1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
2 // vim: ts=8 sw=2 smarttab
4 * Ceph - scalable distributed file system
6 * Copyright (C) 2014 Cloudwatt <libre.licensing@cloudwatt.com>
7 * Copyright (C) 2014 Red Hat <contact@redhat.com>
9 * Author: Loic Dachary <loic@dachary.org>
11 * This library is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU Lesser General Public
13 * License as published by the Free Software Foundation; either
14 * version 2.1 of the License, or (at your option) any later version.
21 #include "include/str_map.h"
22 #include "common/debug.h"
23 #include "crush/CrushWrapper.h"
24 #include "osd/osd_types.h"
25 #include "include/stringify.h"
26 #include "erasure-code/ErasureCodePlugin.h"
27 #include "json_spirit/json_spirit_writer.h"
29 #include "ErasureCodeLrc.h"
31 // re-include our assert to clobber boost's
32 #include "include/assert.h"
34 #define dout_context g_ceph_context
35 #define dout_subsys ceph_subsys_osd
37 #define dout_prefix _prefix(_dout)
41 static ostream
& _prefix(std::ostream
* _dout
)
43 return *_dout
<< "ErasureCodeLrc: ";
46 int ErasureCodeLrc::create_rule(const string
&name
,
50 if (crush
.rule_exists(name
)) {
51 *ss
<< "rule " << name
<< " exists";
54 if (!crush
.name_exists(rule_root
)) {
55 *ss
<< "root item " << rule_root
<< " does not exist";
58 int root
= crush
.get_item_id(rule_root
);
59 if (rule_device_class
.size()) {
60 if (!crush
.class_exists(rule_device_class
)) {
61 *ss
<< "device class " << rule_device_class
<< " does not exist";
64 int c
= crush
.get_class_id(rule_device_class
);
65 if (crush
.class_bucket
.count(root
) == 0 ||
66 crush
.class_bucket
[root
].count(c
) == 0) {
67 *ss
<< "root item " << rule_root
<< " has no devices with class "
71 root
= crush
.class_bucket
[root
][c
];
75 for (rno
= 0; rno
< crush
.get_max_rules(); rno
++) {
76 if (!crush
.rule_exists(rno
) && !crush
.ruleset_exists(rno
))
80 int steps
= 4 + rule_steps
.size();
82 int max_rep
= get_chunk_count();
84 ret
= crush
.add_rule(rno
, steps
, pg_pool_t::TYPE_ERASURE
,
89 ret
= crush
.set_rule_step(rno
, step
++, CRUSH_RULE_SET_CHOOSELEAF_TRIES
, 5, 0);
91 ret
= crush
.set_rule_step(rno
, step
++, CRUSH_RULE_SET_CHOOSE_TRIES
, 100, 0);
93 ret
= crush
.set_rule_step(rno
, step
++, CRUSH_RULE_TAKE
, root
, 0);
95 // [ [ "choose", "rack", 2 ],
96 // [ "chooseleaf", "host", 5 ] ]
97 for (vector
<Step
>::const_iterator i
= rule_steps
.begin();
98 i
!= rule_steps
.end();
100 int op
= i
->op
== "chooseleaf" ?
101 CRUSH_RULE_CHOOSELEAF_INDEP
: CRUSH_RULE_CHOOSE_INDEP
;
102 int type
= crush
.get_type_id(i
->type
);
104 *ss
<< "unknown crush type " << i
->type
;
107 ret
= crush
.set_rule_step(rno
, step
++, op
, i
->n
, type
);
110 ret
= crush
.set_rule_step(rno
, step
++, CRUSH_RULE_EMIT
, 0, 0);
112 crush
.set_rule_name(rno
, name
);
116 int ErasureCodeLrc::layers_description(const ErasureCodeProfile
&profile
,
117 json_spirit::mArray
*description
,
120 if (profile
.count("layers") == 0) {
121 *ss
<< "could not find 'layers' in " << profile
<< std::endl
;
122 return ERROR_LRC_DESCRIPTION
;
124 string str
= profile
.find("layers")->second
;
126 json_spirit::mValue json
;
127 json_spirit::read_or_throw(str
, json
);
129 if (json
.type() != json_spirit::array_type
) {
130 *ss
<< "layers='" << str
131 << "' must be a JSON array but is of type "
132 << json
.type() << " instead" << std::endl
;
133 return ERROR_LRC_ARRAY
;
135 *description
= json
.get_array();
136 } catch (json_spirit::Error_position
&e
) {
137 *ss
<< "failed to parse layers='" << str
<< "'"
138 << " at line " << e
.line_
<< ", column " << e
.column_
139 << " : " << e
.reason_
<< std::endl
;
140 return ERROR_LRC_PARSE_JSON
;
145 int ErasureCodeLrc::layers_parse(string description_string
,
146 json_spirit::mArray description
,
150 for (vector
<json_spirit::mValue
>::iterator i
= description
.begin();
151 i
!= description
.end();
153 if (i
->type() != json_spirit::array_type
) {
154 stringstream json_string
;
155 json_spirit::write(*i
, json_string
);
156 *ss
<< "each element of the array "
157 << description_string
<< " must be a JSON array but "
158 << json_string
.str() << " at position " << position
159 << " is of type " << i
->type() << " instead" << std::endl
;
160 return ERROR_LRC_ARRAY
;
162 json_spirit::mArray layer_json
= i
->get_array();
163 ErasureCodeProfile profile
;
165 for (vector
<json_spirit::mValue
>::iterator j
= layer_json
.begin();
166 j
!= layer_json
.end();
169 if (j
->type() != json_spirit::str_type
) {
170 stringstream element
;
171 json_spirit::write(*j
, element
);
172 *ss
<< "the first element of the entry "
173 << element
.str() << " (first is zero) "
174 << position
<< " in " << description_string
175 << " is of type " << (*j
).type() << " instead of string" << std::endl
;
176 return ERROR_LRC_STR
;
178 layers
.push_back(Layer(j
->get_str()));
179 Layer
&layer
= layers
.back();
180 layer
.chunks_map
= j
->get_str();
181 } else if(index
== 1) {
182 Layer
&layer
= layers
.back();
183 if (j
->type() != json_spirit::str_type
&&
184 j
->type() != json_spirit::obj_type
) {
185 stringstream element
;
186 json_spirit::write(*j
, element
);
187 *ss
<< "the second element of the entry "
188 << element
.str() << " (first is zero) "
189 << position
<< " in " << description_string
190 << " is of type " << (*j
).type() << " instead of string or object"
192 return ERROR_LRC_CONFIG_OPTIONS
;
194 if (j
->type() == json_spirit::str_type
) {
195 int err
= get_json_str_map(j
->get_str(), *ss
, &layer
.profile
);
198 } else if (j
->type() == json_spirit::obj_type
) {
199 json_spirit::mObject o
= j
->get_obj();
201 for (map
<string
, json_spirit::mValue
>::iterator i
= o
.begin();
204 layer
.profile
[i
->first
] = i
->second
.get_str();
208 // ignore trailing elements
215 int ErasureCodeLrc::layers_init(ostream
*ss
)
217 ErasureCodePluginRegistry
®istry
= ErasureCodePluginRegistry::instance();
218 for (unsigned int i
= 0; i
< layers
.size(); i
++) {
219 Layer
&layer
= layers
[i
];
221 for(std::string::iterator it
= layer
.chunks_map
.begin();
222 it
!= layer
.chunks_map
.end();
225 layer
.data
.push_back(position
);
227 layer
.coding
.push_back(position
);
228 if (*it
== 'c' || *it
== 'D')
229 layer
.chunks_as_set
.insert(position
);
232 layer
.chunks
= layer
.data
;
233 layer
.chunks
.insert(layer
.chunks
.end(),
234 layer
.coding
.begin(), layer
.coding
.end());
235 if (layer
.profile
.find("k") == layer
.profile
.end())
236 layer
.profile
["k"] = stringify(layer
.data
.size());
237 if (layer
.profile
.find("m") == layer
.profile
.end())
238 layer
.profile
["m"] = stringify(layer
.coding
.size());
239 if (layer
.profile
.find("plugin") == layer
.profile
.end())
240 layer
.profile
["plugin"] = "jerasure";
241 if (layer
.profile
.find("technique") == layer
.profile
.end())
242 layer
.profile
["technique"] = "reed_sol_van";
243 int err
= registry
.factory(layer
.profile
["plugin"],
254 int ErasureCodeLrc::layers_sanity_checks(string description_string
,
259 if (layers
.size() < 1) {
260 *ss
<< "layers parameter has " << layers
.size()
261 << " which is less than the minimum of one. "
262 << description_string
<< std::endl
;
263 return ERROR_LRC_LAYERS_COUNT
;
265 for (vector
<Layer
>::const_iterator layer
= layers
.begin();
266 layer
!= layers
.end();
268 if (chunk_count
!= layer
->chunks_map
.length()) {
269 *ss
<< "the first element of the array at position "
270 << position
<< " (starting from zero) "
271 << " is the string '" << layer
->chunks_map
272 << " found in the layers parameter "
273 << description_string
<< ". It is expected to be "
274 << chunk_count
<< " characters long but is "
275 << layer
->chunks_map
.length() << " characters long instead "
277 return ERROR_LRC_MAPPING_SIZE
;
283 int ErasureCodeLrc::parse(ErasureCodeProfile
&profile
,
286 int r
= ErasureCode::parse(profile
, ss
);
290 return parse_rule(profile
, ss
);
293 const string
ErasureCodeLrc::DEFAULT_KML("-1");
295 int ErasureCodeLrc::parse_kml(ErasureCodeProfile
&profile
,
298 int err
= ErasureCode::parse(profile
, ss
);
299 const int DEFAULT_INT
= -1;
301 err
|= to_int("k", profile
, &k
, DEFAULT_KML
, ss
);
302 err
|= to_int("m", profile
, &m
, DEFAULT_KML
, ss
);
303 err
|= to_int("l", profile
, &l
, DEFAULT_KML
, ss
);
305 if (k
== DEFAULT_INT
&& m
== DEFAULT_INT
&& l
== DEFAULT_INT
)
308 if ((k
!= DEFAULT_INT
|| m
!= DEFAULT_INT
|| l
!= DEFAULT_INT
) &&
309 (k
== DEFAULT_INT
|| m
== DEFAULT_INT
|| l
== DEFAULT_INT
)) {
310 *ss
<< "All of k, m, l must be set or none of them in "
311 << profile
<< std::endl
;
312 return ERROR_LRC_ALL_OR_NOTHING
;
315 const char *generated
[] = { "mapping",
319 for (int i
= 0; i
< 3; i
++) {
320 if (profile
.count(generated
[i
])) {
321 *ss
<< "The " << generated
[i
] << " parameter cannot be set "
322 << "when k, m, l are set in " << profile
<< std::endl
;
323 return ERROR_LRC_GENERATED
;
328 *ss
<< "k + m must be a multiple of l in "
329 << profile
<< std::endl
;
330 return ERROR_LRC_K_M_MODULO
;
333 int local_group_count
= (k
+ m
) / l
;
335 if (k
% local_group_count
) {
336 *ss
<< "k must be a multiple of (k + m) / l in "
337 << profile
<< std::endl
;
338 return ERROR_LRC_K_MODULO
;
341 if (m
% local_group_count
) {
342 *ss
<< "m must be a multiple of (k + m) / l in "
343 << profile
<< std::endl
;
344 return ERROR_LRC_M_MODULO
;
348 for (int i
= 0; i
< local_group_count
; i
++) {
349 mapping
+= string(k
/ local_group_count
, 'D') +
350 string(m
/ local_group_count
, '_') + "_";
352 profile
["mapping"] = mapping
;
354 string layers
= "[ ";
358 for (int i
= 0; i
< local_group_count
; i
++) {
359 layers
+= string(k
/ local_group_count
, 'D') +
360 string(m
/ local_group_count
, 'c') + "_";
362 layers
+= "\", \"\" ],";
365 for (int i
= 0; i
< local_group_count
; i
++) {
367 for (int j
= 0; j
< local_group_count
; j
++) {
369 layers
+= string(l
, 'D') + "c";
371 layers
+= string(l
+ 1, '_');
373 layers
+= "\", \"\" ],";
375 profile
["layers"] = layers
+ "]";
377 ErasureCodeProfile::const_iterator parameter
;
378 string rule_locality
;
379 parameter
= profile
.find("crush-locality");
380 if (parameter
!= profile
.end())
381 rule_locality
= parameter
->second
;
382 string rule_failure_domain
= "host";
383 parameter
= profile
.find("crush-failure-domain");
384 if (parameter
!= profile
.end())
385 rule_failure_domain
= parameter
->second
;
387 if (rule_locality
!= "") {
389 rule_steps
.push_back(Step("choose", rule_locality
,
391 rule_steps
.push_back(Step("chooseleaf", rule_failure_domain
,
393 } else if (rule_failure_domain
!= "") {
395 rule_steps
.push_back(Step("chooseleaf", rule_failure_domain
, 0));
401 int ErasureCodeLrc::parse_rule(ErasureCodeProfile
&profile
,
405 err
|= to_string("crush-root", profile
,
408 err
|= to_string("crush-device-class", profile
,
412 if (profile
.count("crush-steps") != 0) {
414 string str
= profile
.find("crush-steps")->second
;
415 json_spirit::mArray description
;
417 json_spirit::mValue json
;
418 json_spirit::read_or_throw(str
, json
);
420 if (json
.type() != json_spirit::array_type
) {
421 *ss
<< "crush-steps='" << str
422 << "' must be a JSON array but is of type "
423 << json
.type() << " instead" << std::endl
;
424 return ERROR_LRC_ARRAY
;
426 description
= json
.get_array();
427 } catch (json_spirit::Error_position
&e
) {
428 *ss
<< "failed to parse crush-steps='" << str
<< "'"
429 << " at line " << e
.line_
<< ", column " << e
.column_
430 << " : " << e
.reason_
<< std::endl
;
431 return ERROR_LRC_PARSE_JSON
;
435 for (vector
<json_spirit::mValue
>::iterator i
= description
.begin();
436 i
!= description
.end();
438 if (i
->type() != json_spirit::array_type
) {
439 stringstream json_string
;
440 json_spirit::write(*i
, json_string
);
441 *ss
<< "element of the array "
442 << str
<< " must be a JSON array but "
443 << json_string
.str() << " at position " << position
444 << " is of type " << i
->type() << " instead" << std::endl
;
445 return ERROR_LRC_ARRAY
;
447 int r
= parse_rule_step(str
, i
->get_array(), ss
);
455 int ErasureCodeLrc::parse_rule_step(string description_string
,
456 json_spirit::mArray description
,
459 stringstream json_string
;
460 json_spirit::write(description
, json_string
);
465 for (vector
<json_spirit::mValue
>::iterator i
= description
.begin();
466 i
!= description
.end();
468 if ((position
== 0 || position
== 1) &&
469 i
->type() != json_spirit::str_type
) {
470 *ss
<< "element " << position
<< " of the array "
471 << json_string
.str() << " found in " << description_string
472 << " must be a JSON string but is of type "
473 << i
->type() << " instead" << std::endl
;
474 return position
== 0 ? ERROR_LRC_RULE_OP
: ERROR_LRC_RULE_TYPE
;
476 if (position
== 2 && i
->type() != json_spirit::int_type
) {
477 *ss
<< "element " << position
<< " of the array "
478 << json_string
.str() << " found in " << description_string
479 << " must be a JSON int but is of type "
480 << i
->type() << " instead" << std::endl
;
481 return ERROR_LRC_RULE_N
;
491 rule_steps
.push_back(Step(op
, type
, n
));
495 int ErasureCodeLrc::init(ErasureCodeProfile
&profile
,
500 r
= parse_kml(profile
, ss
);
504 r
= parse(profile
, ss
);
508 json_spirit::mArray description
;
509 r
= layers_description(profile
, &description
, ss
);
513 string description_string
= profile
.find("layers")->second
;
515 dout(10) << "init(" << description_string
<< ")" << dendl
;
517 r
= layers_parse(description_string
, description
, ss
);
525 if (profile
.count("mapping") == 0) {
526 *ss
<< "the 'mapping' profile is missing from " << profile
;
527 return ERROR_LRC_MAPPING
;
529 string mapping
= profile
.find("mapping")->second
;
530 data_chunk_count
= 0;
531 for(std::string::iterator it
= mapping
.begin(); it
!= mapping
.end(); ++it
) {
535 chunk_count
= mapping
.length();
537 r
= layers_sanity_checks(description_string
, ss
);
542 // When initialized with kml, the profile parameters
543 // that were generated should not be stored because
544 // they would otherwise be exposed to the caller.
546 if (profile
.find("l") != profile
.end() &&
547 profile
.find("l")->second
!= DEFAULT_KML
) {
548 profile
.erase("mapping");
549 profile
.erase("layers");
551 ErasureCode::init(profile
, ss
);
555 set
<int> ErasureCodeLrc::get_erasures(const set
<int> &want
,
556 const set
<int> &available
) const
559 set_difference(want
.begin(), want
.end(),
560 available
.begin(), available
.end(),
561 inserter(result
, result
.end()));
565 unsigned int ErasureCodeLrc::get_chunk_size(unsigned int object_size
) const
567 return layers
.front().erasure_code
->get_chunk_size(object_size
);
570 void p(const set
<int> &s
) { cerr
<< s
; } // for gdb
572 int ErasureCodeLrc::minimum_to_decode(const set
<int> &want_to_read
,
573 const set
<int> &available_chunks
,
576 dout(20) << __func__
<< " want_to_read " << want_to_read
577 << " available_chunks " << available_chunks
<< dendl
;
579 set
<int> erasures_total
;
580 set
<int> erasures_not_recovered
;
581 set
<int> erasures_want
;
582 for (unsigned int i
= 0; i
< get_chunk_count(); ++i
) {
583 if (available_chunks
.count(i
) == 0) {
584 erasures_total
.insert(i
);
585 erasures_not_recovered
.insert(i
);
586 if (want_to_read
.count(i
) != 0)
587 erasures_want
.insert(i
);
594 // When no chunk is missing there is no need to read more than what
597 if (erasures_want
.empty()) {
598 *minimum
= want_to_read
;
599 dout(20) << __func__
<< " minimum == want_to_read == "
600 << want_to_read
<< dendl
;
607 // Try to recover erasures with as few chunks as possible.
609 for (vector
<Layer
>::reverse_iterator i
= layers
.rbegin();
613 // If this layer has no chunk that we want, skip it.
616 set_intersection(want_to_read
.begin(), want_to_read
.end(),
617 i
->chunks_as_set
.begin(), i
->chunks_as_set
.end(),
618 inserter(layer_want
, layer_want
.end()));
619 if (layer_want
.empty())
622 // Are some of the chunks we want missing ?
624 set
<int> layer_erasures
;
625 set_intersection(layer_want
.begin(), layer_want
.end(),
626 erasures_want
.begin(), erasures_want
.end(),
627 inserter(layer_erasures
, layer_erasures
.end()));
628 set
<int> layer_minimum
;
629 if (layer_erasures
.empty()) {
631 // The chunks we want are available, this is the minimum we need
634 layer_minimum
= layer_want
;
637 set_intersection(i
->chunks_as_set
.begin(), i
->chunks_as_set
.end(),
638 erasures_not_recovered
.begin(), erasures_not_recovered
.end(),
639 inserter(erasures
, erasures
.end()));
641 if (erasures
.size() > i
->erasure_code
->get_coding_chunk_count()) {
643 // There are too many erasures for this layer to recover: skip
644 // it and hope that an upper layer will be do better.
649 // Get all available chunks in that layer to recover the
652 set_difference(i
->chunks_as_set
.begin(), i
->chunks_as_set
.end(),
653 erasures_not_recovered
.begin(), erasures_not_recovered
.end(),
654 inserter(layer_minimum
, layer_minimum
.end()));
656 // Chunks recovered by this layer are removed from the list of
657 // erasures so that upper levels do not attempt to recover
660 for (set
<int>::const_iterator j
= erasures
.begin();
663 erasures_not_recovered
.erase(*j
);
664 if (erasures_want
.count(*j
))
665 erasures_want
.erase(*j
);
669 minimum
->insert(layer_minimum
.begin(), layer_minimum
.end());
671 if (erasures_want
.empty()) {
672 minimum
->insert(want_to_read
.begin(), want_to_read
.end());
673 for (set
<int>::const_iterator i
= erasures_total
.begin();
674 i
!= erasures_total
.end();
676 if (minimum
->count(*i
))
679 dout(20) << __func__
<< " minimum = " << *minimum
<< dendl
;
688 // The previous strategy failed to recover from all erasures.
690 // Try to recover as many chunks as possible, even from layers
691 // that do not contain chunks that we want, in the hope that it
692 // will help the upper layers.
694 set
<int> erasures_total
;
695 for (unsigned int i
= 0; i
< get_chunk_count(); ++i
) {
696 if (available_chunks
.count(i
) == 0)
697 erasures_total
.insert(i
);
700 for (vector
<Layer
>::reverse_iterator i
= layers
.rbegin();
703 set
<int> layer_erasures
;
704 set_intersection(i
->chunks_as_set
.begin(), i
->chunks_as_set
.end(),
705 erasures_total
.begin(), erasures_total
.end(),
706 inserter(layer_erasures
, layer_erasures
.end()));
708 // If this layer has no erasure, skip it
710 if (layer_erasures
.empty())
713 if (layer_erasures
.size() > 0 &&
714 layer_erasures
.size() <= i
->erasure_code
->get_coding_chunk_count()) {
716 // chunks recovered by this layer are removed from the list of
717 // erasures so that upper levels know they can rely on their
720 for (set
<int>::const_iterator j
= layer_erasures
.begin();
721 j
!= layer_erasures
.end();
723 erasures_total
.erase(*j
);
727 if (erasures_total
.empty()) {
729 // Do not try to be smart about what chunks are necessary to
730 // recover, use all available chunks.
732 *minimum
= available_chunks
;
733 dout(20) << __func__
<< " minimum == available_chunks == "
734 << available_chunks
<< dendl
;
739 derr
<< __func__
<< " not enough chunks in " << available_chunks
740 << " to read " << want_to_read
<< dendl
;
744 int ErasureCodeLrc::encode_chunks(const set
<int> &want_to_encode
,
745 map
<int, bufferlist
> *encoded
)
747 unsigned int top
= layers
.size();
748 for (vector
<Layer
>::reverse_iterator i
= layers
.rbegin();
752 if (includes(i
->chunks_as_set
.begin(), i
->chunks_as_set
.end(),
753 want_to_encode
.begin(), want_to_encode
.end()))
757 for (unsigned int i
= top
; i
< layers
.size(); ++i
) {
758 const Layer
&layer
= layers
[i
];
759 set
<int> layer_want_to_encode
;
760 map
<int, bufferlist
> layer_encoded
;
762 for (vector
<int>::const_iterator c
= layer
.chunks
.begin();
763 c
!= layer
.chunks
.end();
765 layer_encoded
[j
] = (*encoded
)[*c
];
766 if (want_to_encode
.find(*c
) != want_to_encode
.end())
767 layer_want_to_encode
.insert(j
);
770 int err
= layer
.erasure_code
->encode_chunks(layer_want_to_encode
,
773 derr
<< __func__
<< " layer " << layer
.chunks_map
774 << " failed with " << err
<< " trying to encode "
775 << layer_want_to_encode
<< dendl
;
782 int ErasureCodeLrc::decode_chunks(const set
<int> &want_to_read
,
783 const map
<int, bufferlist
> &chunks
,
784 map
<int, bufferlist
> *decoded
)
786 set
<int> available_chunks
;
788 for (unsigned int i
= 0; i
< get_chunk_count(); ++i
) {
789 if (chunks
.count(i
) != 0)
790 available_chunks
.insert(i
);
795 set
<int> want_to_read_erasures
;
797 for (vector
<Layer
>::reverse_iterator layer
= layers
.rbegin();
798 layer
!= layers
.rend();
800 set
<int> layer_erasures
;
801 set_intersection(layer
->chunks_as_set
.begin(), layer
->chunks_as_set
.end(),
802 erasures
.begin(), erasures
.end(),
803 inserter(layer_erasures
, layer_erasures
.end()));
805 if (layer_erasures
.size() >
806 layer
->erasure_code
->get_coding_chunk_count()) {
807 // skip because there are too many erasures for this layer to recover
808 } else if(layer_erasures
.size() == 0) {
809 // skip because all chunks are already available
811 set
<int> layer_want_to_read
;
812 map
<int, bufferlist
> layer_chunks
;
813 map
<int, bufferlist
> layer_decoded
;
815 for (vector
<int>::const_iterator c
= layer
->chunks
.begin();
816 c
!= layer
->chunks
.end();
819 // Pick chunks from *decoded* instead of *chunks* to re-use
820 // chunks recovered by previous layers. In other words
821 // *chunks* does not change but *decoded* gradually improves
822 // as more layers recover from erasures.
824 if (erasures
.count(*c
) == 0)
825 layer_chunks
[j
] = (*decoded
)[*c
];
826 if (want_to_read
.count(*c
) != 0)
827 layer_want_to_read
.insert(j
);
828 layer_decoded
[j
] = (*decoded
)[*c
];
831 int err
= layer
->erasure_code
->decode_chunks(layer_want_to_read
,
835 derr
<< __func__
<< " layer " << layer
->chunks_map
836 << " failed with " << err
<< " trying to decode "
837 << layer_want_to_read
<< " with " << available_chunks
<< dendl
;
841 for (vector
<int>::const_iterator c
= layer
->chunks
.begin();
842 c
!= layer
->chunks
.end();
844 (*decoded
)[*c
] = layer_decoded
[j
];
846 if (erasures
.count(*c
) != 0)
849 want_to_read_erasures
.clear();
850 set_intersection(erasures
.begin(), erasures
.end(),
851 want_to_read
.begin(), want_to_read
.end(),
852 inserter(want_to_read_erasures
, want_to_read_erasures
.end()));
853 if (want_to_read_erasures
.size() == 0)
858 if (want_to_read_erasures
.size() > 0) {
859 derr
<< __func__
<< " want to read " << want_to_read
860 << " with available_chunks = " << available_chunks
861 << " end up being unable to read " << want_to_read_erasures
<< dendl
;