linux-ext4 - [PATCH 3/4] jbd2: Move lockdep tracking to journal

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Date:	Thu, 16 Jun 2016 12:42:15 +0200
From:	Jan Kara <jack@...e.cz>
To:	Ted Tso <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, Eryu Guan <eguan@...hat.com>,
	Jan Kara <jack@...e.cz>
Subject: [PATCH 3/4] jbd2: Move lockdep tracking to journal_s

Currently lockdep map is tracked in each journal handle. To be able to
expand lockdep support to cover also other cases where we depend on
transaction commit and where handle is not available, move lockdep map
into struct journal_s. Since this makes the lockdep map shared for all
handles, we have to use rwsem_acquire_read() for acquisitions now.

Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/jbd2/journal.c     |  4 ++++
 fs/jbd2/transaction.c | 11 +++--------
 include/linux/jbd2.h  | 16 ++++++++++++----
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b31852f76f46..208e4058040b 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1091,6 +1091,7 @@ static void jbd2_stats_proc_exit(journal_t *journal)
 
 static journal_t * journal_init_common (void)
 {
+	static struct lock_class_key jbd2_trans_commit_key;
 	journal_t *journal;
 	int err;
 
@@ -1126,6 +1127,9 @@ static journal_t * journal_init_common (void)
 
 	spin_lock_init(&journal->j_history_lock);
 
+	lockdep_init_map(&journal->j_trans_commit_map, "jbd2_handle",
+			 &jbd2_trans_commit_key, 0);
+
 	return journal;
 }
 
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 41249538c047..c0065040c5be 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -382,13 +382,11 @@ repeat:
 	read_unlock(&journal->j_state_lock);
 	current->journal_info = handle;
 
-	lock_map_acquire(&handle->h_lockdep_map);
+	rwsem_acquire_read(&journal->j_trans_commit_map, 0, 0, _THIS_IP_);
 	jbd2_journal_free_transaction(new_transaction);
 	return 0;
 }
 
-static struct lock_class_key jbd2_handle_key;
-
 /* Allocate a new handle.  This should probably be in a slab... */
 static handle_t *new_handle(int nblocks)
 {
@@ -398,9 +396,6 @@ static handle_t *new_handle(int nblocks)
 	handle->h_buffer_credits = nblocks;
 	handle->h_ref = 1;
 
-	lockdep_init_map(&handle->h_lockdep_map, "jbd2_handle",
-						&jbd2_handle_key, 0);
-
 	return handle;
 }
 
@@ -672,7 +667,7 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
 	if (need_to_start)
 		jbd2_log_start_commit(journal, tid);
 
-	lock_map_release(&handle->h_lockdep_map);
+	rwsem_release(&journal->j_trans_commit_map, 1, _THIS_IP_);
 	handle->h_buffer_credits = nblocks;
 	ret = start_this_handle(journal, handle, gfp_mask);
 	return ret;
@@ -1750,7 +1745,7 @@ int jbd2_journal_stop(handle_t *handle)
 			wake_up(&journal->j_wait_transaction_locked);
 	}
 
-	lock_map_release(&handle->h_lockdep_map);
+	rwsem_release(&journal->j_trans_commit_map, 1, _THIS_IP_);
 
 	if (wait_for_commit)
 		err = jbd2_log_wait_commit(journal, tid);
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index efb232c5f668..f6232b28eadc 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -491,10 +491,6 @@ struct jbd2_journal_handle
 
 	unsigned long		h_start_jiffies;
 	unsigned int		h_requested_credits;
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-	struct lockdep_map	h_lockdep_map;
-#endif
 };
 
 
@@ -1035,6 +1031,18 @@ struct journal_s
 
 	/* Precomputed journal UUID checksum for seeding other checksums */
 	__u32 j_csum_seed;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	/*
+	 * Lockdep entity to track transaction commit dependencies. Handles
+	 * hold this "lock" for read, when we wait for commit, we acquire the
+	 * "lock" for writing. This matches the properties of jbd2 journalling
+	 * where the running transaction has to wait for all handles to be
+	 * dropped to commit that transaction and also acquiring a handle may
+	 * require transaction commit to finish.
+	 */
+	struct lockdep_map	j_trans_commit_map;
+#endif
 };
 
 /* journal feature predicate functions */
-- 
2.6.6

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