patch-2.4.15 linux/fs/jbd/checkpoint.c

• Lines: 609
• Date: Fri Nov 9 14:25:04 2001
• Orig file: v2.4.14/linux/fs/jbd/checkpoint.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.14/linux/fs/jbd/checkpoint.c linux/fs/jbd/checkpoint.c
@@ -0,0 +1,608 @@
+/*
+ * linux/fs/checkpoint.c
+ * 
+ * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
+ *
+ * Copyright 1999 Red Hat Software --- 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.
+ *
+ * Checkpoint routines for the generic filesystem journaling code.  
+ * Part of the ext2fs journaling system.  
+ *
+ * Checkpointing is the process of ensuring that a section of the log is
+ * committed fully to disk, so that that portion of the log can be
+ * reused.
+ */
+
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/locks.h>
+
+extern spinlock_t journal_datalist_lock;
+
+/*
+ * Unlink a buffer from a transaction. 
+ *
+ * Called with journal_datalist_lock held.
+ */
+
+static inline void __buffer_unlink(struct journal_head *jh)
+{
+	transaction_t *transaction;
+
+	transaction = jh->b_cp_transaction;
+	jh->b_cp_transaction = NULL;
+
+	jh->b_cpnext->b_cpprev = jh->b_cpprev;
+	jh->b_cpprev->b_cpnext = jh->b_cpnext;
+	if (transaction->t_checkpoint_list == jh)
+		transaction->t_checkpoint_list = jh->b_cpnext;
+	if (transaction->t_checkpoint_list == jh)
+		transaction->t_checkpoint_list = NULL;
+}
+
+/*
+ * Try to release a checkpointed buffer from its transaction.
+ * Returns 1 if we released it.
+ * Requires journal_datalist_lock
+ */
+static int __try_to_free_cp_buf(struct journal_head *jh)
+{
+	int ret = 0;
+	struct buffer_head *bh = jh2bh(jh);
+
+	if (jh->b_jlist == BJ_None && !buffer_locked(bh) && !buffer_dirty(bh)) {
+		JBUFFER_TRACE(jh, "remove from checkpoint list");
+		__journal_remove_checkpoint(jh);
+		__journal_remove_journal_head(bh);
+		BUFFER_TRACE(bh, "release");
+		/* BUF_LOCKED -> BUF_CLEAN (fwiw) */
+		refile_buffer(bh);
+		__brelse(bh);
+		ret = 1;
+	}
+	return ret;
+}
+
+/*
+ * log_wait_for_space: wait until there is space in the journal.
+ *
+ * Called with the journal already locked, but it will be unlocked if we have
+ * to wait for a checkpoint to free up some space in the log.
+ */
+
+void log_wait_for_space(journal_t *journal, int nblocks)
+{
+	while (log_space_left(journal) < nblocks) {
+		if (journal->j_flags & JFS_ABORT)
+			return;
+		unlock_journal(journal);
+		down(&journal->j_checkpoint_sem);
+		lock_journal(journal);
+		
+		/* Test again, another process may have checkpointed
+		 * while we were waiting for the checkpoint lock */
+		if (log_space_left(journal) < nblocks) {
+			log_do_checkpoint(journal, nblocks);
+		}
+		up(&journal->j_checkpoint_sem);
+	}
+}
+
+/*
+ * Clean up a transaction's checkpoint list.  
+ *
+ * We wait for any pending IO to complete and make sure any clean
+ * buffers are removed from the transaction. 
+ *
+ * Return 1 if we performed any actions which might have destroyed the
+ * checkpoint.  (journal_remove_checkpoint() deletes the transaction when
+ * the last checkpoint buffer is cleansed)
+ *
+ * Called with the journal locked.
+ * Called with journal_datalist_lock held.
+ */
+static int __cleanup_transaction(journal_t *journal, transaction_t *transaction)
+{
+	struct journal_head *jh, *next_jh, *last_jh;
+	struct buffer_head *bh;
+	int ret = 0;
+
+	assert_spin_locked(&journal_datalist_lock);
+	jh = transaction->t_checkpoint_list;
+	if (!jh)
+		return 0;
+
+	last_jh = jh->b_cpprev;
+	next_jh = jh;
+	do {
+		jh = next_jh;
+		bh = jh2bh(jh);
+		if (buffer_locked(bh)) {
+			atomic_inc(&bh->b_count);
+			spin_unlock(&journal_datalist_lock);
+			unlock_journal(journal);
+			wait_on_buffer(bh);
+			/* the journal_head may have gone by now */
+			BUFFER_TRACE(bh, "brelse");
+			__brelse(bh);
+			goto out_return_1;
+		}
+		
+		if (jh->b_transaction != NULL) {
+			transaction_t *transaction = jh->b_transaction;
+			tid_t tid = transaction->t_tid;
+
+			spin_unlock(&journal_datalist_lock);
+			log_start_commit(journal, transaction);
+			unlock_journal(journal);
+			log_wait_commit(journal, tid);
+			goto out_return_1;
+		}
+
+		/*
+		 * We used to test for (jh->b_list != BUF_CLEAN) here.
+		 * But unmap_underlying_metadata() can place buffer onto
+		 * BUF_CLEAN. Since refile_buffer() no longer takes buffers
+		 * off checkpoint lists, we cope with it here
+		 */
+		/*
+		 * AKPM: I think the buffer_jdirty test is redundant - it
+		 * shouldn't have NULL b_transaction?
+		 */
+		next_jh = jh->b_cpnext;
+		if (!buffer_dirty(bh) && !buffer_jdirty(bh)) {
+			BUFFER_TRACE(bh, "remove from checkpoint");
+			__journal_remove_checkpoint(jh);
+			__journal_remove_journal_head(bh);
+			refile_buffer(bh);
+			__brelse(bh);
+			ret = 1;
+		}
+		
+		jh = next_jh;
+	} while (jh != last_jh);
+
+	return ret;
+out_return_1:
+	lock_journal(journal);
+	spin_lock(&journal_datalist_lock);
+	return 1;
+}
+
+#define NR_BATCH	64
+
+static void __flush_batch(struct buffer_head **bhs, int *batch_count)
+{
+	int i;
+
+	spin_unlock(&journal_datalist_lock);
+	ll_rw_block(WRITE, *batch_count, bhs);
+	run_task_queue(&tq_disk);
+	spin_lock(&journal_datalist_lock);
+	for (i = 0; i < *batch_count; i++) {
+		struct buffer_head *bh = bhs[i];
+		clear_bit(BH_JWrite, &bh->b_state);
+		BUFFER_TRACE(bh, "brelse");
+		__brelse(bh);
+	}
+	*batch_count = 0;
+}
+
+/*
+ * Try to flush one buffer from the checkpoint list to disk.
+ *
+ * Return 1 if something happened which requires us to abort the current
+ * scan of the checkpoint list.  
+ *
+ * Called with journal_datalist_lock held.
+ */
+static int __flush_buffer(journal_t *journal, struct journal_head *jh,
+			struct buffer_head **bhs, int *batch_count,
+			int *drop_count)
+{
+	struct buffer_head *bh = jh2bh(jh);
+	int ret = 0;
+
+	if (buffer_dirty(bh) && !buffer_locked(bh) && jh->b_jlist == BJ_None) {
+		J_ASSERT_JH(jh, jh->b_transaction == NULL);
+		
+		/*
+		 * Important: we are about to write the buffer, and
+		 * possibly block, while still holding the journal lock.
+		 * We cannot afford to let the transaction logic start
+		 * messing around with this buffer before we write it to
+		 * disk, as that would break recoverability.  
+		 */
+		BUFFER_TRACE(bh, "queue");
+		atomic_inc(&bh->b_count);
+		J_ASSERT_BH(bh, !test_bit(BH_JWrite, &bh->b_state));
+		set_bit(BH_JWrite, &bh->b_state);
+		bhs[*batch_count] = bh;
+		(*batch_count)++;
+		if (*batch_count == NR_BATCH) {
+			__flush_batch(bhs, batch_count);
+			ret = 1;
+		}
+	} else {
+		int last_buffer = 0;
+		if (jh->b_cpnext == jh) {
+			/* We may be about to drop the transaction.  Tell the
+			 * caller that the lists have changed.
+			 */
+			last_buffer = 1;
+		}
+		if (__try_to_free_cp_buf(jh)) {
+			(*drop_count)++;
+			ret = last_buffer;
+		}
+	}
+	return ret;
+}
+
+	
+/*
+ * Perform an actual checkpoint.  We don't write out only enough to
+ * satisfy the current blocked requests: rather we submit a reasonably
+ * sized chunk of the outstanding data to disk at once for
+ * efficiency.  log_wait_for_space() will retry if we didn't free enough.
+ * 
+ * However, we _do_ take into account the amount requested so that once
+ * the IO has been queued, we can return as soon as enough of it has
+ * completed to disk.  
+ *
+ * The journal should be locked before calling this function.
+ */
+
+/* @@@ `nblocks' is unused.  Should it be used? */
+int log_do_checkpoint (journal_t *journal, int nblocks)
+{
+	transaction_t *transaction, *last_transaction, *next_transaction;
+	int result;
+	int target;
+	int batch_count = 0;
+	struct buffer_head *bhs[NR_BATCH];
+
+	jbd_debug(1, "Start checkpoint\n");
+
+	/* 
+	 * First thing: if there are any transactions in the log which
+	 * don't need checkpointing, just eliminate them from the
+	 * journal straight away.  
+	 */
+	result = cleanup_journal_tail(journal);
+	jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
+	if (result <= 0)
+		return result;
+
+	/*
+	 * OK, we need to start writing disk blocks.  Try to free up a
+	 * quarter of the log in a single checkpoint if we can.
+	 */
+	/*
+	 * AKPM: check this code.  I had a feeling a while back that it
+	 * degenerates into a busy loop at unmount time.
+	 */
+	target = (journal->j_last - journal->j_first) / 4;
+
+	spin_lock(&journal_datalist_lock);
+repeat:
+	transaction = journal->j_checkpoint_transactions;
+	if (transaction == NULL)
+		goto done;
+	last_transaction = transaction->t_cpprev;
+	next_transaction = transaction;
+
+	do {
+		struct journal_head *jh, *last_jh, *next_jh;
+		int drop_count = 0;
+		int cleanup_ret, retry = 0;
+
+		transaction = next_transaction;
+		next_transaction = transaction->t_cpnext;
+		jh = transaction->t_checkpoint_list;
+		last_jh = jh->b_cpprev;
+		next_jh = jh;
+		do {
+			jh = next_jh;
+			next_jh = jh->b_cpnext;
+			retry = __flush_buffer(journal, jh, bhs, &batch_count,
+						&drop_count);
+		} while (jh != last_jh && !retry);
+		if (batch_count) {
+			__flush_batch(bhs, &batch_count);
+			goto repeat;
+		}
+		if (retry)
+			goto repeat;
+		/*
+		 * We have walked the whole transaction list without
+		 * finding anything to write to disk.  We had better be
+		 * able to make some progress or we are in trouble. 
+		 */
+		cleanup_ret = __cleanup_transaction(journal, transaction);
+		J_ASSERT(drop_count != 0 || cleanup_ret != 0);
+		goto repeat;	/* __cleanup may have dropped lock */
+	} while (transaction != last_transaction);
+
+done:
+	spin_unlock(&journal_datalist_lock);
+	result = cleanup_journal_tail(journal);
+	if (result < 0)
+		return result;
+	
+	return 0;
+}
+
+/*
+ * Check the list of checkpoint transactions for the journal to see if
+ * we have already got rid of any since the last update of the log tail
+ * in the journal superblock.  If so, we can instantly roll the
+ * superblock forward to remove those transactions from the log.
+ * 
+ * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
+ * 
+ * Called with the journal lock held.
+ *
+ * This is the only part of the journaling code which really needs to be
+ * aware of transaction aborts.  Checkpointing involves writing to the
+ * main filesystem area rather than to the journal, so it can proceed
+ * even in abort state, but we must not update the journal superblock if
+ * we have an abort error outstanding.
+ */
+
+int cleanup_journal_tail(journal_t *journal)
+{
+	transaction_t * transaction;
+	tid_t		first_tid;
+	unsigned long	blocknr, freed;
+
+	/* OK, work out the oldest transaction remaining in the log, and
+	 * the log block it starts at. 
+	 * 
+	 * If the log is now empty, we need to work out which is the
+	 * next transaction ID we will write, and where it will
+	 * start. */
+
+	/* j_checkpoint_transactions needs locking */
+	spin_lock(&journal_datalist_lock);
+	transaction = journal->j_checkpoint_transactions;
+	if (transaction) {
+		first_tid = transaction->t_tid;
+		blocknr = transaction->t_log_start;
+	} else if ((transaction = journal->j_committing_transaction) != NULL) {
+		first_tid = transaction->t_tid;
+		blocknr = transaction->t_log_start;
+	} else if ((transaction = journal->j_running_transaction) != NULL) {
+		first_tid = transaction->t_tid;
+		blocknr = journal->j_head;
+	} else {
+		first_tid = journal->j_transaction_sequence;
+		blocknr = journal->j_head;
+	}
+	spin_unlock(&journal_datalist_lock);
+	J_ASSERT (blocknr != 0);
+
+	/* If the oldest pinned transaction is at the tail of the log
+           already then there's not much we can do right now. */
+	if (journal->j_tail_sequence == first_tid)
+		return 1;
+
+	/* OK, update the superblock to recover the freed space.
+	 * Physical blocks come first: have we wrapped beyond the end of
+	 * the log?  */
+	freed = blocknr - journal->j_tail;
+	if (blocknr < journal->j_tail)
+		freed = freed + journal->j_last - journal->j_first;
+
+	jbd_debug(1,
+		  "Cleaning journal tail from %d to %d (offset %lu), "
+		  "freeing %lu\n",
+		  journal->j_tail_sequence, first_tid, blocknr, freed);
+
+	journal->j_free += freed;
+	journal->j_tail_sequence = first_tid;
+	journal->j_tail = blocknr;
+	if (!(journal->j_flags & JFS_ABORT))
+		journal_update_superblock(journal, 1);
+	return 0;
+}
+
+
+/* Checkpoint list management */
+
+/*
+ * journal_clean_checkpoint_list
+ *
+ * Find all the written-back checkpoint buffers in the journal and release them.
+ *
+ * Called with the journal locked.
+ * Called with journal_datalist_lock held.
+ * Returns number of bufers reaped (for debug)
+ */
+
+int __journal_clean_checkpoint_list(journal_t *journal)
+{
+	transaction_t *transaction, *last_transaction, *next_transaction;
+	int ret = 0;
+
+	transaction = journal->j_checkpoint_transactions;
+	if (transaction == 0)
+		goto out;
+
+	last_transaction = transaction->t_cpprev;
+	next_transaction = transaction;
+	do {
+		struct journal_head *jh;
+
+		transaction = next_transaction;
+		next_transaction = transaction->t_cpnext;
+		jh = transaction->t_checkpoint_list;
+		if (jh) {
+			struct journal_head *last_jh = jh->b_cpprev;
+			struct journal_head *next_jh = jh;
+			do {
+				struct buffer_head *bh;
+
+				jh = next_jh;
+				next_jh = jh->b_cpnext;
+				bh = jh2bh(jh);
+				ret += __try_to_free_cp_buf(jh);
+			} while (jh != last_jh);
+		}
+	} 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
+ * list until they have been rewritten, at which point this function is
+ * called to remove the buffer from the existing transaction's
+ * checkpoint list.  
+ *
+ * This function is called with the journal locked.
+ * This function is called with journal_datalist_lock held.
+ */
+
+void __journal_remove_checkpoint(struct journal_head *jh)
+{
+	transaction_t *transaction;
+	journal_t *journal;
+
+	JBUFFER_TRACE(jh, "entry");
+	
+	if ((transaction = jh->b_cp_transaction) == NULL) {
+		JBUFFER_TRACE(jh, "not on transaction");
+		goto out;
+	}
+
+	journal = transaction->t_journal;
+
+	__buffer_unlink(jh);
+
+	if (transaction->t_checkpoint_list != NULL)
+		goto out;
+	JBUFFER_TRACE(jh, "transaction has no more buffers");
+
+	/* There is one special case to worry about: if we have just
+           pulled the buffer off a committing transaction's forget list,
+           then even if the checkpoint list is empty, the transaction
+           obviously cannot be dropped! */
+
+	if (transaction == journal->j_committing_transaction) {
+		JBUFFER_TRACE(jh, "belongs to committing transaction");
+		goto out;
+	}
+
+	/* OK, that was the last buffer for the transaction: we can now
+	   safely remove this transaction from the log */
+
+	__journal_drop_transaction(journal, transaction);
+
+	/* Just in case anybody was waiting for more transactions to be
+           checkpointed... */
+	wake_up(&journal->j_wait_logspace);
+out:
+	JBUFFER_TRACE(jh, "exit");
+}
+
+void journal_remove_checkpoint(struct journal_head *jh)
+{
+	spin_lock(&journal_datalist_lock);
+	__journal_remove_checkpoint(jh);
+	spin_unlock(&journal_datalist_lock);
+}
+
+/*
+ * 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 journal_datalist_lock held.
+ */
+void __journal_insert_checkpoint(struct journal_head *jh, 
+			       transaction_t *transaction)
+{
+	JBUFFER_TRACE(jh, "entry");
+	J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jdirty(jh2bh(jh)));
+	J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
+
+	assert_spin_locked(&journal_datalist_lock);
+	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;
+}
+
+void journal_insert_checkpoint(struct journal_head *jh, 
+			       transaction_t *transaction)
+{
+	spin_lock(&journal_datalist_lock);
+	__journal_insert_checkpoint(jh, transaction);
+	spin_unlock(&journal_datalist_lock);
+}
+
+/*
+ * 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 journal_datalist_lock held.
+ */
+
+void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
+{
+	assert_spin_locked(&journal_datalist_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_ilist == NULL);
+	J_ASSERT (transaction->t_buffers == NULL);
+	J_ASSERT (transaction->t_sync_datalist == NULL);
+	J_ASSERT (transaction->t_async_datalist == NULL);
+	J_ASSERT (transaction->t_forget == NULL);
+	J_ASSERT (transaction->t_iobuf_list == NULL);
+	J_ASSERT (transaction->t_shadow_list == NULL);
+	J_ASSERT (transaction->t_log_list == NULL);
+	J_ASSERT (transaction->t_checkpoint_list == NULL);
+	J_ASSERT (transaction->t_updates == 0);
+	
+	J_ASSERT (transaction->t_journal->j_committing_transaction !=
+					transaction);
+	
+	jbd_debug (1, "Dropping transaction %d, all done\n", 
+		   transaction->t_tid);
+	kfree (transaction);
+}
+