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TOMOYO Linux Cross Reference
Linux/fs/btrfs/transaction.c

Version: ~ [ linux-5.4-rc3 ] ~ [ linux-5.3.6 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.79 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.149 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.196 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.196 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.75 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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  1 /*
  2  * Copyright (C) 2007 Oracle.  All rights reserved.
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public
  6  * License v2 as published by the Free Software Foundation.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 11  * General Public License for more details.
 12  *
 13  * You should have received a copy of the GNU General Public
 14  * License along with this program; if not, write to the
 15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 16  * Boston, MA 021110-1307, USA.
 17  */
 18 
 19 #include <linux/fs.h>
 20 #include <linux/slab.h>
 21 #include <linux/sched.h>
 22 #include <linux/writeback.h>
 23 #include <linux/pagemap.h>
 24 #include <linux/blkdev.h>
 25 #include <linux/uuid.h>
 26 #include "ctree.h"
 27 #include "disk-io.h"
 28 #include "transaction.h"
 29 #include "locking.h"
 30 #include "tree-log.h"
 31 #include "inode-map.h"
 32 #include "volumes.h"
 33 #include "dev-replace.h"
 34 #include "qgroup.h"
 35 
 36 #define BTRFS_ROOT_TRANS_TAG 0
 37 
 38 static const unsigned int btrfs_blocked_trans_types[TRANS_STATE_MAX] = {
 39         [TRANS_STATE_RUNNING]           = 0U,
 40         [TRANS_STATE_BLOCKED]           = (__TRANS_USERSPACE |
 41                                            __TRANS_START),
 42         [TRANS_STATE_COMMIT_START]      = (__TRANS_USERSPACE |
 43                                            __TRANS_START |
 44                                            __TRANS_ATTACH),
 45         [TRANS_STATE_COMMIT_DOING]      = (__TRANS_USERSPACE |
 46                                            __TRANS_START |
 47                                            __TRANS_ATTACH |
 48                                            __TRANS_JOIN),
 49         [TRANS_STATE_UNBLOCKED]         = (__TRANS_USERSPACE |
 50                                            __TRANS_START |
 51                                            __TRANS_ATTACH |
 52                                            __TRANS_JOIN |
 53                                            __TRANS_JOIN_NOLOCK),
 54         [TRANS_STATE_COMPLETED]         = (__TRANS_USERSPACE |
 55                                            __TRANS_START |
 56                                            __TRANS_ATTACH |
 57                                            __TRANS_JOIN |
 58                                            __TRANS_JOIN_NOLOCK),
 59 };
 60 
 61 void btrfs_put_transaction(struct btrfs_transaction *transaction)
 62 {
 63         WARN_ON(atomic_read(&transaction->use_count) == 0);
 64         if (atomic_dec_and_test(&transaction->use_count)) {
 65                 BUG_ON(!list_empty(&transaction->list));
 66                 WARN_ON(!RB_EMPTY_ROOT(&transaction->delayed_refs.href_root));
 67                 if (transaction->delayed_refs.pending_csums)
 68                         printk(KERN_ERR "pending csums is %llu\n",
 69                                transaction->delayed_refs.pending_csums);
 70                 while (!list_empty(&transaction->pending_chunks)) {
 71                         struct extent_map *em;
 72 
 73                         em = list_first_entry(&transaction->pending_chunks,
 74                                               struct extent_map, list);
 75                         list_del_init(&em->list);
 76                         free_extent_map(em);
 77                 }
 78                 kmem_cache_free(btrfs_transaction_cachep, transaction);
 79         }
 80 }
 81 
 82 static void clear_btree_io_tree(struct extent_io_tree *tree)
 83 {
 84         spin_lock(&tree->lock);
 85         while (!RB_EMPTY_ROOT(&tree->state)) {
 86                 struct rb_node *node;
 87                 struct extent_state *state;
 88 
 89                 node = rb_first(&tree->state);
 90                 state = rb_entry(node, struct extent_state, rb_node);
 91                 rb_erase(&state->rb_node, &tree->state);
 92                 RB_CLEAR_NODE(&state->rb_node);
 93                 /*
 94                  * btree io trees aren't supposed to have tasks waiting for
 95                  * changes in the flags of extent states ever.
 96                  */
 97                 ASSERT(!waitqueue_active(&state->wq));
 98                 free_extent_state(state);
 99 
100                 cond_resched_lock(&tree->lock);
101         }
102         spin_unlock(&tree->lock);
103 }
104 
105 static noinline void switch_commit_roots(struct btrfs_transaction *trans,
106                                          struct btrfs_fs_info *fs_info)
107 {
108         struct btrfs_root *root, *tmp;
109 
110         down_write(&fs_info->commit_root_sem);
111         list_for_each_entry_safe(root, tmp, &trans->switch_commits,
112                                  dirty_list) {
113                 list_del_init(&root->dirty_list);
114                 free_extent_buffer(root->commit_root);
115                 root->commit_root = btrfs_root_node(root);
116                 if (is_fstree(root->objectid))
117                         btrfs_unpin_free_ino(root);
118                 clear_btree_io_tree(&root->dirty_log_pages);
119         }
120         up_write(&fs_info->commit_root_sem);
121 }
122 
123 static inline void extwriter_counter_inc(struct btrfs_transaction *trans,
124                                          unsigned int type)
125 {
126         if (type & TRANS_EXTWRITERS)
127                 atomic_inc(&trans->num_extwriters);
128 }
129 
130 static inline void extwriter_counter_dec(struct btrfs_transaction *trans,
131                                          unsigned int type)
132 {
133         if (type & TRANS_EXTWRITERS)
134                 atomic_dec(&trans->num_extwriters);
135 }
136 
137 static inline void extwriter_counter_init(struct btrfs_transaction *trans,
138                                           unsigned int type)
139 {
140         atomic_set(&trans->num_extwriters, ((type & TRANS_EXTWRITERS) ? 1 : 0));
141 }
142 
143 static inline int extwriter_counter_read(struct btrfs_transaction *trans)
144 {
145         return atomic_read(&trans->num_extwriters);
146 }
147 
148 /*
149  * either allocate a new transaction or hop into the existing one
150  */
151 static noinline int join_transaction(struct btrfs_root *root, unsigned int type)
152 {
153         struct btrfs_transaction *cur_trans;
154         struct btrfs_fs_info *fs_info = root->fs_info;
155 
156         spin_lock(&fs_info->trans_lock);
157 loop:
158         /* The file system has been taken offline. No new transactions. */
159         if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
160                 spin_unlock(&fs_info->trans_lock);
161                 return -EROFS;
162         }
163 
164         cur_trans = fs_info->running_transaction;
165         if (cur_trans) {
166                 if (cur_trans->aborted) {
167                         spin_unlock(&fs_info->trans_lock);
168                         return cur_trans->aborted;
169                 }
170                 if (btrfs_blocked_trans_types[cur_trans->state] & type) {
171                         spin_unlock(&fs_info->trans_lock);
172                         return -EBUSY;
173                 }
174                 atomic_inc(&cur_trans->use_count);
175                 atomic_inc(&cur_trans->num_writers);
176                 extwriter_counter_inc(cur_trans, type);
177                 spin_unlock(&fs_info->trans_lock);
178                 return 0;
179         }
180         spin_unlock(&fs_info->trans_lock);
181 
182         /*
183          * If we are ATTACH, we just want to catch the current transaction,
184          * and commit it. If there is no transaction, just return ENOENT.
185          */
186         if (type == TRANS_ATTACH)
187                 return -ENOENT;
188 
189         /*
190          * JOIN_NOLOCK only happens during the transaction commit, so
191          * it is impossible that ->running_transaction is NULL
192          */
193         BUG_ON(type == TRANS_JOIN_NOLOCK);
194 
195         cur_trans = kmem_cache_alloc(btrfs_transaction_cachep, GFP_NOFS);
196         if (!cur_trans)
197                 return -ENOMEM;
198 
199         spin_lock(&fs_info->trans_lock);
200         if (fs_info->running_transaction) {
201                 /*
202                  * someone started a transaction after we unlocked.  Make sure
203                  * to redo the checks above
204                  */
205                 kmem_cache_free(btrfs_transaction_cachep, cur_trans);
206                 goto loop;
207         } else if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
208                 spin_unlock(&fs_info->trans_lock);
209                 kmem_cache_free(btrfs_transaction_cachep, cur_trans);
210                 return -EROFS;
211         }
212 
213         atomic_set(&cur_trans->num_writers, 1);
214         extwriter_counter_init(cur_trans, type);
215         init_waitqueue_head(&cur_trans->writer_wait);
216         init_waitqueue_head(&cur_trans->commit_wait);
217         cur_trans->state = TRANS_STATE_RUNNING;
218         /*
219          * One for this trans handle, one so it will live on until we
220          * commit the transaction.
221          */
222         atomic_set(&cur_trans->use_count, 2);
223         cur_trans->have_free_bgs = 0;
224         cur_trans->start_time = get_seconds();
225         cur_trans->dirty_bg_run = 0;
226 
227         cur_trans->delayed_refs.href_root = RB_ROOT;
228         cur_trans->delayed_refs.dirty_extent_root = RB_ROOT;
229         atomic_set(&cur_trans->delayed_refs.num_entries, 0);
230         cur_trans->delayed_refs.num_heads_ready = 0;
231         cur_trans->delayed_refs.pending_csums = 0;
232         cur_trans->delayed_refs.num_heads = 0;
233         cur_trans->delayed_refs.flushing = 0;
234         cur_trans->delayed_refs.run_delayed_start = 0;
235         cur_trans->delayed_refs.qgroup_to_skip = 0;
236 
237         /*
238          * although the tree mod log is per file system and not per transaction,
239          * the log must never go across transaction boundaries.
240          */
241         smp_mb();
242         if (!list_empty(&fs_info->tree_mod_seq_list))
243                 WARN(1, KERN_ERR "BTRFS: tree_mod_seq_list not empty when "
244                         "creating a fresh transaction\n");
245         if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log))
246                 WARN(1, KERN_ERR "BTRFS: tree_mod_log rb tree not empty when "
247                         "creating a fresh transaction\n");
248         atomic64_set(&fs_info->tree_mod_seq, 0);
249 
250         spin_lock_init(&cur_trans->delayed_refs.lock);
251 
252         INIT_LIST_HEAD(&cur_trans->pending_snapshots);
253         INIT_LIST_HEAD(&cur_trans->pending_chunks);
254         INIT_LIST_HEAD(&cur_trans->switch_commits);
255         INIT_LIST_HEAD(&cur_trans->pending_ordered);
256         INIT_LIST_HEAD(&cur_trans->dirty_bgs);
257         INIT_LIST_HEAD(&cur_trans->io_bgs);
258         mutex_init(&cur_trans->cache_write_mutex);
259         cur_trans->num_dirty_bgs = 0;
260         spin_lock_init(&cur_trans->dirty_bgs_lock);
261         list_add_tail(&cur_trans->list, &fs_info->trans_list);
262         extent_io_tree_init(&cur_trans->dirty_pages,
263                              fs_info->btree_inode->i_mapping);
264         fs_info->generation++;
265         cur_trans->transid = fs_info->generation;
266         fs_info->running_transaction = cur_trans;
267         cur_trans->aborted = 0;
268         spin_unlock(&fs_info->trans_lock);
269 
270         return 0;
271 }
272 
273 /*
274  * this does all the record keeping required to make sure that a reference
275  * counted root is properly recorded in a given transaction.  This is required
276  * to make sure the old root from before we joined the transaction is deleted
277  * when the transaction commits
278  */
279 static int record_root_in_trans(struct btrfs_trans_handle *trans,
280                                struct btrfs_root *root)
281 {
282         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
283             root->last_trans < trans->transid) {
284                 WARN_ON(root == root->fs_info->extent_root);
285                 WARN_ON(root->commit_root != root->node);
286 
287                 /*
288                  * see below for IN_TRANS_SETUP usage rules
289                  * we have the reloc mutex held now, so there
290                  * is only one writer in this function
291                  */
292                 set_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state);
293 
294                 /* make sure readers find IN_TRANS_SETUP before
295                  * they find our root->last_trans update
296                  */
297                 smp_wmb();
298 
299                 spin_lock(&root->fs_info->fs_roots_radix_lock);
300                 if (root->last_trans == trans->transid) {
301                         spin_unlock(&root->fs_info->fs_roots_radix_lock);
302                         return 0;
303                 }
304                 radix_tree_tag_set(&root->fs_info->fs_roots_radix,
305                            (unsigned long)root->root_key.objectid,
306                            BTRFS_ROOT_TRANS_TAG);
307                 spin_unlock(&root->fs_info->fs_roots_radix_lock);
308                 root->last_trans = trans->transid;
309 
310                 /* this is pretty tricky.  We don't want to
311                  * take the relocation lock in btrfs_record_root_in_trans
312                  * unless we're really doing the first setup for this root in
313                  * this transaction.
314                  *
315                  * Normally we'd use root->last_trans as a flag to decide
316                  * if we want to take the expensive mutex.
317                  *
318                  * But, we have to set root->last_trans before we
319                  * init the relocation root, otherwise, we trip over warnings
320                  * in ctree.c.  The solution used here is to flag ourselves
321                  * with root IN_TRANS_SETUP.  When this is 1, we're still
322                  * fixing up the reloc trees and everyone must wait.
323                  *
324                  * When this is zero, they can trust root->last_trans and fly
325                  * through btrfs_record_root_in_trans without having to take the
326                  * lock.  smp_wmb() makes sure that all the writes above are
327                  * done before we pop in the zero below
328                  */
329                 btrfs_init_reloc_root(trans, root);
330                 smp_mb__before_atomic();
331                 clear_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state);
332         }
333         return 0;
334 }
335 
336 
337 int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
338                                struct btrfs_root *root)
339 {
340         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
341                 return 0;
342 
343         /*
344          * see record_root_in_trans for comments about IN_TRANS_SETUP usage
345          * and barriers
346          */
347         smp_rmb();
348         if (root->last_trans == trans->transid &&
349             !test_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state))
350                 return 0;
351 
352         mutex_lock(&root->fs_info->reloc_mutex);
353         record_root_in_trans(trans, root);
354         mutex_unlock(&root->fs_info->reloc_mutex);
355 
356         return 0;
357 }
358 
359 static inline int is_transaction_blocked(struct btrfs_transaction *trans)
360 {
361         return (trans->state >= TRANS_STATE_BLOCKED &&
362                 trans->state < TRANS_STATE_UNBLOCKED &&
363                 !trans->aborted);
364 }
365 
366 /* wait for commit against the current transaction to become unblocked
367  * when this is done, it is safe to start a new transaction, but the current
368  * transaction might not be fully on disk.
369  */
370 static void wait_current_trans(struct btrfs_root *root)
371 {
372         struct btrfs_transaction *cur_trans;
373 
374         spin_lock(&root->fs_info->trans_lock);
375         cur_trans = root->fs_info->running_transaction;
376         if (cur_trans && is_transaction_blocked(cur_trans)) {
377                 atomic_inc(&cur_trans->use_count);
378                 spin_unlock(&root->fs_info->trans_lock);
379 
380                 wait_event(root->fs_info->transaction_wait,
381                            cur_trans->state >= TRANS_STATE_UNBLOCKED ||
382                            cur_trans->aborted);
383                 btrfs_put_transaction(cur_trans);
384         } else {
385                 spin_unlock(&root->fs_info->trans_lock);
386         }
387 }
388 
389 static int may_wait_transaction(struct btrfs_root *root, int type)
390 {
391         if (root->fs_info->log_root_recovering)
392                 return 0;
393 
394         if (type == TRANS_USERSPACE)
395                 return 1;
396 
397         if (type == TRANS_START &&
398             !atomic_read(&root->fs_info->open_ioctl_trans))
399                 return 1;
400 
401         return 0;
402 }
403 
404 static inline bool need_reserve_reloc_root(struct btrfs_root *root)
405 {
406         if (!root->fs_info->reloc_ctl ||
407             !test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
408             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
409             root->reloc_root)
410                 return false;
411 
412         return true;
413 }
414 
415 static struct btrfs_trans_handle *
416 start_transaction(struct btrfs_root *root, u64 num_items, unsigned int type,
417                   enum btrfs_reserve_flush_enum flush)
418 {
419         struct btrfs_trans_handle *h;
420         struct btrfs_transaction *cur_trans;
421         u64 num_bytes = 0;
422         u64 qgroup_reserved = 0;
423         bool reloc_reserved = false;
424         int ret;
425 
426         /* Send isn't supposed to start transactions. */
427         ASSERT(current->journal_info != BTRFS_SEND_TRANS_STUB);
428 
429         if (test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state))
430                 return ERR_PTR(-EROFS);
431 
432         if (current->journal_info) {
433                 WARN_ON(type & TRANS_EXTWRITERS);
434                 h = current->journal_info;
435                 h->use_count++;
436                 WARN_ON(h->use_count > 2);
437                 h->orig_rsv = h->block_rsv;
438                 h->block_rsv = NULL;
439                 goto got_it;
440         }
441 
442         /*
443          * Do the reservation before we join the transaction so we can do all
444          * the appropriate flushing if need be.
445          */
446         if (num_items > 0 && root != root->fs_info->chunk_root) {
447                 if (root->fs_info->quota_enabled &&
448                     is_fstree(root->root_key.objectid)) {
449                         qgroup_reserved = num_items * root->nodesize;
450                         ret = btrfs_qgroup_reserve(root, qgroup_reserved);
451                         if (ret)
452                                 return ERR_PTR(ret);
453                 }
454 
455                 num_bytes = btrfs_calc_trans_metadata_size(root, num_items);
456                 /*
457                  * Do the reservation for the relocation root creation
458                  */
459                 if (need_reserve_reloc_root(root)) {
460                         num_bytes += root->nodesize;
461                         reloc_reserved = true;
462                 }
463 
464                 ret = btrfs_block_rsv_add(root,
465                                           &root->fs_info->trans_block_rsv,
466                                           num_bytes, flush);
467                 if (ret)
468                         goto reserve_fail;
469         }
470 again:
471         h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
472         if (!h) {
473                 ret = -ENOMEM;
474                 goto alloc_fail;
475         }
476 
477         /*
478          * If we are JOIN_NOLOCK we're already committing a transaction and
479          * waiting on this guy, so we don't need to do the sb_start_intwrite
480          * because we're already holding a ref.  We need this because we could
481          * have raced in and did an fsync() on a file which can kick a commit
482          * and then we deadlock with somebody doing a freeze.
483          *
484          * If we are ATTACH, it means we just want to catch the current
485          * transaction and commit it, so we needn't do sb_start_intwrite(). 
486          */
487         if (type & __TRANS_FREEZABLE)
488                 sb_start_intwrite(root->fs_info->sb);
489 
490         if (may_wait_transaction(root, type))
491                 wait_current_trans(root);
492 
493         do {
494                 ret = join_transaction(root, type);
495                 if (ret == -EBUSY) {
496                         wait_current_trans(root);
497                         if (unlikely(type == TRANS_ATTACH))
498                                 ret = -ENOENT;
499                 }
500         } while (ret == -EBUSY);
501 
502         if (ret < 0) {
503                 /* We must get the transaction if we are JOIN_NOLOCK. */
504                 BUG_ON(type == TRANS_JOIN_NOLOCK);
505                 goto join_fail;
506         }
507 
508         cur_trans = root->fs_info->running_transaction;
509 
510         h->transid = cur_trans->transid;
511         h->transaction = cur_trans;
512         h->blocks_used = 0;
513         h->bytes_reserved = 0;
514         h->chunk_bytes_reserved = 0;
515         h->root = root;
516         h->delayed_ref_updates = 0;
517         h->use_count = 1;
518         h->adding_csums = 0;
519         h->block_rsv = NULL;
520         h->orig_rsv = NULL;
521         h->aborted = 0;
522         h->qgroup_reserved = 0;
523         h->delayed_ref_elem.seq = 0;
524         h->type = type;
525         h->allocating_chunk = false;
526         h->reloc_reserved = false;
527         h->sync = false;
528         INIT_LIST_HEAD(&h->qgroup_ref_list);
529         INIT_LIST_HEAD(&h->new_bgs);
530         INIT_LIST_HEAD(&h->ordered);
531 
532         smp_mb();
533         if (cur_trans->state >= TRANS_STATE_BLOCKED &&
534             may_wait_transaction(root, type)) {
535                 current->journal_info = h;
536                 btrfs_commit_transaction(h, root);
537                 goto again;
538         }
539 
540         if (num_bytes) {
541                 trace_btrfs_space_reservation(root->fs_info, "transaction",
542                                               h->transid, num_bytes, 1);
543                 h->block_rsv = &root->fs_info->trans_block_rsv;
544                 h->bytes_reserved = num_bytes;
545                 h->reloc_reserved = reloc_reserved;
546         }
547         h->qgroup_reserved = qgroup_reserved;
548 
549 got_it:
550         btrfs_record_root_in_trans(h, root);
551 
552         if (!current->journal_info && type != TRANS_USERSPACE)
553                 current->journal_info = h;
554         return h;
555 
556 join_fail:
557         if (type & __TRANS_FREEZABLE)
558                 sb_end_intwrite(root->fs_info->sb);
559         kmem_cache_free(btrfs_trans_handle_cachep, h);
560 alloc_fail:
561         if (num_bytes)
562                 btrfs_block_rsv_release(root, &root->fs_info->trans_block_rsv,
563                                         num_bytes);
564 reserve_fail:
565         if (qgroup_reserved)
566                 btrfs_qgroup_free(root, qgroup_reserved);
567         return ERR_PTR(ret);
568 }
569 
570 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
571                                                    int num_items)
572 {
573         return start_transaction(root, num_items, TRANS_START,
574                                  BTRFS_RESERVE_FLUSH_ALL);
575 }
576 
577 struct btrfs_trans_handle *btrfs_start_transaction_lflush(
578                                         struct btrfs_root *root, int num_items)
579 {
580         return start_transaction(root, num_items, TRANS_START,
581                                  BTRFS_RESERVE_FLUSH_LIMIT);
582 }
583 
584 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root)
585 {
586         return start_transaction(root, 0, TRANS_JOIN, 0);
587 }
588 
589 struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root)
590 {
591         return start_transaction(root, 0, TRANS_JOIN_NOLOCK, 0);
592 }
593 
594 struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root)
595 {
596         return start_transaction(root, 0, TRANS_USERSPACE, 0);
597 }
598 
599 /*
600  * btrfs_attach_transaction() - catch the running transaction
601  *
602  * It is used when we want to commit the current the transaction, but
603  * don't want to start a new one.
604  *
605  * Note: If this function return -ENOENT, it just means there is no
606  * running transaction. But it is possible that the inactive transaction
607  * is still in the memory, not fully on disk. If you hope there is no
608  * inactive transaction in the fs when -ENOENT is returned, you should
609  * invoke
610  *     btrfs_attach_transaction_barrier()
611  */
612 struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root)
613 {
614         return start_transaction(root, 0, TRANS_ATTACH, 0);
615 }
616 
617 /*
618  * btrfs_attach_transaction_barrier() - catch the running transaction
619  *
620  * It is similar to the above function, the differentia is this one
621  * will wait for all the inactive transactions until they fully
622  * complete.
623  */
624 struct btrfs_trans_handle *
625 btrfs_attach_transaction_barrier(struct btrfs_root *root)
626 {
627         struct btrfs_trans_handle *trans;
628 
629         trans = start_transaction(root, 0, TRANS_ATTACH, 0);
630         if (IS_ERR(trans) && PTR_ERR(trans) == -ENOENT)
631                 btrfs_wait_for_commit(root, 0);
632 
633         return trans;
634 }
635 
636 /* wait for a transaction commit to be fully complete */
637 static noinline void wait_for_commit(struct btrfs_root *root,
638                                     struct btrfs_transaction *commit)
639 {
640         wait_event(commit->commit_wait, commit->state == TRANS_STATE_COMPLETED);
641 }
642 
643 int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
644 {
645         struct btrfs_transaction *cur_trans = NULL, *t;
646         int ret = 0;
647 
648         if (transid) {
649                 if (transid <= root->fs_info->last_trans_committed)
650                         goto out;
651 
652                 /* find specified transaction */
653                 spin_lock(&root->fs_info->trans_lock);
654                 list_for_each_entry(t, &root->fs_info->trans_list, list) {
655                         if (t->transid == transid) {
656                                 cur_trans = t;
657                                 atomic_inc(&cur_trans->use_count);
658                                 ret = 0;
659                                 break;
660                         }
661                         if (t->transid > transid) {
662                                 ret = 0;
663                                 break;
664                         }
665                 }
666                 spin_unlock(&root->fs_info->trans_lock);
667 
668                 /*
669                  * The specified transaction doesn't exist, or we
670                  * raced with btrfs_commit_transaction
671                  */
672                 if (!cur_trans) {
673                         if (transid > root->fs_info->last_trans_committed)
674                                 ret = -EINVAL;
675                         goto out;
676                 }
677         } else {
678                 /* find newest transaction that is committing | committed */
679                 spin_lock(&root->fs_info->trans_lock);
680                 list_for_each_entry_reverse(t, &root->fs_info->trans_list,
681                                             list) {
682                         if (t->state >= TRANS_STATE_COMMIT_START) {
683                                 if (t->state == TRANS_STATE_COMPLETED)
684                                         break;
685                                 cur_trans = t;
686                                 atomic_inc(&cur_trans->use_count);
687                                 break;
688                         }
689                 }
690                 spin_unlock(&root->fs_info->trans_lock);
691                 if (!cur_trans)
692                         goto out;  /* nothing committing|committed */
693         }
694 
695         wait_for_commit(root, cur_trans);
696         btrfs_put_transaction(cur_trans);
697 out:
698         return ret;
699 }
700 
701 void btrfs_throttle(struct btrfs_root *root)
702 {
703         if (!atomic_read(&root->fs_info->open_ioctl_trans))
704                 wait_current_trans(root);
705 }
706 
707 static int should_end_transaction(struct btrfs_trans_handle *trans,
708                                   struct btrfs_root *root)
709 {
710         if (root->fs_info->global_block_rsv.space_info->full &&
711             btrfs_check_space_for_delayed_refs(trans, root))
712                 return 1;
713 
714         return !!btrfs_block_rsv_check(root, &root->fs_info->global_block_rsv, 5);
715 }
716 
717 int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
718                                  struct btrfs_root *root)
719 {
720         struct btrfs_transaction *cur_trans = trans->transaction;
721         int updates;
722         int err;
723 
724         smp_mb();
725         if (cur_trans->state >= TRANS_STATE_BLOCKED ||
726             cur_trans->delayed_refs.flushing)
727                 return 1;
728 
729         updates = trans->delayed_ref_updates;
730         trans->delayed_ref_updates = 0;
731         if (updates) {
732                 err = btrfs_run_delayed_refs(trans, root, updates * 2);
733                 if (err) /* Error code will also eval true */
734                         return err;
735         }
736 
737         return should_end_transaction(trans, root);
738 }
739 
740 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
741                           struct btrfs_root *root, int throttle)
742 {
743         struct btrfs_transaction *cur_trans = trans->transaction;
744         struct btrfs_fs_info *info = root->fs_info;
745         unsigned long cur = trans->delayed_ref_updates;
746         int lock = (trans->type != TRANS_JOIN_NOLOCK);
747         int err = 0;
748         int must_run_delayed_refs = 0;
749 
750         if (trans->use_count > 1) {
751                 trans->use_count--;
752                 trans->block_rsv = trans->orig_rsv;
753                 return 0;
754         }
755 
756         btrfs_trans_release_metadata(trans, root);
757         trans->block_rsv = NULL;
758 
759         if (!list_empty(&trans->new_bgs))
760                 btrfs_create_pending_block_groups(trans, root);
761 
762         if (!list_empty(&trans->ordered)) {
763                 spin_lock(&info->trans_lock);
764                 list_splice_init(&trans->ordered, &cur_trans->pending_ordered);
765                 spin_unlock(&info->trans_lock);
766         }
767 
768         trans->delayed_ref_updates = 0;
769         if (!trans->sync) {
770                 must_run_delayed_refs =
771                         btrfs_should_throttle_delayed_refs(trans, root);
772                 cur = max_t(unsigned long, cur, 32);
773 
774                 /*
775                  * don't make the caller wait if they are from a NOLOCK
776                  * or ATTACH transaction, it will deadlock with commit
777                  */
778                 if (must_run_delayed_refs == 1 &&
779                     (trans->type & (__TRANS_JOIN_NOLOCK | __TRANS_ATTACH)))
780                         must_run_delayed_refs = 2;
781         }
782 
783         if (trans->qgroup_reserved) {
784                 /*
785                  * the same root has to be passed here between start_transaction
786                  * and end_transaction. Subvolume quota depends on this.
787                  */
788                 btrfs_qgroup_free(trans->root, trans->qgroup_reserved);
789                 trans->qgroup_reserved = 0;
790         }
791 
792         btrfs_trans_release_metadata(trans, root);
793         trans->block_rsv = NULL;
794 
795         if (!list_empty(&trans->new_bgs))
796                 btrfs_create_pending_block_groups(trans, root);
797 
798         btrfs_trans_release_chunk_metadata(trans);
799 
800         if (lock && !atomic_read(&root->fs_info->open_ioctl_trans) &&
801             should_end_transaction(trans, root) &&
802             ACCESS_ONCE(cur_trans->state) == TRANS_STATE_RUNNING) {
803                 spin_lock(&info->trans_lock);
804                 if (cur_trans->state == TRANS_STATE_RUNNING)
805                         cur_trans->state = TRANS_STATE_BLOCKED;
806                 spin_unlock(&info->trans_lock);
807         }
808 
809         if (lock && ACCESS_ONCE(cur_trans->state) == TRANS_STATE_BLOCKED) {
810                 if (throttle)
811                         return btrfs_commit_transaction(trans, root);
812                 else
813                         wake_up_process(info->transaction_kthread);
814         }
815 
816         if (trans->type & __TRANS_FREEZABLE)
817                 sb_end_intwrite(root->fs_info->sb);
818 
819         WARN_ON(cur_trans != info->running_transaction);
820         WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
821         atomic_dec(&cur_trans->num_writers);
822         extwriter_counter_dec(cur_trans, trans->type);
823 
824         smp_mb();
825         if (waitqueue_active(&cur_trans->writer_wait))
826                 wake_up(&cur_trans->writer_wait);
827         btrfs_put_transaction(cur_trans);
828 
829         if (current->journal_info == trans)
830                 current->journal_info = NULL;
831 
832         if (throttle)
833                 btrfs_run_delayed_iputs(root);
834 
835         if (trans->aborted ||
836             test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state)) {
837                 wake_up_process(info->transaction_kthread);
838                 err = -EIO;
839         }
840         assert_qgroups_uptodate(trans);
841 
842         kmem_cache_free(btrfs_trans_handle_cachep, trans);
843         if (must_run_delayed_refs) {
844                 btrfs_async_run_delayed_refs(root, cur,
845                                              must_run_delayed_refs == 1);
846         }
847         return err;
848 }
849 
850 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
851                           struct btrfs_root *root)
852 {
853         return __btrfs_end_transaction(trans, root, 0);
854 }
855 
856 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
857                                    struct btrfs_root *root)
858 {
859         return __btrfs_end_transaction(trans, root, 1);
860 }
861 
862 /*
863  * when btree blocks are allocated, they have some corresponding bits set for
864  * them in one of two extent_io trees.  This is used to make sure all of
865  * those extents are sent to disk but does not wait on them
866  */
867 int btrfs_write_marked_extents(struct btrfs_root *root,
868                                struct extent_io_tree *dirty_pages, int mark)
869 {
870         int err = 0;
871         int werr = 0;
872         struct address_space *mapping = root->fs_info->btree_inode->i_mapping;
873         struct extent_state *cached_state = NULL;
874         u64 start = 0;
875         u64 end;
876 
877         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
878                                       mark, &cached_state)) {
879                 bool wait_writeback = false;
880 
881                 err = convert_extent_bit(dirty_pages, start, end,
882                                          EXTENT_NEED_WAIT,
883                                          mark, &cached_state, GFP_NOFS);
884                 /*
885                  * convert_extent_bit can return -ENOMEM, which is most of the
886                  * time a temporary error. So when it happens, ignore the error
887                  * and wait for writeback of this range to finish - because we
888                  * failed to set the bit EXTENT_NEED_WAIT for the range, a call
889                  * to btrfs_wait_marked_extents() would not know that writeback
890                  * for this range started and therefore wouldn't wait for it to
891                  * finish - we don't want to commit a superblock that points to
892                  * btree nodes/leafs for which writeback hasn't finished yet
893                  * (and without errors).
894                  * We cleanup any entries left in the io tree when committing
895                  * the transaction (through clear_btree_io_tree()).
896                  */
897                 if (err == -ENOMEM) {
898                         err = 0;
899                         wait_writeback = true;
900                 }
901                 if (!err)
902                         err = filemap_fdatawrite_range(mapping, start, end);
903                 if (err)
904                         werr = err;
905                 else if (wait_writeback)
906                         werr = filemap_fdatawait_range(mapping, start, end);
907                 free_extent_state(cached_state);
908                 cached_state = NULL;
909                 cond_resched();
910                 start = end + 1;
911         }
912         return werr;
913 }
914 
915 /*
916  * when btree blocks are allocated, they have some corresponding bits set for
917  * them in one of two extent_io trees.  This is used to make sure all of
918  * those extents are on disk for transaction or log commit.  We wait
919  * on all the pages and clear them from the dirty pages state tree
920  */
921 int btrfs_wait_marked_extents(struct btrfs_root *root,
922                               struct extent_io_tree *dirty_pages, int mark)
923 {
924         int err = 0;
925         int werr = 0;
926         struct address_space *mapping = root->fs_info->btree_inode->i_mapping;
927         struct extent_state *cached_state = NULL;
928         u64 start = 0;
929         u64 end;
930         struct btrfs_inode *btree_ino = BTRFS_I(root->fs_info->btree_inode);
931         bool errors = false;
932 
933         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
934                                       EXTENT_NEED_WAIT, &cached_state)) {
935                 /*
936                  * Ignore -ENOMEM errors returned by clear_extent_bit().
937                  * When committing the transaction, we'll remove any entries
938                  * left in the io tree. For a log commit, we don't remove them
939                  * after committing the log because the tree can be accessed
940                  * concurrently - we do it only at transaction commit time when
941                  * it's safe to do it (through clear_btree_io_tree()).
942                  */
943                 err = clear_extent_bit(dirty_pages, start, end,
944                                        EXTENT_NEED_WAIT,
945                                        0, 0, &cached_state, GFP_NOFS);
946                 if (err == -ENOMEM)
947                         err = 0;
948                 if (!err)
949                         err = filemap_fdatawait_range(mapping, start, end);
950                 if (err)
951                         werr = err;
952                 free_extent_state(cached_state);
953                 cached_state = NULL;
954                 cond_resched();
955                 start = end + 1;
956         }
957         if (err)
958                 werr = err;
959 
960         if (root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID) {
961                 if ((mark & EXTENT_DIRTY) &&
962                     test_and_clear_bit(BTRFS_INODE_BTREE_LOG1_ERR,
963                                        &btree_ino->runtime_flags))
964                         errors = true;
965 
966                 if ((mark & EXTENT_NEW) &&
967                     test_and_clear_bit(BTRFS_INODE_BTREE_LOG2_ERR,
968                                        &btree_ino->runtime_flags))
969                         errors = true;
970         } else {
971                 if (test_and_clear_bit(BTRFS_INODE_BTREE_ERR,
972                                        &btree_ino->runtime_flags))
973                         errors = true;
974         }
975 
976         if (errors && !werr)
977                 werr = -EIO;
978 
979         return werr;
980 }
981 
982 /*
983  * when btree blocks are allocated, they have some corresponding bits set for
984  * them in one of two extent_io trees.  This is used to make sure all of
985  * those extents are on disk for transaction or log commit
986  */
987 static int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
988                                 struct extent_io_tree *dirty_pages, int mark)
989 {
990         int ret;
991         int ret2;
992         struct blk_plug plug;
993 
994         blk_start_plug(&plug);
995         ret = btrfs_write_marked_extents(root, dirty_pages, mark);
996         blk_finish_plug(&plug);
997         ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);
998 
999         if (ret)
1000                 return ret;
1001         if (ret2)
1002                 return ret2;
1003         return 0;
1004 }
1005 
1006 static int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
1007                                      struct btrfs_root *root)
1008 {
1009         int ret;
1010 
1011         ret = btrfs_write_and_wait_marked_extents(root,
1012                                            &trans->transaction->dirty_pages,
1013                                            EXTENT_DIRTY);
1014         clear_btree_io_tree(&trans->transaction->dirty_pages);
1015 
1016         return ret;
1017 }
1018 
1019 /*
1020  * this is used to update the root pointer in the tree of tree roots.
1021  *
1022  * But, in the case of the extent allocation tree, updating the root
1023  * pointer may allocate blocks which may change the root of the extent
1024  * allocation tree.
1025  *
1026  * So, this loops and repeats and makes sure the cowonly root didn't
1027  * change while the root pointer was being updated in the metadata.
1028  */
1029 static int update_cowonly_root(struct btrfs_trans_handle *trans,
1030                                struct btrfs_root *root)
1031 {
1032         int ret;
1033         u64 old_root_bytenr;
1034         u64 old_root_used;
1035         struct btrfs_root *tree_root = root->fs_info->tree_root;
1036 
1037         old_root_used = btrfs_root_used(&root->root_item);
1038 
1039         while (1) {
1040                 old_root_bytenr = btrfs_root_bytenr(&root->root_item);
1041                 if (old_root_bytenr == root->node->start &&
1042                     old_root_used == btrfs_root_used(&root->root_item))
1043                         break;
1044 
1045                 btrfs_set_root_node(&root->root_item, root->node);
1046                 ret = btrfs_update_root(trans, tree_root,
1047                                         &root->root_key,
1048                                         &root->root_item);
1049                 if (ret)
1050                         return ret;
1051 
1052                 old_root_used = btrfs_root_used(&root->root_item);
1053         }
1054 
1055         return 0;
1056 }
1057 
1058 /*
1059  * update all the cowonly tree roots on disk
1060  *
1061  * The error handling in this function may not be obvious. Any of the
1062  * failures will cause the file system to go offline. We still need
1063  * to clean up the delayed refs.
1064  */
1065 static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
1066                                          struct btrfs_root *root)
1067 {
1068         struct btrfs_fs_info *fs_info = root->fs_info;
1069         struct list_head *dirty_bgs = &trans->transaction->dirty_bgs;
1070         struct list_head *io_bgs = &trans->transaction->io_bgs;
1071         struct list_head *next;
1072         struct extent_buffer *eb;
1073         int ret;
1074 
1075         eb = btrfs_lock_root_node(fs_info->tree_root);
1076         ret = btrfs_cow_block(trans, fs_info->tree_root, eb, NULL,
1077                               0, &eb);
1078         btrfs_tree_unlock(eb);
1079         free_extent_buffer(eb);
1080 
1081         if (ret)
1082                 return ret;
1083 
1084         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1085         if (ret)
1086                 return ret;
1087 
1088         ret = btrfs_run_dev_stats(trans, root->fs_info);
1089         if (ret)
1090                 return ret;
1091         ret = btrfs_run_dev_replace(trans, root->fs_info);
1092         if (ret)
1093                 return ret;
1094         ret = btrfs_run_qgroups(trans, root->fs_info);
1095         if (ret)
1096                 return ret;
1097 
1098         ret = btrfs_setup_space_cache(trans, root);
1099         if (ret)
1100                 return ret;
1101 
1102         /* run_qgroups might have added some more refs */
1103         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1104         if (ret)
1105                 return ret;
1106 again:
1107         while (!list_empty(&fs_info->dirty_cowonly_roots)) {
1108                 next = fs_info->dirty_cowonly_roots.next;
1109                 list_del_init(next);
1110                 root = list_entry(next, struct btrfs_root, dirty_list);
1111                 clear_bit(BTRFS_ROOT_DIRTY, &root->state);
1112 
1113                 if (root != fs_info->extent_root)
1114                         list_add_tail(&root->dirty_list,
1115                                       &trans->transaction->switch_commits);
1116                 ret = update_cowonly_root(trans, root);
1117                 if (ret)
1118                         return ret;
1119                 ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1120                 if (ret)
1121                         return ret;
1122         }
1123 
1124         while (!list_empty(dirty_bgs) || !list_empty(io_bgs)) {
1125                 ret = btrfs_write_dirty_block_groups(trans, root);
1126                 if (ret)
1127                         return ret;
1128                 ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1129                 if (ret)
1130                         return ret;
1131         }
1132 
1133         if (!list_empty(&fs_info->dirty_cowonly_roots))
1134                 goto again;
1135 
1136         list_add_tail(&fs_info->extent_root->dirty_list,
1137                       &trans->transaction->switch_commits);
1138         btrfs_after_dev_replace_commit(fs_info);
1139 
1140         return 0;
1141 }
1142 
1143 /*
1144  * dead roots are old snapshots that need to be deleted.  This allocates
1145  * a dirty root struct and adds it into the list of dead roots that need to
1146  * be deleted
1147  */
1148 void btrfs_add_dead_root(struct btrfs_root *root)
1149 {
1150         spin_lock(&root->fs_info->trans_lock);
1151         if (list_empty(&root->root_list))
1152                 list_add_tail(&root->root_list, &root->fs_info->dead_roots);
1153         spin_unlock(&root->fs_info->trans_lock);
1154 }
1155 
1156 /*
1157  * update all the cowonly tree roots on disk
1158  */
1159 static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
1160                                     struct btrfs_root *root)
1161 {
1162         struct btrfs_root *gang[8];
1163         struct btrfs_fs_info *fs_info = root->fs_info;
1164         int i;
1165         int ret;
1166         int err = 0;
1167 
1168         spin_lock(&fs_info->fs_roots_radix_lock);
1169         while (1) {
1170                 ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
1171                                                  (void **)gang, 0,
1172                                                  ARRAY_SIZE(gang),
1173                                                  BTRFS_ROOT_TRANS_TAG);
1174                 if (ret == 0)
1175                         break;
1176                 for (i = 0; i < ret; i++) {
1177                         root = gang[i];
1178                         radix_tree_tag_clear(&fs_info->fs_roots_radix,
1179                                         (unsigned long)root->root_key.objectid,
1180                                         BTRFS_ROOT_TRANS_TAG);
1181                         spin_unlock(&fs_info->fs_roots_radix_lock);
1182 
1183                         btrfs_free_log(trans, root);
1184                         btrfs_update_reloc_root(trans, root);
1185                         btrfs_orphan_commit_root(trans, root);
1186 
1187                         btrfs_save_ino_cache(root, trans);
1188 
1189                         /* see comments in should_cow_block() */
1190                         clear_bit(BTRFS_ROOT_FORCE_COW, &root->state);
1191                         smp_mb__after_atomic();
1192 
1193                         if (root->commit_root != root->node) {
1194                                 list_add_tail(&root->dirty_list,
1195                                         &trans->transaction->switch_commits);
1196                                 btrfs_set_root_node(&root->root_item,
1197                                                     root->node);
1198                         }
1199 
1200                         err = btrfs_update_root(trans, fs_info->tree_root,
1201                                                 &root->root_key,
1202                                                 &root->root_item);
1203                         spin_lock(&fs_info->fs_roots_radix_lock);
1204                         if (err)
1205                                 break;
1206                 }
1207         }
1208         spin_unlock(&fs_info->fs_roots_radix_lock);
1209         return err;
1210 }
1211 
1212 /*
1213  * defrag a given btree.
1214  * Every leaf in the btree is read and defragged.
1215  */
1216 int btrfs_defrag_root(struct btrfs_root *root)
1217 {
1218         struct btrfs_fs_info *info = root->fs_info;
1219         struct btrfs_trans_handle *trans;
1220         int ret;
1221 
1222         if (test_and_set_bit(BTRFS_ROOT_DEFRAG_RUNNING, &root->state))
1223                 return 0;
1224 
1225         while (1) {
1226                 trans = btrfs_start_transaction(root, 0);
1227                 if (IS_ERR(trans))
1228                         return PTR_ERR(trans);
1229 
1230                 ret = btrfs_defrag_leaves(trans, root);
1231 
1232                 btrfs_end_transaction(trans, root);
1233                 btrfs_btree_balance_dirty(info->tree_root);
1234                 cond_resched();
1235 
1236                 if (btrfs_fs_closing(root->fs_info) || ret != -EAGAIN)
1237                         break;
1238 
1239                 if (btrfs_defrag_cancelled(root->fs_info)) {
1240                         pr_debug("BTRFS: defrag_root cancelled\n");
1241                         ret = -EAGAIN;
1242                         break;
1243                 }
1244         }
1245         clear_bit(BTRFS_ROOT_DEFRAG_RUNNING, &root->state);
1246         return ret;
1247 }
1248 
1249 /*
1250  * new snapshots need to be created at a very specific time in the
1251  * transaction commit.  This does the actual creation.
1252  *
1253  * Note:
1254  * If the error which may affect the commitment of the current transaction
1255  * happens, we should return the error number. If the error which just affect
1256  * the creation of the pending snapshots, just return 0.
1257  */
1258 static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
1259                                    struct btrfs_fs_info *fs_info,
1260                                    struct btrfs_pending_snapshot *pending)
1261 {
1262         struct btrfs_key key;
1263         struct btrfs_root_item *new_root_item;
1264         struct btrfs_root *tree_root = fs_info->tree_root;
1265         struct btrfs_root *root = pending->root;
1266         struct btrfs_root *parent_root;
1267         struct btrfs_block_rsv *rsv;
1268         struct inode *parent_inode;
1269         struct btrfs_path *path;
1270         struct btrfs_dir_item *dir_item;
1271         struct dentry *dentry;
1272         struct extent_buffer *tmp;
1273         struct extent_buffer *old;
1274         struct timespec cur_time = CURRENT_TIME;
1275         int ret = 0;
1276         u64 to_reserve = 0;
1277         u64 index = 0;
1278         u64 objectid;
1279         u64 root_flags;
1280         uuid_le new_uuid;
1281 
1282         path = btrfs_alloc_path();
1283         if (!path) {
1284                 pending->error = -ENOMEM;
1285                 return 0;
1286         }
1287 
1288         new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
1289         if (!new_root_item) {
1290                 pending->error = -ENOMEM;
1291                 goto root_item_alloc_fail;
1292         }
1293 
1294         pending->error = btrfs_find_free_objectid(tree_root, &objectid);
1295         if (pending->error)
1296                 goto no_free_objectid;
1297 
1298         /*
1299          * Make qgroup to skip current new snapshot's qgroupid, as it is
1300          * accounted by later btrfs_qgroup_inherit().
1301          */
1302         btrfs_set_skip_qgroup(trans, objectid);
1303 
1304         btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
1305 
1306         if (to_reserve > 0) {
1307                 pending->error = btrfs_block_rsv_add(root,
1308                                                      &pending->block_rsv,
1309                                                      to_reserve,
1310                                                      BTRFS_RESERVE_NO_FLUSH);
1311                 if (pending->error)
1312                         goto clear_skip_qgroup;
1313         }
1314 
1315         key.objectid = objectid;
1316         key.offset = (u64)-1;
1317         key.type = BTRFS_ROOT_ITEM_KEY;
1318 
1319         rsv = trans->block_rsv;
1320         trans->block_rsv = &pending->block_rsv;
1321         trans->bytes_reserved = trans->block_rsv->reserved;
1322 
1323         dentry = pending->dentry;
1324         parent_inode = pending->dir;
1325         parent_root = BTRFS_I(parent_inode)->root;
1326         record_root_in_trans(trans, parent_root);
1327 
1328         /*
1329          * insert the directory item
1330          */
1331         ret = btrfs_set_inode_index(parent_inode, &index);
1332         BUG_ON(ret); /* -ENOMEM */
1333 
1334         /* check if there is a file/dir which has the same name. */
1335         dir_item = btrfs_lookup_dir_item(NULL, parent_root, path,
1336                                          btrfs_ino(parent_inode),
1337                                          dentry->d_name.name,
1338                                          dentry->d_name.len, 0);
1339         if (dir_item != NULL && !IS_ERR(dir_item)) {
1340                 pending->error = -EEXIST;
1341                 goto dir_item_existed;
1342         } else if (IS_ERR(dir_item)) {
1343                 ret = PTR_ERR(dir_item);
1344                 btrfs_abort_transaction(trans, root, ret);
1345                 goto fail;
1346         }
1347         btrfs_release_path(path);
1348 
1349         /*
1350          * pull in the delayed directory update
1351          * and the delayed inode item
1352          * otherwise we corrupt the FS during
1353          * snapshot
1354          */
1355         ret = btrfs_run_delayed_items(trans, root);
1356         if (ret) {      /* Transaction aborted */
1357                 btrfs_abort_transaction(trans, root, ret);
1358                 goto fail;
1359         }
1360 
1361         record_root_in_trans(trans, root);
1362         btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
1363         memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
1364         btrfs_check_and_init_root_item(new_root_item);
1365 
1366         root_flags = btrfs_root_flags(new_root_item);
1367         if (pending->readonly)
1368                 root_flags |= BTRFS_ROOT_SUBVOL_RDONLY;
1369         else
1370                 root_flags &= ~BTRFS_ROOT_SUBVOL_RDONLY;
1371         btrfs_set_root_flags(new_root_item, root_flags);
1372 
1373         btrfs_set_root_generation_v2(new_root_item,
1374                         trans->transid);
1375         uuid_le_gen(&new_uuid);
1376         memcpy(new_root_item->uuid, new_uuid.b, BTRFS_UUID_SIZE);
1377         memcpy(new_root_item->parent_uuid, root->root_item.uuid,
1378                         BTRFS_UUID_SIZE);
1379         if (!(root_flags & BTRFS_ROOT_SUBVOL_RDONLY)) {
1380                 memset(new_root_item->received_uuid, 0,
1381                        sizeof(new_root_item->received_uuid));
1382                 memset(&new_root_item->stime, 0, sizeof(new_root_item->stime));
1383                 memset(&new_root_item->rtime, 0, sizeof(new_root_item->rtime));
1384                 btrfs_set_root_stransid(new_root_item, 0);
1385                 btrfs_set_root_rtransid(new_root_item, 0);
1386         }
1387         btrfs_set_stack_timespec_sec(&new_root_item->otime, cur_time.tv_sec);
1388         btrfs_set_stack_timespec_nsec(&new_root_item->otime, cur_time.tv_nsec);
1389         btrfs_set_root_otransid(new_root_item, trans->transid);
1390 
1391         old = btrfs_lock_root_node(root);
1392         ret = btrfs_cow_block(trans, root, old, NULL, 0, &old);
1393         if (ret) {
1394                 btrfs_tree_unlock(old);
1395                 free_extent_buffer(old);
1396                 btrfs_abort_transaction(trans, root, ret);
1397                 goto fail;
1398         }
1399 
1400         btrfs_set_lock_blocking(old);
1401 
1402         ret = btrfs_copy_root(trans, root, old, &tmp, objectid);
1403         /* clean up in any case */
1404         btrfs_tree_unlock(old);
1405         free_extent_buffer(old);
1406         if (ret) {
1407                 btrfs_abort_transaction(trans, root, ret);
1408                 goto fail;
1409         }
1410         /* see comments in should_cow_block() */
1411         set_bit(BTRFS_ROOT_FORCE_COW, &root->state);
1412         smp_wmb();
1413 
1414         btrfs_set_root_node(new_root_item, tmp);
1415         /* record when the snapshot was created in key.offset */
1416         key.offset = trans->transid;
1417         ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
1418         btrfs_tree_unlock(tmp);
1419         free_extent_buffer(tmp);
1420         if (ret) {
1421                 btrfs_abort_transaction(trans, root, ret);
1422                 goto fail;
1423         }
1424 
1425         /*
1426          * insert root back/forward references
1427          */
1428         ret = btrfs_add_root_ref(trans, tree_root, objectid,
1429                                  parent_root->root_key.objectid,
1430                                  btrfs_ino(parent_inode), index,
1431                                  dentry->d_name.name, dentry->d_name.len);
1432         if (ret) {
1433                 btrfs_abort_transaction(trans, root, ret);
1434                 goto fail;
1435         }
1436 
1437         key.offset = (u64)-1;
1438         pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
1439         if (IS_ERR(pending->snap)) {
1440                 ret = PTR_ERR(pending->snap);
1441                 btrfs_abort_transaction(trans, root, ret);
1442                 goto fail;
1443         }
1444 
1445         ret = btrfs_reloc_post_snapshot(trans, pending);
1446         if (ret) {
1447                 btrfs_abort_transaction(trans, root, ret);
1448                 goto fail;
1449         }
1450 
1451         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1452         if (ret) {
1453                 btrfs_abort_transaction(trans, root, ret);
1454                 goto fail;
1455         }
1456 
1457         ret = btrfs_insert_dir_item(trans, parent_root,
1458                                     dentry->d_name.name, dentry->d_name.len,
1459                                     parent_inode, &key,
1460                                     BTRFS_FT_DIR, index);
1461         /* We have check then name at the beginning, so it is impossible. */
1462         BUG_ON(ret == -EEXIST || ret == -EOVERFLOW);
1463         if (ret) {
1464                 btrfs_abort_transaction(trans, root, ret);
1465                 goto fail;
1466         }
1467 
1468         btrfs_i_size_write(parent_inode, parent_inode->i_size +
1469                                          dentry->d_name.len * 2);
1470         parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
1471         ret = btrfs_update_inode_fallback(trans, parent_root, parent_inode);
1472         if (ret) {
1473                 btrfs_abort_transaction(trans, root, ret);
1474                 goto fail;
1475         }
1476         ret = btrfs_uuid_tree_add(trans, fs_info->uuid_root, new_uuid.b,
1477                                   BTRFS_UUID_KEY_SUBVOL, objectid);
1478         if (ret) {
1479                 btrfs_abort_transaction(trans, root, ret);
1480                 goto fail;
1481         }
1482         if (!btrfs_is_empty_uuid(new_root_item->received_uuid)) {
1483                 ret = btrfs_uuid_tree_add(trans, fs_info->uuid_root,
1484                                           new_root_item->received_uuid,
1485                                           BTRFS_UUID_KEY_RECEIVED_SUBVOL,
1486                                           objectid);
1487                 if (ret && ret != -EEXIST) {
1488                         btrfs_abort_transaction(trans, root, ret);
1489                         goto fail;
1490                 }
1491         }
1492 
1493         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1494         if (ret) {
1495                 btrfs_abort_transaction(trans, root, ret);
1496                 goto fail;
1497         }
1498 
1499         /*
1500          * account qgroup counters before qgroup_inherit()
1501          */
1502         ret = btrfs_qgroup_prepare_account_extents(trans, fs_info);
1503         if (ret)
1504                 goto fail;
1505         ret = btrfs_qgroup_account_extents(trans, fs_info);
1506         if (ret)
1507                 goto fail;
1508         ret = btrfs_qgroup_inherit(trans, fs_info,
1509                                    root->root_key.objectid,
1510                                    objectid, pending->inherit);
1511         if (ret) {
1512                 btrfs_abort_transaction(trans, root, ret);
1513                 goto fail;
1514         }
1515 
1516 fail:
1517         pending->error = ret;
1518 dir_item_existed:
1519         trans->block_rsv = rsv;
1520         trans->bytes_reserved = 0;
1521 clear_skip_qgroup:
1522         btrfs_clear_skip_qgroup(trans);
1523 no_free_objectid:
1524         kfree(new_root_item);
1525 root_item_alloc_fail:
1526         btrfs_free_path(path);
1527         return ret;
1528 }
1529 
1530 /*
1531  * create all the snapshots we've scheduled for creation
1532  */
1533 static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
1534                                              struct btrfs_fs_info *fs_info)
1535 {
1536         struct btrfs_pending_snapshot *pending, *next;
1537         struct list_head *head = &trans->transaction->pending_snapshots;
1538         int ret = 0;
1539 
1540         list_for_each_entry_safe(pending, next, head, list) {
1541                 list_del(&pending->list);
1542                 ret = create_pending_snapshot(trans, fs_info, pending);
1543                 if (ret)
1544                         break;
1545         }
1546         return ret;
1547 }
1548 
1549 static void update_super_roots(struct btrfs_root *root)
1550 {
1551         struct btrfs_root_item *root_item;
1552         struct btrfs_super_block *super;
1553 
1554         super = root->fs_info->super_copy;
1555 
1556         root_item = &root->fs_info->chunk_root->root_item;
1557         super->chunk_root = root_item->bytenr;
1558         super->chunk_root_generation = root_item->generation;
1559         super->chunk_root_level = root_item->level;
1560 
1561         root_item = &root->fs_info->tree_root->root_item;
1562         super->root = root_item->bytenr;
1563         super->generation = root_item->generation;
1564         super->root_level = root_item->level;
1565         if (btrfs_test_opt(root, SPACE_CACHE))
1566                 super->cache_generation = root_item->generation;
1567         if (root->fs_info->update_uuid_tree_gen)
1568                 super->uuid_tree_generation = root_item->generation;
1569 }
1570 
1571 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
1572 {
1573         struct btrfs_transaction *trans;
1574         int ret = 0;
1575 
1576         spin_lock(&info->trans_lock);
1577         trans = info->running_transaction;
1578         if (trans)
1579                 ret = (trans->state >= TRANS_STATE_COMMIT_START);
1580         spin_unlock(&info->trans_lock);
1581         return ret;
1582 }
1583 
1584 int btrfs_transaction_blocked(struct btrfs_fs_info *info)
1585 {
1586         struct btrfs_transaction *trans;
1587         int ret = 0;
1588 
1589         spin_lock(&info->trans_lock);
1590         trans = info->running_transaction;
1591         if (trans)
1592                 ret = is_transaction_blocked(trans);
1593         spin_unlock(&info->trans_lock);
1594         return ret;
1595 }
1596 
1597 /*
1598  * wait for the current transaction commit to start and block subsequent
1599  * transaction joins
1600  */
1601 static void wait_current_trans_commit_start(struct btrfs_root *root,
1602                                             struct btrfs_transaction *trans)
1603 {
1604         wait_event(root->fs_info->transaction_blocked_wait,
1605                    trans->state >= TRANS_STATE_COMMIT_START ||
1606                    trans->aborted);
1607 }
1608 
1609 /*
1610  * wait for the current transaction to start and then become unblocked.
1611  * caller holds ref.
1612  */
1613 static void wait_current_trans_commit_start_and_unblock(struct btrfs_root *root,
1614                                          struct btrfs_transaction *trans)
1615 {
1616         wait_event(root->fs_info->transaction_wait,
1617                    trans->state >= TRANS_STATE_UNBLOCKED ||
1618                    trans->aborted);
1619 }
1620 
1621 /*
1622  * commit transactions asynchronously. once btrfs_commit_transaction_async
1623  * returns, any subsequent transaction will not be allowed to join.
1624  */
1625 struct btrfs_async_commit {
1626         struct btrfs_trans_handle *newtrans;
1627         struct btrfs_root *root;
1628         struct work_struct work;
1629 };
1630 
1631 static void do_async_commit(struct work_struct *work)
1632 {
1633         struct btrfs_async_commit *ac =
1634                 container_of(work, struct btrfs_async_commit, work);
1635 
1636         /*
1637          * We've got freeze protection passed with the transaction.
1638          * Tell lockdep about it.
1639          */
1640         if (ac->newtrans->type & __TRANS_FREEZABLE)
1641                 rwsem_acquire_read(
1642                      &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
1643                      0, 1, _THIS_IP_);
1644 
1645         current->journal_info = ac->newtrans;
1646 
1647         btrfs_commit_transaction(ac->newtrans, ac->root);
1648         kfree(ac);
1649 }
1650 
1651 int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
1652                                    struct btrfs_root *root,
1653                                    int wait_for_unblock)
1654 {
1655         struct btrfs_async_commit *ac;
1656         struct btrfs_transaction *cur_trans;
1657 
1658         ac = kmalloc(sizeof(*ac), GFP_NOFS);
1659         if (!ac)
1660                 return -ENOMEM;
1661 
1662         INIT_WORK(&ac->work, do_async_commit);
1663         ac->root = root;
1664         ac->newtrans = btrfs_join_transaction(root);
1665         if (IS_ERR(ac->newtrans)) {
1666                 int err = PTR_ERR(ac->newtrans);
1667                 kfree(ac);
1668                 return err;
1669         }
1670 
1671         /* take transaction reference */
1672         cur_trans = trans->transaction;
1673         atomic_inc(&cur_trans->use_count);
1674 
1675         btrfs_end_transaction(trans, root);
1676 
1677         /*
1678          * Tell lockdep we've released the freeze rwsem, since the
1679          * async commit thread will be the one to unlock it.
1680          */
1681         if (ac->newtrans->type & __TRANS_FREEZABLE)
1682                 rwsem_release(
1683                         &root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
1684                         1, _THIS_IP_);
1685 
1686         schedule_work(&ac->work);
1687 
1688         /* wait for transaction to start and unblock */
1689         if (wait_for_unblock)
1690                 wait_current_trans_commit_start_and_unblock(root, cur_trans);
1691         else
1692                 wait_current_trans_commit_start(root, cur_trans);
1693 
1694         if (current->journal_info == trans)
1695                 current->journal_info = NULL;
1696 
1697         btrfs_put_transaction(cur_trans);
1698         return 0;
1699 }
1700 
1701 
1702 static void cleanup_transaction(struct btrfs_trans_handle *trans,
1703                                 struct btrfs_root *root, int err)
1704 {
1705         struct btrfs_transaction *cur_trans = trans->transaction;
1706         DEFINE_WAIT(wait);
1707 
1708         WARN_ON(trans->use_count > 1);
1709 
1710         btrfs_abort_transaction(trans, root, err);
1711 
1712         spin_lock(&root->fs_info->trans_lock);
1713 
1714         /*
1715          * If the transaction is removed from the list, it means this
1716          * transaction has been committed successfully, so it is impossible
1717          * to call the cleanup function.
1718          */
1719         BUG_ON(list_empty(&cur_trans->list));
1720 
1721         list_del_init(&cur_trans->list);
1722         if (cur_trans == root->fs_info->running_transaction) {
1723                 cur_trans->state = TRANS_STATE_COMMIT_DOING;
1724                 spin_unlock(&root->fs_info->trans_lock);
1725                 wait_event(cur_trans->writer_wait,
1726                            atomic_read(&cur_trans->num_writers) == 1);
1727 
1728                 spin_lock(&root->fs_info->trans_lock);
1729         }
1730         spin_unlock(&root->fs_info->trans_lock);
1731 
1732         btrfs_cleanup_one_transaction(trans->transaction, root);
1733 
1734         spin_lock(&root->fs_info->trans_lock);
1735         if (cur_trans == root->fs_info->running_transaction)
1736                 root->fs_info->running_transaction = NULL;
1737         spin_unlock(&root->fs_info->trans_lock);
1738 
1739         if (trans->type & __TRANS_FREEZABLE)
1740                 sb_end_intwrite(root->fs_info->sb);
1741         btrfs_put_transaction(cur_trans);
1742         btrfs_put_transaction(cur_trans);
1743 
1744         trace_btrfs_transaction_commit(root);
1745 
1746         if (current->journal_info == trans)
1747                 current->journal_info = NULL;
1748         btrfs_scrub_cancel(root->fs_info);
1749 
1750         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1751 }
1752 
1753 static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
1754 {
1755         if (btrfs_test_opt(fs_info->tree_root, FLUSHONCOMMIT))
1756                 return btrfs_start_delalloc_roots(fs_info, 1, -1);
1757         return 0;
1758 }
1759 
1760 static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
1761 {
1762         if (btrfs_test_opt(fs_info->tree_root, FLUSHONCOMMIT))
1763                 btrfs_wait_ordered_roots(fs_info, -1);
1764 }
1765 
1766 static inline void
1767 btrfs_wait_pending_ordered(struct btrfs_transaction *cur_trans,
1768                            struct btrfs_fs_info *fs_info)
1769 {
1770         struct btrfs_ordered_extent *ordered;
1771 
1772         spin_lock(&fs_info->trans_lock);
1773         while (!list_empty(&cur_trans->pending_ordered)) {
1774                 ordered = list_first_entry(&cur_trans->pending_ordered,
1775                                            struct btrfs_ordered_extent,
1776                                            trans_list);
1777                 list_del_init(&ordered->trans_list);
1778                 spin_unlock(&fs_info->trans_lock);
1779 
1780                 wait_event(ordered->wait, test_bit(BTRFS_ORDERED_COMPLETE,
1781                                                    &ordered->flags));
1782                 btrfs_put_ordered_extent(ordered);
1783                 spin_lock(&fs_info->trans_lock);
1784         }
1785         spin_unlock(&fs_info->trans_lock);
1786 }
1787 
1788 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
1789                              struct btrfs_root *root)
1790 {
1791         struct btrfs_transaction *cur_trans = trans->transaction;
1792         struct btrfs_transaction *prev_trans = NULL;
1793         struct btrfs_inode *btree_ino = BTRFS_I(root->fs_info->btree_inode);
1794         int ret;
1795 
1796         /* Stop the commit early if ->aborted is set */
1797         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1798                 ret = cur_trans->aborted;
1799                 btrfs_end_transaction(trans, root);
1800                 return ret;
1801         }
1802 
1803         /* make a pass through all the delayed refs we have so far
1804          * any runnings procs may add more while we are here
1805          */
1806         ret = btrfs_run_delayed_refs(trans, root, 0);
1807         if (ret) {
1808                 btrfs_end_transaction(trans, root);
1809                 return ret;
1810         }
1811 
1812         btrfs_trans_release_metadata(trans, root);
1813         trans->block_rsv = NULL;
1814         if (trans->qgroup_reserved) {
1815                 btrfs_qgroup_free(root, trans->qgroup_reserved);
1816                 trans->qgroup_reserved = 0;
1817         }
1818 
1819         cur_trans = trans->transaction;
1820 
1821         /*
1822          * set the flushing flag so procs in this transaction have to
1823          * start sending their work down.
1824          */
1825         cur_trans->delayed_refs.flushing = 1;
1826         smp_wmb();
1827 
1828         if (!list_empty(&trans->new_bgs))
1829                 btrfs_create_pending_block_groups(trans, root);
1830 
1831         ret = btrfs_run_delayed_refs(trans, root, 0);
1832         if (ret) {
1833                 btrfs_end_transaction(trans, root);
1834                 return ret;
1835         }
1836 
1837         if (!cur_trans->dirty_bg_run) {
1838                 int run_it = 0;
1839 
1840                 /* this mutex is also taken before trying to set
1841                  * block groups readonly.  We need to make sure
1842                  * that nobody has set a block group readonly
1843                  * after a extents from that block group have been
1844                  * allocated for cache files.  btrfs_set_block_group_ro
1845                  * will wait for the transaction to commit if it
1846                  * finds dirty_bg_run = 1
1847                  *
1848                  * The dirty_bg_run flag is also used to make sure only
1849                  * one process starts all the block group IO.  It wouldn't
1850                  * hurt to have more than one go through, but there's no
1851                  * real advantage to it either.
1852                  */
1853                 mutex_lock(&root->fs_info->ro_block_group_mutex);
1854                 if (!cur_trans->dirty_bg_run) {
1855                         run_it = 1;
1856                         cur_trans->dirty_bg_run = 1;
1857                 }
1858                 mutex_unlock(&root->fs_info->ro_block_group_mutex);
1859 
1860                 if (run_it)
1861                         ret = btrfs_start_dirty_block_groups(trans, root);
1862         }
1863         if (ret) {
1864                 btrfs_end_transaction(trans, root);
1865                 return ret;
1866         }
1867 
1868         spin_lock(&root->fs_info->trans_lock);
1869         list_splice_init(&trans->ordered, &cur_trans->pending_ordered);
1870         if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
1871                 spin_unlock(&root->fs_info->trans_lock);
1872                 atomic_inc(&cur_trans->use_count);
1873                 ret = btrfs_end_transaction(trans, root);
1874 
1875                 wait_for_commit(root, cur_trans);
1876 
1877                 if (unlikely(cur_trans->aborted))
1878                         ret = cur_trans->aborted;
1879 
1880                 btrfs_put_transaction(cur_trans);
1881 
1882                 return ret;
1883         }
1884 
1885         cur_trans->state = TRANS_STATE_COMMIT_START;
1886         wake_up(&root->fs_info->transaction_blocked_wait);
1887 
1888         if (cur_trans->list.prev != &root->fs_info->trans_list) {
1889                 prev_trans = list_entry(cur_trans->list.prev,
1890                                         struct btrfs_transaction, list);
1891                 if (prev_trans->state != TRANS_STATE_COMPLETED) {
1892                         atomic_inc(&prev_trans->use_count);
1893                         spin_unlock(&root->fs_info->trans_lock);
1894 
1895                         wait_for_commit(root, prev_trans);
1896                         ret = prev_trans->aborted;
1897 
1898                         btrfs_put_transaction(prev_trans);
1899                         if (ret)
1900                                 goto cleanup_transaction;
1901                 } else {
1902                         spin_unlock(&root->fs_info->trans_lock);
1903                 }
1904         } else {
1905                 spin_unlock(&root->fs_info->trans_lock);
1906         }
1907 
1908         extwriter_counter_dec(cur_trans, trans->type);
1909 
1910         ret = btrfs_start_delalloc_flush(root->fs_info);
1911         if (ret)
1912                 goto cleanup_transaction;
1913 
1914         ret = btrfs_run_delayed_items(trans, root);
1915         if (ret)
1916                 goto cleanup_transaction;
1917 
1918         wait_event(cur_trans->writer_wait,
1919                    extwriter_counter_read(cur_trans) == 0);
1920 
1921         /* some pending stuffs might be added after the previous flush. */
1922         ret = btrfs_run_delayed_items(trans, root);
1923         if (ret)
1924                 goto cleanup_transaction;
1925 
1926         btrfs_wait_delalloc_flush(root->fs_info);
1927 
1928         btrfs_wait_pending_ordered(cur_trans, root->fs_info);
1929 
1930         btrfs_scrub_pause(root);
1931         /*
1932          * Ok now we need to make sure to block out any other joins while we
1933          * commit the transaction.  We could have started a join before setting
1934          * COMMIT_DOING so make sure to wait for num_writers to == 1 again.
1935          */
1936         spin_lock(&root->fs_info->trans_lock);
1937         cur_trans->state = TRANS_STATE_COMMIT_DOING;
1938         spin_unlock(&root->fs_info->trans_lock);
1939         wait_event(cur_trans->writer_wait,
1940                    atomic_read(&cur_trans->num_writers) == 1);
1941 
1942         /* ->aborted might be set after the previous check, so check it */
1943         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1944                 ret = cur_trans->aborted;
1945                 goto scrub_continue;
1946         }
1947         /*
1948          * the reloc mutex makes sure that we stop
1949          * the balancing code from coming in and moving
1950          * extents around in the middle of the commit
1951          */
1952         mutex_lock(&root->fs_info->reloc_mutex);
1953 
1954         /*
1955          * We needn't worry about the delayed items because we will
1956          * deal with them in create_pending_snapshot(), which is the
1957          * core function of the snapshot creation.
1958          */
1959         ret = create_pending_snapshots(trans, root->fs_info);
1960         if (ret) {
1961                 mutex_unlock(&root->fs_info->reloc_mutex);
1962                 goto scrub_continue;
1963         }
1964 
1965         /*
1966          * We insert the dir indexes of the snapshots and update the inode
1967          * of the snapshots' parents after the snapshot creation, so there
1968          * are some delayed items which are not dealt with. Now deal with
1969          * them.
1970          *
1971          * We needn't worry that this operation will corrupt the snapshots,
1972          * because all the tree which are snapshoted will be forced to COW
1973          * the nodes and leaves.
1974          */
1975         ret = btrfs_run_delayed_items(trans, root);
1976         if (ret) {
1977                 mutex_unlock(&root->fs_info->reloc_mutex);
1978                 goto scrub_continue;
1979         }
1980 
1981         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1982         if (ret) {
1983                 mutex_unlock(&root->fs_info->reloc_mutex);
1984                 goto scrub_continue;
1985         }
1986 
1987         /* Reocrd old roots for later qgroup accounting */
1988         ret = btrfs_qgroup_prepare_account_extents(trans, root->fs_info);
1989         if (ret) {
1990                 mutex_unlock(&root->fs_info->reloc_mutex);
1991                 goto scrub_continue;
1992         }
1993 
1994         /*
1995          * make sure none of the code above managed to slip in a
1996          * delayed item
1997          */
1998         btrfs_assert_delayed_root_empty(root);
1999 
2000         WARN_ON(cur_trans != trans->transaction);
2001 
2002         /* btrfs_commit_tree_roots is responsible for getting the
2003          * various roots consistent with each other.  Every pointer
2004          * in the tree of tree roots has to point to the most up to date
2005          * root for every subvolume and other tree.  So, we have to keep
2006          * the tree logging code from jumping in and changing any
2007          * of the trees.
2008          *
2009          * At this point in the commit, there can't be any tree-log
2010          * writers, but a little lower down we drop the trans mutex
2011          * and let new people in.  By holding the tree_log_mutex
2012          * from now until after the super is written, we avoid races
2013          * with the tree-log code.
2014          */
2015         mutex_lock(&root->fs_info->tree_log_mutex);
2016 
2017         ret = commit_fs_roots(trans, root);
2018         if (ret) {
2019                 mutex_unlock(&root->fs_info->tree_log_mutex);
2020                 mutex_unlock(&root->fs_info->reloc_mutex);
2021                 goto scrub_continue;
2022         }
2023 
2024         /*
2025          * Since the transaction is done, we can apply the pending changes
2026          * before the next transaction.
2027          */
2028         btrfs_apply_pending_changes(root->fs_info);
2029 
2030         /* commit_fs_roots gets rid of all the tree log roots, it is now
2031          * safe to free the root of tree log roots
2032          */
2033         btrfs_free_log_root_tree(trans, root->fs_info);
2034 
2035         /*
2036          * Since fs roots are all committed, we can get a quite accurate
2037          * new_roots. So let's do quota accounting.
2038          */
2039         ret = btrfs_qgroup_account_extents(trans, root->fs_info);
2040         if (ret < 0) {
2041                 mutex_unlock(&root->fs_info->tree_log_mutex);
2042                 mutex_unlock(&root->fs_info->reloc_mutex);
2043                 goto scrub_continue;
2044         }
2045 
2046         ret = commit_cowonly_roots(trans, root);
2047         if (ret) {
2048                 mutex_unlock(&root->fs_info->tree_log_mutex);
2049                 mutex_unlock(&root->fs_info->reloc_mutex);
2050                 goto scrub_continue;
2051         }
2052 
2053         /*
2054          * The tasks which save the space cache and inode cache may also
2055          * update ->aborted, check it.
2056          */
2057         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
2058                 ret = cur_trans->aborted;
2059                 mutex_unlock(&root->fs_info->tree_log_mutex);
2060                 mutex_unlock(&root->fs_info->reloc_mutex);
2061                 goto scrub_continue;
2062         }
2063 
2064         btrfs_prepare_extent_commit(trans, root);
2065 
2066         cur_trans = root->fs_info->running_transaction;
2067 
2068         btrfs_set_root_node(&root->fs_info->tree_root->root_item,
2069                             root->fs_info->tree_root->node);
2070         list_add_tail(&root->fs_info->tree_root->dirty_list,
2071                       &cur_trans->switch_commits);
2072 
2073         btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
2074                             root->fs_info->chunk_root->node);
2075         list_add_tail(&root->fs_info->chunk_root->dirty_list,
2076                       &cur_trans->switch_commits);
2077 
2078         switch_commit_roots(cur_trans, root->fs_info);
2079 
2080         assert_qgroups_uptodate(trans);
2081         ASSERT(list_empty(&cur_trans->dirty_bgs));
2082         ASSERT(list_empty(&cur_trans->io_bgs));
2083         update_super_roots(root);
2084 
2085         btrfs_set_super_log_root(root->fs_info->super_copy, 0);
2086         btrfs_set_super_log_root_level(root->fs_info->super_copy, 0);
2087         memcpy(root->fs_info->super_for_commit, root->fs_info->super_copy,
2088                sizeof(*root->fs_info->super_copy));
2089 
2090         btrfs_update_commit_device_size(root->fs_info);
2091         btrfs_update_commit_device_bytes_used(root, cur_trans);
2092 
2093         clear_bit(BTRFS_INODE_BTREE_LOG1_ERR, &btree_ino->runtime_flags);
2094         clear_bit(BTRFS_INODE_BTREE_LOG2_ERR, &btree_ino->runtime_flags);
2095 
2096         btrfs_trans_release_chunk_metadata(trans);
2097 
2098         spin_lock(&root->fs_info->trans_lock);
2099         cur_trans->state = TRANS_STATE_UNBLOCKED;
2100         root->fs_info->running_transaction = NULL;
2101         spin_unlock(&root->fs_info->trans_lock);
2102         mutex_unlock(&root->fs_info->reloc_mutex);
2103 
2104         wake_up(&root->fs_info->transaction_wait);
2105 
2106         ret = btrfs_write_and_wait_transaction(trans, root);
2107         if (ret) {
2108                 btrfs_error(root->fs_info, ret,
2109                             "Error while writing out transaction");
2110                 mutex_unlock(&root->fs_info->tree_log_mutex);
2111                 goto scrub_continue;
2112         }
2113 
2114         ret = write_ctree_super(trans, root, 0);
2115         if (ret) {
2116                 mutex_unlock(&root->fs_info->tree_log_mutex);
2117                 goto scrub_continue;
2118         }
2119 
2120         /*
2121          * the super is written, we can safely allow the tree-loggers
2122          * to go about their business
2123          */
2124         mutex_unlock(&root->fs_info->tree_log_mutex);
2125 
2126         btrfs_finish_extent_commit(trans, root);
2127 
2128         if (cur_trans->have_free_bgs)
2129                 btrfs_clear_space_info_full(root->fs_info);
2130 
2131         root->fs_info->last_trans_committed = cur_trans->transid;
2132         /*
2133          * We needn't acquire the lock here because there is no other task
2134          * which can change it.
2135          */
2136         cur_trans->state = TRANS_STATE_COMPLETED;
2137         wake_up(&cur_trans->commit_wait);
2138 
2139         spin_lock(&root->fs_info->trans_lock);
2140         list_del_init(&cur_trans->list);
2141         spin_unlock(&root->fs_info->trans_lock);
2142 
2143         btrfs_put_transaction(cur_trans);
2144         btrfs_put_transaction(cur_trans);
2145 
2146         if (trans->type & __TRANS_FREEZABLE)
2147                 sb_end_intwrite(root->fs_info->sb);
2148 
2149         trace_btrfs_transaction_commit(root);
2150 
2151         btrfs_scrub_continue(root);
2152 
2153         if (current->journal_info == trans)
2154                 current->journal_info = NULL;
2155 
2156         kmem_cache_free(btrfs_trans_handle_cachep, trans);
2157 
2158         if (current != root->fs_info->transaction_kthread &&
2159             current != root->fs_info->cleaner_kthread)
2160                 btrfs_run_delayed_iputs(root);
2161 
2162         return ret;
2163 
2164 scrub_continue:
2165         btrfs_scrub_continue(root);
2166 cleanup_transaction:
2167         btrfs_trans_release_metadata(trans, root);
2168         btrfs_trans_release_chunk_metadata(trans);
2169         trans->block_rsv = NULL;
2170         if (trans->qgroup_reserved) {
2171                 btrfs_qgroup_free(root, trans->qgroup_reserved);
2172                 trans->qgroup_reserved = 0;
2173         }
2174         btrfs_warn(root->fs_info, "Skipping commit of aborted transaction.");
2175         if (current->journal_info == trans)
2176                 current->journal_info = NULL;
2177         cleanup_transaction(trans, root, ret);
2178 
2179         return ret;
2180 }
2181 
2182 /*
2183  * return < 0 if error
2184  * 0 if there are no more dead_roots at the time of call
2185  * 1 there are more to be processed, call me again
2186  *
2187  * The return value indicates there are certainly more snapshots to delete, but
2188  * if there comes a new one during processing, it may return 0. We don't mind,
2189  * because btrfs_commit_super will poke cleaner thread and it will process it a
2190  * few seconds later.
2191  */
2192 int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
2193 {
2194         int ret;
2195         struct btrfs_fs_info *fs_info = root->fs_info;
2196 
2197         spin_lock(&fs_info->trans_lock);
2198         if (list_empty(&fs_info->dead_roots)) {
2199                 spin_unlock(&fs_info->trans_lock);
2200                 return 0;
2201         }
2202         root = list_first_entry(&fs_info->dead_roots,
2203                         struct btrfs_root, root_list);
2204         list_del_init(&root->root_list);
2205         spin_unlock(&fs_info->trans_lock);
2206 
2207         pr_debug("BTRFS: cleaner removing %llu\n", root->objectid);
2208 
2209         btrfs_kill_all_delayed_nodes(root);
2210 
2211         if (btrfs_header_backref_rev(root->node) <
2212                         BTRFS_MIXED_BACKREF_REV)
2213                 ret = btrfs_drop_snapshot(root, NULL, 0, 0);
2214         else
2215                 ret = btrfs_drop_snapshot(root, NULL, 1, 0);
2216 
2217         return (ret < 0) ? 0 : 1;
2218 }
2219 
2220 void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info)
2221 {
2222         unsigned long prev;
2223         unsigned long bit;
2224 
2225         prev = xchg(&fs_info->pending_changes, 0);
2226         if (!prev)
2227                 return;
2228 
2229         bit = 1 << BTRFS_PENDING_SET_INODE_MAP_CACHE;
2230         if (prev & bit)
2231                 btrfs_set_opt(fs_info->mount_opt, INODE_MAP_CACHE);
2232         prev &= ~bit;
2233 
2234         bit = 1 << BTRFS_PENDING_CLEAR_INODE_MAP_CACHE;
2235         if (prev & bit)
2236                 btrfs_clear_opt(fs_info->mount_opt, INODE_MAP_CACHE);
2237         prev &= ~bit;
2238 
2239         bit = 1 << BTRFS_PENDING_COMMIT;
2240         if (prev & bit)
2241                 btrfs_debug(fs_info, "pending commit done");
2242         prev &= ~bit;
2243 
2244         if (prev)
2245                 btrfs_warn(fs_info,
2246                         "unknown pending changes left 0x%lx, ignoring", prev);
2247 }
2248 

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