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>
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 546c3b3..c78841e 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -88,14 +88,13 @@
* 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 @@
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;
}
@@ -180,21 +176,6 @@
}
/*
- * 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
* buffers. Note that we take the buffers in the opposite ordering
@@ -222,15 +203,9 @@
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 @@
* 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 @@
* 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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
* 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 423cb6d..c18b46f 100644
--- a/include/linux/journal-head.h
+++ b/include/linux/journal-head.h
@@ -66,6 +66,8 @@
* 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;
