On 9/19/20 6:24 AM, Harshad Shirwadkar wrote:
This patch implements following APIs in JBD2 to allow for fast
commits:
jbd2_fc_start(): Start a new fast commit. This function waits for any
existing fast commit or full commit to complete.
jbd2_fc_stop(): Stop fast commit. This function ends current fast
commit and wakes up either the journal thread or the other fast commit
waiting for current fast commit to complete.
jbd2_fc_stop_do_commit(): Stop fast commit and perform a full
commit. This is same as above but also performs a full commit.
This patch also adds a cleanup handler in journal_t that is called
after every full and fast commit.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
---
fs/ext4/fast_commit.c | 8 ++++++
fs/jbd2/commit.c | 19 ++++++++++++
fs/jbd2/journal.c | 67 +++++++++++++++++++++++++++++++++++++++++++
include/linux/jbd2.h | 21 ++++++++++++++
4 files changed, 115 insertions(+)
diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
index 0dad8bdb1253..f2d11b4c6b62 100644
--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -8,11 +8,19 @@
* Ext4 fast commits routines.
*/
#include "ext4_jbd2.h"
+/*
+ * Fast commit cleanup routine. This is called after every fast commit and
+ * full commit. full is true if we are called after a full commit.
+ */
+static void ext4_fc_cleanup(journal_t *journal, int full)
+{
+}
void ext4_fc_init(struct super_block *sb, journal_t *journal)
{
if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
return;
+ journal->j_fc_cleanup_callback = ext4_fc_cleanup;
if (jbd2_fc_init(journal, EXT4_NUM_FC_BLKS)) {
pr_warn("Error while enabling fast commits, turning off.");
ext4_clear_feature_fast_commit(sb);
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 6d2da8ad0e6f..ba35ecb18616 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -413,6 +413,20 @@ void jbd2_journal_commit_transaction(journal_t *journal)
J_ASSERT(journal->j_running_transaction != NULL);
J_ASSERT(journal->j_committing_transaction == NULL);
+ write_lock(&journal->j_state_lock);
+ journal->j_flags |= JBD2_FULL_COMMIT_ONGOING;
Shouldn't we set this flag only after the while loop ends and before
releasing the write lock()? Like how we are doing in jbd2_fc_start()?
+ while (journal->j_flags & JBD2_FAST_COMMIT_ONGOING) {
+ DEFINE_WAIT(wait);
+
+ prepare_to_wait(&journal->j_wait_fc, &wait,
+ TASK_UNINTERRUPTIBLE);
+ write_unlock(&journal->j_state_lock);
+ schedule();
+ write_lock(&journal->j_state_lock);
+ finish_wait(&journal->j_wait_fc, &wait);
+ }
+ write_unlock(&journal->j_state_lock);
+
commit_transaction = journal->j_running_transaction;
trace_jbd2_start_commit(journal, commit_transaction);
@@ -1119,12 +1133,16 @@ void jbd2_journal_commit_transaction(journal_t *journal)
if (journal->j_commit_callback)
journal->j_commit_callback(journal, commit_transaction);
+ if (journal->j_fc_cleanup_callback)
+ journal->j_fc_cleanup_callback(journal, 1);
trace_jbd2_end_commit(journal, commit_transaction);
jbd_debug(1, "JBD2: commit %d complete, head %d\n",
journal->j_commit_sequence, journal->j_tail_sequence);
write_lock(&journal->j_state_lock);
+ journal->j_flags &= ~JBD2_FULL_COMMIT_ONGOING;
+ journal->j_flags &= ~JBD2_FAST_COMMIT_ONGOING;
spin_lock(&journal->j_list_lock);
commit_transaction->t_state = T_FINISHED;
/* Check if the transaction can be dropped now that we are finished */
@@ -1136,6 +1154,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
spin_unlock(&journal->j_list_lock);
write_unlock(&journal->j_state_lock);
wake_up(&journal->j_wait_done_commit);
+ wake_up(&journal->j_wait_fc);
/*
* Calculate overall stats
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 736a1736619f..17a30a2c38f9 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -714,6 +714,72 @@ int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
return err;
}
+/*
+ * Start a fast commit. If there's an ongoing fast or full commit wait for
+ * it to complete. Returns 0 if a new fast commit was started. Returns -EALREADY
+ * if a fast commit is not needed, either because there's an already a commit
+ * going on or this tid has already been committed. Returns -EINVAL if no jbd2
+ * commit has yet been performed.
+ */
+int jbd2_fc_start(journal_t *journal, tid_t tid)
+{
+ /*
+ * Fast commits only allowed if at least one full commit has
+ * been processed.
+ */
+ if (!journal->j_stats.ts_tid)
+ return -EINVAL;
+
+ if (tid <= journal->j_commit_sequence)
+ return -EALREADY;
+
+ write_lock(&journal->j_state_lock);
+ if (journal->j_flags & JBD2_FULL_COMMIT_ONGOING ||
+ (journal->j_flags & JBD2_FAST_COMMIT_ONGOING)) {
+ DEFINE_WAIT(wait);
+
+ prepare_to_wait(&journal->j_wait_fc, &wait,
+ TASK_UNINTERRUPTIBLE);
+ write_unlock(&journal->j_state_lock);
+ schedule();
+ finish_wait(&journal->j_wait_fc, &wait);
+ return -EALREADY;
+ }
+ journal->j_flags |= JBD2_FAST_COMMIT_ONGOING;
+ write_unlock(&journal->j_state_lock);
+
+ return 0;
+}
+
+/*
+ * Stop a fast commit. If fallback is set, this function starts commit of
+ * TID tid before any other fast commit can start.
+ */
+static int __jbd2_fc_stop(journal_t *journal, tid_t tid, bool fallback)
+{
+ if (journal->j_fc_cleanup_callback)
+ journal->j_fc_cleanup_callback(journal, 0);
+ write_lock(&journal->j_state_lock);
+ journal->j_flags &= ~JBD2_FAST_COMMIT_ONGOING;
+ if (fallback)
+ journal->j_flags |= JBD2_FULL_COMMIT_ONGOING;
+ write_unlock(&journal->j_state_lock);
+ wake_up(&journal->j_wait_fc);
+ if (fallback)
+ return jbd2_complete_transaction(journal, tid);
+ return 0;
+}
+
+int jbd2_fc_stop(journal_t *journal)
+{
+ return __jbd2_fc_stop(journal, 0, 0);
+}
+
+int jbd2_fc_stop_do_commit(journal_t *journal, tid_t tid)
+{
+ return __jbd2_fc_stop(journal, tid, 1);
+}
+
/* Return 1 when transaction with given tid has already committed. */
int jbd2_transaction_committed(journal_t *journal, tid_t tid)
{
@@ -1140,6 +1206,7 @@ static journal_t *journal_init_common(struct block_device *bdev,
init_waitqueue_head(&journal->j_wait_commit);
init_waitqueue_head(&journal->j_wait_updates);
init_waitqueue_head(&journal->j_wait_reserved);
+ init_waitqueue_head(&journal->j_wait_fc);
mutex_init(&journal->j_abort_mutex);
mutex_init(&journal->j_barrier);
mutex_init(&journal->j_checkpoint_mutex);
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 36f65a818366..aad986a9f3ff 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -858,6 +858,13 @@ struct journal_s
*/
wait_queue_head_t j_wait_reserved;
+ /**
+ * @j_wait_fc:
+ *
+ * Wait queue to wait for completion of async fast commits.
+ */
+ wait_queue_head_t j_wait_fc;
If we follow the naming convention then j_fc_wait, will be more
convenient.
+
/**
* @j_checkpoint_mutex:
*
@@ -1208,6 +1215,15 @@ struct journal_s
*/
struct lockdep_map j_trans_commit_map;
#endif
+
+ /**
+ * @j_fc_cleanup_callback:
+ *
+ * Clean-up after fast commit or full commit. JBD2 calls this function
+ * after every commit operation.
+ */
+ void (*j_fc_cleanup_callback)(struct journal_s *journal, int);
+
};
#define jbd2_might_wait_for_commit(j) \
@@ -1292,6 +1308,8 @@ JBD2_FEATURE_INCOMPAT_FUNCS(fast_commit, FAST_COMMIT)
#define JBD2_ABORT_ON_SYNCDATA_ERR 0x040 /* Abort the journal on file
* data write error in ordered
* mode */
+#define JBD2_FAST_COMMIT_ONGOING 0x100 /* Fast commit is ongoing */
+#define JBD2_FULL_COMMIT_ONGOING 0x200 /* Full commit is ongoing */
/*
* Function declarations for the journaling transaction and buffer
@@ -1546,6 +1564,9 @@ extern int jbd2_cleanup_journal_tail(journal_t *);
/* Fast commit related APIs */
int jbd2_fc_init(journal_t *journal, int num_fc_blks);
+int jbd2_fc_start(journal_t *journal, tid_t tid);
+int jbd2_fc_stop(journal_t *journal);
+int jbd2_fc_stop_do_commit(journal_t *journal, tid_t tid);
/*
* is_journal_abort
*
