Commit 932bb305 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
Browse files

jbd2: remove bh_state lock from checkpointing code 



All accesses to checkpointing entries in journal_head are protected
by j_list_lock. Thus __jbd2_journal_remove_checkpoint() doesn't really
need bh_state lock.

Also the only part of journal head that the rest of checkpointing code
needs to check is jh->b_transaction which is safe to read under
j_list_lock.

So we can safely remove bh_state lock from all of checkpointing code which
makes it considerably prettier.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent c254c9ec

fs/jbd2/checkpoint.c

+7 −52
Original line number Diff line number Diff line
@@ -88,14 +88,13 @@ static inline void __buffer_relink_io(struct journal_head *jh) 
 * whole transaction.

 *

 * Requires j_list_lock

 * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it

 */

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) &&

	if (jh->b_transaction == NULL && !buffer_locked(bh) &&

	    !buffer_dirty(bh) && !buffer_write_io_error(bh)) {

		/*

		 * Get our reference so that bh cannot be freed before
@@ -104,11 +103,8 @@ static int __try_to_free_cp_buf(struct journal_head *jh) 
		get_bh(bh);

		JBUFFER_TRACE(jh, "remove from checkpoint list");

		ret = __jbd2_journal_remove_checkpoint(jh) + 1;

		jbd_unlock_bh_state(bh);

		BUFFER_TRACE(bh, "release");

		__brelse(bh);

	} else {

		jbd_unlock_bh_state(bh);

	}

	return ret;

}
@@ -179,21 +175,6 @@ void __jbd2_log_wait_for_space(journal_t *journal) 
	}

}



/*

 * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.

 * The caller must restart a list walk.  Wait for someone else to run

 * jbd_unlock_bh_state().

 */

static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)

	__releases(journal->j_list_lock)

{

	get_bh(bh);

	spin_unlock(&journal->j_list_lock);

	jbd_lock_bh_state(bh);

	jbd_unlock_bh_state(bh);

	put_bh(bh);

}



/*

 * Clean up transaction's list of buffers submitted for io.

 * We wait for any pending IO to complete and remove any clean
@@ -222,15 +203,9 @@ restart: 
	while (!released && transaction->t_checkpoint_io_list) {

		jh = transaction->t_checkpoint_io_list;

		bh = jh2bh(jh);

		if (!jbd_trylock_bh_state(bh)) {

			jbd_sync_bh(journal, bh);

			spin_lock(&journal->j_list_lock);

			goto restart;

		}

		get_bh(bh);

		if (buffer_locked(bh)) {

			spin_unlock(&journal->j_list_lock);

			jbd_unlock_bh_state(bh);

			wait_on_buffer(bh);

			/* the journal_head may have gone by now */

			BUFFER_TRACE(bh, "brelse");
@@ -246,7 +221,6 @@ restart: 
		 * it has been written out and so we can drop it from the list

		 */

		released = __jbd2_journal_remove_checkpoint(jh);

		jbd_unlock_bh_state(bh);

		__brelse(bh);

	}
@@ -280,7 +254,6 @@ __flush_batch(journal_t *journal, int *batch_count) 
 * be written out.

 *

 * Called with j_list_lock held and drops it if 1 is returned

 * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it

 */

static int __process_buffer(journal_t *journal, struct journal_head *jh,

			    int *batch_count, transaction_t *transaction)
@@ -291,7 +264,6 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh, 
	if (buffer_locked(bh)) {

		get_bh(bh);

		spin_unlock(&journal->j_list_lock);

		jbd_unlock_bh_state(bh);

		wait_on_buffer(bh);

		/* the journal_head may have gone by now */

		BUFFER_TRACE(bh, "brelse");
@@ -303,7 +275,6 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh, 


		transaction->t_chp_stats.cs_forced_to_close++;

		spin_unlock(&journal->j_list_lock);

		jbd_unlock_bh_state(bh);

		if (unlikely(journal->j_flags & JBD2_UNMOUNT))

			/*

			 * The journal thread is dead; so starting and
@@ -322,11 +293,9 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh, 
		if (unlikely(buffer_write_io_error(bh)))

			ret = -EIO;

		get_bh(bh);

		J_ASSERT_JH(jh, !buffer_jbddirty(bh));

		BUFFER_TRACE(bh, "remove from checkpoint");

		__jbd2_journal_remove_checkpoint(jh);

		spin_unlock(&journal->j_list_lock);

		jbd_unlock_bh_state(bh);

		__brelse(bh);

	} else {

		/*
@@ -341,7 +310,6 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh, 
		J_ASSERT_BH(bh, !buffer_jwrite(bh));

		journal->j_chkpt_bhs[*batch_count] = bh;

		__buffer_relink_io(jh);

		jbd_unlock_bh_state(bh);

		transaction->t_chp_stats.cs_written++;

		(*batch_count)++;

		if (*batch_count == JBD2_NR_BATCH) {
@@ -405,15 +373,7 @@ restart: 
		int retry = 0, err;



		while (!retry && transaction->t_checkpoint_list) {

			struct buffer_head *bh;



			jh = transaction->t_checkpoint_list;

			bh = jh2bh(jh);

			if (!jbd_trylock_bh_state(bh)) {

				jbd_sync_bh(journal, bh);

				retry = 1;

				break;

			}

			retry = __process_buffer(journal, jh, &batch_count,

						 transaction);

			if (retry < 0 && !result)
@@ -529,8 +489,6 @@ static int journal_clean_one_cp_list(struct journal_head *jh, int *released) 
	do {

		jh = next_jh;

		next_jh = jh->b_cpnext;

		/* Use trylock because of the ranking */

		if (jbd_trylock_bh_state(jh2bh(jh))) {

		ret = __try_to_free_cp_buf(jh);

		if (ret) {

			freed++;
@@ -539,7 +497,6 @@ static int journal_clean_one_cp_list(struct journal_head *jh, int *released) 
				return freed;

			}

		}

		}

		/*

		 * This function only frees up some memory

		 * if possible so we dont have an obligation
@@ -620,9 +577,7 @@ out: 
 * The function can free jh and bh.

 *

 * This function is called with j_list_lock held.

 * This function is called with jbd_lock_bh_state(jh2bh(jh))

 */



int __jbd2_journal_remove_checkpoint(struct journal_head *jh)

{

	struct transaction_chp_stats_s *stats;

include/linux/journal-head.h

+2 −0
Original line number Diff line number Diff line
@@ -66,6 +66,8 @@ struct journal_head { 
	 * transaction (if there is one).  Only applies to buffers on a

	 * transaction's data or metadata journaling list.

	 * [j_list_lock] [jbd_lock_bh_state()]

	 * Either of these locks is enough for reading, both are needed for

	 * changes.

	 */

	transaction_t *b_transaction;

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