linux-ext4 - [PATCH v15 31/43] fs/jbd2: use a weaker annotation in journal handling

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Message-Id: <20250513100730.12664-32-byungchul@sk.com>
Date: Tue, 13 May 2025 19:07:18 +0900
From: Byungchul Park <byungchul@...com>
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Subject: [PATCH v15 31/43] fs/jbd2: use a weaker annotation in journal handling

jbd2 journal handling code doesn't want jbd2_might_wait_for_commit()
to be placed between start_this_handle() and stop_this_handle().  So it
marks the region with rwsem_acquire_read() and rwsem_release().

However, the annotation is too strong for that purpose.  We don't have
to use more than try lock annotation for that.

rwsem_acquire_read() implies:

   1. might be a waiter on contention of the lock.
   2. enter to the critical section of the lock.

All we need in here is to act 2, not 1.  So trylock version of
annotation is sufficient for that purpose.  Now that dept partially
relies on lockdep annotaions, dept interpets rwsem_acquire_read() as a
potential wait and might report a deadlock by the wait.

Replace it with trylock version of annotation.

Signed-off-by: Byungchul Park <byungchul@...com>
---
 fs/jbd2/transaction.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index cbc4785462f5..7de227a2a6f8 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -441,7 +441,7 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
 	read_unlock(&journal->j_state_lock);
 	current->journal_info = handle;
 
-	rwsem_acquire_read(&journal->j_trans_commit_map, 0, 0, _THIS_IP_);
+	rwsem_acquire_read(&journal->j_trans_commit_map, 0, 1, _THIS_IP_);
 	jbd2_journal_free_transaction(new_transaction);
 	/*
 	 * Ensure that no allocations done while the transaction is open are
-- 
2.17.1