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TOMOYO Linux Cross Reference
Linux/fs/jbd2/commit.c

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  1 /*
  2  * linux/fs/jbd2/commit.c
  3  *
  4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
  5  *
  6  * Copyright 1998 Red Hat corp --- All Rights Reserved
  7  *
  8  * This file is part of the Linux kernel and is made available under
  9  * the terms of the GNU General Public License, version 2, or at your
 10  * option, any later version, incorporated herein by reference.
 11  *
 12  * Journal commit routines for the generic filesystem journaling code;
 13  * part of the ext2fs journaling system.
 14  */
 15 
 16 #include <linux/time.h>
 17 #include <linux/fs.h>
 18 #include <linux/jbd2.h>
 19 #include <linux/errno.h>
 20 #include <linux/slab.h>
 21 #include <linux/mm.h>
 22 #include <linux/pagemap.h>
 23 #include <linux/jiffies.h>
 24 #include <linux/crc32.h>
 25 #include <linux/writeback.h>
 26 #include <linux/backing-dev.h>
 27 #include <linux/bio.h>
 28 #include <linux/blkdev.h>
 29 #include <linux/bitops.h>
 30 #include <trace/events/jbd2.h>
 31 
 32 /*
 33  * IO end handler for temporary buffer_heads handling writes to the journal.
 34  */
 35 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
 36 {
 37         struct buffer_head *orig_bh = bh->b_private;
 38 
 39         BUFFER_TRACE(bh, "");
 40         if (uptodate)
 41                 set_buffer_uptodate(bh);
 42         else
 43                 clear_buffer_uptodate(bh);
 44         if (orig_bh) {
 45                 clear_bit_unlock(BH_Shadow, &orig_bh->b_state);
 46                 smp_mb__after_atomic();
 47                 wake_up_bit(&orig_bh->b_state, BH_Shadow);
 48         }
 49         unlock_buffer(bh);
 50 }
 51 
 52 /*
 53  * When an ext4 file is truncated, it is possible that some pages are not
 54  * successfully freed, because they are attached to a committing transaction.
 55  * After the transaction commits, these pages are left on the LRU, with no
 56  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
 57  * by the VM, but their apparent absence upsets the VM accounting, and it makes
 58  * the numbers in /proc/meminfo look odd.
 59  *
 60  * So here, we have a buffer which has just come off the forget list.  Look to
 61  * see if we can strip all buffers from the backing page.
 62  *
 63  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
 64  * caller provided us with a ref against the buffer, and we drop that here.
 65  */
 66 static void release_buffer_page(struct buffer_head *bh)
 67 {
 68         struct page *page;
 69 
 70         if (buffer_dirty(bh))
 71                 goto nope;
 72         if (atomic_read(&bh->b_count) != 1)
 73                 goto nope;
 74         page = bh->b_page;
 75         if (!page)
 76                 goto nope;
 77         if (page->mapping)
 78                 goto nope;
 79 
 80         /* OK, it's a truncated page */
 81         if (!trylock_page(page))
 82                 goto nope;
 83 
 84         page_cache_get(page);
 85         __brelse(bh);
 86         try_to_free_buffers(page);
 87         unlock_page(page);
 88         page_cache_release(page);
 89         return;
 90 
 91 nope:
 92         __brelse(bh);
 93 }
 94 
 95 static void jbd2_commit_block_csum_set(journal_t *j, struct buffer_head *bh)
 96 {
 97         struct commit_header *h;
 98         __u32 csum;
 99 
100         if (!jbd2_journal_has_csum_v2or3(j))
101                 return;
102 
103         h = (struct commit_header *)(bh->b_data);
104         h->h_chksum_type = 0;
105         h->h_chksum_size = 0;
106         h->h_chksum[0] = 0;
107         csum = jbd2_chksum(j, j->j_csum_seed, bh->b_data, j->j_blocksize);
108         h->h_chksum[0] = cpu_to_be32(csum);
109 }
110 
111 /*
112  * Done it all: now submit the commit record.  We should have
113  * cleaned up our previous buffers by now, so if we are in abort
114  * mode we can now just skip the rest of the journal write
115  * entirely.
116  *
117  * Returns 1 if the journal needs to be aborted or 0 on success
118  */
119 static int journal_submit_commit_record(journal_t *journal,
120                                         transaction_t *commit_transaction,
121                                         struct buffer_head **cbh,
122                                         __u32 crc32_sum)
123 {
124         struct commit_header *tmp;
125         struct buffer_head *bh;
126         int ret;
127         struct timespec now = current_kernel_time();
128 
129         *cbh = NULL;
130 
131         if (is_journal_aborted(journal))
132                 return 0;
133 
134         bh = jbd2_journal_get_descriptor_buffer(journal);
135         if (!bh)
136                 return 1;
137 
138         tmp = (struct commit_header *)bh->b_data;
139         tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
140         tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
141         tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
142         tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
143         tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
144 
145         if (JBD2_HAS_COMPAT_FEATURE(journal,
146                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
147                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
148                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
149                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
150         }
151         jbd2_commit_block_csum_set(journal, bh);
152 
153         BUFFER_TRACE(bh, "submit commit block");
154         lock_buffer(bh);
155         clear_buffer_dirty(bh);
156         set_buffer_uptodate(bh);
157         bh->b_end_io = journal_end_buffer_io_sync;
158 
159         if (journal->j_flags & JBD2_BARRIER &&
160             !JBD2_HAS_INCOMPAT_FEATURE(journal,
161                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT))
162                 ret = submit_bh(WRITE_SYNC | WRITE_FLUSH_FUA, bh);
163         else
164                 ret = submit_bh(WRITE_SYNC, bh);
165 
166         *cbh = bh;
167         return ret;
168 }
169 
170 /*
171  * This function along with journal_submit_commit_record
172  * allows to write the commit record asynchronously.
173  */
174 static int journal_wait_on_commit_record(journal_t *journal,
175                                          struct buffer_head *bh)
176 {
177         int ret = 0;
178 
179         clear_buffer_dirty(bh);
180         wait_on_buffer(bh);
181 
182         if (unlikely(!buffer_uptodate(bh)))
183                 ret = -EIO;
184         put_bh(bh);            /* One for getblk() */
185 
186         return ret;
187 }
188 
189 /*
190  * write the filemap data using writepage() address_space_operations.
191  * We don't do block allocation here even for delalloc. We don't
192  * use writepages() because with dealyed allocation we may be doing
193  * block allocation in writepages().
194  */
195 static int journal_submit_inode_data_buffers(struct address_space *mapping)
196 {
197         int ret;
198         struct writeback_control wbc = {
199                 .sync_mode =  WB_SYNC_ALL,
200                 .nr_to_write = mapping->nrpages * 2,
201                 .range_start = 0,
202                 .range_end = i_size_read(mapping->host),
203         };
204 
205         ret = generic_writepages(mapping, &wbc);
206         return ret;
207 }
208 
209 /*
210  * Submit all the data buffers of inode associated with the transaction to
211  * disk.
212  *
213  * We are in a committing transaction. Therefore no new inode can be added to
214  * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
215  * operate on from being released while we write out pages.
216  */
217 static int journal_submit_data_buffers(journal_t *journal,
218                 transaction_t *commit_transaction)
219 {
220         struct jbd2_inode *jinode;
221         int err, ret = 0;
222         struct address_space *mapping;
223 
224         spin_lock(&journal->j_list_lock);
225         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
226                 mapping = jinode->i_vfs_inode->i_mapping;
227                 set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
228                 spin_unlock(&journal->j_list_lock);
229                 /*
230                  * submit the inode data buffers. We use writepage
231                  * instead of writepages. Because writepages can do
232                  * block allocation  with delalloc. We need to write
233                  * only allocated blocks here.
234                  */
235                 trace_jbd2_submit_inode_data(jinode->i_vfs_inode);
236                 err = journal_submit_inode_data_buffers(mapping);
237                 if (!ret)
238                         ret = err;
239                 spin_lock(&journal->j_list_lock);
240                 J_ASSERT(jinode->i_transaction == commit_transaction);
241                 clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
242                 smp_mb__after_atomic();
243                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
244         }
245         spin_unlock(&journal->j_list_lock);
246         return ret;
247 }
248 
249 /*
250  * Wait for data submitted for writeout, refile inodes to proper
251  * transaction if needed.
252  *
253  */
254 static int journal_finish_inode_data_buffers(journal_t *journal,
255                 transaction_t *commit_transaction)
256 {
257         struct jbd2_inode *jinode, *next_i;
258         int err, ret = 0;
259 
260         /* For locking, see the comment in journal_submit_data_buffers() */
261         spin_lock(&journal->j_list_lock);
262         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
263                 set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
264                 spin_unlock(&journal->j_list_lock);
265                 err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
266                 if (err) {
267                         /*
268                          * Because AS_EIO is cleared by
269                          * filemap_fdatawait_range(), set it again so
270                          * that user process can get -EIO from fsync().
271                          */
272                         set_bit(AS_EIO,
273                                 &jinode->i_vfs_inode->i_mapping->flags);
274 
275                         if (!ret)
276                                 ret = err;
277                 }
278                 spin_lock(&journal->j_list_lock);
279                 clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
280                 smp_mb__after_atomic();
281                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
282         }
283 
284         /* Now refile inode to proper lists */
285         list_for_each_entry_safe(jinode, next_i,
286                                  &commit_transaction->t_inode_list, i_list) {
287                 list_del(&jinode->i_list);
288                 if (jinode->i_next_transaction) {
289                         jinode->i_transaction = jinode->i_next_transaction;
290                         jinode->i_next_transaction = NULL;
291                         list_add(&jinode->i_list,
292                                 &jinode->i_transaction->t_inode_list);
293                 } else {
294                         jinode->i_transaction = NULL;
295                 }
296         }
297         spin_unlock(&journal->j_list_lock);
298 
299         return ret;
300 }
301 
302 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
303 {
304         struct page *page = bh->b_page;
305         char *addr;
306         __u32 checksum;
307 
308         addr = kmap_atomic(page);
309         checksum = crc32_be(crc32_sum,
310                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
311         kunmap_atomic(addr);
312 
313         return checksum;
314 }
315 
316 static void write_tag_block(journal_t *j, journal_block_tag_t *tag,
317                                    unsigned long long block)
318 {
319         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
320         if (JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_64BIT))
321                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
322 }
323 
324 static void jbd2_descr_block_csum_set(journal_t *j,
325                                       struct buffer_head *bh)
326 {
327         struct jbd2_journal_block_tail *tail;
328         __u32 csum;
329 
330         if (!jbd2_journal_has_csum_v2or3(j))
331                 return;
332 
333         tail = (struct jbd2_journal_block_tail *)(bh->b_data + j->j_blocksize -
334                         sizeof(struct jbd2_journal_block_tail));
335         tail->t_checksum = 0;
336         csum = jbd2_chksum(j, j->j_csum_seed, bh->b_data, j->j_blocksize);
337         tail->t_checksum = cpu_to_be32(csum);
338 }
339 
340 static void jbd2_block_tag_csum_set(journal_t *j, journal_block_tag_t *tag,
341                                     struct buffer_head *bh, __u32 sequence)
342 {
343         journal_block_tag3_t *tag3 = (journal_block_tag3_t *)tag;
344         struct page *page = bh->b_page;
345         __u8 *addr;
346         __u32 csum32;
347         __be32 seq;
348 
349         if (!jbd2_journal_has_csum_v2or3(j))
350                 return;
351 
352         seq = cpu_to_be32(sequence);
353         addr = kmap_atomic(page);
354         csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&seq, sizeof(seq));
355         csum32 = jbd2_chksum(j, csum32, addr + offset_in_page(bh->b_data),
356                              bh->b_size);
357         kunmap_atomic(addr);
358 
359         if (JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V3))
360                 tag3->t_checksum = cpu_to_be32(csum32);
361         else
362                 tag->t_checksum = cpu_to_be16(csum32);
363 }
364 /*
365  * jbd2_journal_commit_transaction
366  *
367  * The primary function for committing a transaction to the log.  This
368  * function is called by the journal thread to begin a complete commit.
369  */
370 void jbd2_journal_commit_transaction(journal_t *journal)
371 {
372         struct transaction_stats_s stats;
373         transaction_t *commit_transaction;
374         struct journal_head *jh;
375         struct buffer_head *descriptor;
376         struct buffer_head **wbuf = journal->j_wbuf;
377         int bufs;
378         int flags;
379         int err;
380         unsigned long long blocknr;
381         ktime_t start_time;
382         u64 commit_time;
383         char *tagp = NULL;
384         journal_header_t *header;
385         journal_block_tag_t *tag = NULL;
386         int space_left = 0;
387         int first_tag = 0;
388         int tag_flag;
389         int i;
390         int tag_bytes = journal_tag_bytes(journal);
391         struct buffer_head *cbh = NULL; /* For transactional checksums */
392         __u32 crc32_sum = ~0;
393         struct blk_plug plug;
394         /* Tail of the journal */
395         unsigned long first_block;
396         tid_t first_tid;
397         int update_tail;
398         int csum_size = 0;
399         LIST_HEAD(io_bufs);
400         LIST_HEAD(log_bufs);
401 
402         if (jbd2_journal_has_csum_v2or3(journal))
403                 csum_size = sizeof(struct jbd2_journal_block_tail);
404 
405         /*
406          * First job: lock down the current transaction and wait for
407          * all outstanding updates to complete.
408          */
409 
410         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
411         if (journal->j_flags & JBD2_FLUSHED) {
412                 jbd_debug(3, "super block updated\n");
413                 mutex_lock(&journal->j_checkpoint_mutex);
414                 /*
415                  * We hold j_checkpoint_mutex so tail cannot change under us.
416                  * We don't need any special data guarantees for writing sb
417                  * since journal is empty and it is ok for write to be
418                  * flushed only with transaction commit.
419                  */
420                 jbd2_journal_update_sb_log_tail(journal,
421                                                 journal->j_tail_sequence,
422                                                 journal->j_tail,
423                                                 WRITE_SYNC);
424                 mutex_unlock(&journal->j_checkpoint_mutex);
425         } else {
426                 jbd_debug(3, "superblock not updated\n");
427         }
428 
429         J_ASSERT(journal->j_running_transaction != NULL);
430         J_ASSERT(journal->j_committing_transaction == NULL);
431 
432         commit_transaction = journal->j_running_transaction;
433 
434         trace_jbd2_start_commit(journal, commit_transaction);
435         jbd_debug(1, "JBD2: starting commit of transaction %d\n",
436                         commit_transaction->t_tid);
437 
438         write_lock(&journal->j_state_lock);
439         J_ASSERT(commit_transaction->t_state == T_RUNNING);
440         commit_transaction->t_state = T_LOCKED;
441 
442         trace_jbd2_commit_locking(journal, commit_transaction);
443         stats.run.rs_wait = commit_transaction->t_max_wait;
444         stats.run.rs_request_delay = 0;
445         stats.run.rs_locked = jiffies;
446         if (commit_transaction->t_requested)
447                 stats.run.rs_request_delay =
448                         jbd2_time_diff(commit_transaction->t_requested,
449                                        stats.run.rs_locked);
450         stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
451                                               stats.run.rs_locked);
452 
453         spin_lock(&commit_transaction->t_handle_lock);
454         while (atomic_read(&commit_transaction->t_updates)) {
455                 DEFINE_WAIT(wait);
456 
457                 prepare_to_wait(&journal->j_wait_updates, &wait,
458                                         TASK_UNINTERRUPTIBLE);
459                 if (atomic_read(&commit_transaction->t_updates)) {
460                         spin_unlock(&commit_transaction->t_handle_lock);
461                         write_unlock(&journal->j_state_lock);
462                         schedule();
463                         write_lock(&journal->j_state_lock);
464                         spin_lock(&commit_transaction->t_handle_lock);
465                 }
466                 finish_wait(&journal->j_wait_updates, &wait);
467         }
468         spin_unlock(&commit_transaction->t_handle_lock);
469 
470         J_ASSERT (atomic_read(&commit_transaction->t_outstanding_credits) <=
471                         journal->j_max_transaction_buffers);
472 
473         /*
474          * First thing we are allowed to do is to discard any remaining
475          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
476          * that there are no such buffers: if a large filesystem
477          * operation like a truncate needs to split itself over multiple
478          * transactions, then it may try to do a jbd2_journal_restart() while
479          * there are still BJ_Reserved buffers outstanding.  These must
480          * be released cleanly from the current transaction.
481          *
482          * In this case, the filesystem must still reserve write access
483          * again before modifying the buffer in the new transaction, but
484          * we do not require it to remember exactly which old buffers it
485          * has reserved.  This is consistent with the existing behaviour
486          * that multiple jbd2_journal_get_write_access() calls to the same
487          * buffer are perfectly permissible.
488          */
489         while (commit_transaction->t_reserved_list) {
490                 jh = commit_transaction->t_reserved_list;
491                 JBUFFER_TRACE(jh, "reserved, unused: refile");
492                 /*
493                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
494                  * leave undo-committed data.
495                  */
496                 if (jh->b_committed_data) {
497                         struct buffer_head *bh = jh2bh(jh);
498 
499                         jbd_lock_bh_state(bh);
500                         jbd2_free(jh->b_committed_data, bh->b_size);
501                         jh->b_committed_data = NULL;
502                         jbd_unlock_bh_state(bh);
503                 }
504                 jbd2_journal_refile_buffer(journal, jh);
505         }
506 
507         /*
508          * Now try to drop any written-back buffers from the journal's
509          * checkpoint lists.  We do this *before* commit because it potentially
510          * frees some memory
511          */
512         spin_lock(&journal->j_list_lock);
513         __jbd2_journal_clean_checkpoint_list(journal, false);
514         spin_unlock(&journal->j_list_lock);
515 
516         jbd_debug(3, "JBD2: commit phase 1\n");
517 
518         /*
519          * Clear revoked flag to reflect there is no revoked buffers
520          * in the next transaction which is going to be started.
521          */
522         jbd2_clear_buffer_revoked_flags(journal);
523 
524         /*
525          * Switch to a new revoke table.
526          */
527         jbd2_journal_switch_revoke_table(journal);
528 
529         /*
530          * Reserved credits cannot be claimed anymore, free them
531          */
532         atomic_sub(atomic_read(&journal->j_reserved_credits),
533                    &commit_transaction->t_outstanding_credits);
534 
535         trace_jbd2_commit_flushing(journal, commit_transaction);
536         stats.run.rs_flushing = jiffies;
537         stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,
538                                              stats.run.rs_flushing);
539 
540         commit_transaction->t_state = T_FLUSH;
541         journal->j_committing_transaction = commit_transaction;
542         journal->j_running_transaction = NULL;
543         start_time = ktime_get();
544         commit_transaction->t_log_start = journal->j_head;
545         wake_up(&journal->j_wait_transaction_locked);
546         write_unlock(&journal->j_state_lock);
547 
548         jbd_debug(3, "JBD2: commit phase 2a\n");
549 
550         /*
551          * Now start flushing things to disk, in the order they appear
552          * on the transaction lists.  Data blocks go first.
553          */
554         err = journal_submit_data_buffers(journal, commit_transaction);
555         if (err)
556                 jbd2_journal_abort(journal, err);
557 
558         blk_start_plug(&plug);
559         jbd2_journal_write_revoke_records(journal, commit_transaction,
560                                           &log_bufs, WRITE_SYNC);
561 
562         jbd_debug(3, "JBD2: commit phase 2b\n");
563 
564         /*
565          * Way to go: we have now written out all of the data for a
566          * transaction!  Now comes the tricky part: we need to write out
567          * metadata.  Loop over the transaction's entire buffer list:
568          */
569         write_lock(&journal->j_state_lock);
570         commit_transaction->t_state = T_COMMIT;
571         write_unlock(&journal->j_state_lock);
572 
573         trace_jbd2_commit_logging(journal, commit_transaction);
574         stats.run.rs_logging = jiffies;
575         stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
576                                                stats.run.rs_logging);
577         stats.run.rs_blocks =
578                 atomic_read(&commit_transaction->t_outstanding_credits);
579         stats.run.rs_blocks_logged = 0;
580 
581         J_ASSERT(commit_transaction->t_nr_buffers <=
582                  atomic_read(&commit_transaction->t_outstanding_credits));
583 
584         err = 0;
585         bufs = 0;
586         descriptor = NULL;
587         while (commit_transaction->t_buffers) {
588 
589                 /* Find the next buffer to be journaled... */
590 
591                 jh = commit_transaction->t_buffers;
592 
593                 /* If we're in abort mode, we just un-journal the buffer and
594                    release it. */
595 
596                 if (is_journal_aborted(journal)) {
597                         clear_buffer_jbddirty(jh2bh(jh));
598                         JBUFFER_TRACE(jh, "journal is aborting: refile");
599                         jbd2_buffer_abort_trigger(jh,
600                                                   jh->b_frozen_data ?
601                                                   jh->b_frozen_triggers :
602                                                   jh->b_triggers);
603                         jbd2_journal_refile_buffer(journal, jh);
604                         /* If that was the last one, we need to clean up
605                          * any descriptor buffers which may have been
606                          * already allocated, even if we are now
607                          * aborting. */
608                         if (!commit_transaction->t_buffers)
609                                 goto start_journal_io;
610                         continue;
611                 }
612 
613                 /* Make sure we have a descriptor block in which to
614                    record the metadata buffer. */
615 
616                 if (!descriptor) {
617                         J_ASSERT (bufs == 0);
618 
619                         jbd_debug(4, "JBD2: get descriptor\n");
620 
621                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
622                         if (!descriptor) {
623                                 jbd2_journal_abort(journal, -EIO);
624                                 continue;
625                         }
626 
627                         jbd_debug(4, "JBD2: got buffer %llu (%p)\n",
628                                 (unsigned long long)descriptor->b_blocknr,
629                                 descriptor->b_data);
630                         header = (journal_header_t *)descriptor->b_data;
631                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
632                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
633                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
634 
635                         tagp = &descriptor->b_data[sizeof(journal_header_t)];
636                         space_left = descriptor->b_size -
637                                                 sizeof(journal_header_t);
638                         first_tag = 1;
639                         set_buffer_jwrite(descriptor);
640                         set_buffer_dirty(descriptor);
641                         wbuf[bufs++] = descriptor;
642 
643                         /* Record it so that we can wait for IO
644                            completion later */
645                         BUFFER_TRACE(descriptor, "ph3: file as descriptor");
646                         jbd2_file_log_bh(&log_bufs, descriptor);
647                 }
648 
649                 /* Where is the buffer to be written? */
650 
651                 err = jbd2_journal_next_log_block(journal, &blocknr);
652                 /* If the block mapping failed, just abandon the buffer
653                    and repeat this loop: we'll fall into the
654                    refile-on-abort condition above. */
655                 if (err) {
656                         jbd2_journal_abort(journal, err);
657                         continue;
658                 }
659 
660                 /*
661                  * start_this_handle() uses t_outstanding_credits to determine
662                  * the free space in the log, but this counter is changed
663                  * by jbd2_journal_next_log_block() also.
664                  */
665                 atomic_dec(&commit_transaction->t_outstanding_credits);
666 
667                 /* Bump b_count to prevent truncate from stumbling over
668                    the shadowed buffer!  @@@ This can go if we ever get
669                    rid of the shadow pairing of buffers. */
670                 atomic_inc(&jh2bh(jh)->b_count);
671 
672                 /*
673                  * Make a temporary IO buffer with which to write it out
674                  * (this will requeue the metadata buffer to BJ_Shadow).
675                  */
676                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
677                 JBUFFER_TRACE(jh, "ph3: write metadata");
678                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
679                                                 jh, &wbuf[bufs], blocknr);
680                 if (flags < 0) {
681                         jbd2_journal_abort(journal, flags);
682                         continue;
683                 }
684                 jbd2_file_log_bh(&io_bufs, wbuf[bufs]);
685 
686                 /* Record the new block's tag in the current descriptor
687                    buffer */
688 
689                 tag_flag = 0;
690                 if (flags & 1)
691                         tag_flag |= JBD2_FLAG_ESCAPE;
692                 if (!first_tag)
693                         tag_flag |= JBD2_FLAG_SAME_UUID;
694 
695                 tag = (journal_block_tag_t *) tagp;
696                 write_tag_block(journal, tag, jh2bh(jh)->b_blocknr);
697                 tag->t_flags = cpu_to_be16(tag_flag);
698                 jbd2_block_tag_csum_set(journal, tag, wbuf[bufs],
699                                         commit_transaction->t_tid);
700                 tagp += tag_bytes;
701                 space_left -= tag_bytes;
702                 bufs++;
703 
704                 if (first_tag) {
705                         memcpy (tagp, journal->j_uuid, 16);
706                         tagp += 16;
707                         space_left -= 16;
708                         first_tag = 0;
709                 }
710 
711                 /* If there's no more to do, or if the descriptor is full,
712                    let the IO rip! */
713 
714                 if (bufs == journal->j_wbufsize ||
715                     commit_transaction->t_buffers == NULL ||
716                     space_left < tag_bytes + 16 + csum_size) {
717 
718                         jbd_debug(4, "JBD2: Submit %d IOs\n", bufs);
719 
720                         /* Write an end-of-descriptor marker before
721                            submitting the IOs.  "tag" still points to
722                            the last tag we set up. */
723 
724                         tag->t_flags |= cpu_to_be16(JBD2_FLAG_LAST_TAG);
725 
726                         jbd2_descr_block_csum_set(journal, descriptor);
727 start_journal_io:
728                         for (i = 0; i < bufs; i++) {
729                                 struct buffer_head *bh = wbuf[i];
730                                 /*
731                                  * Compute checksum.
732                                  */
733                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
734                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
735                                         crc32_sum =
736                                             jbd2_checksum_data(crc32_sum, bh);
737                                 }
738 
739                                 lock_buffer(bh);
740                                 clear_buffer_dirty(bh);
741                                 set_buffer_uptodate(bh);
742                                 bh->b_end_io = journal_end_buffer_io_sync;
743                                 submit_bh(WRITE_SYNC, bh);
744                         }
745                         cond_resched();
746                         stats.run.rs_blocks_logged += bufs;
747 
748                         /* Force a new descriptor to be generated next
749                            time round the loop. */
750                         descriptor = NULL;
751                         bufs = 0;
752                 }
753         }
754 
755         err = journal_finish_inode_data_buffers(journal, commit_transaction);
756         if (err) {
757                 printk(KERN_WARNING
758                         "JBD2: Detected IO errors while flushing file data "
759                        "on %s\n", journal->j_devname);
760                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
761                         jbd2_journal_abort(journal, err);
762                 err = 0;
763         }
764 
765         /*
766          * Get current oldest transaction in the log before we issue flush
767          * to the filesystem device. After the flush we can be sure that
768          * blocks of all older transactions are checkpointed to persistent
769          * storage and we will be safe to update journal start in the
770          * superblock with the numbers we get here.
771          */
772         update_tail =
773                 jbd2_journal_get_log_tail(journal, &first_tid, &first_block);
774 
775         write_lock(&journal->j_state_lock);
776         if (update_tail) {
777                 long freed = first_block - journal->j_tail;
778 
779                 if (first_block < journal->j_tail)
780                         freed += journal->j_last - journal->j_first;
781                 /* Update tail only if we free significant amount of space */
782                 if (freed < journal->j_maxlen / 4)
783                         update_tail = 0;
784         }
785         J_ASSERT(commit_transaction->t_state == T_COMMIT);
786         commit_transaction->t_state = T_COMMIT_DFLUSH;
787         write_unlock(&journal->j_state_lock);
788 
789         /* 
790          * If the journal is not located on the file system device,
791          * then we must flush the file system device before we issue
792          * the commit record
793          */
794         if (commit_transaction->t_need_data_flush &&
795             (journal->j_fs_dev != journal->j_dev) &&
796             (journal->j_flags & JBD2_BARRIER))
797                 blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL);
798 
799         /* Done it all: now write the commit record asynchronously. */
800         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
801                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
802                 err = journal_submit_commit_record(journal, commit_transaction,
803                                                  &cbh, crc32_sum);
804                 if (err)
805                         __jbd2_journal_abort_hard(journal);
806         }
807 
808         blk_finish_plug(&plug);
809 
810         /* Lo and behold: we have just managed to send a transaction to
811            the log.  Before we can commit it, wait for the IO so far to
812            complete.  Control buffers being written are on the
813            transaction's t_log_list queue, and metadata buffers are on
814            the io_bufs list.
815 
816            Wait for the buffers in reverse order.  That way we are
817            less likely to be woken up until all IOs have completed, and
818            so we incur less scheduling load.
819         */
820 
821         jbd_debug(3, "JBD2: commit phase 3\n");
822 
823         while (!list_empty(&io_bufs)) {
824                 struct buffer_head *bh = list_entry(io_bufs.prev,
825                                                     struct buffer_head,
826                                                     b_assoc_buffers);
827 
828                 wait_on_buffer(bh);
829                 cond_resched();
830 
831                 if (unlikely(!buffer_uptodate(bh)))
832                         err = -EIO;
833                 jbd2_unfile_log_bh(bh);
834 
835                 /*
836                  * The list contains temporary buffer heads created by
837                  * jbd2_journal_write_metadata_buffer().
838                  */
839                 BUFFER_TRACE(bh, "dumping temporary bh");
840                 __brelse(bh);
841                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
842                 free_buffer_head(bh);
843 
844                 /* We also have to refile the corresponding shadowed buffer */
845                 jh = commit_transaction->t_shadow_list->b_tprev;
846                 bh = jh2bh(jh);
847                 clear_buffer_jwrite(bh);
848                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
849                 J_ASSERT_BH(bh, !buffer_shadow(bh));
850 
851                 /* The metadata is now released for reuse, but we need
852                    to remember it against this transaction so that when
853                    we finally commit, we can do any checkpointing
854                    required. */
855                 JBUFFER_TRACE(jh, "file as BJ_Forget");
856                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
857                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
858                 __brelse(bh);
859         }
860 
861         J_ASSERT (commit_transaction->t_shadow_list == NULL);
862 
863         jbd_debug(3, "JBD2: commit phase 4\n");
864 
865         /* Here we wait for the revoke record and descriptor record buffers */
866         while (!list_empty(&log_bufs)) {
867                 struct buffer_head *bh;
868 
869                 bh = list_entry(log_bufs.prev, struct buffer_head, b_assoc_buffers);
870                 wait_on_buffer(bh);
871                 cond_resched();
872 
873                 if (unlikely(!buffer_uptodate(bh)))
874                         err = -EIO;
875 
876                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
877                 clear_buffer_jwrite(bh);
878                 jbd2_unfile_log_bh(bh);
879                 __brelse(bh);           /* One for getblk */
880                 /* AKPM: bforget here */
881         }
882 
883         if (err)
884                 jbd2_journal_abort(journal, err);
885 
886         jbd_debug(3, "JBD2: commit phase 5\n");
887         write_lock(&journal->j_state_lock);
888         J_ASSERT(commit_transaction->t_state == T_COMMIT_DFLUSH);
889         commit_transaction->t_state = T_COMMIT_JFLUSH;
890         write_unlock(&journal->j_state_lock);
891 
892         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
893                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
894                 err = journal_submit_commit_record(journal, commit_transaction,
895                                                 &cbh, crc32_sum);
896                 if (err)
897                         __jbd2_journal_abort_hard(journal);
898         }
899         if (cbh)
900                 err = journal_wait_on_commit_record(journal, cbh);
901         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
902                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT) &&
903             journal->j_flags & JBD2_BARRIER) {
904                 blkdev_issue_flush(journal->j_dev, GFP_NOFS, NULL);
905         }
906 
907         if (err)
908                 jbd2_journal_abort(journal, err);
909 
910         /*
911          * Now disk caches for filesystem device are flushed so we are safe to
912          * erase checkpointed transactions from the log by updating journal
913          * superblock.
914          */
915         if (update_tail)
916                 jbd2_update_log_tail(journal, first_tid, first_block);
917 
918         /* End of a transaction!  Finally, we can do checkpoint
919            processing: any buffers committed as a result of this
920            transaction can be removed from any checkpoint list it was on
921            before. */
922 
923         jbd_debug(3, "JBD2: commit phase 6\n");
924 
925         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
926         J_ASSERT(commit_transaction->t_buffers == NULL);
927         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
928         J_ASSERT(commit_transaction->t_shadow_list == NULL);
929 
930 restart_loop:
931         /*
932          * As there are other places (journal_unmap_buffer()) adding buffers
933          * to this list we have to be careful and hold the j_list_lock.
934          */
935         spin_lock(&journal->j_list_lock);
936         while (commit_transaction->t_forget) {
937                 transaction_t *cp_transaction;
938                 struct buffer_head *bh;
939                 int try_to_free = 0;
940 
941                 jh = commit_transaction->t_forget;
942                 spin_unlock(&journal->j_list_lock);
943                 bh = jh2bh(jh);
944                 /*
945                  * Get a reference so that bh cannot be freed before we are
946                  * done with it.
947                  */
948                 get_bh(bh);
949                 jbd_lock_bh_state(bh);
950                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction);
951 
952                 /*
953                  * If there is undo-protected committed data against
954                  * this buffer, then we can remove it now.  If it is a
955                  * buffer needing such protection, the old frozen_data
956                  * field now points to a committed version of the
957                  * buffer, so rotate that field to the new committed
958                  * data.
959                  *
960                  * Otherwise, we can just throw away the frozen data now.
961                  *
962                  * We also know that the frozen data has already fired
963                  * its triggers if they exist, so we can clear that too.
964                  */
965                 if (jh->b_committed_data) {
966                         jbd2_free(jh->b_committed_data, bh->b_size);
967                         jh->b_committed_data = NULL;
968                         if (jh->b_frozen_data) {
969                                 jh->b_committed_data = jh->b_frozen_data;
970                                 jh->b_frozen_data = NULL;
971                                 jh->b_frozen_triggers = NULL;
972                         }
973                 } else if (jh->b_frozen_data) {
974                         jbd2_free(jh->b_frozen_data, bh->b_size);
975                         jh->b_frozen_data = NULL;
976                         jh->b_frozen_triggers = NULL;
977                 }
978 
979                 spin_lock(&journal->j_list_lock);
980                 cp_transaction = jh->b_cp_transaction;
981                 if (cp_transaction) {
982                         JBUFFER_TRACE(jh, "remove from old cp transaction");
983                         cp_transaction->t_chp_stats.cs_dropped++;
984                         __jbd2_journal_remove_checkpoint(jh);
985                 }
986 
987                 /* Only re-checkpoint the buffer_head if it is marked
988                  * dirty.  If the buffer was added to the BJ_Forget list
989                  * by jbd2_journal_forget, it may no longer be dirty and
990                  * there's no point in keeping a checkpoint record for
991                  * it. */
992 
993                 /*
994                 * A buffer which has been freed while still being journaled by
995                 * a previous transaction.
996                 */
997                 if (buffer_freed(bh)) {
998                         /*
999                          * If the running transaction is the one containing
1000                          * "add to orphan" operation (b_next_transaction !=
1001                          * NULL), we have to wait for that transaction to
1002                          * commit before we can really get rid of the buffer.
1003                          * So just clear b_modified to not confuse transaction
1004                          * credit accounting and refile the buffer to
1005                          * BJ_Forget of the running transaction. If the just
1006                          * committed transaction contains "add to orphan"
1007                          * operation, we can completely invalidate the buffer
1008                          * now. We are rather through in that since the
1009                          * buffer may be still accessible when blocksize <
1010                          * pagesize and it is attached to the last partial
1011                          * page.
1012                          */
1013                         jh->b_modified = 0;
1014                         if (!jh->b_next_transaction) {
1015                                 clear_buffer_freed(bh);
1016                                 clear_buffer_jbddirty(bh);
1017                                 clear_buffer_mapped(bh);
1018                                 clear_buffer_new(bh);
1019                                 clear_buffer_req(bh);
1020                                 bh->b_bdev = NULL;
1021                         }
1022                 }
1023 
1024                 if (buffer_jbddirty(bh)) {
1025                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
1026                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
1027                         if (is_journal_aborted(journal))
1028                                 clear_buffer_jbddirty(bh);
1029                 } else {
1030                         J_ASSERT_BH(bh, !buffer_dirty(bh));
1031                         /*
1032                          * The buffer on BJ_Forget list and not jbddirty means
1033                          * it has been freed by this transaction and hence it
1034                          * could not have been reallocated until this
1035                          * transaction has committed. *BUT* it could be
1036                          * reallocated once we have written all the data to
1037                          * disk and before we process the buffer on BJ_Forget
1038                          * list.
1039                          */
1040                         if (!jh->b_next_transaction)
1041                                 try_to_free = 1;
1042                 }
1043                 JBUFFER_TRACE(jh, "refile or unfile buffer");
1044                 __jbd2_journal_refile_buffer(jh);
1045                 jbd_unlock_bh_state(bh);
1046                 if (try_to_free)
1047                         release_buffer_page(bh);        /* Drops bh reference */
1048                 else
1049                         __brelse(bh);
1050                 cond_resched_lock(&journal->j_list_lock);
1051         }
1052         spin_unlock(&journal->j_list_lock);
1053         /*
1054          * This is a bit sleazy.  We use j_list_lock to protect transition
1055          * of a transaction into T_FINISHED state and calling
1056          * __jbd2_journal_drop_transaction(). Otherwise we could race with
1057          * other checkpointing code processing the transaction...
1058          */
1059         write_lock(&journal->j_state_lock);
1060         spin_lock(&journal->j_list_lock);
1061         /*
1062          * Now recheck if some buffers did not get attached to the transaction
1063          * while the lock was dropped...
1064          */
1065         if (commit_transaction->t_forget) {
1066                 spin_unlock(&journal->j_list_lock);
1067                 write_unlock(&journal->j_state_lock);
1068                 goto restart_loop;
1069         }
1070 
1071         /* Add the transaction to the checkpoint list
1072          * __journal_remove_checkpoint() can not destroy transaction
1073          * under us because it is not marked as T_FINISHED yet */
1074         if (journal->j_checkpoint_transactions == NULL) {
1075                 journal->j_checkpoint_transactions = commit_transaction;
1076                 commit_transaction->t_cpnext = commit_transaction;
1077                 commit_transaction->t_cpprev = commit_transaction;
1078         } else {
1079                 commit_transaction->t_cpnext =
1080                         journal->j_checkpoint_transactions;
1081                 commit_transaction->t_cpprev =
1082                         commit_transaction->t_cpnext->t_cpprev;
1083                 commit_transaction->t_cpnext->t_cpprev =
1084                         commit_transaction;
1085                 commit_transaction->t_cpprev->t_cpnext =
1086                                 commit_transaction;
1087         }
1088         spin_unlock(&journal->j_list_lock);
1089 
1090         /* Done with this transaction! */
1091 
1092         jbd_debug(3, "JBD2: commit phase 7\n");
1093 
1094         J_ASSERT(commit_transaction->t_state == T_COMMIT_JFLUSH);
1095 
1096         commit_transaction->t_start = jiffies;
1097         stats.run.rs_logging = jbd2_time_diff(stats.run.rs_logging,
1098                                               commit_transaction->t_start);
1099 
1100         /*
1101          * File the transaction statistics
1102          */
1103         stats.ts_tid = commit_transaction->t_tid;
1104         stats.run.rs_handle_count =
1105                 atomic_read(&commit_transaction->t_handle_count);
1106         trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
1107                              commit_transaction->t_tid, &stats.run);
1108         stats.ts_requested = (commit_transaction->t_requested) ? 1 : 0;
1109 
1110         commit_transaction->t_state = T_COMMIT_CALLBACK;
1111         J_ASSERT(commit_transaction == journal->j_committing_transaction);
1112         journal->j_commit_sequence = commit_transaction->t_tid;
1113         journal->j_committing_transaction = NULL;
1114         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
1115 
1116         /*
1117          * weight the commit time higher than the average time so we don't
1118          * react too strongly to vast changes in the commit time
1119          */
1120         if (likely(journal->j_average_commit_time))
1121                 journal->j_average_commit_time = (commit_time +
1122                                 journal->j_average_commit_time*3) / 4;
1123         else
1124                 journal->j_average_commit_time = commit_time;
1125 
1126         write_unlock(&journal->j_state_lock);
1127 
1128         if (journal->j_commit_callback)
1129                 journal->j_commit_callback(journal, commit_transaction);
1130 
1131         trace_jbd2_end_commit(journal, commit_transaction);
1132         jbd_debug(1, "JBD2: commit %d complete, head %d\n",
1133                   journal->j_commit_sequence, journal->j_tail_sequence);
1134 
1135         write_lock(&journal->j_state_lock);
1136         spin_lock(&journal->j_list_lock);
1137         commit_transaction->t_state = T_FINISHED;
1138         /* Check if the transaction can be dropped now that we are finished */
1139         if (commit_transaction->t_checkpoint_list == NULL &&
1140             commit_transaction->t_checkpoint_io_list == NULL) {
1141                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1142                 jbd2_journal_free_transaction(commit_transaction);
1143         }
1144         spin_unlock(&journal->j_list_lock);
1145         write_unlock(&journal->j_state_lock);
1146         wake_up(&journal->j_wait_done_commit);
1147 
1148         /*
1149          * Calculate overall stats
1150          */
1151         spin_lock(&journal->j_history_lock);
1152         journal->j_stats.ts_tid++;
1153         journal->j_stats.ts_requested += stats.ts_requested;
1154         journal->j_stats.run.rs_wait += stats.run.rs_wait;
1155         journal->j_stats.run.rs_request_delay += stats.run.rs_request_delay;
1156         journal->j_stats.run.rs_running += stats.run.rs_running;
1157         journal->j_stats.run.rs_locked += stats.run.rs_locked;
1158         journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
1159         journal->j_stats.run.rs_logging += stats.run.rs_logging;
1160         journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
1161         journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
1162         journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
1163         spin_unlock(&journal->j_history_lock);
1164 }
1165 

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