merged with one from the next scan. */
if (si > count && !scan->hit_final_extent)
last_ei = scan->ext_info + --si - 1;
/* We don't bother reallocating any trailing slots. */
scan->ei_count = si;
if (scan->hit_final_extent)
break;
else
scan->scan_start = last_ei->ext_logical + last_ei->ext_length;
if (si >= count)
break;
}
return true;
}
#else
extern bool
extent_scan_read (struct extent_scan *scan ATTRIBUTE_UNUSED)
{
scan->initial_scan_failed = true;
errno = ENOTSUP;
return false;
}
#endif
|
