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TOMOYO Linux Cross Reference
Linux/fs/ext4/extents_status.c

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  1 /*
  2  *  fs/ext4/extents_status.c
  3  *
  4  * Written by Yongqiang Yang <xiaoqiangnk@gmail.com>
  5  * Modified by
  6  *      Allison Henderson <achender@linux.vnet.ibm.com>
  7  *      Hugh Dickins <hughd@google.com>
  8  *      Zheng Liu <wenqing.lz@taobao.com>
  9  *
 10  * Ext4 extents status tree core functions.
 11  */
 12 #include <linux/list_sort.h>
 13 #include <linux/proc_fs.h>
 14 #include <linux/seq_file.h>
 15 #include "ext4.h"
 16 
 17 #include <trace/events/ext4.h>
 18 
 19 /*
 20  * According to previous discussion in Ext4 Developer Workshop, we
 21  * will introduce a new structure called io tree to track all extent
 22  * status in order to solve some problems that we have met
 23  * (e.g. Reservation space warning), and provide extent-level locking.
 24  * Delay extent tree is the first step to achieve this goal.  It is
 25  * original built by Yongqiang Yang.  At that time it is called delay
 26  * extent tree, whose goal is only track delayed extents in memory to
 27  * simplify the implementation of fiemap and bigalloc, and introduce
 28  * lseek SEEK_DATA/SEEK_HOLE support.  That is why it is still called
 29  * delay extent tree at the first commit.  But for better understand
 30  * what it does, it has been rename to extent status tree.
 31  *
 32  * Step1:
 33  * Currently the first step has been done.  All delayed extents are
 34  * tracked in the tree.  It maintains the delayed extent when a delayed
 35  * allocation is issued, and the delayed extent is written out or
 36  * invalidated.  Therefore the implementation of fiemap and bigalloc
 37  * are simplified, and SEEK_DATA/SEEK_HOLE are introduced.
 38  *
 39  * The following comment describes the implemenmtation of extent
 40  * status tree and future works.
 41  *
 42  * Step2:
 43  * In this step all extent status are tracked by extent status tree.
 44  * Thus, we can first try to lookup a block mapping in this tree before
 45  * finding it in extent tree.  Hence, single extent cache can be removed
 46  * because extent status tree can do a better job.  Extents in status
 47  * tree are loaded on-demand.  Therefore, the extent status tree may not
 48  * contain all of the extents in a file.  Meanwhile we define a shrinker
 49  * to reclaim memory from extent status tree because fragmented extent
 50  * tree will make status tree cost too much memory.  written/unwritten/-
 51  * hole extents in the tree will be reclaimed by this shrinker when we
 52  * are under high memory pressure.  Delayed extents will not be
 53  * reclimed because fiemap, bigalloc, and seek_data/hole need it.
 54  */
 55 
 56 /*
 57  * Extent status tree implementation for ext4.
 58  *
 59  *
 60  * ==========================================================================
 61  * Extent status tree tracks all extent status.
 62  *
 63  * 1. Why we need to implement extent status tree?
 64  *
 65  * Without extent status tree, ext4 identifies a delayed extent by looking
 66  * up page cache, this has several deficiencies - complicated, buggy,
 67  * and inefficient code.
 68  *
 69  * FIEMAP, SEEK_HOLE/DATA, bigalloc, and writeout all need to know if a
 70  * block or a range of blocks are belonged to a delayed extent.
 71  *
 72  * Let us have a look at how they do without extent status tree.
 73  *   -- FIEMAP
 74  *      FIEMAP looks up page cache to identify delayed allocations from holes.
 75  *
 76  *   -- SEEK_HOLE/DATA
 77  *      SEEK_HOLE/DATA has the same problem as FIEMAP.
 78  *
 79  *   -- bigalloc
 80  *      bigalloc looks up page cache to figure out if a block is
 81  *      already under delayed allocation or not to determine whether
 82  *      quota reserving is needed for the cluster.
 83  *
 84  *   -- writeout
 85  *      Writeout looks up whole page cache to see if a buffer is
 86  *      mapped, If there are not very many delayed buffers, then it is
 87  *      time comsuming.
 88  *
 89  * With extent status tree implementation, FIEMAP, SEEK_HOLE/DATA,
 90  * bigalloc and writeout can figure out if a block or a range of
 91  * blocks is under delayed allocation(belonged to a delayed extent) or
 92  * not by searching the extent tree.
 93  *
 94  *
 95  * ==========================================================================
 96  * 2. Ext4 extent status tree impelmentation
 97  *
 98  *   -- extent
 99  *      A extent is a range of blocks which are contiguous logically and
100  *      physically.  Unlike extent in extent tree, this extent in ext4 is
101  *      a in-memory struct, there is no corresponding on-disk data.  There
102  *      is no limit on length of extent, so an extent can contain as many
103  *      blocks as they are contiguous logically and physically.
104  *
105  *   -- extent status tree
106  *      Every inode has an extent status tree and all allocation blocks
107  *      are added to the tree with different status.  The extent in the
108  *      tree are ordered by logical block no.
109  *
110  *   -- operations on a extent status tree
111  *      There are three important operations on a delayed extent tree: find
112  *      next extent, adding a extent(a range of blocks) and removing a extent.
113  *
114  *   -- race on a extent status tree
115  *      Extent status tree is protected by inode->i_es_lock.
116  *
117  *   -- memory consumption
118  *      Fragmented extent tree will make extent status tree cost too much
119  *      memory.  Hence, we will reclaim written/unwritten/hole extents from
120  *      the tree under a heavy memory pressure.
121  *
122  *
123  * ==========================================================================
124  * 3. Performance analysis
125  *
126  *   -- overhead
127  *      1. There is a cache extent for write access, so if writes are
128  *      not very random, adding space operaions are in O(1) time.
129  *
130  *   -- gain
131  *      2. Code is much simpler, more readable, more maintainable and
132  *      more efficient.
133  *
134  *
135  * ==========================================================================
136  * 4. TODO list
137  *
138  *   -- Refactor delayed space reservation
139  *
140  *   -- Extent-level locking
141  */
142 
143 static struct kmem_cache *ext4_es_cachep;
144 
145 static int __es_insert_extent(struct inode *inode, struct extent_status *newes);
146 static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
147                               ext4_lblk_t end);
148 static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan);
149 static int __es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
150                        struct ext4_inode_info *locked_ei);
151 
152 int __init ext4_init_es(void)
153 {
154         ext4_es_cachep = kmem_cache_create("ext4_extent_status",
155                                            sizeof(struct extent_status),
156                                            0, (SLAB_RECLAIM_ACCOUNT), NULL);
157         if (ext4_es_cachep == NULL)
158                 return -ENOMEM;
159         return 0;
160 }
161 
162 void ext4_exit_es(void)
163 {
164         if (ext4_es_cachep)
165                 kmem_cache_destroy(ext4_es_cachep);
166 }
167 
168 void ext4_es_init_tree(struct ext4_es_tree *tree)
169 {
170         tree->root = RB_ROOT;
171         tree->cache_es = NULL;
172 }
173 
174 #ifdef ES_DEBUG__
175 static void ext4_es_print_tree(struct inode *inode)
176 {
177         struct ext4_es_tree *tree;
178         struct rb_node *node;
179 
180         printk(KERN_DEBUG "status extents for inode %lu:", inode->i_ino);
181         tree = &EXT4_I(inode)->i_es_tree;
182         node = rb_first(&tree->root);
183         while (node) {
184                 struct extent_status *es;
185                 es = rb_entry(node, struct extent_status, rb_node);
186                 printk(KERN_DEBUG " [%u/%u) %llu %x",
187                        es->es_lblk, es->es_len,
188                        ext4_es_pblock(es), ext4_es_status(es));
189                 node = rb_next(node);
190         }
191         printk(KERN_DEBUG "\n");
192 }
193 #else
194 #define ext4_es_print_tree(inode)
195 #endif
196 
197 static inline ext4_lblk_t ext4_es_end(struct extent_status *es)
198 {
199         BUG_ON(es->es_lblk + es->es_len < es->es_lblk);
200         return es->es_lblk + es->es_len - 1;
201 }
202 
203 /*
204  * search through the tree for an delayed extent with a given offset.  If
205  * it can't be found, try to find next extent.
206  */
207 static struct extent_status *__es_tree_search(struct rb_root *root,
208                                               ext4_lblk_t lblk)
209 {
210         struct rb_node *node = root->rb_node;
211         struct extent_status *es = NULL;
212 
213         while (node) {
214                 es = rb_entry(node, struct extent_status, rb_node);
215                 if (lblk < es->es_lblk)
216                         node = node->rb_left;
217                 else if (lblk > ext4_es_end(es))
218                         node = node->rb_right;
219                 else
220                         return es;
221         }
222 
223         if (es && lblk < es->es_lblk)
224                 return es;
225 
226         if (es && lblk > ext4_es_end(es)) {
227                 node = rb_next(&es->rb_node);
228                 return node ? rb_entry(node, struct extent_status, rb_node) :
229                               NULL;
230         }
231 
232         return NULL;
233 }
234 
235 /*
236  * ext4_es_find_delayed_extent_range: find the 1st delayed extent covering
237  * @es->lblk if it exists, otherwise, the next extent after @es->lblk.
238  *
239  * @inode: the inode which owns delayed extents
240  * @lblk: the offset where we start to search
241  * @end: the offset where we stop to search
242  * @es: delayed extent that we found
243  */
244 void ext4_es_find_delayed_extent_range(struct inode *inode,
245                                  ext4_lblk_t lblk, ext4_lblk_t end,
246                                  struct extent_status *es)
247 {
248         struct ext4_es_tree *tree = NULL;
249         struct extent_status *es1 = NULL;
250         struct rb_node *node;
251 
252         BUG_ON(es == NULL);
253         BUG_ON(end < lblk);
254         trace_ext4_es_find_delayed_extent_range_enter(inode, lblk);
255 
256         read_lock(&EXT4_I(inode)->i_es_lock);
257         tree = &EXT4_I(inode)->i_es_tree;
258 
259         /* find extent in cache firstly */
260         es->es_lblk = es->es_len = es->es_pblk = 0;
261         if (tree->cache_es) {
262                 es1 = tree->cache_es;
263                 if (in_range(lblk, es1->es_lblk, es1->es_len)) {
264                         es_debug("%u cached by [%u/%u) %llu %x\n",
265                                  lblk, es1->es_lblk, es1->es_len,
266                                  ext4_es_pblock(es1), ext4_es_status(es1));
267                         goto out;
268                 }
269         }
270 
271         es1 = __es_tree_search(&tree->root, lblk);
272 
273 out:
274         if (es1 && !ext4_es_is_delayed(es1)) {
275                 while ((node = rb_next(&es1->rb_node)) != NULL) {
276                         es1 = rb_entry(node, struct extent_status, rb_node);
277                         if (es1->es_lblk > end) {
278                                 es1 = NULL;
279                                 break;
280                         }
281                         if (ext4_es_is_delayed(es1))
282                                 break;
283                 }
284         }
285 
286         if (es1 && ext4_es_is_delayed(es1)) {
287                 tree->cache_es = es1;
288                 es->es_lblk = es1->es_lblk;
289                 es->es_len = es1->es_len;
290                 es->es_pblk = es1->es_pblk;
291         }
292 
293         read_unlock(&EXT4_I(inode)->i_es_lock);
294 
295         trace_ext4_es_find_delayed_extent_range_exit(inode, es);
296 }
297 
298 static void ext4_es_list_add(struct inode *inode)
299 {
300         struct ext4_inode_info *ei = EXT4_I(inode);
301         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
302 
303         if (!list_empty(&ei->i_es_list))
304                 return;
305 
306         spin_lock(&sbi->s_es_lock);
307         if (list_empty(&ei->i_es_list)) {
308                 list_add_tail(&ei->i_es_list, &sbi->s_es_list);
309                 sbi->s_es_nr_inode++;
310         }
311         spin_unlock(&sbi->s_es_lock);
312 }
313 
314 static void ext4_es_list_del(struct inode *inode)
315 {
316         struct ext4_inode_info *ei = EXT4_I(inode);
317         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
318 
319         spin_lock(&sbi->s_es_lock);
320         if (!list_empty(&ei->i_es_list)) {
321                 list_del_init(&ei->i_es_list);
322                 sbi->s_es_nr_inode--;
323                 WARN_ON_ONCE(sbi->s_es_nr_inode < 0);
324         }
325         spin_unlock(&sbi->s_es_lock);
326 }
327 
328 static struct extent_status *
329 ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
330                      ext4_fsblk_t pblk)
331 {
332         struct extent_status *es;
333         es = kmem_cache_alloc(ext4_es_cachep, GFP_ATOMIC);
334         if (es == NULL)
335                 return NULL;
336         es->es_lblk = lblk;
337         es->es_len = len;
338         es->es_pblk = pblk;
339 
340         /*
341          * We don't count delayed extent because we never try to reclaim them
342          */
343         if (!ext4_es_is_delayed(es)) {
344                 if (!EXT4_I(inode)->i_es_shk_nr++)
345                         ext4_es_list_add(inode);
346                 percpu_counter_inc(&EXT4_SB(inode->i_sb)->
347                                         s_es_stats.es_stats_shk_cnt);
348         }
349 
350         EXT4_I(inode)->i_es_all_nr++;
351         percpu_counter_inc(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
352 
353         return es;
354 }
355 
356 static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
357 {
358         EXT4_I(inode)->i_es_all_nr--;
359         percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
360 
361         /* Decrease the shrink counter when this es is not delayed */
362         if (!ext4_es_is_delayed(es)) {
363                 BUG_ON(EXT4_I(inode)->i_es_shk_nr == 0);
364                 if (!--EXT4_I(inode)->i_es_shk_nr)
365                         ext4_es_list_del(inode);
366                 percpu_counter_dec(&EXT4_SB(inode->i_sb)->
367                                         s_es_stats.es_stats_shk_cnt);
368         }
369 
370         kmem_cache_free(ext4_es_cachep, es);
371 }
372 
373 /*
374  * Check whether or not two extents can be merged
375  * Condition:
376  *  - logical block number is contiguous
377  *  - physical block number is contiguous
378  *  - status is equal
379  */
380 static int ext4_es_can_be_merged(struct extent_status *es1,
381                                  struct extent_status *es2)
382 {
383         if (ext4_es_type(es1) != ext4_es_type(es2))
384                 return 0;
385 
386         if (((__u64) es1->es_len) + es2->es_len > EXT_MAX_BLOCKS) {
387                 pr_warn("ES assertion failed when merging extents. "
388                         "The sum of lengths of es1 (%d) and es2 (%d) "
389                         "is bigger than allowed file size (%d)\n",
390                         es1->es_len, es2->es_len, EXT_MAX_BLOCKS);
391                 WARN_ON(1);
392                 return 0;
393         }
394 
395         if (((__u64) es1->es_lblk) + es1->es_len != es2->es_lblk)
396                 return 0;
397 
398         if ((ext4_es_is_written(es1) || ext4_es_is_unwritten(es1)) &&
399             (ext4_es_pblock(es1) + es1->es_len == ext4_es_pblock(es2)))
400                 return 1;
401 
402         if (ext4_es_is_hole(es1))
403                 return 1;
404 
405         /* we need to check delayed extent is without unwritten status */
406         if (ext4_es_is_delayed(es1) && !ext4_es_is_unwritten(es1))
407                 return 1;
408 
409         return 0;
410 }
411 
412 static struct extent_status *
413 ext4_es_try_to_merge_left(struct inode *inode, struct extent_status *es)
414 {
415         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
416         struct extent_status *es1;
417         struct rb_node *node;
418 
419         node = rb_prev(&es->rb_node);
420         if (!node)
421                 return es;
422 
423         es1 = rb_entry(node, struct extent_status, rb_node);
424         if (ext4_es_can_be_merged(es1, es)) {
425                 es1->es_len += es->es_len;
426                 if (ext4_es_is_referenced(es))
427                         ext4_es_set_referenced(es1);
428                 rb_erase(&es->rb_node, &tree->root);
429                 ext4_es_free_extent(inode, es);
430                 es = es1;
431         }
432 
433         return es;
434 }
435 
436 static struct extent_status *
437 ext4_es_try_to_merge_right(struct inode *inode, struct extent_status *es)
438 {
439         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
440         struct extent_status *es1;
441         struct rb_node *node;
442 
443         node = rb_next(&es->rb_node);
444         if (!node)
445                 return es;
446 
447         es1 = rb_entry(node, struct extent_status, rb_node);
448         if (ext4_es_can_be_merged(es, es1)) {
449                 es->es_len += es1->es_len;
450                 if (ext4_es_is_referenced(es1))
451                         ext4_es_set_referenced(es);
452                 rb_erase(node, &tree->root);
453                 ext4_es_free_extent(inode, es1);
454         }
455 
456         return es;
457 }
458 
459 #ifdef ES_AGGRESSIVE_TEST
460 #include "ext4_extents.h"       /* Needed when ES_AGGRESSIVE_TEST is defined */
461 
462 static void ext4_es_insert_extent_ext_check(struct inode *inode,
463                                             struct extent_status *es)
464 {
465         struct ext4_ext_path *path = NULL;
466         struct ext4_extent *ex;
467         ext4_lblk_t ee_block;
468         ext4_fsblk_t ee_start;
469         unsigned short ee_len;
470         int depth, ee_status, es_status;
471 
472         path = ext4_find_extent(inode, es->es_lblk, NULL, EXT4_EX_NOCACHE);
473         if (IS_ERR(path))
474                 return;
475 
476         depth = ext_depth(inode);
477         ex = path[depth].p_ext;
478 
479         if (ex) {
480 
481                 ee_block = le32_to_cpu(ex->ee_block);
482                 ee_start = ext4_ext_pblock(ex);
483                 ee_len = ext4_ext_get_actual_len(ex);
484 
485                 ee_status = ext4_ext_is_unwritten(ex) ? 1 : 0;
486                 es_status = ext4_es_is_unwritten(es) ? 1 : 0;
487 
488                 /*
489                  * Make sure ex and es are not overlap when we try to insert
490                  * a delayed/hole extent.
491                  */
492                 if (!ext4_es_is_written(es) && !ext4_es_is_unwritten(es)) {
493                         if (in_range(es->es_lblk, ee_block, ee_len)) {
494                                 pr_warn("ES insert assertion failed for "
495                                         "inode: %lu we can find an extent "
496                                         "at block [%d/%d/%llu/%c], but we "
497                                         "want to add a delayed/hole extent "
498                                         "[%d/%d/%llu/%x]\n",
499                                         inode->i_ino, ee_block, ee_len,
500                                         ee_start, ee_status ? 'u' : 'w',
501                                         es->es_lblk, es->es_len,
502                                         ext4_es_pblock(es), ext4_es_status(es));
503                         }
504                         goto out;
505                 }
506 
507                 /*
508                  * We don't check ee_block == es->es_lblk, etc. because es
509                  * might be a part of whole extent, vice versa.
510                  */
511                 if (es->es_lblk < ee_block ||
512                     ext4_es_pblock(es) != ee_start + es->es_lblk - ee_block) {
513                         pr_warn("ES insert assertion failed for inode: %lu "
514                                 "ex_status [%d/%d/%llu/%c] != "
515                                 "es_status [%d/%d/%llu/%c]\n", inode->i_ino,
516                                 ee_block, ee_len, ee_start,
517                                 ee_status ? 'u' : 'w', es->es_lblk, es->es_len,
518                                 ext4_es_pblock(es), es_status ? 'u' : 'w');
519                         goto out;
520                 }
521 
522                 if (ee_status ^ es_status) {
523                         pr_warn("ES insert assertion failed for inode: %lu "
524                                 "ex_status [%d/%d/%llu/%c] != "
525                                 "es_status [%d/%d/%llu/%c]\n", inode->i_ino,
526                                 ee_block, ee_len, ee_start,
527                                 ee_status ? 'u' : 'w', es->es_lblk, es->es_len,
528                                 ext4_es_pblock(es), es_status ? 'u' : 'w');
529                 }
530         } else {
531                 /*
532                  * We can't find an extent on disk.  So we need to make sure
533                  * that we don't want to add an written/unwritten extent.
534                  */
535                 if (!ext4_es_is_delayed(es) && !ext4_es_is_hole(es)) {
536                         pr_warn("ES insert assertion failed for inode: %lu "
537                                 "can't find an extent at block %d but we want "
538                                 "to add a written/unwritten extent "
539                                 "[%d/%d/%llu/%x]\n", inode->i_ino,
540                                 es->es_lblk, es->es_lblk, es->es_len,
541                                 ext4_es_pblock(es), ext4_es_status(es));
542                 }
543         }
544 out:
545         ext4_ext_drop_refs(path);
546         kfree(path);
547 }
548 
549 static void ext4_es_insert_extent_ind_check(struct inode *inode,
550                                             struct extent_status *es)
551 {
552         struct ext4_map_blocks map;
553         int retval;
554 
555         /*
556          * Here we call ext4_ind_map_blocks to lookup a block mapping because
557          * 'Indirect' structure is defined in indirect.c.  So we couldn't
558          * access direct/indirect tree from outside.  It is too dirty to define
559          * this function in indirect.c file.
560          */
561 
562         map.m_lblk = es->es_lblk;
563         map.m_len = es->es_len;
564 
565         retval = ext4_ind_map_blocks(NULL, inode, &map, 0);
566         if (retval > 0) {
567                 if (ext4_es_is_delayed(es) || ext4_es_is_hole(es)) {
568                         /*
569                          * We want to add a delayed/hole extent but this
570                          * block has been allocated.
571                          */
572                         pr_warn("ES insert assertion failed for inode: %lu "
573                                 "We can find blocks but we want to add a "
574                                 "delayed/hole extent [%d/%d/%llu/%x]\n",
575                                 inode->i_ino, es->es_lblk, es->es_len,
576                                 ext4_es_pblock(es), ext4_es_status(es));
577                         return;
578                 } else if (ext4_es_is_written(es)) {
579                         if (retval != es->es_len) {
580                                 pr_warn("ES insert assertion failed for "
581                                         "inode: %lu retval %d != es_len %d\n",
582                                         inode->i_ino, retval, es->es_len);
583                                 return;
584                         }
585                         if (map.m_pblk != ext4_es_pblock(es)) {
586                                 pr_warn("ES insert assertion failed for "
587                                         "inode: %lu m_pblk %llu != "
588                                         "es_pblk %llu\n",
589                                         inode->i_ino, map.m_pblk,
590                                         ext4_es_pblock(es));
591                                 return;
592                         }
593                 } else {
594                         /*
595                          * We don't need to check unwritten extent because
596                          * indirect-based file doesn't have it.
597                          */
598                         BUG_ON(1);
599                 }
600         } else if (retval == 0) {
601                 if (ext4_es_is_written(es)) {
602                         pr_warn("ES insert assertion failed for inode: %lu "
603                                 "We can't find the block but we want to add "
604                                 "a written extent [%d/%d/%llu/%x]\n",
605                                 inode->i_ino, es->es_lblk, es->es_len,
606                                 ext4_es_pblock(es), ext4_es_status(es));
607                         return;
608                 }
609         }
610 }
611 
612 static inline void ext4_es_insert_extent_check(struct inode *inode,
613                                                struct extent_status *es)
614 {
615         /*
616          * We don't need to worry about the race condition because
617          * caller takes i_data_sem locking.
618          */
619         BUG_ON(!rwsem_is_locked(&EXT4_I(inode)->i_data_sem));
620         if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
621                 ext4_es_insert_extent_ext_check(inode, es);
622         else
623                 ext4_es_insert_extent_ind_check(inode, es);
624 }
625 #else
626 static inline void ext4_es_insert_extent_check(struct inode *inode,
627                                                struct extent_status *es)
628 {
629 }
630 #endif
631 
632 static int __es_insert_extent(struct inode *inode, struct extent_status *newes)
633 {
634         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
635         struct rb_node **p = &tree->root.rb_node;
636         struct rb_node *parent = NULL;
637         struct extent_status *es;
638 
639         while (*p) {
640                 parent = *p;
641                 es = rb_entry(parent, struct extent_status, rb_node);
642 
643                 if (newes->es_lblk < es->es_lblk) {
644                         if (ext4_es_can_be_merged(newes, es)) {
645                                 /*
646                                  * Here we can modify es_lblk directly
647                                  * because it isn't overlapped.
648                                  */
649                                 es->es_lblk = newes->es_lblk;
650                                 es->es_len += newes->es_len;
651                                 if (ext4_es_is_written(es) ||
652                                     ext4_es_is_unwritten(es))
653                                         ext4_es_store_pblock(es,
654                                                              newes->es_pblk);
655                                 es = ext4_es_try_to_merge_left(inode, es);
656                                 goto out;
657                         }
658                         p = &(*p)->rb_left;
659                 } else if (newes->es_lblk > ext4_es_end(es)) {
660                         if (ext4_es_can_be_merged(es, newes)) {
661                                 es->es_len += newes->es_len;
662                                 es = ext4_es_try_to_merge_right(inode, es);
663                                 goto out;
664                         }
665                         p = &(*p)->rb_right;
666                 } else {
667                         BUG_ON(1);
668                         return -EINVAL;
669                 }
670         }
671 
672         es = ext4_es_alloc_extent(inode, newes->es_lblk, newes->es_len,
673                                   newes->es_pblk);
674         if (!es)
675                 return -ENOMEM;
676         rb_link_node(&es->rb_node, parent, p);
677         rb_insert_color(&es->rb_node, &tree->root);
678 
679 out:
680         tree->cache_es = es;
681         return 0;
682 }
683 
684 /*
685  * ext4_es_insert_extent() adds information to an inode's extent
686  * status tree.
687  *
688  * Return 0 on success, error code on failure.
689  */
690 int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
691                           ext4_lblk_t len, ext4_fsblk_t pblk,
692                           unsigned int status)
693 {
694         struct extent_status newes;
695         ext4_lblk_t end = lblk + len - 1;
696         int err = 0;
697 
698         es_debug("add [%u/%u) %llu %x to extent status tree of inode %lu\n",
699                  lblk, len, pblk, status, inode->i_ino);
700 
701         if (!len)
702                 return 0;
703 
704         BUG_ON(end < lblk);
705 
706         if ((status & EXTENT_STATUS_DELAYED) &&
707             (status & EXTENT_STATUS_WRITTEN)) {
708                 ext4_warning(inode->i_sb, "Inserting extent [%u/%u] as "
709                                 " delayed and written which can potentially "
710                                 " cause data loss.", lblk, len);
711                 WARN_ON(1);
712         }
713 
714         newes.es_lblk = lblk;
715         newes.es_len = len;
716         ext4_es_store_pblock_status(&newes, pblk, status);
717         trace_ext4_es_insert_extent(inode, &newes);
718 
719         ext4_es_insert_extent_check(inode, &newes);
720 
721         write_lock(&EXT4_I(inode)->i_es_lock);
722         err = __es_remove_extent(inode, lblk, end);
723         if (err != 0)
724                 goto error;
725 retry:
726         err = __es_insert_extent(inode, &newes);
727         if (err == -ENOMEM && __es_shrink(EXT4_SB(inode->i_sb),
728                                           128, EXT4_I(inode)))
729                 goto retry;
730         if (err == -ENOMEM && !ext4_es_is_delayed(&newes))
731                 err = 0;
732 
733 error:
734         write_unlock(&EXT4_I(inode)->i_es_lock);
735 
736         ext4_es_print_tree(inode);
737 
738         return err;
739 }
740 
741 /*
742  * ext4_es_cache_extent() inserts information into the extent status
743  * tree if and only if there isn't information about the range in
744  * question already.
745  */
746 void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
747                           ext4_lblk_t len, ext4_fsblk_t pblk,
748                           unsigned int status)
749 {
750         struct extent_status *es;
751         struct extent_status newes;
752         ext4_lblk_t end = lblk + len - 1;
753 
754         newes.es_lblk = lblk;
755         newes.es_len = len;
756         ext4_es_store_pblock_status(&newes, pblk, status);
757         trace_ext4_es_cache_extent(inode, &newes);
758 
759         if (!len)
760                 return;
761 
762         BUG_ON(end < lblk);
763 
764         write_lock(&EXT4_I(inode)->i_es_lock);
765 
766         es = __es_tree_search(&EXT4_I(inode)->i_es_tree.root, lblk);
767         if (!es || es->es_lblk > end)
768                 __es_insert_extent(inode, &newes);
769         write_unlock(&EXT4_I(inode)->i_es_lock);
770 }
771 
772 /*
773  * ext4_es_lookup_extent() looks up an extent in extent status tree.
774  *
775  * ext4_es_lookup_extent is called by ext4_map_blocks/ext4_da_map_blocks.
776  *
777  * Return: 1 on found, 0 on not
778  */
779 int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
780                           struct extent_status *es)
781 {
782         struct ext4_es_tree *tree;
783         struct ext4_es_stats *stats;
784         struct extent_status *es1 = NULL;
785         struct rb_node *node;
786         int found = 0;
787 
788         trace_ext4_es_lookup_extent_enter(inode, lblk);
789         es_debug("lookup extent in block %u\n", lblk);
790 
791         tree = &EXT4_I(inode)->i_es_tree;
792         read_lock(&EXT4_I(inode)->i_es_lock);
793 
794         /* find extent in cache firstly */
795         es->es_lblk = es->es_len = es->es_pblk = 0;
796         if (tree->cache_es) {
797                 es1 = tree->cache_es;
798                 if (in_range(lblk, es1->es_lblk, es1->es_len)) {
799                         es_debug("%u cached by [%u/%u)\n",
800                                  lblk, es1->es_lblk, es1->es_len);
801                         found = 1;
802                         goto out;
803                 }
804         }
805 
806         node = tree->root.rb_node;
807         while (node) {
808                 es1 = rb_entry(node, struct extent_status, rb_node);
809                 if (lblk < es1->es_lblk)
810                         node = node->rb_left;
811                 else if (lblk > ext4_es_end(es1))
812                         node = node->rb_right;
813                 else {
814                         found = 1;
815                         break;
816                 }
817         }
818 
819 out:
820         stats = &EXT4_SB(inode->i_sb)->s_es_stats;
821         if (found) {
822                 BUG_ON(!es1);
823                 es->es_lblk = es1->es_lblk;
824                 es->es_len = es1->es_len;
825                 es->es_pblk = es1->es_pblk;
826                 if (!ext4_es_is_referenced(es1))
827                         ext4_es_set_referenced(es1);
828                 stats->es_stats_cache_hits++;
829         } else {
830                 stats->es_stats_cache_misses++;
831         }
832 
833         read_unlock(&EXT4_I(inode)->i_es_lock);
834 
835         trace_ext4_es_lookup_extent_exit(inode, es, found);
836         return found;
837 }
838 
839 static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
840                               ext4_lblk_t end)
841 {
842         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
843         struct rb_node *node;
844         struct extent_status *es;
845         struct extent_status orig_es;
846         ext4_lblk_t len1, len2;
847         ext4_fsblk_t block;
848         int err;
849 
850 retry:
851         err = 0;
852         es = __es_tree_search(&tree->root, lblk);
853         if (!es)
854                 goto out;
855         if (es->es_lblk > end)
856                 goto out;
857 
858         /* Simply invalidate cache_es. */
859         tree->cache_es = NULL;
860 
861         orig_es.es_lblk = es->es_lblk;
862         orig_es.es_len = es->es_len;
863         orig_es.es_pblk = es->es_pblk;
864 
865         len1 = lblk > es->es_lblk ? lblk - es->es_lblk : 0;
866         len2 = ext4_es_end(es) > end ? ext4_es_end(es) - end : 0;
867         if (len1 > 0)
868                 es->es_len = len1;
869         if (len2 > 0) {
870                 if (len1 > 0) {
871                         struct extent_status newes;
872 
873                         newes.es_lblk = end + 1;
874                         newes.es_len = len2;
875                         block = 0x7FDEADBEEFULL;
876                         if (ext4_es_is_written(&orig_es) ||
877                             ext4_es_is_unwritten(&orig_es))
878                                 block = ext4_es_pblock(&orig_es) +
879                                         orig_es.es_len - len2;
880                         ext4_es_store_pblock_status(&newes, block,
881                                                     ext4_es_status(&orig_es));
882                         err = __es_insert_extent(inode, &newes);
883                         if (err) {
884                                 es->es_lblk = orig_es.es_lblk;
885                                 es->es_len = orig_es.es_len;
886                                 if ((err == -ENOMEM) &&
887                                     __es_shrink(EXT4_SB(inode->i_sb),
888                                                         128, EXT4_I(inode)))
889                                         goto retry;
890                                 goto out;
891                         }
892                 } else {
893                         es->es_lblk = end + 1;
894                         es->es_len = len2;
895                         if (ext4_es_is_written(es) ||
896                             ext4_es_is_unwritten(es)) {
897                                 block = orig_es.es_pblk + orig_es.es_len - len2;
898                                 ext4_es_store_pblock(es, block);
899                         }
900                 }
901                 goto out;
902         }
903 
904         if (len1 > 0) {
905                 node = rb_next(&es->rb_node);
906                 if (node)
907                         es = rb_entry(node, struct extent_status, rb_node);
908                 else
909                         es = NULL;
910         }
911 
912         while (es && ext4_es_end(es) <= end) {
913                 node = rb_next(&es->rb_node);
914                 rb_erase(&es->rb_node, &tree->root);
915                 ext4_es_free_extent(inode, es);
916                 if (!node) {
917                         es = NULL;
918                         break;
919                 }
920                 es = rb_entry(node, struct extent_status, rb_node);
921         }
922 
923         if (es && es->es_lblk < end + 1) {
924                 ext4_lblk_t orig_len = es->es_len;
925 
926                 len1 = ext4_es_end(es) - end;
927                 es->es_lblk = end + 1;
928                 es->es_len = len1;
929                 if (ext4_es_is_written(es) || ext4_es_is_unwritten(es)) {
930                         block = es->es_pblk + orig_len - len1;
931                         ext4_es_store_pblock(es, block);
932                 }
933         }
934 
935 out:
936         return err;
937 }
938 
939 /*
940  * ext4_es_remove_extent() removes a space from a extent status tree.
941  *
942  * Return 0 on success, error code on failure.
943  */
944 int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
945                           ext4_lblk_t len)
946 {
947         ext4_lblk_t end;
948         int err = 0;
949 
950         trace_ext4_es_remove_extent(inode, lblk, len);
951         es_debug("remove [%u/%u) from extent status tree of inode %lu\n",
952                  lblk, len, inode->i_ino);
953 
954         if (!len)
955                 return err;
956 
957         end = lblk + len - 1;
958         BUG_ON(end < lblk);
959 
960         /*
961          * ext4_clear_inode() depends on us taking i_es_lock unconditionally
962          * so that we are sure __es_shrink() is done with the inode before it
963          * is reclaimed.
964          */
965         write_lock(&EXT4_I(inode)->i_es_lock);
966         err = __es_remove_extent(inode, lblk, end);
967         write_unlock(&EXT4_I(inode)->i_es_lock);
968         ext4_es_print_tree(inode);
969         return err;
970 }
971 
972 static int __es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
973                        struct ext4_inode_info *locked_ei)
974 {
975         struct ext4_inode_info *ei;
976         struct ext4_es_stats *es_stats;
977         ktime_t start_time;
978         u64 scan_time;
979         int nr_to_walk;
980         int nr_shrunk = 0;
981         int retried = 0, nr_skipped = 0;
982 
983         es_stats = &sbi->s_es_stats;
984         start_time = ktime_get();
985 
986 retry:
987         spin_lock(&sbi->s_es_lock);
988         nr_to_walk = sbi->s_es_nr_inode;
989         while (nr_to_walk-- > 0) {
990                 if (list_empty(&sbi->s_es_list)) {
991                         spin_unlock(&sbi->s_es_lock);
992                         goto out;
993                 }
994                 ei = list_first_entry(&sbi->s_es_list, struct ext4_inode_info,
995                                       i_es_list);
996                 /* Move the inode to the tail */
997                 list_move_tail(&ei->i_es_list, &sbi->s_es_list);
998 
999                 /*
1000                  * Normally we try hard to avoid shrinking precached inodes,
1001                  * but we will as a last resort.
1002                  */
1003                 if (!retried && ext4_test_inode_state(&ei->vfs_inode,
1004                                                 EXT4_STATE_EXT_PRECACHED)) {
1005                         nr_skipped++;
1006                         continue;
1007                 }
1008 
1009                 if (ei == locked_ei || !write_trylock(&ei->i_es_lock)) {
1010                         nr_skipped++;
1011                         continue;
1012                 }
1013                 /*
1014                  * Now we hold i_es_lock which protects us from inode reclaim
1015                  * freeing inode under us
1016                  */
1017                 spin_unlock(&sbi->s_es_lock);
1018 
1019                 nr_shrunk += es_reclaim_extents(ei, &nr_to_scan);
1020                 write_unlock(&ei->i_es_lock);
1021 
1022                 if (nr_to_scan <= 0)
1023                         goto out;
1024                 spin_lock(&sbi->s_es_lock);
1025         }
1026         spin_unlock(&sbi->s_es_lock);
1027 
1028         /*
1029          * If we skipped any inodes, and we weren't able to make any
1030          * forward progress, try again to scan precached inodes.
1031          */
1032         if ((nr_shrunk == 0) && nr_skipped && !retried) {
1033                 retried++;
1034                 goto retry;
1035         }
1036 
1037         if (locked_ei && nr_shrunk == 0)
1038                 nr_shrunk = es_reclaim_extents(locked_ei, &nr_to_scan);
1039 
1040 out:
1041         scan_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1042         if (likely(es_stats->es_stats_scan_time))
1043                 es_stats->es_stats_scan_time = (scan_time +
1044                                 es_stats->es_stats_scan_time*3) / 4;
1045         else
1046                 es_stats->es_stats_scan_time = scan_time;
1047         if (scan_time > es_stats->es_stats_max_scan_time)
1048                 es_stats->es_stats_max_scan_time = scan_time;
1049         if (likely(es_stats->es_stats_shrunk))
1050                 es_stats->es_stats_shrunk = (nr_shrunk +
1051                                 es_stats->es_stats_shrunk*3) / 4;
1052         else
1053                 es_stats->es_stats_shrunk = nr_shrunk;
1054 
1055         trace_ext4_es_shrink(sbi->s_sb, nr_shrunk, scan_time,
1056                              nr_skipped, retried);
1057         return nr_shrunk;
1058 }
1059 
1060 static unsigned long ext4_es_count(struct shrinker *shrink,
1061                                    struct shrink_control *sc)
1062 {
1063         unsigned long nr;
1064         struct ext4_sb_info *sbi;
1065 
1066         sbi = container_of(shrink, struct ext4_sb_info, s_es_shrinker);
1067         nr = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
1068         trace_ext4_es_shrink_count(sbi->s_sb, sc->nr_to_scan, nr);
1069         return nr;
1070 }
1071 
1072 static unsigned long ext4_es_scan(struct shrinker *shrink,
1073                                   struct shrink_control *sc)
1074 {
1075         struct ext4_sb_info *sbi = container_of(shrink,
1076                                         struct ext4_sb_info, s_es_shrinker);
1077         int nr_to_scan = sc->nr_to_scan;
1078         int ret, nr_shrunk;
1079 
1080         ret = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
1081         trace_ext4_es_shrink_scan_enter(sbi->s_sb, nr_to_scan, ret);
1082 
1083         if (!nr_to_scan)
1084                 return ret;
1085 
1086         nr_shrunk = __es_shrink(sbi, nr_to_scan, NULL);
1087 
1088         trace_ext4_es_shrink_scan_exit(sbi->s_sb, nr_shrunk, ret);
1089         return nr_shrunk;
1090 }
1091 
1092 int ext4_seq_es_shrinker_info_show(struct seq_file *seq, void *v)
1093 {
1094         struct ext4_sb_info *sbi = EXT4_SB((struct super_block *) seq->private);
1095         struct ext4_es_stats *es_stats = &sbi->s_es_stats;
1096         struct ext4_inode_info *ei, *max = NULL;
1097         unsigned int inode_cnt = 0;
1098 
1099         if (v != SEQ_START_TOKEN)
1100                 return 0;
1101 
1102         /* here we just find an inode that has the max nr. of objects */
1103         spin_lock(&sbi->s_es_lock);
1104         list_for_each_entry(ei, &sbi->s_es_list, i_es_list) {
1105                 inode_cnt++;
1106                 if (max && max->i_es_all_nr < ei->i_es_all_nr)
1107                         max = ei;
1108                 else if (!max)
1109                         max = ei;
1110         }
1111         spin_unlock(&sbi->s_es_lock);
1112 
1113         seq_printf(seq, "stats:\n  %lld objects\n  %lld reclaimable objects\n",
1114                    percpu_counter_sum_positive(&es_stats->es_stats_all_cnt),
1115                    percpu_counter_sum_positive(&es_stats->es_stats_shk_cnt));
1116         seq_printf(seq, "  %lu/%lu cache hits/misses\n",
1117                    es_stats->es_stats_cache_hits,
1118                    es_stats->es_stats_cache_misses);
1119         if (inode_cnt)
1120                 seq_printf(seq, "  %d inodes on list\n", inode_cnt);
1121 
1122         seq_printf(seq, "average:\n  %llu us scan time\n",
1123             div_u64(es_stats->es_stats_scan_time, 1000));
1124         seq_printf(seq, "  %lu shrunk objects\n", es_stats->es_stats_shrunk);
1125         if (inode_cnt)
1126                 seq_printf(seq,
1127                     "maximum:\n  %lu inode (%u objects, %u reclaimable)\n"
1128                     "  %llu us max scan time\n",
1129                     max->vfs_inode.i_ino, max->i_es_all_nr, max->i_es_shk_nr,
1130                     div_u64(es_stats->es_stats_max_scan_time, 1000));
1131 
1132         return 0;
1133 }
1134 
1135 int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
1136 {
1137         int err;
1138 
1139         /* Make sure we have enough bits for physical block number */
1140         BUILD_BUG_ON(ES_SHIFT < 48);
1141         INIT_LIST_HEAD(&sbi->s_es_list);
1142         sbi->s_es_nr_inode = 0;
1143         spin_lock_init(&sbi->s_es_lock);
1144         sbi->s_es_stats.es_stats_shrunk = 0;
1145         sbi->s_es_stats.es_stats_cache_hits = 0;
1146         sbi->s_es_stats.es_stats_cache_misses = 0;
1147         sbi->s_es_stats.es_stats_scan_time = 0;
1148         sbi->s_es_stats.es_stats_max_scan_time = 0;
1149         err = percpu_counter_init(&sbi->s_es_stats.es_stats_all_cnt, 0, GFP_KERNEL);
1150         if (err)
1151                 return err;
1152         err = percpu_counter_init(&sbi->s_es_stats.es_stats_shk_cnt, 0, GFP_KERNEL);
1153         if (err)
1154                 goto err1;
1155 
1156         sbi->s_es_shrinker.scan_objects = ext4_es_scan;
1157         sbi->s_es_shrinker.count_objects = ext4_es_count;
1158         sbi->s_es_shrinker.seeks = DEFAULT_SEEKS;
1159         err = register_shrinker(&sbi->s_es_shrinker);
1160         if (err)
1161                 goto err2;
1162 
1163         return 0;
1164 
1165 err2:
1166         percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
1167 err1:
1168         percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
1169         return err;
1170 }
1171 
1172 void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi)
1173 {
1174         percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
1175         percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
1176         unregister_shrinker(&sbi->s_es_shrinker);
1177 }
1178 
1179 /*
1180  * Shrink extents in given inode from ei->i_es_shrink_lblk till end. Scan at
1181  * most *nr_to_scan extents, update *nr_to_scan accordingly.
1182  *
1183  * Return 0 if we hit end of tree / interval, 1 if we exhausted nr_to_scan.
1184  * Increment *nr_shrunk by the number of reclaimed extents. Also update
1185  * ei->i_es_shrink_lblk to where we should continue scanning.
1186  */
1187 static int es_do_reclaim_extents(struct ext4_inode_info *ei, ext4_lblk_t end,
1188                                  int *nr_to_scan, int *nr_shrunk)
1189 {
1190         struct inode *inode = &ei->vfs_inode;
1191         struct ext4_es_tree *tree = &ei->i_es_tree;
1192         struct extent_status *es;
1193         struct rb_node *node;
1194 
1195         es = __es_tree_search(&tree->root, ei->i_es_shrink_lblk);
1196         if (!es)
1197                 goto out_wrap;
1198         node = &es->rb_node;
1199         while (*nr_to_scan > 0) {
1200                 if (es->es_lblk > end) {
1201                         ei->i_es_shrink_lblk = end + 1;
1202                         return 0;
1203                 }
1204 
1205                 (*nr_to_scan)--;
1206                 node = rb_next(&es->rb_node);
1207                 /*
1208                  * We can't reclaim delayed extent from status tree because
1209                  * fiemap, bigallic, and seek_data/hole need to use it.
1210                  */
1211                 if (ext4_es_is_delayed(es))
1212                         goto next;
1213                 if (ext4_es_is_referenced(es)) {
1214                         ext4_es_clear_referenced(es);
1215                         goto next;
1216                 }
1217 
1218                 rb_erase(&es->rb_node, &tree->root);
1219                 ext4_es_free_extent(inode, es);
1220                 (*nr_shrunk)++;
1221 next:
1222                 if (!node)
1223                         goto out_wrap;
1224                 es = rb_entry(node, struct extent_status, rb_node);
1225         }
1226         ei->i_es_shrink_lblk = es->es_lblk;
1227         return 1;
1228 out_wrap:
1229         ei->i_es_shrink_lblk = 0;
1230         return 0;
1231 }
1232 
1233 static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan)
1234 {
1235         struct inode *inode = &ei->vfs_inode;
1236         int nr_shrunk = 0;
1237         ext4_lblk_t start = ei->i_es_shrink_lblk;
1238         static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,
1239                                       DEFAULT_RATELIMIT_BURST);
1240 
1241         if (ei->i_es_shk_nr == 0)
1242                 return 0;
1243 
1244         if (ext4_test_inode_state(inode, EXT4_STATE_EXT_PRECACHED) &&
1245             __ratelimit(&_rs))
1246                 ext4_warning(inode->i_sb, "forced shrink of precached extents");
1247 
1248         if (!es_do_reclaim_extents(ei, EXT_MAX_BLOCKS, nr_to_scan, &nr_shrunk) &&
1249             start != 0)
1250                 es_do_reclaim_extents(ei, start - 1, nr_to_scan, &nr_shrunk);
1251 
1252         ei->i_es_tree.cache_es = NULL;
1253         return nr_shrunk;
1254 }
1255 

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