commit.c
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上传日期:2013-02-24
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- /*
- * linux/fs/commit.c
- *
- * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
- *
- * Copyright 1998 Red Hat corp --- All Rights Reserved
- *
- * This file is part of the Linux kernel and is made available under
- * the terms of the GNU General Public License, version 2, or at your
- * option, any later version, incorporated herein by reference.
- *
- * Journal commit routines for the generic filesystem journaling code;
- * part of the ext2fs journaling system.
- */
- #include <linux/sched.h>
- #include <linux/fs.h>
- #include <linux/jbd.h>
- #include <linux/errno.h>
- #include <linux/slab.h>
- #include <linux/locks.h>
- #include <linux/smp_lock.h>
- extern spinlock_t journal_datalist_lock;
- /*
- * Default IO end handler for temporary BJ_IO buffer_heads.
- */
- void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
- {
- BUFFER_TRACE(bh, "");
- mark_buffer_uptodate(bh, uptodate);
- unlock_buffer(bh);
- }
- /*
- * journal_commit_transaction
- *
- * The primary function for committing a transaction to the log. This
- * function is called by the journal thread to begin a complete commit.
- */
- void journal_commit_transaction(journal_t *journal)
- {
- transaction_t *commit_transaction;
- struct journal_head *jh, *new_jh, *descriptor;
- struct journal_head *next_jh, *last_jh;
- struct buffer_head *wbuf[64];
- int bufs;
- int flags;
- int err;
- unsigned long blocknr;
- char *tagp = NULL;
- journal_header_t *header;
- journal_block_tag_t *tag = NULL;
- int space_left = 0;
- int first_tag = 0;
- int tag_flag;
- int i;
- /*
- * First job: lock down the current transaction and wait for
- * all outstanding updates to complete.
- */
- lock_journal(journal); /* Protect journal->j_running_transaction */
- #ifdef COMMIT_STATS
- spin_lock(&journal_datalist_lock);
- summarise_journal_usage(journal);
- spin_unlock(&journal_datalist_lock);
- #endif
- lock_kernel();
-
- J_ASSERT (journal->j_running_transaction != NULL);
- J_ASSERT (journal->j_committing_transaction == NULL);
- commit_transaction = journal->j_running_transaction;
- J_ASSERT (commit_transaction->t_state == T_RUNNING);
- jbd_debug (1, "JBD: starting commit of transaction %dn",
- commit_transaction->t_tid);
- commit_transaction->t_state = T_LOCKED;
- while (commit_transaction->t_updates != 0) {
- unlock_journal(journal);
- sleep_on(&journal->j_wait_updates);
- lock_journal(journal);
- }
- J_ASSERT (commit_transaction->t_outstanding_credits <=
- journal->j_max_transaction_buffers);
- /* Do we need to erase the effects of a prior journal_flush? */
- if (journal->j_flags & JFS_FLUSHED) {
- jbd_debug(3, "super block updatedn");
- journal_update_superblock(journal, 1);
- } else {
- jbd_debug(3, "superblock not updatedn");
- }
- /*
- * First thing we are allowed to do is to discard any remaining
- * BJ_Reserved buffers. Note, it is _not_ permissible to assume
- * that there are no such buffers: if a large filesystem
- * operation like a truncate needs to split itself over multiple
- * transactions, then it may try to do a journal_restart() while
- * there are still BJ_Reserved buffers outstanding. These must
- * be released cleanly from the current transaction.
- *
- * In this case, the filesystem must still reserve write access
- * again before modifying the buffer in the new transaction, but
- * we do not require it to remember exactly which old buffers it
- * has reserved. This is consistent with the existing behaviour
- * that multiple journal_get_write_access() calls to the same
- * buffer are perfectly permissable.
- */
- while (commit_transaction->t_reserved_list) {
- jh = commit_transaction->t_reserved_list;
- JBUFFER_TRACE(jh, "reserved, unused: refile");
- journal_refile_buffer(jh);
- }
- /*
- * Now try to drop any written-back buffers from the journal's
- * checkpoint lists. We do this *before* commit because it potentially
- * frees some memory
- */
- spin_lock(&journal_datalist_lock);
- __journal_clean_checkpoint_list(journal);
- spin_unlock(&journal_datalist_lock);
- /* First part of the commit: force the revoke list out to disk.
- * The revoke code generates its own metadata blocks on disk for this.
- *
- * It is important that we do this while the transaction is
- * still locked. Generating the revoke records should not
- * generate any IO stalls, so this should be quick; and doing
- * the work while we have the transaction locked means that we
- * only ever have to maintain the revoke list for one
- * transaction at a time.
- */
- jbd_debug (3, "JBD: commit phase 1n");
- journal_write_revoke_records(journal, commit_transaction);
- /*
- * Now that we have built the revoke records, we can start
- * reusing the revoke list for a new running transaction. We
- * can now safely start committing the old transaction: time to
- * get a new running transaction for incoming filesystem updates
- */
- commit_transaction->t_state = T_FLUSH;
- wake_up(&journal->j_wait_transaction_locked);
- journal->j_committing_transaction = commit_transaction;
- journal->j_running_transaction = NULL;
- commit_transaction->t_log_start = journal->j_head;
- unlock_kernel();
-
- jbd_debug (3, "JBD: commit phase 2n");
- /*
- * Now start flushing things to disk, in the order they appear
- * on the transaction lists. Data blocks go first.
- */
- /*
- * Whenever we unlock the journal and sleep, things can get added
- * onto ->t_datalist, so we have to keep looping back to write_out_data
- * until we *know* that the list is empty.
- */
- write_out_data:
- /*
- * Cleanup any flushed data buffers from the data list. Even in
- * abort mode, we want to flush this out as soon as possible.
- *
- * We take journal_datalist_lock to protect the lists from
- * journal_try_to_free_buffers().
- */
- spin_lock(&journal_datalist_lock);
- write_out_data_locked:
- bufs = 0;
- next_jh = commit_transaction->t_sync_datalist;
- if (next_jh == NULL)
- goto sync_datalist_empty;
- last_jh = next_jh->b_tprev;
- do {
- struct buffer_head *bh;
- jh = next_jh;
- next_jh = jh->b_tnext;
- bh = jh2bh(jh);
- if (!buffer_locked(bh)) {
- if (buffer_dirty(bh)) {
- BUFFER_TRACE(bh, "start journal writeout");
- atomic_inc(&bh->b_count);
- wbuf[bufs++] = bh;
- } else {
- BUFFER_TRACE(bh, "writeout complete: unfile");
- __journal_unfile_buffer(jh);
- jh->b_transaction = NULL;
- __journal_remove_journal_head(bh);
- refile_buffer(bh);
- __brelse(bh);
- }
- }
- if (bufs == ARRAY_SIZE(wbuf)) {
- /*
- * Major speedup: start here on the next scan
- */
- J_ASSERT(commit_transaction->t_sync_datalist != 0);
- commit_transaction->t_sync_datalist = jh;
- break;
- }
- } while (jh != last_jh);
- if (bufs || current->need_resched) {
- jbd_debug(2, "submit %d writesn", bufs);
- spin_unlock(&journal_datalist_lock);
- unlock_journal(journal);
- if (bufs)
- ll_rw_block(WRITE, bufs, wbuf);
- if (current->need_resched)
- schedule();
- journal_brelse_array(wbuf, bufs);
- lock_journal(journal);
- spin_lock(&journal_datalist_lock);
- if (bufs)
- goto write_out_data_locked;
- }
- /*
- * Wait for all previously submitted IO on the data list to complete.
- */
- jh = commit_transaction->t_sync_datalist;
- if (jh == NULL)
- goto sync_datalist_empty;
- do {
- struct buffer_head *bh;
- jh = jh->b_tprev; /* Wait on the last written */
- bh = jh2bh(jh);
- if (buffer_locked(bh)) {
- spin_unlock(&journal_datalist_lock);
- unlock_journal(journal);
- wait_on_buffer(bh);
- /* the journal_head may have been removed now */
- lock_journal(journal);
- goto write_out_data;
- } else if (buffer_dirty(bh)) {
- goto write_out_data_locked;
- }
- } while (jh != commit_transaction->t_sync_datalist);
- goto write_out_data_locked;
- sync_datalist_empty:
- /*
- * Wait for all the async writepage data. As they become unlocked
- * in end_buffer_io_async(), the only place where they can be
- * reaped is in try_to_free_buffers(), and we're locked against
- * that.
- */
- while ((jh = commit_transaction->t_async_datalist)) {
- struct buffer_head *bh = jh2bh(jh);
- if (buffer_locked(bh)) {
- spin_unlock(&journal_datalist_lock);
- unlock_journal(journal);
- wait_on_buffer(bh);
- lock_journal(journal);
- spin_lock(&journal_datalist_lock);
- continue; /* List may have changed */
- }
- if (jh->b_next_transaction) {
- /*
- * For writepage() buffers in journalled data mode: a
- * later transaction may want the buffer for "metadata"
- */
- __journal_refile_buffer(jh);
- } else {
- BUFFER_TRACE(bh, "finished async writeout: unfile");
- __journal_unfile_buffer(jh);
- jh->b_transaction = NULL;
- __journal_remove_journal_head(bh);
- BUFFER_TRACE(bh, "finished async writeout: refile");
- /* It can sometimes be on BUF_LOCKED due to migration
- * from syncdata to asyncdata */
- if (bh->b_list != BUF_CLEAN)
- refile_buffer(bh);
- __brelse(bh);
- }
- }
- spin_unlock(&journal_datalist_lock);
- /*
- * If we found any dirty or locked buffers, then we should have
- * looped back up to the write_out_data label. If there weren't
- * any then journal_clean_data_list should have wiped the list
- * clean by now, so check that it is in fact empty.
- */
- J_ASSERT (commit_transaction->t_sync_datalist == NULL);
- J_ASSERT (commit_transaction->t_async_datalist == NULL);
- jbd_debug (3, "JBD: commit phase 3n");
- /*
- * Way to go: we have now written out all of the data for a
- * transaction! Now comes the tricky part: we need to write out
- * metadata. Loop over the transaction's entire buffer list:
- */
- commit_transaction->t_state = T_COMMIT;
- descriptor = 0;
- bufs = 0;
- while (commit_transaction->t_buffers) {
- /* Find the next buffer to be journaled... */
- jh = commit_transaction->t_buffers;
- /* If we're in abort mode, we just un-journal the buffer and
- release it for background writing. */
- if (is_journal_aborted(journal)) {
- JBUFFER_TRACE(jh, "journal is aborting: refile");
- journal_refile_buffer(jh);
- /* If that was the last one, we need to clean up
- * any descriptor buffers which may have been
- * already allocated, even if we are now
- * aborting. */
- if (!commit_transaction->t_buffers)
- goto start_journal_io;
- continue;
- }
- /* Make sure we have a descriptor block in which to
- record the metadata buffer. */
- if (!descriptor) {
- struct buffer_head *bh;
- J_ASSERT (bufs == 0);
- jbd_debug(4, "JBD: get descriptorn");
- descriptor = journal_get_descriptor_buffer(journal);
- if (!descriptor) {
- __journal_abort_hard(journal);
- continue;
- }
-
- bh = jh2bh(descriptor);
- jbd_debug(4, "JBD: got buffer %ld (%p)n",
- bh->b_blocknr, bh->b_data);
- header = (journal_header_t *)&bh->b_data[0];
- header->h_magic = htonl(JFS_MAGIC_NUMBER);
- header->h_blocktype = htonl(JFS_DESCRIPTOR_BLOCK);
- header->h_sequence = htonl(commit_transaction->t_tid);
- tagp = &bh->b_data[sizeof(journal_header_t)];
- space_left = bh->b_size - sizeof(journal_header_t);
- first_tag = 1;
- set_bit(BH_JWrite, &bh->b_state);
- wbuf[bufs++] = bh;
- /* Record it so that we can wait for IO
- completion later */
- BUFFER_TRACE(bh, "ph3: file as descriptor");
- journal_file_buffer(descriptor, commit_transaction,
- BJ_LogCtl);
- }
- /* Where is the buffer to be written? */
- err = journal_next_log_block(journal, &blocknr);
- /* If the block mapping failed, just abandon the buffer
- and repeat this loop: we'll fall into the
- refile-on-abort condition above. */
- if (err) {
- __journal_abort_hard(journal);
- continue;
- }
- /* Bump b_count to prevent truncate from stumbling over
- the shadowed buffer! @@@ This can go if we ever get
- rid of the BJ_IO/BJ_Shadow pairing of buffers. */
- atomic_inc(&jh2bh(jh)->b_count);
- /* Make a temporary IO buffer with which to write it out
- (this will requeue both the metadata buffer and the
- temporary IO buffer). new_bh goes on BJ_IO*/
- set_bit(BH_JWrite, &jh2bh(jh)->b_state);
- /*
- * akpm: journal_write_metadata_buffer() sets
- * new_bh->b_transaction to commit_transaction.
- * We need to clean this up before we release new_bh
- * (which is of type BJ_IO)
- */
- JBUFFER_TRACE(jh, "ph3: write metadata");
- flags = journal_write_metadata_buffer(commit_transaction,
- jh, &new_jh, blocknr);
- set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
- set_bit(BH_Lock, &jh2bh(new_jh)->b_state);
- wbuf[bufs++] = jh2bh(new_jh);
- /* Record the new block's tag in the current descriptor
- buffer */
- tag_flag = 0;
- if (flags & 1)
- tag_flag |= JFS_FLAG_ESCAPE;
- if (!first_tag)
- tag_flag |= JFS_FLAG_SAME_UUID;
- tag = (journal_block_tag_t *) tagp;
- tag->t_blocknr = htonl(jh2bh(jh)->b_blocknr);
- tag->t_flags = htonl(tag_flag);
- tagp += sizeof(journal_block_tag_t);
- space_left -= sizeof(journal_block_tag_t);
- if (first_tag) {
- memcpy (tagp, journal->j_uuid, 16);
- tagp += 16;
- space_left -= 16;
- first_tag = 0;
- }
- /* If there's no more to do, or if the descriptor is full,
- let the IO rip! */
- if (bufs == ARRAY_SIZE(wbuf) ||
- commit_transaction->t_buffers == NULL ||
- space_left < sizeof(journal_block_tag_t) + 16) {
- jbd_debug(4, "JBD: Submit %d IOsn", bufs);
- /* Write an end-of-descriptor marker before
- submitting the IOs. "tag" still points to
- the last tag we set up. */
- tag->t_flags |= htonl(JFS_FLAG_LAST_TAG);
- start_journal_io:
- unlock_journal(journal);
- for (i=0; i<bufs; i++) {
- struct buffer_head *bh = wbuf[i];
- clear_bit(BH_Dirty, &bh->b_state);
- bh->b_end_io = journal_end_buffer_io_sync;
- submit_bh(WRITE, bh);
- }
- if (current->need_resched)
- schedule();
- lock_journal(journal);
- /* Force a new descriptor to be generated next
- time round the loop. */
- descriptor = NULL;
- bufs = 0;
- }
- }
- /* Lo and behold: we have just managed to send a transaction to
- the log. Before we can commit it, wait for the IO so far to
- complete. Control buffers being written are on the
- transaction's t_log_list queue, and metadata buffers are on
- the t_iobuf_list queue.
- Wait for the transactions in reverse order. That way we are
- less likely to be woken up until all IOs have completed, and
- so we incur less scheduling load.
- */
- jbd_debug(3, "JBD: commit phase 4n");
- /* akpm: these are BJ_IO, and journal_datalist_lock is not needed */
- wait_for_iobuf:
- while (commit_transaction->t_iobuf_list != NULL) {
- struct buffer_head *bh;
- jh = commit_transaction->t_iobuf_list->b_tprev;
- bh = jh2bh(jh);
- if (buffer_locked(bh)) {
- unlock_journal(journal);
- wait_on_buffer(bh);
- lock_journal(journal);
- goto wait_for_iobuf;
- }
- clear_bit(BH_JWrite, &jh2bh(jh)->b_state);
- JBUFFER_TRACE(jh, "ph4: unfile after journal write");
- journal_unfile_buffer(jh);
- /*
- * akpm: don't put back a buffer_head with stale pointers
- * dangling around.
- */
- J_ASSERT_JH(jh, jh->b_transaction != NULL);
- jh->b_transaction = NULL;
- /*
- * ->t_iobuf_list should contain only dummy buffer_heads
- * which were created by journal_write_metadata_buffer().
- */
- bh = jh2bh(jh);
- BUFFER_TRACE(bh, "dumping temporary bh");
- journal_unlock_journal_head(jh);
- __brelse(bh);
- J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
- put_unused_buffer_head(bh);
- /* We also have to unlock and free the corresponding
- shadowed buffer */
- jh = commit_transaction->t_shadow_list->b_tprev;
- bh = jh2bh(jh);
- clear_bit(BH_JWrite, &bh->b_state);
- J_ASSERT_BH(bh, buffer_jdirty(bh));
- /* The metadata is now released for reuse, but we need
- to remember it against this transaction so that when
- we finally commit, we can do any checkpointing
- required. */
- JBUFFER_TRACE(jh, "file as BJ_Forget");
- journal_file_buffer(jh, commit_transaction, BJ_Forget);
- /* Wake up any transactions which were waiting for this
- IO to complete */
- wake_up(&bh->b_wait);
- JBUFFER_TRACE(jh, "brelse shadowed buffer");
- __brelse(bh);
- }
- J_ASSERT (commit_transaction->t_shadow_list == NULL);
- jbd_debug(3, "JBD: commit phase 5n");
- /* Here we wait for the revoke record and descriptor record buffers */
- wait_for_ctlbuf:
- while (commit_transaction->t_log_list != NULL) {
- struct buffer_head *bh;
- jh = commit_transaction->t_log_list->b_tprev;
- bh = jh2bh(jh);
- if (buffer_locked(bh)) {
- unlock_journal(journal);
- wait_on_buffer(bh);
- lock_journal(journal);
- goto wait_for_ctlbuf;
- }
- BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
- clear_bit(BH_JWrite, &bh->b_state);
- journal_unfile_buffer(jh);
- jh->b_transaction = NULL;
- journal_unlock_journal_head(jh);
- put_bh(bh); /* One for getblk */
- }
- jbd_debug(3, "JBD: commit phase 6n");
- if (is_journal_aborted(journal))
- goto skip_commit;
- /* Done it all: now write the commit record. We should have
- * cleaned up our previous buffers by now, so if we are in abort
- * mode we can now just skip the rest of the journal write
- * entirely. */
- descriptor = journal_get_descriptor_buffer(journal);
- if (!descriptor) {
- __journal_abort_hard(journal);
- goto skip_commit;
- }
-
- /* AKPM: buglet - add `i' to tmp! */
- for (i = 0; i < jh2bh(descriptor)->b_size; i += 512) {
- journal_header_t *tmp =
- (journal_header_t*)jh2bh(descriptor)->b_data;
- tmp->h_magic = htonl(JFS_MAGIC_NUMBER);
- tmp->h_blocktype = htonl(JFS_COMMIT_BLOCK);
- tmp->h_sequence = htonl(commit_transaction->t_tid);
- }
- unlock_journal(journal);
- JBUFFER_TRACE(descriptor, "write commit block");
- {
- struct buffer_head *bh = jh2bh(descriptor);
- clear_bit(BH_Dirty, &bh->b_state);
- bh->b_end_io = journal_end_buffer_io_sync;
- submit_bh(WRITE, bh);
- wait_on_buffer(bh);
- put_bh(bh); /* One for getblk() */
- journal_unlock_journal_head(descriptor);
- }
- lock_journal(journal);
- /* End of a transaction! Finally, we can do checkpoint
- processing: any buffers committed as a result of this
- transaction can be removed from any checkpoint list it was on
- before. */
- skip_commit:
- jbd_debug(3, "JBD: commit phase 7n");
- J_ASSERT(commit_transaction->t_sync_datalist == NULL);
- J_ASSERT(commit_transaction->t_async_datalist == NULL);
- J_ASSERT(commit_transaction->t_buffers == NULL);
- J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
- J_ASSERT(commit_transaction->t_iobuf_list == NULL);
- J_ASSERT(commit_transaction->t_shadow_list == NULL);
- J_ASSERT(commit_transaction->t_log_list == NULL);
- while (commit_transaction->t_forget) {
- transaction_t *cp_transaction;
- struct buffer_head *bh;
- jh = commit_transaction->t_forget;
- J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
- jh->b_transaction == journal->j_running_transaction);
- /*
- * If there is undo-protected committed data against
- * this buffer, then we can remove it now. If it is a
- * buffer needing such protection, the old frozen_data
- * field now points to a committed version of the
- * buffer, so rotate that field to the new committed
- * data.
- *
- * Otherwise, we can just throw away the frozen data now.
- */
- if (jh->b_committed_data) {
- kfree(jh->b_committed_data);
- jh->b_committed_data = NULL;
- if (jh->b_frozen_data) {
- jh->b_committed_data = jh->b_frozen_data;
- jh->b_frozen_data = NULL;
- }
- } else if (jh->b_frozen_data) {
- kfree(jh->b_frozen_data);
- jh->b_frozen_data = NULL;
- }
- spin_lock(&journal_datalist_lock);
- cp_transaction = jh->b_cp_transaction;
- if (cp_transaction) {
- JBUFFER_TRACE(jh, "remove from old cp transaction");
- J_ASSERT_JH(jh, commit_transaction != cp_transaction);
- __journal_remove_checkpoint(jh);
- }
- /* Only re-checkpoint the buffer_head if it is marked
- * dirty. If the buffer was added to the BJ_Forget list
- * by journal_forget, it may no longer be dirty and
- * there's no point in keeping a checkpoint record for
- * it. */
- bh = jh2bh(jh);
- if (buffer_jdirty(bh)) {
- JBUFFER_TRACE(jh, "add to new checkpointing trans");
- __journal_insert_checkpoint(jh, commit_transaction);
- JBUFFER_TRACE(jh, "refile for checkpoint writeback");
- __journal_refile_buffer(jh);
- } else {
- J_ASSERT_BH(bh, !buffer_dirty(bh));
- J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
- __journal_unfile_buffer(jh);
- jh->b_transaction = 0;
- __journal_remove_journal_head(bh);
- __brelse(bh);
- }
- spin_unlock(&journal_datalist_lock);
- }
- /* Done with this transaction! */
- jbd_debug(3, "JBD: commit phase 8n");
- J_ASSERT (commit_transaction->t_state == T_COMMIT);
- commit_transaction->t_state = T_FINISHED;
- J_ASSERT (commit_transaction == journal->j_committing_transaction);
- journal->j_commit_sequence = commit_transaction->t_tid;
- journal->j_committing_transaction = NULL;
- spin_lock(&journal_datalist_lock);
- if (commit_transaction->t_checkpoint_list == NULL) {
- __journal_drop_transaction(journal, commit_transaction);
- } else {
- if (journal->j_checkpoint_transactions == NULL) {
- journal->j_checkpoint_transactions = commit_transaction;
- commit_transaction->t_cpnext = commit_transaction;
- commit_transaction->t_cpprev = commit_transaction;
- } else {
- commit_transaction->t_cpnext =
- journal->j_checkpoint_transactions;
- commit_transaction->t_cpprev =
- commit_transaction->t_cpnext->t_cpprev;
- commit_transaction->t_cpnext->t_cpprev =
- commit_transaction;
- commit_transaction->t_cpprev->t_cpnext =
- commit_transaction;
- }
- }
- spin_unlock(&journal_datalist_lock);
- jbd_debug(1, "JBD: commit %d complete, head %dn",
- journal->j_commit_sequence, journal->j_tail_sequence);
- unlock_journal(journal);
- wake_up(&journal->j_wait_done_commit);
- }