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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/rbtree.h>
 13 #include <linux/list_sort.h>
 14 #include <linux/proc_fs.h>
 15 #include <linux/seq_file.h>
 16 #include "ext4.h"
 17 #include "extents_status.h"
 18 
 19 #include <trace/events/ext4.h>
 20 
 21 /*
 22  * According to previous discussion in Ext4 Developer Workshop, we
 23  * will introduce a new structure called io tree to track all extent
 24  * status in order to solve some problems that we have met
 25  * (e.g. Reservation space warning), and provide extent-level locking.
 26  * Delay extent tree is the first step to achieve this goal.  It is
 27  * original built by Yongqiang Yang.  At that time it is called delay
 28  * extent tree, whose goal is only track delayed extents in memory to
 29  * simplify the implementation of fiemap and bigalloc, and introduce
 30  * lseek SEEK_DATA/SEEK_HOLE support.  That is why it is still called
 31  * delay extent tree at the first commit.  But for better understand
 32  * what it does, it has been rename to extent status tree.
 33  *
 34  * Step1:
 35  * Currently the first step has been done.  All delayed extents are
 36  * tracked in the tree.  It maintains the delayed extent when a delayed
 37  * allocation is issued, and the delayed extent is written out or
 38  * invalidated.  Therefore the implementation of fiemap and bigalloc
 39  * are simplified, and SEEK_DATA/SEEK_HOLE are introduced.
 40  *
 41  * The following comment describes the implemenmtation of extent
 42  * status tree and future works.
 43  *
 44  * Step2:
 45  * In this step all extent status are tracked by extent status tree.
 46  * Thus, we can first try to lookup a block mapping in this tree before
 47  * finding it in extent tree.  Hence, single extent cache can be removed
 48  * because extent status tree can do a better job.  Extents in status
 49  * tree are loaded on-demand.  Therefore, the extent status tree may not
 50  * contain all of the extents in a file.  Meanwhile we define a shrinker
 51  * to reclaim memory from extent status tree because fragmented extent
 52  * tree will make status tree cost too much memory.  written/unwritten/-
 53  * hole extents in the tree will be reclaimed by this shrinker when we
 54  * are under high memory pressure.  Delayed extents will not be
 55  * reclimed because fiemap, bigalloc, and seek_data/hole need it.
 56  */
 57 
 58 /*
 59  * Extent status tree implementation for ext4.
 60  *
 61  *
 62  * ==========================================================================
 63  * Extent status tree tracks all extent status.
 64  *
 65  * 1. Why we need to implement extent status tree?
 66  *
 67  * Without extent status tree, ext4 identifies a delayed extent by looking
 68  * up page cache, this has several deficiencies - complicated, buggy,
 69  * and inefficient code.
 70  *
 71  * FIEMAP, SEEK_HOLE/DATA, bigalloc, and writeout all need to know if a
 72  * block or a range of blocks are belonged to a delayed extent.
 73  *
 74  * Let us have a look at how they do without extent status tree.
 75  *   -- FIEMAP
 76  *      FIEMAP looks up page cache to identify delayed allocations from holes.
 77  *
 78  *   -- SEEK_HOLE/DATA
 79  *      SEEK_HOLE/DATA has the same problem as FIEMAP.
 80  *
 81  *   -- bigalloc
 82  *      bigalloc looks up page cache to figure out if a block is
 83  *      already under delayed allocation or not to determine whether
 84  *      quota reserving is needed for the cluster.
 85  *
 86  *   -- writeout
 87  *      Writeout looks up whole page cache to see if a buffer is
 88  *      mapped, If there are not very many delayed buffers, then it is
 89  *      time comsuming.
 90  *
 91  * With extent status tree implementation, FIEMAP, SEEK_HOLE/DATA,
 92  * bigalloc and writeout can figure out if a block or a range of
 93  * blocks is under delayed allocation(belonged to a delayed extent) or
 94  * not by searching the extent tree.
 95  *
 96  *
 97  * ==========================================================================
 98  * 2. Ext4 extent status tree impelmentation
 99  *
100  *   -- extent
101  *      A extent is a range of blocks which are contiguous logically and
102  *      physically.  Unlike extent in extent tree, this extent in ext4 is
103  *      a in-memory struct, there is no corresponding on-disk data.  There
104  *      is no limit on length of extent, so an extent can contain as many
105  *      blocks as they are contiguous logically and physically.
106  *
107  *   -- extent status tree
108  *      Every inode has an extent status tree and all allocation blocks
109  *      are added to the tree with different status.  The extent in the
110  *      tree are ordered by logical block no.
111  *
112  *   -- operations on a extent status tree
113  *      There are three important operations on a delayed extent tree: find
114  *      next extent, adding a extent(a range of blocks) and removing a extent.
115  *
116  *   -- race on a extent status tree
117  *      Extent status tree is protected by inode->i_es_lock.
118  *
119  *   -- memory consumption
120  *      Fragmented extent tree will make extent status tree cost too much
121  *      memory.  Hence, we will reclaim written/unwritten/hole extents from
122  *      the tree under a heavy memory pressure.
123  *
124  *
125  * ==========================================================================
126  * 3. Performance analysis
127  *
128  *   -- overhead
129  *      1. There is a cache extent for write access, so if writes are
130  *      not very random, adding space operaions are in O(1) time.
131  *
132  *   -- gain
133  *      2. Code is much simpler, more readable, more maintainable and
134  *      more efficient.
135  *
136  *
137  * ==========================================================================
138  * 4. TODO list
139  *
140  *   -- Refactor delayed space reservation
141  *
142  *   -- Extent-level locking
143  */
144 
145 static struct kmem_cache *ext4_es_cachep;
146 
147 static int __es_insert_extent(struct inode *inode, struct extent_status *newes);
148 static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
149                               ext4_lblk_t end);
150 static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan);
151 static int __es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
152                        struct ext4_inode_info *locked_ei);
153 
154 int __init ext4_init_es(void)
155 {
156         ext4_es_cachep = kmem_cache_create("ext4_extent_status",
157                                            sizeof(struct extent_status),
158                                            0, (SLAB_RECLAIM_ACCOUNT), NULL);
159         if (ext4_es_cachep == NULL)
160                 return -ENOMEM;
161         return 0;
162 }
163 
164 void ext4_exit_es(void)
165 {
166         if (ext4_es_cachep)
167                 kmem_cache_destroy(ext4_es_cachep);
168 }
169 
170 void ext4_es_init_tree(struct ext4_es_tree *tree)
171 {
172         tree->root = RB_ROOT;
173         tree->cache_es = NULL;
174 }
175 
176 #ifdef ES_DEBUG__
177 static void ext4_es_print_tree(struct inode *inode)
178 {
179         struct ext4_es_tree *tree;
180         struct rb_node *node;
181 
182         printk(KERN_DEBUG "status extents for inode %lu:", inode->i_ino);
183         tree = &EXT4_I(inode)->i_es_tree;
184         node = rb_first(&tree->root);
185         while (node) {
186                 struct extent_status *es;
187                 es = rb_entry(node, struct extent_status, rb_node);
188                 printk(KERN_DEBUG " [%u/%u) %llu %x",
189                        es->es_lblk, es->es_len,
190                        ext4_es_pblock(es), ext4_es_status(es));
191                 node = rb_next(node);
192         }
193         printk(KERN_DEBUG "\n");
194 }
195 #else
196 #define ext4_es_print_tree(inode)
197 #endif
198 
199 static inline ext4_lblk_t ext4_es_end(struct extent_status *es)
200 {
201         BUG_ON(es->es_lblk + es->es_len < es->es_lblk);
202         return es->es_lblk + es->es_len - 1;
203 }
204 
205 /*
206  * search through the tree for an delayed extent with a given offset.  If
207  * it can't be found, try to find next extent.
208  */
209 static struct extent_status *__es_tree_search(struct rb_root *root,
210                                               ext4_lblk_t lblk)
211 {
212         struct rb_node *node = root->rb_node;
213         struct extent_status *es = NULL;
214 
215         while (node) {
216                 es = rb_entry(node, struct extent_status, rb_node);
217                 if (lblk < es->es_lblk)
218                         node = node->rb_left;
219                 else if (lblk > ext4_es_end(es))
220                         node = node->rb_right;
221                 else
222                         return es;
223         }
224 
225         if (es && lblk < es->es_lblk)
226                 return es;
227 
228         if (es && lblk > ext4_es_end(es)) {
229                 node = rb_next(&es->rb_node);
230                 return node ? rb_entry(node, struct extent_status, rb_node) :
231                               NULL;
232         }
233 
234         return NULL;
235 }
236 
237 /*
238  * ext4_es_find_delayed_extent_range: find the 1st delayed extent covering
239  * @es->lblk if it exists, otherwise, the next extent after @es->lblk.
240  *
241  * @inode: the inode which owns delayed extents
242  * @lblk: the offset where we start to search
243  * @end: the offset where we stop to search
244  * @es: delayed extent that we found
245  */
246 void ext4_es_find_delayed_extent_range(struct inode *inode,
247                                  ext4_lblk_t lblk, ext4_lblk_t end,
248                                  struct extent_status *es)
249 {
250         struct ext4_es_tree *tree = NULL;
251         struct extent_status *es1 = NULL;
252         struct rb_node *node;
253 
254         BUG_ON(es == NULL);
255         BUG_ON(end < lblk);
256         trace_ext4_es_find_delayed_extent_range_enter(inode, lblk);
257 
258         read_lock(&EXT4_I(inode)->i_es_lock);
259         tree = &EXT4_I(inode)->i_es_tree;
260 
261         /* find extent in cache firstly */
262         es->es_lblk = es->es_len = es->es_pblk = 0;
263         if (tree->cache_es) {
264                 es1 = tree->cache_es;
265                 if (in_range(lblk, es1->es_lblk, es1->es_len)) {
266                         es_debug("%u cached by [%u/%u) %llu %x\n",
267                                  lblk, es1->es_lblk, es1->es_len,
268                                  ext4_es_pblock(es1), ext4_es_status(es1));
269                         goto out;
270                 }
271         }
272 
273         es1 = __es_tree_search(&tree->root, lblk);
274 
275 out:
276         if (es1 && !ext4_es_is_delayed(es1)) {
277                 while ((node = rb_next(&es1->rb_node)) != NULL) {
278                         es1 = rb_entry(node, struct extent_status, rb_node);
279                         if (es1->es_lblk > end) {
280                                 es1 = NULL;
281                                 break;
282                         }
283                         if (ext4_es_is_delayed(es1))
284                                 break;
285                 }
286         }
287 
288         if (es1 && ext4_es_is_delayed(es1)) {
289                 tree->cache_es = es1;
290                 es->es_lblk = es1->es_lblk;
291                 es->es_len = es1->es_len;
292                 es->es_pblk = es1->es_pblk;
293         }
294 
295         read_unlock(&EXT4_I(inode)->i_es_lock);
296 
297         trace_ext4_es_find_delayed_extent_range_exit(inode, es);
298 }
299 
300 static void ext4_es_list_add(struct inode *inode)
301 {
302         struct ext4_inode_info *ei = EXT4_I(inode);
303         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
304 
305         if (!list_empty(&ei->i_es_list))
306                 return;
307 
308         spin_lock(&sbi->s_es_lock);
309         if (list_empty(&ei->i_es_list)) {
310                 list_add_tail(&ei->i_es_list, &sbi->s_es_list);
311                 sbi->s_es_nr_inode++;
312         }
313         spin_unlock(&sbi->s_es_lock);
314 }
315 
316 static void ext4_es_list_del(struct inode *inode)
317 {
318         struct ext4_inode_info *ei = EXT4_I(inode);
319         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
320 
321         spin_lock(&sbi->s_es_lock);
322         if (!list_empty(&ei->i_es_list)) {
323                 list_del_init(&ei->i_es_list);
324                 sbi->s_es_nr_inode--;
325                 WARN_ON_ONCE(sbi->s_es_nr_inode < 0);
326         }
327         spin_unlock(&sbi->s_es_lock);
328 }
329 
330 static struct extent_status *
331 ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
332                      ext4_fsblk_t pblk)
333 {
334         struct extent_status *es;
335         es = kmem_cache_alloc(ext4_es_cachep, GFP_ATOMIC);
336         if (es == NULL)
337                 return NULL;
338         es->es_lblk = lblk;
339         es->es_len = len;
340         es->es_pblk = pblk;
341 
342         /*
343          * We don't count delayed extent because we never try to reclaim them
344          */
345         if (!ext4_es_is_delayed(es)) {
346                 if (!EXT4_I(inode)->i_es_shk_nr++)
347                         ext4_es_list_add(inode);
348                 percpu_counter_inc(&EXT4_SB(inode->i_sb)->
349                                         s_es_stats.es_stats_shk_cnt);
350         }
351 
352         EXT4_I(inode)->i_es_all_nr++;
353         percpu_counter_inc(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
354 
355         return es;
356 }
357 
358 static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
359 {
360         EXT4_I(inode)->i_es_all_nr--;
361         percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
362 
363         /* Decrease the shrink counter when this es is not delayed */
364         if (!ext4_es_is_delayed(es)) {
365                 BUG_ON(EXT4_I(inode)->i_es_shk_nr == 0);
366                 if (!--EXT4_I(inode)->i_es_shk_nr)
367                         ext4_es_list_del(inode);
368                 percpu_counter_dec(&EXT4_SB(inode->i_sb)->
369                                         s_es_stats.es_stats_shk_cnt);
370         }
371 
372         kmem_cache_free(ext4_es_cachep, es);
373 }
374 
375 /*
376  * Check whether or not two extents can be merged
377  * Condition:
378  *  - logical block number is contiguous
379  *  - physical block number is contiguous
380  *  - status is equal
381  */
382 static int ext4_es_can_be_merged(struct extent_status *es1,
383                                  struct extent_status *es2)
384 {
385         if (ext4_es_type(es1) != ext4_es_type(es2))
386                 return 0;
387 
388         if (((__u64) es1->es_len) + es2->es_len > EXT_MAX_BLOCKS) {
389                 pr_warn("ES assertion failed when merging extents. "
390                         "The sum of lengths of es1 (%d) and es2 (%d) "
391                         "is bigger than allowed file size (%d)\n",
392                         es1->es_len, es2->es_len, EXT_MAX_BLOCKS);
393                 WARN_ON(1);
394                 return 0;
395         }
396 
397         if (((__u64) es1->es_lblk) + es1->es_len != es2->es_lblk)
398                 return 0;
399 
400         if ((ext4_es_is_written(es1) || ext4_es_is_unwritten(es1)) &&
401             (ext4_es_pblock(es1) + es1->es_len == ext4_es_pblock(es2)))
402                 return 1;
403 
404         if (ext4_es_is_hole(es1))
405                 return 1;
406 
407         /* we need to check delayed extent is without unwritten status */
408         if (ext4_es_is_delayed(es1) && !ext4_es_is_unwritten(es1))
409                 return 1;
410 
411         return 0;
412 }
413 
414 static struct extent_status *
415 ext4_es_try_to_merge_left(struct inode *inode, struct extent_status *es)
416 {
417         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
418         struct extent_status *es1;
419         struct rb_node *node;
420 
421         node = rb_prev(&es->rb_node);
422         if (!node)
423                 return es;
424 
425         es1 = rb_entry(node, struct extent_status, rb_node);
426         if (ext4_es_can_be_merged(es1, es)) {
427                 es1->es_len += es->es_len;
428                 if (ext4_es_is_referenced(es))
429                         ext4_es_set_referenced(es1);
430                 rb_erase(&es->rb_node, &tree->root);
431                 ext4_es_free_extent(inode, es);
432                 es = es1;
433         }
434 
435         return es;
436 }
437 
438 static struct extent_status *
439 ext4_es_try_to_merge_right(struct inode *inode, struct extent_status *es)
440 {
441         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
442         struct extent_status *es1;
443         struct rb_node *node;
444 
445         node = rb_next(&es->rb_node);
446         if (!node)
447                 return es;
448 
449         es1 = rb_entry(node, struct extent_status, rb_node);
450         if (ext4_es_can_be_merged(es, es1)) {
451                 es->es_len += es1->es_len;
452                 if (ext4_es_is_referenced(es1))
453                         ext4_es_set_referenced(es);
454                 rb_erase(node, &tree->root);
455                 ext4_es_free_extent(inode, es1);
456         }
457 
458         return es;
459 }
460 
461 #ifdef ES_AGGRESSIVE_TEST
462 #include "ext4_extents.h"       /* Needed when ES_AGGRESSIVE_TEST is defined */
463 
464 static void ext4_es_insert_extent_ext_check(struct inode *inode,
465                                             struct extent_status *es)
466 {
467         struct ext4_ext_path *path = NULL;
468         struct ext4_extent *ex;
469         ext4_lblk_t ee_block;
470         ext4_fsblk_t ee_start;
471         unsigned short ee_len;
472         int depth, ee_status, es_status;
473 
474         path = ext4_find_extent(inode, es->es_lblk, NULL, EXT4_EX_NOCACHE);
475         if (IS_ERR(path))
476                 return;
477 
478         depth = ext_depth(inode);
479         ex = path[depth].p_ext;
480 
481         if (ex) {
482 
483                 ee_block = le32_to_cpu(ex->ee_block);
484                 ee_start = ext4_ext_pblock(ex);
485                 ee_len = ext4_ext_get_actual_len(ex);
486 
487                 ee_status = ext4_ext_is_unwritten(ex) ? 1 : 0;
488                 es_status = ext4_es_is_unwritten(es) ? 1 : 0;
489 
490                 /*
491                  * Make sure ex and es are not overlap when we try to insert
492                  * a delayed/hole extent.
493                  */
494                 if (!ext4_es_is_written(es) && !ext4_es_is_unwritten(es)) {
495                         if (in_range(es->es_lblk, ee_block, ee_len)) {
496                                 pr_warn("ES insert assertion failed for "
497                                         "inode: %lu we can find an extent "
498                                         "at block [%d/%d/%llu/%c], but we "
499                                         "want to add a delayed/hole extent "
500                                         "[%d/%d/%llu/%x]\n",
501                                         inode->i_ino, ee_block, ee_len,
502                                         ee_start, ee_status ? 'u' : 'w',
503                                         es->es_lblk, es->es_len,
504                                         ext4_es_pblock(es), ext4_es_status(es));
505                         }
506                         goto out;
507                 }
508 
509                 /*
510                  * We don't check ee_block == es->es_lblk, etc. because es
511                  * might be a part of whole extent, vice versa.
512                  */
513                 if (es->es_lblk < ee_block ||
514                     ext4_es_pblock(es) != ee_start + es->es_lblk - ee_block) {
515                         pr_warn("ES insert assertion failed for inode: %lu "
516                                 "ex_status [%d/%d/%llu/%c] != "
517                                 "es_status [%d/%d/%llu/%c]\n", inode->i_ino,
518                                 ee_block, ee_len, ee_start,
519                                 ee_status ? 'u' : 'w', es->es_lblk, es->es_len,
520                                 ext4_es_pblock(es), es_status ? 'u' : 'w');
521                         goto out;
522                 }
523 
524                 if (ee_status ^ es_status) {
525                         pr_warn("ES insert assertion failed for inode: %lu "
526                                 "ex_status [%d/%d/%llu/%c] != "
527                                 "es_status [%d/%d/%llu/%c]\n", inode->i_ino,
528                                 ee_block, ee_len, ee_start,
529                                 ee_status ? 'u' : 'w', es->es_lblk, es->es_len,
530                                 ext4_es_pblock(es), es_status ? 'u' : 'w');
531                 }
532         } else {
533                 /*
534                  * We can't find an extent on disk.  So we need to make sure
535                  * that we don't want to add an written/unwritten extent.
536                  */
537                 if (!ext4_es_is_delayed(es) && !ext4_es_is_hole(es)) {
538                         pr_warn("ES insert assertion failed for inode: %lu "
539                                 "can't find an extent at block %d but we want "
540                                 "to add a written/unwritten extent "
541                                 "[%d/%d/%llu/%x]\n", inode->i_ino,
542                                 es->es_lblk, es->es_lblk, es->es_len,
543                                 ext4_es_pblock(es), ext4_es_status(es));
544                 }
545         }
546 out:
547         ext4_ext_drop_refs(path);
548         kfree(path);
549 }
550 
551 static void ext4_es_insert_extent_ind_check(struct inode *inode,
552                                             struct extent_status *es)
553 {
554         struct ext4_map_blocks map;
555         int retval;
556 
557         /*
558          * Here we call ext4_ind_map_blocks to lookup a block mapping because
559          * 'Indirect' structure is defined in indirect.c.  So we couldn't
560          * access direct/indirect tree from outside.  It is too dirty to define
561          * this function in indirect.c file.
562          */
563 
564         map.m_lblk = es->es_lblk;
565         map.m_len = es->es_len;
566 
567         retval = ext4_ind_map_blocks(NULL, inode, &map, 0);
568         if (retval > 0) {
569                 if (ext4_es_is_delayed(es) || ext4_es_is_hole(es)) {
570                         /*
571                          * We want to add a delayed/hole extent but this
572                          * block has been allocated.
573                          */
574                         pr_warn("ES insert assertion failed for inode: %lu "
575                                 "We can find blocks but we want to add a "
576                                 "delayed/hole extent [%d/%d/%llu/%x]\n",
577                                 inode->i_ino, es->es_lblk, es->es_len,
578                                 ext4_es_pblock(es), ext4_es_status(es));
579                         return;
580                 } else if (ext4_es_is_written(es)) {
581                         if (retval != es->es_len) {
582                                 pr_warn("ES insert assertion failed for "
583                                         "inode: %lu retval %d != es_len %d\n",
584                                         inode->i_ino, retval, es->es_len);
585                                 return;
586                         }
587                         if (map.m_pblk != ext4_es_pblock(es)) {
588                                 pr_warn("ES insert assertion failed for "
589                                         "inode: %lu m_pblk %llu != "
590                                         "es_pblk %llu\n",
591                                         inode->i_ino, map.m_pblk,
592                                         ext4_es_pblock(es));
593                                 return;
594                         }
595                 } else {
596                         /*
597                          * We don't need to check unwritten extent because
598                          * indirect-based file doesn't have it.
599                          */
600                         BUG_ON(1);
601                 }
602         } else if (retval == 0) {
603                 if (ext4_es_is_written(es)) {
604                         pr_warn("ES insert assertion failed for inode: %lu "
605                                 "We can't find the block but we want to add "
606                                 "a written extent [%d/%d/%llu/%x]\n",
607                                 inode->i_ino, es->es_lblk, es->es_len,
608                                 ext4_es_pblock(es), ext4_es_status(es));
609                         return;
610                 }
611         }
612 }
613 
614 static inline void ext4_es_insert_extent_check(struct inode *inode,
615                                                struct extent_status *es)
616 {
617         /*
618          * We don't need to worry about the race condition because
619          * caller takes i_data_sem locking.
620          */
621         BUG_ON(!rwsem_is_locked(&EXT4_I(inode)->i_data_sem));
622         if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
623                 ext4_es_insert_extent_ext_check(inode, es);
624         else
625                 ext4_es_insert_extent_ind_check(inode, es);
626 }
627 #else
628 static inline void ext4_es_insert_extent_check(struct inode *inode,
629                                                struct extent_status *es)
630 {
631 }
632 #endif
633 
634 static int __es_insert_extent(struct inode *inode, struct extent_status *newes)
635 {
636         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
637         struct rb_node **p = &tree->root.rb_node;
638         struct rb_node *parent = NULL;
639         struct extent_status *es;
640 
641         while (*p) {
642                 parent = *p;
643                 es = rb_entry(parent, struct extent_status, rb_node);
644 
645                 if (newes->es_lblk < es->es_lblk) {
646                         if (ext4_es_can_be_merged(newes, es)) {
647                                 /*
648                                  * Here we can modify es_lblk directly
649                                  * because it isn't overlapped.
650                                  */
651                                 es->es_lblk = newes->es_lblk;
652                                 es->es_len += newes->es_len;
653                                 if (ext4_es_is_written(es) ||
654                                     ext4_es_is_unwritten(es))
655                                         ext4_es_store_pblock(es,
656                                                              newes->es_pblk);
657                                 es = ext4_es_try_to_merge_left(inode, es);
658                                 goto out;
659                         }
660                         p = &(*p)->rb_left;
661                 } else if (newes->es_lblk > ext4_es_end(es)) {
662                         if (ext4_es_can_be_merged(es, newes)) {
663                                 es->es_len += newes->es_len;
664                                 es = ext4_es_try_to_merge_right(inode, es);
665                                 goto out;
666                         }
667                         p = &(*p)->rb_right;
668                 } else {
669                         BUG_ON(1);
670                         return -EINVAL;
671                 }
672         }
673 
674         es = ext4_es_alloc_extent(inode, newes->es_lblk, newes->es_len,
675                                   newes->es_pblk);
676         if (!es)
677                 return -ENOMEM;
678         rb_link_node(&es->rb_node, parent, p);
679         rb_insert_color(&es->rb_node, &tree->root);
680 
681 out:
682         tree->cache_es = es;
683         return 0;
684 }
685 
686 /*
687  * ext4_es_insert_extent() adds information to an inode's extent
688  * status tree.
689  *
690  * Return 0 on success, error code on failure.
691  */
692 int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
693                           ext4_lblk_t len, ext4_fsblk_t pblk,
694                           unsigned int status)
695 {
696         struct extent_status newes;
697         ext4_lblk_t end = lblk + len - 1;
698         int err = 0;
699 
700         es_debug("add [%u/%u) %llu %x to extent status tree of inode %lu\n",
701                  lblk, len, pblk, status, inode->i_ino);
702 
703         if (!len)
704                 return 0;
705 
706         BUG_ON(end < lblk);
707 
708         newes.es_lblk = lblk;
709         newes.es_len = len;
710         ext4_es_store_pblock_status(&newes, pblk, status);
711         trace_ext4_es_insert_extent(inode, &newes);
712 
713         ext4_es_insert_extent_check(inode, &newes);
714 
715         write_lock(&EXT4_I(inode)->i_es_lock);
716         err = __es_remove_extent(inode, lblk, end);
717         if (err != 0)
718                 goto error;
719 retry:
720         err = __es_insert_extent(inode, &newes);
721         if (err == -ENOMEM && __es_shrink(EXT4_SB(inode->i_sb),
722                                           128, EXT4_I(inode)))
723                 goto retry;
724         if (err == -ENOMEM && !ext4_es_is_delayed(&newes))
725                 err = 0;
726 
727 error:
728         write_unlock(&EXT4_I(inode)->i_es_lock);
729 
730         ext4_es_print_tree(inode);
731 
732         return err;
733 }
734 
735 /*
736  * ext4_es_cache_extent() inserts information into the extent status
737  * tree if and only if there isn't information about the range in
738  * question already.
739  */
740 void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
741                           ext4_lblk_t len, ext4_fsblk_t pblk,
742                           unsigned int status)
743 {
744         struct extent_status *es;
745         struct extent_status newes;
746         ext4_lblk_t end = lblk + len - 1;
747 
748         newes.es_lblk = lblk;
749         newes.es_len = len;
750         ext4_es_store_pblock_status(&newes, pblk, status);
751         trace_ext4_es_cache_extent(inode, &newes);
752 
753         if (!len)
754                 return;
755 
756         BUG_ON(end < lblk);
757 
758         write_lock(&EXT4_I(inode)->i_es_lock);
759 
760         es = __es_tree_search(&EXT4_I(inode)->i_es_tree.root, lblk);
761         if (!es || es->es_lblk > end)
762                 __es_insert_extent(inode, &newes);
763         write_unlock(&EXT4_I(inode)->i_es_lock);
764 }
765 
766 /*
767  * ext4_es_lookup_extent() looks up an extent in extent status tree.
768  *
769  * ext4_es_lookup_extent is called by ext4_map_blocks/ext4_da_map_blocks.
770  *
771  * Return: 1 on found, 0 on not
772  */
773 int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
774                           struct extent_status *es)
775 {
776         struct ext4_es_tree *tree;
777         struct ext4_es_stats *stats;
778         struct extent_status *es1 = NULL;
779         struct rb_node *node;
780         int found = 0;
781 
782         trace_ext4_es_lookup_extent_enter(inode, lblk);
783         es_debug("lookup extent in block %u\n", lblk);
784 
785         tree = &EXT4_I(inode)->i_es_tree;
786         read_lock(&EXT4_I(inode)->i_es_lock);
787 
788         /* find extent in cache firstly */
789         es->es_lblk = es->es_len = es->es_pblk = 0;
790         if (tree->cache_es) {
791                 es1 = tree->cache_es;
792                 if (in_range(lblk, es1->es_lblk, es1->es_len)) {
793                         es_debug("%u cached by [%u/%u)\n",
794                                  lblk, es1->es_lblk, es1->es_len);
795                         found = 1;
796                         goto out;
797                 }
798         }
799 
800         node = tree->root.rb_node;
801         while (node) {
802                 es1 = rb_entry(node, struct extent_status, rb_node);
803                 if (lblk < es1->es_lblk)
804                         node = node->rb_left;
805                 else if (lblk > ext4_es_end(es1))
806                         node = node->rb_right;
807                 else {
808                         found = 1;
809                         break;
810                 }
811         }
812 
813 out:
814         stats = &EXT4_SB(inode->i_sb)->s_es_stats;
815         if (found) {
816                 BUG_ON(!es1);
817                 es->es_lblk = es1->es_lblk;
818                 es->es_len = es1->es_len;
819                 es->es_pblk = es1->es_pblk;
820                 if (!ext4_es_is_referenced(es))
821                         ext4_es_set_referenced(es);
822                 stats->es_stats_cache_hits++;
823         } else {
824                 stats->es_stats_cache_misses++;
825         }
826 
827         read_unlock(&EXT4_I(inode)->i_es_lock);
828 
829         trace_ext4_es_lookup_extent_exit(inode, es, found);
830         return found;
831 }
832 
833 static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
834                               ext4_lblk_t end)
835 {
836         struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
837         struct rb_node *node;
838         struct extent_status *es;
839         struct extent_status orig_es;
840         ext4_lblk_t len1, len2;
841         ext4_fsblk_t block;
842         int err;
843 
844 retry:
845         err = 0;
846         es = __es_tree_search(&tree->root, lblk);
847         if (!es)
848                 goto out;
849         if (es->es_lblk > end)
850                 goto out;
851 
852         /* Simply invalidate cache_es. */
853         tree->cache_es = NULL;
854 
855         orig_es.es_lblk = es->es_lblk;
856         orig_es.es_len = es->es_len;
857         orig_es.es_pblk = es->es_pblk;
858 
859         len1 = lblk > es->es_lblk ? lblk - es->es_lblk : 0;
860         len2 = ext4_es_end(es) > end ? ext4_es_end(es) - end : 0;
861         if (len1 > 0)
862                 es->es_len = len1;
863         if (len2 > 0) {
864                 if (len1 > 0) {
865                         struct extent_status newes;
866 
867                         newes.es_lblk = end + 1;
868                         newes.es_len = len2;
869                         block = 0x7FDEADBEEFULL;
870                         if (ext4_es_is_written(&orig_es) ||
871                             ext4_es_is_unwritten(&orig_es))
872                                 block = ext4_es_pblock(&orig_es) +
873                                         orig_es.es_len - len2;
874                         ext4_es_store_pblock_status(&newes, block,
875                                                     ext4_es_status(&orig_es));
876                         err = __es_insert_extent(inode, &newes);
877                         if (err) {
878                                 es->es_lblk = orig_es.es_lblk;
879                                 es->es_len = orig_es.es_len;
880                                 if ((err == -ENOMEM) &&
881                                     __es_shrink(EXT4_SB(inode->i_sb),
882                                                         128, EXT4_I(inode)))
883                                         goto retry;
884                                 goto out;
885                         }
886                 } else {
887                         es->es_lblk = end + 1;
888                         es->es_len = len2;
889                         if (ext4_es_is_written(es) ||
890                             ext4_es_is_unwritten(es)) {
891                                 block = orig_es.es_pblk + orig_es.es_len - len2;
892                                 ext4_es_store_pblock(es, block);
893                         }
894                 }
895                 goto out;
896         }
897 
898         if (len1 > 0) {
899                 node = rb_next(&es->rb_node);
900                 if (node)
901                         es = rb_entry(node, struct extent_status, rb_node);
902                 else
903                         es = NULL;
904         }
905 
906         while (es && ext4_es_end(es) <= end) {
907                 node = rb_next(&es->rb_node);
908                 rb_erase(&es->rb_node, &tree->root);
909                 ext4_es_free_extent(inode, es);
910                 if (!node) {
911                         es = NULL;
912                         break;
913                 }
914                 es = rb_entry(node, struct extent_status, rb_node);
915         }
916 
917         if (es && es->es_lblk < end + 1) {
918                 ext4_lblk_t orig_len = es->es_len;
919 
920                 len1 = ext4_es_end(es) - end;
921                 es->es_lblk = end + 1;
922                 es->es_len = len1;
923                 if (ext4_es_is_written(es) || ext4_es_is_unwritten(es)) {
924                         block = es->es_pblk + orig_len - len1;
925                         ext4_es_store_pblock(es, block);
926                 }
927         }
928 
929 out:
930         return err;
931 }
932 
933 /*
934  * ext4_es_remove_extent() removes a space from a extent status tree.
935  *
936  * Return 0 on success, error code on failure.
937  */
938 int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
939                           ext4_lblk_t len)
940 {
941         ext4_lblk_t end;
942         int err = 0;
943 
944         trace_ext4_es_remove_extent(inode, lblk, len);
945         es_debug("remove [%u/%u) from extent status tree of inode %lu\n",
946                  lblk, len, inode->i_ino);
947 
948         if (!len)
949                 return err;
950 
951         end = lblk + len - 1;
952         BUG_ON(end < lblk);
953 
954         /*
955          * ext4_clear_inode() depends on us taking i_es_lock unconditionally
956          * so that we are sure __es_shrink() is done with the inode before it
957          * is reclaimed.
958          */
959         write_lock(&EXT4_I(inode)->i_es_lock);
960         err = __es_remove_extent(inode, lblk, end);
961         write_unlock(&EXT4_I(inode)->i_es_lock);
962         ext4_es_print_tree(inode);
963         return err;
964 }
965 
966 static int __es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
967                        struct ext4_inode_info *locked_ei)
968 {
969         struct ext4_inode_info *ei;
970         struct ext4_es_stats *es_stats;
971         ktime_t start_time;
972         u64 scan_time;
973         int nr_to_walk;
974         int nr_shrunk = 0;
975         int retried = 0, nr_skipped = 0;
976 
977         es_stats = &sbi->s_es_stats;
978         start_time = ktime_get();
979 
980 retry:
981         spin_lock(&sbi->s_es_lock);
982         nr_to_walk = sbi->s_es_nr_inode;
983         while (nr_to_walk-- > 0) {
984                 if (list_empty(&sbi->s_es_list)) {
985                         spin_unlock(&sbi->s_es_lock);
986                         goto out;
987                 }
988                 ei = list_first_entry(&sbi->s_es_list, struct ext4_inode_info,
989                                       i_es_list);
990                 /* Move the inode to the tail */
991                 list_move_tail(&ei->i_es_list, &sbi->s_es_list);
992 
993                 /*
994                  * Normally we try hard to avoid shrinking precached inodes,
995                  * but we will as a last resort.
996                  */
997                 if (!retried && ext4_test_inode_state(&ei->vfs_inode,
998                                                 EXT4_STATE_EXT_PRECACHED)) {
999                         nr_skipped++;
1000                         continue;
1001                 }
1002 
1003                 if (ei == locked_ei || !write_trylock(&ei->i_es_lock)) {
1004                         nr_skipped++;
1005                         continue;
1006                 }
1007                 /*
1008                  * Now we hold i_es_lock which protects us from inode reclaim
1009                  * freeing inode under us
1010                  */
1011                 spin_unlock(&sbi->s_es_lock);
1012 
1013                 nr_shrunk += es_reclaim_extents(ei, &nr_to_scan);
1014                 write_unlock(&ei->i_es_lock);
1015 
1016                 if (nr_to_scan <= 0)
1017                         goto out;
1018                 spin_lock(&sbi->s_es_lock);
1019         }
1020         spin_unlock(&sbi->s_es_lock);
1021 
1022         /*
1023          * If we skipped any inodes, and we weren't able to make any
1024          * forward progress, try again to scan precached inodes.
1025          */
1026         if ((nr_shrunk == 0) && nr_skipped && !retried) {
1027                 retried++;
1028                 goto retry;
1029         }
1030 
1031         if (locked_ei && nr_shrunk == 0)
1032                 nr_shrunk = es_reclaim_extents(locked_ei, &nr_to_scan);
1033 
1034 out:
1035         scan_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1036         if (likely(es_stats->es_stats_scan_time))
1037                 es_stats->es_stats_scan_time = (scan_time +
1038                                 es_stats->es_stats_scan_time*3) / 4;
1039         else
1040                 es_stats->es_stats_scan_time = scan_time;
1041         if (scan_time > es_stats->es_stats_max_scan_time)
1042                 es_stats->es_stats_max_scan_time = scan_time;
1043         if (likely(es_stats->es_stats_shrunk))
1044                 es_stats->es_stats_shrunk = (nr_shrunk +
1045                                 es_stats->es_stats_shrunk*3) / 4;
1046         else
1047                 es_stats->es_stats_shrunk = nr_shrunk;
1048 
1049         trace_ext4_es_shrink(sbi->s_sb, nr_shrunk, scan_time,
1050                              nr_skipped, retried);
1051         return nr_shrunk;
1052 }
1053 
1054 static unsigned long ext4_es_count(struct shrinker *shrink,
1055                                    struct shrink_control *sc)
1056 {
1057         unsigned long nr;
1058         struct ext4_sb_info *sbi;
1059 
1060         sbi = container_of(shrink, struct ext4_sb_info, s_es_shrinker);
1061         nr = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
1062         trace_ext4_es_shrink_count(sbi->s_sb, sc->nr_to_scan, nr);
1063         return nr;
1064 }
1065 
1066 static unsigned long ext4_es_scan(struct shrinker *shrink,
1067                                   struct shrink_control *sc)
1068 {
1069         struct ext4_sb_info *sbi = container_of(shrink,
1070                                         struct ext4_sb_info, s_es_shrinker);
1071         int nr_to_scan = sc->nr_to_scan;
1072         int ret, nr_shrunk;
1073 
1074         ret = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
1075         trace_ext4_es_shrink_scan_enter(sbi->s_sb, nr_to_scan, ret);
1076 
1077         if (!nr_to_scan)
1078                 return ret;
1079 
1080         nr_shrunk = __es_shrink(sbi, nr_to_scan, NULL);
1081 
1082         trace_ext4_es_shrink_scan_exit(sbi->s_sb, nr_shrunk, ret);
1083         return nr_shrunk;
1084 }
1085 
1086 static void *ext4_es_seq_shrinker_info_start(struct seq_file *seq, loff_t *pos)
1087 {
1088         return *pos ? NULL : SEQ_START_TOKEN;
1089 }
1090 
1091 static void *
1092 ext4_es_seq_shrinker_info_next(struct seq_file *seq, void *v, loff_t *pos)
1093 {
1094         return NULL;
1095 }
1096 
1097 static int ext4_es_seq_shrinker_info_show(struct seq_file *seq, void *v)
1098 {
1099         struct ext4_sb_info *sbi = seq->private;
1100         struct ext4_es_stats *es_stats = &sbi->s_es_stats;
1101         struct ext4_inode_info *ei, *max = NULL;
1102         unsigned int inode_cnt = 0;
1103 
1104         if (v != SEQ_START_TOKEN)
1105                 return 0;
1106 
1107         /* here we just find an inode that has the max nr. of objects */
1108         spin_lock(&sbi->s_es_lock);
1109         list_for_each_entry(ei, &sbi->s_es_list, i_es_list) {
1110                 inode_cnt++;
1111                 if (max && max->i_es_all_nr < ei->i_es_all_nr)
1112                         max = ei;
1113                 else if (!max)
1114                         max = ei;
1115         }
1116         spin_unlock(&sbi->s_es_lock);
1117 
1118         seq_printf(seq, "stats:\n  %lld objects\n  %lld reclaimable objects\n",
1119                    percpu_counter_sum_positive(&es_stats->es_stats_all_cnt),
1120                    percpu_counter_sum_positive(&es_stats->es_stats_shk_cnt));
1121         seq_printf(seq, "  %lu/%lu cache hits/misses\n",
1122                    es_stats->es_stats_cache_hits,
1123                    es_stats->es_stats_cache_misses);
1124         if (inode_cnt)
1125                 seq_printf(seq, "  %d inodes on list\n", inode_cnt);
1126 
1127         seq_printf(seq, "average:\n  %llu us scan time\n",
1128             div_u64(es_stats->es_stats_scan_time, 1000));
1129         seq_printf(seq, "  %lu shrunk objects\n", es_stats->es_stats_shrunk);
1130         if (inode_cnt)
1131                 seq_printf(seq,
1132                     "maximum:\n  %lu inode (%u objects, %u reclaimable)\n"
1133                     "  %llu us max scan time\n",
1134                     max->vfs_inode.i_ino, max->i_es_all_nr, max->i_es_shk_nr,
1135                     div_u64(es_stats->es_stats_max_scan_time, 1000));
1136 
1137         return 0;
1138 }
1139 
1140 static void ext4_es_seq_shrinker_info_stop(struct seq_file *seq, void *v)
1141 {
1142 }
1143 
1144 static const struct seq_operations ext4_es_seq_shrinker_info_ops = {
1145         .start = ext4_es_seq_shrinker_info_start,
1146         .next  = ext4_es_seq_shrinker_info_next,
1147         .stop  = ext4_es_seq_shrinker_info_stop,
1148         .show  = ext4_es_seq_shrinker_info_show,
1149 };
1150 
1151 static int
1152 ext4_es_seq_shrinker_info_open(struct inode *inode, struct file *file)
1153 {
1154         int ret;
1155 
1156         ret = seq_open(file, &ext4_es_seq_shrinker_info_ops);
1157         if (!ret) {
1158                 struct seq_file *m = file->private_data;
1159                 m->private = PDE_DATA(inode);
1160         }
1161 
1162         return ret;
1163 }
1164 
1165 static int
1166 ext4_es_seq_shrinker_info_release(struct inode *inode, struct file *file)
1167 {
1168         return seq_release(inode, file);
1169 }
1170 
1171 static const struct file_operations ext4_es_seq_shrinker_info_fops = {
1172         .owner          = THIS_MODULE,
1173         .open           = ext4_es_seq_shrinker_info_open,
1174         .read           = seq_read,
1175         .llseek         = seq_lseek,
1176         .release        = ext4_es_seq_shrinker_info_release,
1177 };
1178 
1179 int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
1180 {
1181         int err;
1182 
1183         /* Make sure we have enough bits for physical block number */
1184         BUILD_BUG_ON(ES_SHIFT < 48);
1185         INIT_LIST_HEAD(&sbi->s_es_list);
1186         sbi->s_es_nr_inode = 0;
1187         spin_lock_init(&sbi->s_es_lock);
1188         sbi->s_es_stats.es_stats_shrunk = 0;
1189         sbi->s_es_stats.es_stats_cache_hits = 0;
1190         sbi->s_es_stats.es_stats_cache_misses = 0;
1191         sbi->s_es_stats.es_stats_scan_time = 0;
1192         sbi->s_es_stats.es_stats_max_scan_time = 0;
1193         err = percpu_counter_init(&sbi->s_es_stats.es_stats_all_cnt, 0, GFP_KERNEL);
1194         if (err)
1195                 return err;
1196         err = percpu_counter_init(&sbi->s_es_stats.es_stats_shk_cnt, 0, GFP_KERNEL);
1197         if (err)
1198                 goto err1;
1199 
1200         sbi->s_es_shrinker.scan_objects = ext4_es_scan;
1201         sbi->s_es_shrinker.count_objects = ext4_es_count;
1202         sbi->s_es_shrinker.seeks = DEFAULT_SEEKS;
1203         err = register_shrinker(&sbi->s_es_shrinker);
1204         if (err)
1205                 goto err2;
1206 
1207         if (sbi->s_proc)
1208                 proc_create_data("es_shrinker_info", S_IRUGO, sbi->s_proc,
1209                                  &ext4_es_seq_shrinker_info_fops, sbi);
1210 
1211         return 0;
1212 
1213 err2:
1214         percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
1215 err1:
1216         percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
1217         return err;
1218 }
1219 
1220 void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi)
1221 {
1222         if (sbi->s_proc)
1223                 remove_proc_entry("es_shrinker_info", sbi->s_proc);
1224         percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
1225         percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
1226         unregister_shrinker(&sbi->s_es_shrinker);
1227 }
1228 
1229 /*
1230  * Shrink extents in given inode from ei->i_es_shrink_lblk till end. Scan at
1231  * most *nr_to_scan extents, update *nr_to_scan accordingly.
1232  *
1233  * Return 0 if we hit end of tree / interval, 1 if we exhausted nr_to_scan.
1234  * Increment *nr_shrunk by the number of reclaimed extents. Also update
1235  * ei->i_es_shrink_lblk to where we should continue scanning.
1236  */
1237 static int es_do_reclaim_extents(struct ext4_inode_info *ei, ext4_lblk_t end,
1238                                  int *nr_to_scan, int *nr_shrunk)
1239 {
1240         struct inode *inode = &ei->vfs_inode;
1241         struct ext4_es_tree *tree = &ei->i_es_tree;
1242         struct extent_status *es;
1243         struct rb_node *node;
1244 
1245         es = __es_tree_search(&tree->root, ei->i_es_shrink_lblk);
1246         if (!es)
1247                 goto out_wrap;
1248         node = &es->rb_node;
1249         while (*nr_to_scan > 0) {
1250                 if (es->es_lblk > end) {
1251                         ei->i_es_shrink_lblk = end + 1;
1252                         return 0;
1253                 }
1254 
1255                 (*nr_to_scan)--;
1256                 node = rb_next(&es->rb_node);
1257                 /*
1258                  * We can't reclaim delayed extent from status tree because
1259                  * fiemap, bigallic, and seek_data/hole need to use it.
1260                  */
1261                 if (ext4_es_is_delayed(es))
1262                         goto next;
1263                 if (ext4_es_is_referenced(es)) {
1264                         ext4_es_clear_referenced(es);
1265                         goto next;
1266                 }
1267 
1268                 rb_erase(&es->rb_node, &tree->root);
1269                 ext4_es_free_extent(inode, es);
1270                 (*nr_shrunk)++;
1271 next:
1272                 if (!node)
1273                         goto out_wrap;
1274                 es = rb_entry(node, struct extent_status, rb_node);
1275         }
1276         ei->i_es_shrink_lblk = es->es_lblk;
1277         return 1;
1278 out_wrap:
1279         ei->i_es_shrink_lblk = 0;
1280         return 0;
1281 }
1282 
1283 static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan)
1284 {
1285         struct inode *inode = &ei->vfs_inode;
1286         int nr_shrunk = 0;
1287         ext4_lblk_t start = ei->i_es_shrink_lblk;
1288         static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,
1289                                       DEFAULT_RATELIMIT_BURST);
1290 
1291         if (ei->i_es_shk_nr == 0)
1292                 return 0;
1293 
1294         if (ext4_test_inode_state(inode, EXT4_STATE_EXT_PRECACHED) &&
1295             __ratelimit(&_rs))
1296                 ext4_warning(inode->i_sb, "forced shrink of precached extents");
1297 
1298         if (!es_do_reclaim_extents(ei, EXT_MAX_BLOCKS, nr_to_scan, &nr_shrunk) &&
1299             start != 0)
1300                 es_do_reclaim_extents(ei, start - 1, nr_to_scan, &nr_shrunk);
1301 
1302         ei->i_es_tree.cache_es = NULL;
1303         return nr_shrunk;
1304 }
1305 

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