linux-ext4 - [PATCH v12 26/27] fs/jbd2: Use a weaker annotation in journal handling

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Date: Wed, 21 Feb 2024 18:49:32 +0900
From: Byungchul Park <byungchul@...com>
To: linux-kernel@...r.kernel.org
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Subject: [PATCH v12 26/27] 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. So replaced 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 5f08b5fd105a..2c159a547e15 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -460,7 +460,7 @@ 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