From 932bb305ba2a01cd62809644d569f004e77a4355 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 13 Mar 2012 22:45:25 -0400 Subject: [PATCH] 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: Jan Kara Signed-off-by: "Theodore Ts'o" --- fs/jbd2/checkpoint.c | 59 +++++------------------------------- include/linux/journal-head.h | 2 ++ 2 files changed, 9 insertions(+), 52 deletions(-) diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c index 546c3b300ee..c78841ee81c 100644 --- a/fs/jbd2/checkpoint.c +++ b/fs/jbd2/checkpoint.c @@ -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) @@ -529,15 +489,12 @@ 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++; - if (ret == 2) { - *released = 1; - return freed; - } + ret = __try_to_free_cp_buf(jh); + if (ret) { + freed++; + if (ret == 2) { + *released = 1; + return freed; } } /* @@ -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; diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h index 423cb6d78ee..c18b46f8aee 100644 --- a/include/linux/journal-head.h +++ b/include/linux/journal-head.h @@ -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;