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authorJan Kara <jack@suse.cz>2021-04-06 18:17:59 +0200
committerTheodore Ts'o <tytso@mit.edu>2021-04-09 21:19:32 -0400
commit3b1833e92baba135923af4a07e73fe6e54be5a2f (patch)
tree1217f69aa4503b53d733a74f20536cada00608a4
parent6810fad956df9e5467e8e8a5ac66fda0836c71fa (diff)
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>
-rw-r--r--fs/jbd2/transaction.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 9396666b7314..398d1d9209e2 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -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.