Commit 3b1833e9 authored Apr 06, 2021 by Jan Kara Committed by Theodore Ts'o Apr 09, 2021

ext4: annotate data race in start_this_handle()



Access to journal->j_running_transaction is not protected by appropriate
lock and thus is racy. We are well aware of that and the code handles
the race properly. Just add a comment and data_race() annotation.

Cc: stable@kernel.org
Reported-by:  <syzbot+30774a6acf6a2cf6d535@syzkaller.appspotmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210406161804.20150-1-jack@suse.cz


Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent 6810fad9

fs/jbd2/transaction.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -349,7 +349,12 @@ static int start_this_handle(journal_t journal, handle_t handle,
		}

		alloc_transaction:
		if (!journal->j_running_transaction) {
		/*
		* This check is racy but it is just an optimization of allocating new
		* transaction early if there are high chances we'll need it. If we
		* guess wrong, we'll retry or free unused transaction.
		*/
		if (!data_race(journal->j_running_transaction)) {
		/*
		* If __GFP_FS is not present, then we may be being called from
		* inside the fs writeback layer, so we MUST NOT fail.