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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 <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Jan Kara 2012-03-13 22:45:25 -04:00 committed by Theodore Ts'o
parent c254c9ec14
commit 932bb305ba
2 changed files with 9 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
fs/jbd2/checkpoint.c
View File

@ -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;

2
include/linux/journal-head.h
View File

@ -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;