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Linux/fs/jbd2/commit.c

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  1 // SPDX-License-Identifier: GPL-2.0+
  2 /*
  3  * linux/fs/jbd2/commit.c
  4  *
  5  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
  6  *
  7  * Copyright 1998 Red Hat corp --- All Rights Reserved
  8  *
  9  * Journal commit routines for the generic filesystem journaling code;
 10  * part of the ext2fs journaling system.
 11  */
 12 
 13 #include <linux/time.h>
 14 #include <linux/fs.h>
 15 #include <linux/jbd2.h>
 16 #include <linux/errno.h>
 17 #include <linux/slab.h>
 18 #include <linux/mm.h>
 19 #include <linux/pagemap.h>
 20 #include <linux/jiffies.h>
 21 #include <linux/crc32.h>
 22 #include <linux/writeback.h>
 23 #include <linux/backing-dev.h>
 24 #include <linux/bio.h>
 25 #include <linux/blkdev.h>
 26 #include <linux/bitops.h>
 27 #include <trace/events/jbd2.h>
 28 
 29 /*
 30  * IO end handler for temporary buffer_heads handling writes to the journal.
 31  */
 32 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
 33 {
 34         struct buffer_head *orig_bh = bh->b_private;
 35 
 36         BUFFER_TRACE(bh, "");
 37         if (uptodate)
 38                 set_buffer_uptodate(bh);
 39         else
 40                 clear_buffer_uptodate(bh);
 41         if (orig_bh) {
 42                 clear_bit_unlock(BH_Shadow, &orig_bh->b_state);
 43                 smp_mb__after_atomic();
 44                 wake_up_bit(&orig_bh->b_state, BH_Shadow);
 45         }
 46         unlock_buffer(bh);
 47 }
 48 
 49 /*
 50  * When an ext4 file is truncated, it is possible that some pages are not
 51  * successfully freed, because they are attached to a committing transaction.
 52  * After the transaction commits, these pages are left on the LRU, with no
 53  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
 54  * by the VM, but their apparent absence upsets the VM accounting, and it makes
 55  * the numbers in /proc/meminfo look odd.
 56  *
 57  * So here, we have a buffer which has just come off the forget list.  Look to
 58  * see if we can strip all buffers from the backing page.
 59  *
 60  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
 61  * caller provided us with a ref against the buffer, and we drop that here.
 62  */
 63 static void release_buffer_page(struct buffer_head *bh)
 64 {
 65         struct page *page;
 66 
 67         if (buffer_dirty(bh))
 68                 goto nope;
 69         if (atomic_read(&bh->b_count) != 1)
 70                 goto nope;
 71         page = bh->b_page;
 72         if (!page)
 73                 goto nope;
 74         if (page->mapping)
 75                 goto nope;
 76 
 77         /* OK, it's a truncated page */
 78         if (!trylock_page(page))
 79                 goto nope;
 80 
 81         get_page(page);
 82         __brelse(bh);
 83         try_to_free_buffers(page);
 84         unlock_page(page);
 85         put_page(page);
 86         return;
 87 
 88 nope:
 89         __brelse(bh);
 90 }
 91 
 92 static void jbd2_commit_block_csum_set(journal_t *j, struct buffer_head *bh)
 93 {
 94         struct commit_header *h;
 95         __u32 csum;
 96 
 97         if (!jbd2_journal_has_csum_v2or3(j))
 98                 return;
 99 
100         h = (struct commit_header *)(bh->b_data);
101         h->h_chksum_type = 0;
102         h->h_chksum_size = 0;
103         h->h_chksum[0] = 0;
104         csum = jbd2_chksum(j, j->j_csum_seed, bh->b_data, j->j_blocksize);
105         h->h_chksum[0] = cpu_to_be32(csum);
106 }
107 
108 /*
109  * Done it all: now submit the commit record.  We should have
110  * cleaned up our previous buffers by now, so if we are in abort
111  * mode we can now just skip the rest of the journal write
112  * entirely.
113  *
114  * Returns 1 if the journal needs to be aborted or 0 on success
115  */
116 static int journal_submit_commit_record(journal_t *journal,
117                                         transaction_t *commit_transaction,
118                                         struct buffer_head **cbh,
119                                         __u32 crc32_sum)
120 {
121         struct commit_header *tmp;
122         struct buffer_head *bh;
123         int ret;
124         struct timespec64 now;
125 
126         *cbh = NULL;
127 
128         if (is_journal_aborted(journal))
129                 return 0;
130 
131         bh = jbd2_journal_get_descriptor_buffer(commit_transaction,
132                                                 JBD2_COMMIT_BLOCK);
133         if (!bh)
134                 return 1;
135 
136         tmp = (struct commit_header *)bh->b_data;
137         ktime_get_coarse_real_ts64(&now);
138         tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
139         tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
140 
141         if (jbd2_has_feature_checksum(journal)) {
142                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
143                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
144                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
145         }
146         jbd2_commit_block_csum_set(journal, bh);
147 
148         BUFFER_TRACE(bh, "submit commit block");
149         lock_buffer(bh);
150         clear_buffer_dirty(bh);
151         set_buffer_uptodate(bh);
152         bh->b_end_io = journal_end_buffer_io_sync;
153 
154         if (journal->j_flags & JBD2_BARRIER &&
155             !jbd2_has_feature_async_commit(journal))
156                 ret = submit_bh(REQ_OP_WRITE,
157                         REQ_SYNC | REQ_PREFLUSH | REQ_FUA, bh);
158         else
159                 ret = submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
160 
161         *cbh = bh;
162         return ret;
163 }
164 
165 /*
166  * This function along with journal_submit_commit_record
167  * allows to write the commit record asynchronously.
168  */
169 static int journal_wait_on_commit_record(journal_t *journal,
170                                          struct buffer_head *bh)
171 {
172         int ret = 0;
173 
174         clear_buffer_dirty(bh);
175         wait_on_buffer(bh);
176 
177         if (unlikely(!buffer_uptodate(bh)))
178                 ret = -EIO;
179         put_bh(bh);            /* One for getblk() */
180 
181         return ret;
182 }
183 
184 /*
185  * write the filemap data using writepage() address_space_operations.
186  * We don't do block allocation here even for delalloc. We don't
187  * use writepages() because with delayed allocation we may be doing
188  * block allocation in writepages().
189  */
190 static int journal_submit_inode_data_buffers(struct address_space *mapping,
191                 loff_t dirty_start, loff_t dirty_end)
192 {
193         int ret;
194         struct writeback_control wbc = {
195                 .sync_mode =  WB_SYNC_ALL,
196                 .nr_to_write = mapping->nrpages * 2,
197                 .range_start = dirty_start,
198                 .range_end = dirty_end,
199         };
200 
201         ret = generic_writepages(mapping, &wbc);
202         return ret;
203 }
204 
205 /*
206  * Submit all the data buffers of inode associated with the transaction to
207  * disk.
208  *
209  * We are in a committing transaction. Therefore no new inode can be added to
210  * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
211  * operate on from being released while we write out pages.
212  */
213 static int journal_submit_data_buffers(journal_t *journal,
214                 transaction_t *commit_transaction)
215 {
216         struct jbd2_inode *jinode;
217         int err, ret = 0;
218         struct address_space *mapping;
219 
220         spin_lock(&journal->j_list_lock);
221         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
222                 loff_t dirty_start = jinode->i_dirty_start;
223                 loff_t dirty_end = jinode->i_dirty_end;
224 
225                 if (!(jinode->i_flags & JI_WRITE_DATA))
226                         continue;
227                 mapping = jinode->i_vfs_inode->i_mapping;
228                 jinode->i_flags |= JI_COMMIT_RUNNING;
229                 spin_unlock(&journal->j_list_lock);
230                 /*
231                  * submit the inode data buffers. We use writepage
232                  * instead of writepages. Because writepages can do
233                  * block allocation  with delalloc. We need to write
234                  * only allocated blocks here.
235                  */
236                 trace_jbd2_submit_inode_data(jinode->i_vfs_inode);
237                 err = journal_submit_inode_data_buffers(mapping, dirty_start,
238                                 dirty_end);
239                 if (!ret)
240                         ret = err;
241                 spin_lock(&journal->j_list_lock);
242                 J_ASSERT(jinode->i_transaction == commit_transaction);
243                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
244                 smp_mb();
245                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
246         }
247         spin_unlock(&journal->j_list_lock);
248         return ret;
249 }
250 
251 /*
252  * Wait for data submitted for writeout, refile inodes to proper
253  * transaction if needed.
254  *
255  */
256 static int journal_finish_inode_data_buffers(journal_t *journal,
257                 transaction_t *commit_transaction)
258 {
259         struct jbd2_inode *jinode, *next_i;
260         int err, ret = 0;
261 
262         /* For locking, see the comment in journal_submit_data_buffers() */
263         spin_lock(&journal->j_list_lock);
264         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
265                 loff_t dirty_start = jinode->i_dirty_start;
266                 loff_t dirty_end = jinode->i_dirty_end;
267 
268                 if (!(jinode->i_flags & JI_WAIT_DATA))
269                         continue;
270                 jinode->i_flags |= JI_COMMIT_RUNNING;
271                 spin_unlock(&journal->j_list_lock);
272                 err = filemap_fdatawait_range_keep_errors(
273                                 jinode->i_vfs_inode->i_mapping, dirty_start,
274                                 dirty_end);
275                 if (!ret)
276                         ret = err;
277                 spin_lock(&journal->j_list_lock);
278                 jinode->i_flags &= ~JI_COMMIT_RUNNING;
279                 smp_mb();
280                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
281         }
282 
283         /* Now refile inode to proper lists */
284         list_for_each_entry_safe(jinode, next_i,
285                                  &commit_transaction->t_inode_list, i_list) {
286                 list_del(&jinode->i_list);
287                 if (jinode->i_next_transaction) {
288                         jinode->i_transaction = jinode->i_next_transaction;
289                         jinode->i_next_transaction = NULL;
290                         list_add(&jinode->i_list,
291                                 &jinode->i_transaction->t_inode_list);
292                 } else {
293                         jinode->i_transaction = NULL;
294                         jinode->i_dirty_start = 0;
295                         jinode->i_dirty_end = 0;
296                 }
297         }
298         spin_unlock(&journal->j_list_lock);
299 
300         return ret;
301 }
302 
303 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
304 {
305         struct page *page = bh->b_page;
306         char *addr;
307         __u32 checksum;
308 
309         addr = kmap_atomic(page);
310         checksum = crc32_be(crc32_sum,
311                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
312         kunmap_atomic(addr);
313 
314         return checksum;
315 }
316 
317 static void write_tag_block(journal_t *j, journal_block_tag_t *tag,
318                                    unsigned long long block)
319 {
320         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
321         if (jbd2_has_feature_64bit(j))
322                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
323 }
324 
325 static void jbd2_block_tag_csum_set(journal_t *j, journal_block_tag_t *tag,
326                                     struct buffer_head *bh, __u32 sequence)
327 {
328         journal_block_tag3_t *tag3 = (journal_block_tag3_t *)tag;
329         struct page *page = bh->b_page;
330         __u8 *addr;
331         __u32 csum32;
332         __be32 seq;
333 
334         if (!jbd2_journal_has_csum_v2or3(j))
335                 return;
336 
337         seq = cpu_to_be32(sequence);
338         addr = kmap_atomic(page);
339         csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&seq, sizeof(seq));
340         csum32 = jbd2_chksum(j, csum32, addr + offset_in_page(bh->b_data),
341                              bh->b_size);
342         kunmap_atomic(addr);
343 
344         if (jbd2_has_feature_csum3(j))
345                 tag3->t_checksum = cpu_to_be32(csum32);
346         else
347                 tag->t_checksum = cpu_to_be16(csum32);
348 }
349 /*
350  * jbd2_journal_commit_transaction
351  *
352  * The primary function for committing a transaction to the log.  This
353  * function is called by the journal thread to begin a complete commit.
354  */
355 void jbd2_journal_commit_transaction(journal_t *journal)
356 {
357         struct transaction_stats_s stats;
358         transaction_t *commit_transaction;
359         struct journal_head *jh;
360         struct buffer_head *descriptor;
361         struct buffer_head **wbuf = journal->j_wbuf;
362         int bufs;
363         int flags;
364         int err;
365         unsigned long long blocknr;
366         ktime_t start_time;
367         u64 commit_time;
368         char *tagp = NULL;
369         journal_block_tag_t *tag = NULL;
370         int space_left = 0;
371         int first_tag = 0;
372         int tag_flag;
373         int i;
374         int tag_bytes = journal_tag_bytes(journal);
375         struct buffer_head *cbh = NULL; /* For transactional checksums */
376         __u32 crc32_sum = ~0;
377         struct blk_plug plug;
378         /* Tail of the journal */
379         unsigned long first_block;
380         tid_t first_tid;
381         int update_tail;
382         int csum_size = 0;
383         LIST_HEAD(io_bufs);
384         LIST_HEAD(log_bufs);
385 
386         if (jbd2_journal_has_csum_v2or3(journal))
387                 csum_size = sizeof(struct jbd2_journal_block_tail);
388 
389         /*
390          * First job: lock down the current transaction and wait for
391          * all outstanding updates to complete.
392          */
393 
394         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
395         if (journal->j_flags & JBD2_FLUSHED) {
396                 jbd_debug(3, "super block updated\n");
397                 mutex_lock_io(&journal->j_checkpoint_mutex);
398                 /*
399                  * We hold j_checkpoint_mutex so tail cannot change under us.
400                  * We don't need any special data guarantees for writing sb
401                  * since journal is empty and it is ok for write to be
402                  * flushed only with transaction commit.
403                  */
404                 jbd2_journal_update_sb_log_tail(journal,
405                                                 journal->j_tail_sequence,
406                                                 journal->j_tail,
407                                                 REQ_SYNC);
408                 mutex_unlock(&journal->j_checkpoint_mutex);
409         } else {
410                 jbd_debug(3, "superblock not updated\n");
411         }
412 
413         J_ASSERT(journal->j_running_transaction != NULL);
414         J_ASSERT(journal->j_committing_transaction == NULL);
415 
416         commit_transaction = journal->j_running_transaction;
417 
418         trace_jbd2_start_commit(journal, commit_transaction);
419         jbd_debug(1, "JBD2: starting commit of transaction %d\n",
420                         commit_transaction->t_tid);
421 
422         write_lock(&journal->j_state_lock);
423         J_ASSERT(commit_transaction->t_state == T_RUNNING);
424         commit_transaction->t_state = T_LOCKED;
425 
426         trace_jbd2_commit_locking(journal, commit_transaction);
427         stats.run.rs_wait = commit_transaction->t_max_wait;
428         stats.run.rs_request_delay = 0;
429         stats.run.rs_locked = jiffies;
430         if (commit_transaction->t_requested)
431                 stats.run.rs_request_delay =
432                         jbd2_time_diff(commit_transaction->t_requested,
433                                        stats.run.rs_locked);
434         stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
435                                               stats.run.rs_locked);
436 
437         spin_lock(&commit_transaction->t_handle_lock);
438         while (atomic_read(&commit_transaction->t_updates)) {
439                 DEFINE_WAIT(wait);
440 
441                 prepare_to_wait(&journal->j_wait_updates, &wait,
442                                         TASK_UNINTERRUPTIBLE);
443                 if (atomic_read(&commit_transaction->t_updates)) {
444                         spin_unlock(&commit_transaction->t_handle_lock);
445                         write_unlock(&journal->j_state_lock);
446                         schedule();
447                         write_lock(&journal->j_state_lock);
448                         spin_lock(&commit_transaction->t_handle_lock);
449                 }
450                 finish_wait(&journal->j_wait_updates, &wait);
451         }
452         spin_unlock(&commit_transaction->t_handle_lock);
453         commit_transaction->t_state = T_SWITCH;
454         write_unlock(&journal->j_state_lock);
455 
456         J_ASSERT (atomic_read(&commit_transaction->t_outstanding_credits) <=
457                         journal->j_max_transaction_buffers);
458 
459         /*
460          * First thing we are allowed to do is to discard any remaining
461          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
462          * that there are no such buffers: if a large filesystem
463          * operation like a truncate needs to split itself over multiple
464          * transactions, then it may try to do a jbd2_journal_restart() while
465          * there are still BJ_Reserved buffers outstanding.  These must
466          * be released cleanly from the current transaction.
467          *
468          * In this case, the filesystem must still reserve write access
469          * again before modifying the buffer in the new transaction, but
470          * we do not require it to remember exactly which old buffers it
471          * has reserved.  This is consistent with the existing behaviour
472          * that multiple jbd2_journal_get_write_access() calls to the same
473          * buffer are perfectly permissible.
474          */
475         while (commit_transaction->t_reserved_list) {
476                 jh = commit_transaction->t_reserved_list;
477                 JBUFFER_TRACE(jh, "reserved, unused: refile");
478                 /*
479                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
480                  * leave undo-committed data.
481                  */
482                 if (jh->b_committed_data) {
483                         struct buffer_head *bh = jh2bh(jh);
484 
485                         spin_lock(&jh->b_state_lock);
486                         jbd2_free(jh->b_committed_data, bh->b_size);
487                         jh->b_committed_data = NULL;
488                         spin_unlock(&jh->b_state_lock);
489                 }
490                 jbd2_journal_refile_buffer(journal, jh);
491         }
492 
493         /*
494          * Now try to drop any written-back buffers from the journal's
495          * checkpoint lists.  We do this *before* commit because it potentially
496          * frees some memory
497          */
498         spin_lock(&journal->j_list_lock);
499         __jbd2_journal_clean_checkpoint_list(journal, false);
500         spin_unlock(&journal->j_list_lock);
501 
502         jbd_debug(3, "JBD2: commit phase 1\n");
503 
504         /*
505          * Clear revoked flag to reflect there is no revoked buffers
506          * in the next transaction which is going to be started.
507          */
508         jbd2_clear_buffer_revoked_flags(journal);
509 
510         /*
511          * Switch to a new revoke table.
512          */
513         jbd2_journal_switch_revoke_table(journal);
514 
515         /*
516          * Reserved credits cannot be claimed anymore, free them
517          */
518         atomic_sub(atomic_read(&journal->j_reserved_credits),
519                    &commit_transaction->t_outstanding_credits);
520 
521         write_lock(&journal->j_state_lock);
522         trace_jbd2_commit_flushing(journal, commit_transaction);
523         stats.run.rs_flushing = jiffies;
524         stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,
525                                              stats.run.rs_flushing);
526 
527         commit_transaction->t_state = T_FLUSH;
528         journal->j_committing_transaction = commit_transaction;
529         journal->j_running_transaction = NULL;
530         start_time = ktime_get();
531         commit_transaction->t_log_start = journal->j_head;
532         wake_up(&journal->j_wait_transaction_locked);
533         write_unlock(&journal->j_state_lock);
534 
535         jbd_debug(3, "JBD2: commit phase 2a\n");
536 
537         /*
538          * Now start flushing things to disk, in the order they appear
539          * on the transaction lists.  Data blocks go first.
540          */
541         err = journal_submit_data_buffers(journal, commit_transaction);
542         if (err)
543                 jbd2_journal_abort(journal, err);
544 
545         blk_start_plug(&plug);
546         jbd2_journal_write_revoke_records(commit_transaction, &log_bufs);
547 
548         jbd_debug(3, "JBD2: commit phase 2b\n");
549 
550         /*
551          * Way to go: we have now written out all of the data for a
552          * transaction!  Now comes the tricky part: we need to write out
553          * metadata.  Loop over the transaction's entire buffer list:
554          */
555         write_lock(&journal->j_state_lock);
556         commit_transaction->t_state = T_COMMIT;
557         write_unlock(&journal->j_state_lock);
558 
559         trace_jbd2_commit_logging(journal, commit_transaction);
560         stats.run.rs_logging = jiffies;
561         stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
562                                                stats.run.rs_logging);
563         stats.run.rs_blocks = commit_transaction->t_nr_buffers;
564         stats.run.rs_blocks_logged = 0;
565 
566         J_ASSERT(commit_transaction->t_nr_buffers <=
567                  atomic_read(&commit_transaction->t_outstanding_credits));
568 
569         err = 0;
570         bufs = 0;
571         descriptor = NULL;
572         while (commit_transaction->t_buffers) {
573 
574                 /* Find the next buffer to be journaled... */
575 
576                 jh = commit_transaction->t_buffers;
577 
578                 /* If we're in abort mode, we just un-journal the buffer and
579                    release it. */
580 
581                 if (is_journal_aborted(journal)) {
582                         clear_buffer_jbddirty(jh2bh(jh));
583                         JBUFFER_TRACE(jh, "journal is aborting: refile");
584                         jbd2_buffer_abort_trigger(jh,
585                                                   jh->b_frozen_data ?
586                                                   jh->b_frozen_triggers :
587                                                   jh->b_triggers);
588                         jbd2_journal_refile_buffer(journal, jh);
589                         /* If that was the last one, we need to clean up
590                          * any descriptor buffers which may have been
591                          * already allocated, even if we are now
592                          * aborting. */
593                         if (!commit_transaction->t_buffers)
594                                 goto start_journal_io;
595                         continue;
596                 }
597 
598                 /* Make sure we have a descriptor block in which to
599                    record the metadata buffer. */
600 
601                 if (!descriptor) {
602                         J_ASSERT (bufs == 0);
603 
604                         jbd_debug(4, "JBD2: get descriptor\n");
605 
606                         descriptor = jbd2_journal_get_descriptor_buffer(
607                                                         commit_transaction,
608                                                         JBD2_DESCRIPTOR_BLOCK);
609                         if (!descriptor) {
610                                 jbd2_journal_abort(journal, -EIO);
611                                 continue;
612                         }
613 
614                         jbd_debug(4, "JBD2: got buffer %llu (%p)\n",
615                                 (unsigned long long)descriptor->b_blocknr,
616                                 descriptor->b_data);
617                         tagp = &descriptor->b_data[sizeof(journal_header_t)];
618                         space_left = descriptor->b_size -
619                                                 sizeof(journal_header_t);
620                         first_tag = 1;
621                         set_buffer_jwrite(descriptor);
622                         set_buffer_dirty(descriptor);
623                         wbuf[bufs++] = descriptor;
624 
625                         /* Record it so that we can wait for IO
626                            completion later */
627                         BUFFER_TRACE(descriptor, "ph3: file as descriptor");
628                         jbd2_file_log_bh(&log_bufs, descriptor);
629                 }
630 
631                 /* Where is the buffer to be written? */
632 
633                 err = jbd2_journal_next_log_block(journal, &blocknr);
634                 /* If the block mapping failed, just abandon the buffer
635                    and repeat this loop: we'll fall into the
636                    refile-on-abort condition above. */
637                 if (err) {
638                         jbd2_journal_abort(journal, err);
639                         continue;
640                 }
641 
642                 /*
643                  * start_this_handle() uses t_outstanding_credits to determine
644                  * the free space in the log.
645                  */
646                 atomic_dec(&commit_transaction->t_outstanding_credits);
647 
648                 /* Bump b_count to prevent truncate from stumbling over
649                    the shadowed buffer!  @@@ This can go if we ever get
650                    rid of the shadow pairing of buffers. */
651                 atomic_inc(&jh2bh(jh)->b_count);
652 
653                 /*
654                  * Make a temporary IO buffer with which to write it out
655                  * (this will requeue the metadata buffer to BJ_Shadow).
656                  */
657                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
658                 JBUFFER_TRACE(jh, "ph3: write metadata");
659                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
660                                                 jh, &wbuf[bufs], blocknr);
661                 if (flags < 0) {
662                         jbd2_journal_abort(journal, flags);
663                         continue;
664                 }
665                 jbd2_file_log_bh(&io_bufs, wbuf[bufs]);
666 
667                 /* Record the new block's tag in the current descriptor
668                    buffer */
669 
670                 tag_flag = 0;
671                 if (flags & 1)
672                         tag_flag |= JBD2_FLAG_ESCAPE;
673                 if (!first_tag)
674                         tag_flag |= JBD2_FLAG_SAME_UUID;
675 
676                 tag = (journal_block_tag_t *) tagp;
677                 write_tag_block(journal, tag, jh2bh(jh)->b_blocknr);
678                 tag->t_flags = cpu_to_be16(tag_flag);
679                 jbd2_block_tag_csum_set(journal, tag, wbuf[bufs],
680                                         commit_transaction->t_tid);
681                 tagp += tag_bytes;
682                 space_left -= tag_bytes;
683                 bufs++;
684 
685                 if (first_tag) {
686                         memcpy (tagp, journal->j_uuid, 16);
687                         tagp += 16;
688                         space_left -= 16;
689                         first_tag = 0;
690                 }
691 
692                 /* If there's no more to do, or if the descriptor is full,
693                    let the IO rip! */
694 
695                 if (bufs == journal->j_wbufsize ||
696                     commit_transaction->t_buffers == NULL ||
697                     space_left < tag_bytes + 16 + csum_size) {
698 
699                         jbd_debug(4, "JBD2: Submit %d IOs\n", bufs);
700 
701                         /* Write an end-of-descriptor marker before
702                            submitting the IOs.  "tag" still points to
703                            the last tag we set up. */
704 
705                         tag->t_flags |= cpu_to_be16(JBD2_FLAG_LAST_TAG);
706 start_journal_io:
707                         if (descriptor)
708                                 jbd2_descriptor_block_csum_set(journal,
709                                                         descriptor);
710 
711                         for (i = 0; i < bufs; i++) {
712                                 struct buffer_head *bh = wbuf[i];
713                                 /*
714                                  * Compute checksum.
715                                  */
716                                 if (jbd2_has_feature_checksum(journal)) {
717                                         crc32_sum =
718                                             jbd2_checksum_data(crc32_sum, bh);
719                                 }
720 
721                                 lock_buffer(bh);
722                                 clear_buffer_dirty(bh);
723                                 set_buffer_uptodate(bh);
724                                 bh->b_end_io = journal_end_buffer_io_sync;
725                                 submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
726                         }
727                         cond_resched();
728 
729                         /* Force a new descriptor to be generated next
730                            time round the loop. */
731                         descriptor = NULL;
732                         bufs = 0;
733                 }
734         }
735 
736         err = journal_finish_inode_data_buffers(journal, commit_transaction);
737         if (err) {
738                 printk(KERN_WARNING
739                         "JBD2: Detected IO errors while flushing file data "
740                        "on %s\n", journal->j_devname);
741                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
742                         jbd2_journal_abort(journal, err);
743                 err = 0;
744         }
745 
746         /*
747          * Get current oldest transaction in the log before we issue flush
748          * to the filesystem device. After the flush we can be sure that
749          * blocks of all older transactions are checkpointed to persistent
750          * storage and we will be safe to update journal start in the
751          * superblock with the numbers we get here.
752          */
753         update_tail =
754                 jbd2_journal_get_log_tail(journal, &first_tid, &first_block);
755 
756         write_lock(&journal->j_state_lock);
757         if (update_tail) {
758                 long freed = first_block - journal->j_tail;
759 
760                 if (first_block < journal->j_tail)
761                         freed += journal->j_last - journal->j_first;
762                 /* Update tail only if we free significant amount of space */
763                 if (freed < journal->j_maxlen / 4)
764                         update_tail = 0;
765         }
766         J_ASSERT(commit_transaction->t_state == T_COMMIT);
767         commit_transaction->t_state = T_COMMIT_DFLUSH;
768         write_unlock(&journal->j_state_lock);
769 
770         /* 
771          * If the journal is not located on the file system device,
772          * then we must flush the file system device before we issue
773          * the commit record
774          */
775         if (commit_transaction->t_need_data_flush &&
776             (journal->j_fs_dev != journal->j_dev) &&
777             (journal->j_flags & JBD2_BARRIER))
778                 blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL);
779 
780         /* Done it all: now write the commit record asynchronously. */
781         if (jbd2_has_feature_async_commit(journal)) {
782                 err = journal_submit_commit_record(journal, commit_transaction,
783                                                  &cbh, crc32_sum);
784                 if (err)
785                         jbd2_journal_abort(journal, err);
786         }
787 
788         blk_finish_plug(&plug);
789 
790         /* Lo and behold: we have just managed to send a transaction to
791            the log.  Before we can commit it, wait for the IO so far to
792            complete.  Control buffers being written are on the
793            transaction's t_log_list queue, and metadata buffers are on
794            the io_bufs list.
795 
796            Wait for the buffers in reverse order.  That way we are
797            less likely to be woken up until all IOs have completed, and
798            so we incur less scheduling load.
799         */
800 
801         jbd_debug(3, "JBD2: commit phase 3\n");
802 
803         while (!list_empty(&io_bufs)) {
804                 struct buffer_head *bh = list_entry(io_bufs.prev,
805                                                     struct buffer_head,
806                                                     b_assoc_buffers);
807 
808                 wait_on_buffer(bh);
809                 cond_resched();
810 
811                 if (unlikely(!buffer_uptodate(bh)))
812                         err = -EIO;
813                 jbd2_unfile_log_bh(bh);
814                 stats.run.rs_blocks_logged++;
815 
816                 /*
817                  * The list contains temporary buffer heads created by
818                  * jbd2_journal_write_metadata_buffer().
819                  */
820                 BUFFER_TRACE(bh, "dumping temporary bh");
821                 __brelse(bh);
822                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
823                 free_buffer_head(bh);
824 
825                 /* We also have to refile the corresponding shadowed buffer */
826                 jh = commit_transaction->t_shadow_list->b_tprev;
827                 bh = jh2bh(jh);
828                 clear_buffer_jwrite(bh);
829                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
830                 J_ASSERT_BH(bh, !buffer_shadow(bh));
831 
832                 /* The metadata is now released for reuse, but we need
833                    to remember it against this transaction so that when
834                    we finally commit, we can do any checkpointing
835                    required. */
836                 JBUFFER_TRACE(jh, "file as BJ_Forget");
837                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
838                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
839                 __brelse(bh);
840         }
841 
842         J_ASSERT (commit_transaction->t_shadow_list == NULL);
843 
844         jbd_debug(3, "JBD2: commit phase 4\n");
845 
846         /* Here we wait for the revoke record and descriptor record buffers */
847         while (!list_empty(&log_bufs)) {
848                 struct buffer_head *bh;
849 
850                 bh = list_entry(log_bufs.prev, struct buffer_head, b_assoc_buffers);
851                 wait_on_buffer(bh);
852                 cond_resched();
853 
854                 if (unlikely(!buffer_uptodate(bh)))
855                         err = -EIO;
856 
857                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
858                 clear_buffer_jwrite(bh);
859                 jbd2_unfile_log_bh(bh);
860                 stats.run.rs_blocks_logged++;
861                 __brelse(bh);           /* One for getblk */
862                 /* AKPM: bforget here */
863         }
864 
865         if (err)
866                 jbd2_journal_abort(journal, err);
867 
868         jbd_debug(3, "JBD2: commit phase 5\n");
869         write_lock(&journal->j_state_lock);
870         J_ASSERT(commit_transaction->t_state == T_COMMIT_DFLUSH);
871         commit_transaction->t_state = T_COMMIT_JFLUSH;
872         write_unlock(&journal->j_state_lock);
873 
874         if (!jbd2_has_feature_async_commit(journal)) {
875                 err = journal_submit_commit_record(journal, commit_transaction,
876                                                 &cbh, crc32_sum);
877                 if (err)
878                         jbd2_journal_abort(journal, err);
879         }
880         if (cbh)
881                 err = journal_wait_on_commit_record(journal, cbh);
882         stats.run.rs_blocks_logged++;
883         if (jbd2_has_feature_async_commit(journal) &&
884             journal->j_flags & JBD2_BARRIER) {
885                 blkdev_issue_flush(journal->j_dev, GFP_NOFS, NULL);
886         }
887 
888         if (err)
889                 jbd2_journal_abort(journal, err);
890 
891         WARN_ON_ONCE(
892                 atomic_read(&commit_transaction->t_outstanding_credits) < 0);
893 
894         /*
895          * Now disk caches for filesystem device are flushed so we are safe to
896          * erase checkpointed transactions from the log by updating journal
897          * superblock.
898          */
899         if (update_tail)
900                 jbd2_update_log_tail(journal, first_tid, first_block);
901 
902         /* End of a transaction!  Finally, we can do checkpoint
903            processing: any buffers committed as a result of this
904            transaction can be removed from any checkpoint list it was on
905            before. */
906 
907         jbd_debug(3, "JBD2: commit phase 6\n");
908 
909         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
910         J_ASSERT(commit_transaction->t_buffers == NULL);
911         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
912         J_ASSERT(commit_transaction->t_shadow_list == NULL);
913 
914 restart_loop:
915         /*
916          * As there are other places (journal_unmap_buffer()) adding buffers
917          * to this list we have to be careful and hold the j_list_lock.
918          */
919         spin_lock(&journal->j_list_lock);
920         while (commit_transaction->t_forget) {
921                 transaction_t *cp_transaction;
922                 struct buffer_head *bh;
923                 int try_to_free = 0;
924                 bool drop_ref;
925 
926                 jh = commit_transaction->t_forget;
927                 spin_unlock(&journal->j_list_lock);
928                 bh = jh2bh(jh);
929                 /*
930                  * Get a reference so that bh cannot be freed before we are
931                  * done with it.
932                  */
933                 get_bh(bh);
934                 spin_lock(&jh->b_state_lock);
935                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction);
936 
937                 /*
938                  * If there is undo-protected committed data against
939                  * this buffer, then we can remove it now.  If it is a
940                  * buffer needing such protection, the old frozen_data
941                  * field now points to a committed version of the
942                  * buffer, so rotate that field to the new committed
943                  * data.
944                  *
945                  * Otherwise, we can just throw away the frozen data now.
946                  *
947                  * We also know that the frozen data has already fired
948                  * its triggers if they exist, so we can clear that too.
949                  */
950                 if (jh->b_committed_data) {
951                         jbd2_free(jh->b_committed_data, bh->b_size);
952                         jh->b_committed_data = NULL;
953                         if (jh->b_frozen_data) {
954                                 jh->b_committed_data = jh->b_frozen_data;
955                                 jh->b_frozen_data = NULL;
956                                 jh->b_frozen_triggers = NULL;
957                         }
958                 } else if (jh->b_frozen_data) {
959                         jbd2_free(jh->b_frozen_data, bh->b_size);
960                         jh->b_frozen_data = NULL;
961                         jh->b_frozen_triggers = NULL;
962                 }
963 
964                 spin_lock(&journal->j_list_lock);
965                 cp_transaction = jh->b_cp_transaction;
966                 if (cp_transaction) {
967                         JBUFFER_TRACE(jh, "remove from old cp transaction");
968                         cp_transaction->t_chp_stats.cs_dropped++;
969                         __jbd2_journal_remove_checkpoint(jh);
970                 }
971 
972                 /* Only re-checkpoint the buffer_head if it is marked
973                  * dirty.  If the buffer was added to the BJ_Forget list
974                  * by jbd2_journal_forget, it may no longer be dirty and
975                  * there's no point in keeping a checkpoint record for
976                  * it. */
977 
978                 /*
979                  * A buffer which has been freed while still being journaled
980                  * by a previous transaction, refile the buffer to BJ_Forget of
981                  * the running transaction. If the just committed transaction
982                  * contains "add to orphan" operation, we can completely
983                  * invalidate the buffer now. We are rather through in that
984                  * since the buffer may be still accessible when blocksize <
985                  * pagesize and it is attached to the last partial page.
986                  */
987                 if (buffer_freed(bh) && !jh->b_next_transaction) {
988                         struct address_space *mapping;
989 
990                         clear_buffer_freed(bh);
991                         clear_buffer_jbddirty(bh);
992 
993                         /*
994                          * Block device buffers need to stay mapped all the
995                          * time, so it is enough to clear buffer_jbddirty and
996                          * buffer_freed bits. For the file mapping buffers (i.e.
997                          * journalled data) we need to unmap buffer and clear
998                          * more bits. We also need to be careful about the check
999                          * because the data page mapping can get cleared under
1000                          * our hands. Note that if mapping == NULL, we don't
1001                          * need to make buffer unmapped because the page is
1002                          * already detached from the mapping and buffers cannot
1003                          * get reused.
1004                          */
1005                         mapping = READ_ONCE(bh->b_page->mapping);
1006                         if (mapping && !sb_is_blkdev_sb(mapping->host->i_sb)) {
1007                                 clear_buffer_mapped(bh);
1008                                 clear_buffer_new(bh);
1009                                 clear_buffer_req(bh);
1010                                 bh->b_bdev = NULL;
1011                         }
1012                 }
1013 
1014                 if (buffer_jbddirty(bh)) {
1015                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
1016                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
1017                         if (is_journal_aborted(journal))
1018                                 clear_buffer_jbddirty(bh);
1019                 } else {
1020                         J_ASSERT_BH(bh, !buffer_dirty(bh));
1021                         /*
1022                          * The buffer on BJ_Forget list and not jbddirty means
1023                          * it has been freed by this transaction and hence it
1024                          * could not have been reallocated until this
1025                          * transaction has committed. *BUT* it could be
1026                          * reallocated once we have written all the data to
1027                          * disk and before we process the buffer on BJ_Forget
1028                          * list.
1029                          */
1030                         if (!jh->b_next_transaction)
1031                                 try_to_free = 1;
1032                 }
1033                 JBUFFER_TRACE(jh, "refile or unfile buffer");
1034                 drop_ref = __jbd2_journal_refile_buffer(jh);
1035                 spin_unlock(&jh->b_state_lock);
1036                 if (drop_ref)
1037                         jbd2_journal_put_journal_head(jh);
1038                 if (try_to_free)
1039                         release_buffer_page(bh);        /* Drops bh reference */
1040                 else
1041                         __brelse(bh);
1042                 cond_resched_lock(&journal->j_list_lock);
1043         }
1044         spin_unlock(&journal->j_list_lock);
1045         /*
1046          * This is a bit sleazy.  We use j_list_lock to protect transition
1047          * of a transaction into T_FINISHED state and calling
1048          * __jbd2_journal_drop_transaction(). Otherwise we could race with
1049          * other checkpointing code processing the transaction...
1050          */
1051         write_lock(&journal->j_state_lock);
1052         spin_lock(&journal->j_list_lock);
1053         /*
1054          * Now recheck if some buffers did not get attached to the transaction
1055          * while the lock was dropped...
1056          */
1057         if (commit_transaction->t_forget) {
1058                 spin_unlock(&journal->j_list_lock);
1059                 write_unlock(&journal->j_state_lock);
1060                 goto restart_loop;
1061         }
1062 
1063         /* Add the transaction to the checkpoint list
1064          * __journal_remove_checkpoint() can not destroy transaction
1065          * under us because it is not marked as T_FINISHED yet */
1066         if (journal->j_checkpoint_transactions == NULL) {
1067                 journal->j_checkpoint_transactions = commit_transaction;
1068                 commit_transaction->t_cpnext = commit_transaction;
1069                 commit_transaction->t_cpprev = commit_transaction;
1070         } else {
1071                 commit_transaction->t_cpnext =
1072                         journal->j_checkpoint_transactions;
1073                 commit_transaction->t_cpprev =
1074                         commit_transaction->t_cpnext->t_cpprev;
1075                 commit_transaction->t_cpnext->t_cpprev =
1076                         commit_transaction;
1077                 commit_transaction->t_cpprev->t_cpnext =
1078                                 commit_transaction;
1079         }
1080         spin_unlock(&journal->j_list_lock);
1081 
1082         /* Done with this transaction! */
1083 
1084         jbd_debug(3, "JBD2: commit phase 7\n");
1085 
1086         J_ASSERT(commit_transaction->t_state == T_COMMIT_JFLUSH);
1087 
1088         commit_transaction->t_start = jiffies;
1089         stats.run.rs_logging = jbd2_time_diff(stats.run.rs_logging,
1090                                               commit_transaction->t_start);
1091 
1092         /*
1093          * File the transaction statistics
1094          */
1095         stats.ts_tid = commit_transaction->t_tid;
1096         stats.run.rs_handle_count =
1097                 atomic_read(&commit_transaction->t_handle_count);
1098         trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
1099                              commit_transaction->t_tid, &stats.run);
1100         stats.ts_requested = (commit_transaction->t_requested) ? 1 : 0;
1101 
1102         commit_transaction->t_state = T_COMMIT_CALLBACK;
1103         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1104         journal->j_commit_sequence = commit_transaction->t_tid;
1105         journal->j_committing_transaction = NULL;
1106         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1107 
1108         /*
1109          * weight the commit time higher than the average time so we don't
1110          * react too strongly to vast changes in the commit time
1111          */
1112         if (likely(journal->j_average_commit_time))
1113                 journal->j_average_commit_time = (commit_time +
1114                                 journal->j_average_commit_time*3) / 4;
1115         else
1116                 journal->j_average_commit_time = commit_time;
1117 
1118         write_unlock(&journal->j_state_lock);
1119 
1120         if (journal->j_commit_callback)
1121                 journal->j_commit_callback(journal, commit_transaction);
1122 
1123         trace_jbd2_end_commit(journal, commit_transaction);
1124         jbd_debug(1, "JBD2: commit %d complete, head %d\n",
1125                   journal->j_commit_sequence, journal->j_tail_sequence);
1126 
1127         write_lock(&journal->j_state_lock);
1128         spin_lock(&journal->j_list_lock);
1129         commit_transaction->t_state = T_FINISHED;
1130         /* Check if the transaction can be dropped now that we are finished */
1131         if (commit_transaction->t_checkpoint_list == NULL &&
1132             commit_transaction->t_checkpoint_io_list == NULL) {
1133                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1134                 jbd2_journal_free_transaction(commit_transaction);
1135         }
1136         spin_unlock(&journal->j_list_lock);
1137         write_unlock(&journal->j_state_lock);
1138         wake_up(&journal->j_wait_done_commit);
1139 
1140         /*
1141          * Calculate overall stats
1142          */
1143         spin_lock(&journal->j_history_lock);
1144         journal->j_stats.ts_tid++;
1145         journal->j_stats.ts_requested += stats.ts_requested;
1146         journal->j_stats.run.rs_wait += stats.run.rs_wait;
1147         journal->j_stats.run.rs_request_delay += stats.run.rs_request_delay;
1148         journal->j_stats.run.rs_running += stats.run.rs_running;
1149         journal->j_stats.run.rs_locked += stats.run.rs_locked;
1150         journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
1151         journal->j_stats.run.rs_logging += stats.run.rs_logging;
1152         journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
1153         journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
1154         journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
1155         spin_unlock(&journal->j_history_lock);
1156 }
1157 

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