![Theodore Ts'o](/assets/img/avatar_default.png)
__process_buffer() is only called by jbd2_log_do_checkpoint(), and it had a very complex locking protocol where it would be called with the j_list_lock, and sometimes exit with the lock held (if the return code was 0), or release the lock. This was confusing both to humans and to smatch (which erronously complained that the lock was taken twice). Folding __process_buffer() to the caller allows us to simplify the control flow, making the resulting function easier to read and reason about, and dropping the compiled size of fs/jbd2/checkpoint.c by 150 bytes (over 4% of the text size). Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz>
681 lines
19 KiB
C
681 lines
19 KiB
C
/*
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* linux/fs/jbd2/checkpoint.c
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*
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* Written by Stephen C. Tweedie <sct@redhat.com>, 1999
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*
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* Copyright 1999 Red Hat Software --- All Rights Reserved
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*
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* This file is part of the Linux kernel and is made available under
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* the terms of the GNU General Public License, version 2, or at your
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* option, any later version, incorporated herein by reference.
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*
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* Checkpoint routines for the generic filesystem journaling code.
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* Part of the ext2fs journaling system.
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*
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* Checkpointing is the process of ensuring that a section of the log is
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* committed fully to disk, so that that portion of the log can be
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* reused.
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*/
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/jbd2.h>
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#include <linux/errno.h>
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#include <linux/slab.h>
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#include <linux/blkdev.h>
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#include <trace/events/jbd2.h>
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/*
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* Unlink a buffer from a transaction checkpoint list.
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*
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* Called with j_list_lock held.
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*/
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static inline void __buffer_unlink_first(struct journal_head *jh)
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{
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transaction_t *transaction = jh->b_cp_transaction;
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jh->b_cpnext->b_cpprev = jh->b_cpprev;
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jh->b_cpprev->b_cpnext = jh->b_cpnext;
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if (transaction->t_checkpoint_list == jh) {
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transaction->t_checkpoint_list = jh->b_cpnext;
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if (transaction->t_checkpoint_list == jh)
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transaction->t_checkpoint_list = NULL;
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}
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}
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/*
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* Unlink a buffer from a transaction checkpoint(io) list.
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*
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* Called with j_list_lock held.
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*/
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static inline void __buffer_unlink(struct journal_head *jh)
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{
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transaction_t *transaction = jh->b_cp_transaction;
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__buffer_unlink_first(jh);
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if (transaction->t_checkpoint_io_list == jh) {
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transaction->t_checkpoint_io_list = jh->b_cpnext;
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if (transaction->t_checkpoint_io_list == jh)
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transaction->t_checkpoint_io_list = NULL;
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}
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}
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/*
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* Move a buffer from the checkpoint list to the checkpoint io list
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*
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* Called with j_list_lock held
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*/
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static inline void __buffer_relink_io(struct journal_head *jh)
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{
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transaction_t *transaction = jh->b_cp_transaction;
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__buffer_unlink_first(jh);
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if (!transaction->t_checkpoint_io_list) {
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jh->b_cpnext = jh->b_cpprev = jh;
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} else {
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jh->b_cpnext = transaction->t_checkpoint_io_list;
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jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
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jh->b_cpprev->b_cpnext = jh;
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jh->b_cpnext->b_cpprev = jh;
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}
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transaction->t_checkpoint_io_list = jh;
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}
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/*
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* Try to release a checkpointed buffer from its transaction.
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* Returns 1 if we released it and 2 if we also released the
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* whole transaction.
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*
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* Requires j_list_lock
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*/
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static int __try_to_free_cp_buf(struct journal_head *jh)
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{
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int ret = 0;
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struct buffer_head *bh = jh2bh(jh);
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if (jh->b_transaction == NULL && !buffer_locked(bh) &&
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!buffer_dirty(bh) && !buffer_write_io_error(bh)) {
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/*
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* Get our reference so that bh cannot be freed before
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* we unlock it
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*/
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get_bh(bh);
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JBUFFER_TRACE(jh, "remove from checkpoint list");
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ret = __jbd2_journal_remove_checkpoint(jh) + 1;
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BUFFER_TRACE(bh, "release");
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__brelse(bh);
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}
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return ret;
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}
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/*
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* __jbd2_log_wait_for_space: wait until there is space in the journal.
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*
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* Called under j-state_lock *only*. It will be unlocked if we have to wait
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* for a checkpoint to free up some space in the log.
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*/
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void __jbd2_log_wait_for_space(journal_t *journal)
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{
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int nblocks, space_left;
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/* assert_spin_locked(&journal->j_state_lock); */
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nblocks = jbd2_space_needed(journal);
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while (jbd2_log_space_left(journal) < nblocks) {
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if (journal->j_flags & JBD2_ABORT)
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return;
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write_unlock(&journal->j_state_lock);
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mutex_lock(&journal->j_checkpoint_mutex);
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/*
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* Test again, another process may have checkpointed while we
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* were waiting for the checkpoint lock. If there are no
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* transactions ready to be checkpointed, try to recover
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* journal space by calling cleanup_journal_tail(), and if
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* that doesn't work, by waiting for the currently committing
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* transaction to complete. If there is absolutely no way
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* to make progress, this is either a BUG or corrupted
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* filesystem, so abort the journal and leave a stack
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* trace for forensic evidence.
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*/
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write_lock(&journal->j_state_lock);
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spin_lock(&journal->j_list_lock);
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nblocks = jbd2_space_needed(journal);
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space_left = jbd2_log_space_left(journal);
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if (space_left < nblocks) {
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int chkpt = journal->j_checkpoint_transactions != NULL;
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tid_t tid = 0;
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if (journal->j_committing_transaction)
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tid = journal->j_committing_transaction->t_tid;
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spin_unlock(&journal->j_list_lock);
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write_unlock(&journal->j_state_lock);
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if (chkpt) {
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jbd2_log_do_checkpoint(journal);
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} else if (jbd2_cleanup_journal_tail(journal) == 0) {
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/* We were able to recover space; yay! */
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;
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} else if (tid) {
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/*
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* jbd2_journal_commit_transaction() may want
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* to take the checkpoint_mutex if JBD2_FLUSHED
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* is set. So we need to temporarily drop it.
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*/
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mutex_unlock(&journal->j_checkpoint_mutex);
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jbd2_log_wait_commit(journal, tid);
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write_lock(&journal->j_state_lock);
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continue;
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} else {
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printk(KERN_ERR "%s: needed %d blocks and "
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"only had %d space available\n",
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__func__, nblocks, space_left);
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printk(KERN_ERR "%s: no way to get more "
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"journal space in %s\n", __func__,
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journal->j_devname);
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WARN_ON(1);
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jbd2_journal_abort(journal, 0);
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}
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write_lock(&journal->j_state_lock);
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} else {
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spin_unlock(&journal->j_list_lock);
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}
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mutex_unlock(&journal->j_checkpoint_mutex);
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}
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}
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/*
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* Clean up transaction's list of buffers submitted for io.
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* We wait for any pending IO to complete and remove any clean
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* buffers. Note that we take the buffers in the opposite ordering
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* from the one in which they were submitted for IO.
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*
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* Return 0 on success, and return <0 if some buffers have failed
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* to be written out.
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*
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* Called with j_list_lock held.
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*/
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static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
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{
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struct journal_head *jh;
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struct buffer_head *bh;
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tid_t this_tid;
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int released = 0;
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int ret = 0;
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this_tid = transaction->t_tid;
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restart:
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/* Did somebody clean up the transaction in the meanwhile? */
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if (journal->j_checkpoint_transactions != transaction ||
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transaction->t_tid != this_tid)
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return ret;
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while (!released && transaction->t_checkpoint_io_list) {
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jh = transaction->t_checkpoint_io_list;
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bh = jh2bh(jh);
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get_bh(bh);
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if (buffer_locked(bh)) {
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spin_unlock(&journal->j_list_lock);
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wait_on_buffer(bh);
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/* the journal_head may have gone by now */
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BUFFER_TRACE(bh, "brelse");
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__brelse(bh);
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spin_lock(&journal->j_list_lock);
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goto restart;
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}
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if (unlikely(buffer_write_io_error(bh)))
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ret = -EIO;
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/*
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* Now in whatever state the buffer currently is, we know that
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* it has been written out and so we can drop it from the list
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*/
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released = __jbd2_journal_remove_checkpoint(jh);
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__brelse(bh);
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}
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return ret;
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}
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static void
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__flush_batch(journal_t *journal, int *batch_count)
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{
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int i;
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struct blk_plug plug;
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blk_start_plug(&plug);
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for (i = 0; i < *batch_count; i++)
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write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC);
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blk_finish_plug(&plug);
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for (i = 0; i < *batch_count; i++) {
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struct buffer_head *bh = journal->j_chkpt_bhs[i];
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BUFFER_TRACE(bh, "brelse");
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__brelse(bh);
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}
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*batch_count = 0;
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}
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/*
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* Perform an actual checkpoint. We take the first transaction on the
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* list of transactions to be checkpointed and send all its buffers
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* to disk. We submit larger chunks of data at once.
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*
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* The journal should be locked before calling this function.
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* Called with j_checkpoint_mutex held.
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*/
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int jbd2_log_do_checkpoint(journal_t *journal)
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{
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struct journal_head *jh;
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struct buffer_head *bh;
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transaction_t *transaction;
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tid_t this_tid;
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int err, result, batch_count = 0;
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jbd_debug(1, "Start checkpoint\n");
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/*
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* First thing: if there are any transactions in the log which
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* don't need checkpointing, just eliminate them from the
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* journal straight away.
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*/
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result = jbd2_cleanup_journal_tail(journal);
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trace_jbd2_checkpoint(journal, result);
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jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
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if (result <= 0)
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return result;
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/*
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* OK, we need to start writing disk blocks. Take one transaction
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* and write it.
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*/
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result = 0;
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spin_lock(&journal->j_list_lock);
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if (!journal->j_checkpoint_transactions)
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goto out;
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transaction = journal->j_checkpoint_transactions;
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if (transaction->t_chp_stats.cs_chp_time == 0)
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transaction->t_chp_stats.cs_chp_time = jiffies;
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this_tid = transaction->t_tid;
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restart:
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/*
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* If someone cleaned up this transaction while we slept, we're
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* done (maybe it's a new transaction, but it fell at the same
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* address).
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*/
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if (journal->j_checkpoint_transactions != transaction ||
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transaction->t_tid != this_tid)
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goto out;
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/* checkpoint all of the transaction's buffers */
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while (transaction->t_checkpoint_list) {
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jh = transaction->t_checkpoint_list;
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bh = jh2bh(jh);
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if (buffer_locked(bh)) {
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spin_unlock(&journal->j_list_lock);
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get_bh(bh);
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wait_on_buffer(bh);
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/* the journal_head may have gone by now */
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BUFFER_TRACE(bh, "brelse");
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__brelse(bh);
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goto retry;
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}
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if (jh->b_transaction != NULL) {
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transaction_t *t = jh->b_transaction;
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tid_t tid = t->t_tid;
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transaction->t_chp_stats.cs_forced_to_close++;
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spin_unlock(&journal->j_list_lock);
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if (unlikely(journal->j_flags & JBD2_UNMOUNT))
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/*
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* The journal thread is dead; so
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* starting and waiting for a commit
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* to finish will cause us to wait for
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* a _very_ long time.
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*/
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printk(KERN_ERR
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"JBD2: %s: Waiting for Godot: block %llu\n",
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journal->j_devname, (unsigned long long) bh->b_blocknr);
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jbd2_log_start_commit(journal, tid);
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jbd2_log_wait_commit(journal, tid);
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goto retry;
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}
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if (!buffer_dirty(bh)) {
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if (unlikely(buffer_write_io_error(bh)) && !result)
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result = -EIO;
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get_bh(bh);
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BUFFER_TRACE(bh, "remove from checkpoint");
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__jbd2_journal_remove_checkpoint(jh);
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spin_unlock(&journal->j_list_lock);
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__brelse(bh);
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goto retry;
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}
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/*
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* Important: we are about to write the buffer, and
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* possibly block, while still holding the journal
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* lock. We cannot afford to let the transaction
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* logic start messing around with this buffer before
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* we write it to disk, as that would break
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* recoverability.
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*/
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BUFFER_TRACE(bh, "queue");
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get_bh(bh);
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J_ASSERT_BH(bh, !buffer_jwrite(bh));
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journal->j_chkpt_bhs[batch_count++] = bh;
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__buffer_relink_io(jh);
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transaction->t_chp_stats.cs_written++;
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if ((batch_count == JBD2_NR_BATCH) ||
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need_resched() ||
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spin_needbreak(&journal->j_list_lock))
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goto unlock_and_flush;
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}
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if (batch_count) {
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unlock_and_flush:
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spin_unlock(&journal->j_list_lock);
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retry:
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if (batch_count)
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__flush_batch(journal, &batch_count);
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spin_lock(&journal->j_list_lock);
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goto restart;
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}
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/*
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* Now we issued all of the transaction's buffers, let's deal
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* with the buffers that are out for I/O.
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*/
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err = __wait_cp_io(journal, transaction);
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if (!result)
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result = err;
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out:
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spin_unlock(&journal->j_list_lock);
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if (result < 0)
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jbd2_journal_abort(journal, result);
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else
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result = jbd2_cleanup_journal_tail(journal);
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return (result < 0) ? result : 0;
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}
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/*
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* Check the list of checkpoint transactions for the journal to see if
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* we have already got rid of any since the last update of the log tail
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* in the journal superblock. If so, we can instantly roll the
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* superblock forward to remove those transactions from the log.
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*
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* Return <0 on error, 0 on success, 1 if there was nothing to clean up.
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*
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* Called with the journal lock held.
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*
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* This is the only part of the journaling code which really needs to be
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* aware of transaction aborts. Checkpointing involves writing to the
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* main filesystem area rather than to the journal, so it can proceed
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* even in abort state, but we must not update the super block if
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* checkpointing may have failed. Otherwise, we would lose some metadata
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* buffers which should be written-back to the filesystem.
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*/
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int jbd2_cleanup_journal_tail(journal_t *journal)
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{
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tid_t first_tid;
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unsigned long blocknr;
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if (is_journal_aborted(journal))
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return 1;
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if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
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return 1;
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J_ASSERT(blocknr != 0);
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/*
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* We need to make sure that any blocks that were recently written out
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* --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
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* we drop the transactions from the journal. It's unlikely this will
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* be necessary, especially with an appropriately sized journal, but we
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* need this to guarantee correctness. Fortunately
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* jbd2_cleanup_journal_tail() doesn't get called all that often.
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*/
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if (journal->j_flags & JBD2_BARRIER)
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blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
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__jbd2_update_log_tail(journal, first_tid, blocknr);
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return 0;
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}
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/* Checkpoint list management */
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/*
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* journal_clean_one_cp_list
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*
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* Find all the written-back checkpoint buffers in the given list and
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* release them.
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*
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* Called with the journal locked.
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* Called with j_list_lock held.
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* Returns number of buffers reaped (for debug)
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*/
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static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
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{
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struct journal_head *last_jh;
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struct journal_head *next_jh = jh;
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int ret, freed = 0;
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*released = 0;
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if (!jh)
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return 0;
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last_jh = jh->b_cpprev;
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do {
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jh = next_jh;
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next_jh = jh->b_cpnext;
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ret = __try_to_free_cp_buf(jh);
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if (ret) {
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freed++;
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if (ret == 2) {
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*released = 1;
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return freed;
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}
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}
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/*
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* This function only frees up some memory
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* if possible so we dont have an obligation
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* to finish processing. Bail out if preemption
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* requested:
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*/
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if (need_resched())
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return freed;
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} while (jh != last_jh);
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return freed;
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}
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/*
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* journal_clean_checkpoint_list
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*
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* Find all the written-back checkpoint buffers in the journal and release them.
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*
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* Called with the journal locked.
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* Called with j_list_lock held.
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* Returns number of buffers reaped (for debug)
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*/
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int __jbd2_journal_clean_checkpoint_list(journal_t *journal)
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{
|
|
transaction_t *transaction, *last_transaction, *next_transaction;
|
|
int ret = 0;
|
|
int released;
|
|
|
|
transaction = journal->j_checkpoint_transactions;
|
|
if (!transaction)
|
|
goto out;
|
|
|
|
last_transaction = transaction->t_cpprev;
|
|
next_transaction = transaction;
|
|
do {
|
|
transaction = next_transaction;
|
|
next_transaction = transaction->t_cpnext;
|
|
ret += journal_clean_one_cp_list(transaction->
|
|
t_checkpoint_list, &released);
|
|
/*
|
|
* This function only frees up some memory if possible so we
|
|
* dont have an obligation to finish processing. Bail out if
|
|
* preemption requested:
|
|
*/
|
|
if (need_resched())
|
|
goto out;
|
|
if (released)
|
|
continue;
|
|
/*
|
|
* It is essential that we are as careful as in the case of
|
|
* t_checkpoint_list with removing the buffer from the list as
|
|
* we can possibly see not yet submitted buffers on io_list
|
|
*/
|
|
ret += journal_clean_one_cp_list(transaction->
|
|
t_checkpoint_io_list, &released);
|
|
if (need_resched())
|
|
goto out;
|
|
} while (transaction != last_transaction);
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* journal_remove_checkpoint: called after a buffer has been committed
|
|
* to disk (either by being write-back flushed to disk, or being
|
|
* committed to the log).
|
|
*
|
|
* We cannot safely clean a transaction out of the log until all of the
|
|
* buffer updates committed in that transaction have safely been stored
|
|
* elsewhere on disk. To achieve this, all of the buffers in a
|
|
* transaction need to be maintained on the transaction's checkpoint
|
|
* lists until they have been rewritten, at which point this function is
|
|
* called to remove the buffer from the existing transaction's
|
|
* checkpoint lists.
|
|
*
|
|
* The function returns 1 if it frees the transaction, 0 otherwise.
|
|
* The function can free jh and bh.
|
|
*
|
|
* This function is called with j_list_lock held.
|
|
*/
|
|
int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
|
|
{
|
|
struct transaction_chp_stats_s *stats;
|
|
transaction_t *transaction;
|
|
journal_t *journal;
|
|
int ret = 0;
|
|
|
|
JBUFFER_TRACE(jh, "entry");
|
|
|
|
if ((transaction = jh->b_cp_transaction) == NULL) {
|
|
JBUFFER_TRACE(jh, "not on transaction");
|
|
goto out;
|
|
}
|
|
journal = transaction->t_journal;
|
|
|
|
JBUFFER_TRACE(jh, "removing from transaction");
|
|
__buffer_unlink(jh);
|
|
jh->b_cp_transaction = NULL;
|
|
jbd2_journal_put_journal_head(jh);
|
|
|
|
if (transaction->t_checkpoint_list != NULL ||
|
|
transaction->t_checkpoint_io_list != NULL)
|
|
goto out;
|
|
|
|
/*
|
|
* There is one special case to worry about: if we have just pulled the
|
|
* buffer off a running or committing transaction's checkpoing list,
|
|
* then even if the checkpoint list is empty, the transaction obviously
|
|
* cannot be dropped!
|
|
*
|
|
* The locking here around t_state is a bit sleazy.
|
|
* See the comment at the end of jbd2_journal_commit_transaction().
|
|
*/
|
|
if (transaction->t_state != T_FINISHED)
|
|
goto out;
|
|
|
|
/* OK, that was the last buffer for the transaction: we can now
|
|
safely remove this transaction from the log */
|
|
stats = &transaction->t_chp_stats;
|
|
if (stats->cs_chp_time)
|
|
stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
|
|
jiffies);
|
|
trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
|
|
transaction->t_tid, stats);
|
|
|
|
__jbd2_journal_drop_transaction(journal, transaction);
|
|
jbd2_journal_free_transaction(transaction);
|
|
ret = 1;
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* journal_insert_checkpoint: put a committed buffer onto a checkpoint
|
|
* list so that we know when it is safe to clean the transaction out of
|
|
* the log.
|
|
*
|
|
* Called with the journal locked.
|
|
* Called with j_list_lock held.
|
|
*/
|
|
void __jbd2_journal_insert_checkpoint(struct journal_head *jh,
|
|
transaction_t *transaction)
|
|
{
|
|
JBUFFER_TRACE(jh, "entry");
|
|
J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
|
|
J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
|
|
|
|
/* Get reference for checkpointing transaction */
|
|
jbd2_journal_grab_journal_head(jh2bh(jh));
|
|
jh->b_cp_transaction = transaction;
|
|
|
|
if (!transaction->t_checkpoint_list) {
|
|
jh->b_cpnext = jh->b_cpprev = jh;
|
|
} else {
|
|
jh->b_cpnext = transaction->t_checkpoint_list;
|
|
jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
|
|
jh->b_cpprev->b_cpnext = jh;
|
|
jh->b_cpnext->b_cpprev = jh;
|
|
}
|
|
transaction->t_checkpoint_list = jh;
|
|
}
|
|
|
|
/*
|
|
* We've finished with this transaction structure: adios...
|
|
*
|
|
* The transaction must have no links except for the checkpoint by this
|
|
* point.
|
|
*
|
|
* Called with the journal locked.
|
|
* Called with j_list_lock held.
|
|
*/
|
|
|
|
void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
|
|
{
|
|
assert_spin_locked(&journal->j_list_lock);
|
|
if (transaction->t_cpnext) {
|
|
transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
|
|
transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
|
|
if (journal->j_checkpoint_transactions == transaction)
|
|
journal->j_checkpoint_transactions =
|
|
transaction->t_cpnext;
|
|
if (journal->j_checkpoint_transactions == transaction)
|
|
journal->j_checkpoint_transactions = NULL;
|
|
}
|
|
|
|
J_ASSERT(transaction->t_state == T_FINISHED);
|
|
J_ASSERT(transaction->t_buffers == NULL);
|
|
J_ASSERT(transaction->t_forget == NULL);
|
|
J_ASSERT(transaction->t_shadow_list == NULL);
|
|
J_ASSERT(transaction->t_checkpoint_list == NULL);
|
|
J_ASSERT(transaction->t_checkpoint_io_list == NULL);
|
|
J_ASSERT(atomic_read(&transaction->t_updates) == 0);
|
|
J_ASSERT(journal->j_committing_transaction != transaction);
|
|
J_ASSERT(journal->j_running_transaction != transaction);
|
|
|
|
trace_jbd2_drop_transaction(journal, transaction);
|
|
|
|
jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
|
|
}
|