From: Zhang Yi yi.zhang@huawei.com
[ Upstream commit a89573ce4ad32f19f43ec669771726817e185be0 ]
We catch an assert problem in jbd2_journal_commit_transaction() when doing fsstress and request falut injection tests. The problem is happened in a race condition between jbd2_journal_commit_transaction() and ext4_end_io_end(). Firstly, ext4_writepages() writeback dirty pages and start reserved handle, and then the journal was aborted due to some previous metadata IO error, jbd2_journal_abort() start to commit current running transaction, the committing procedure could be raced by ext4_end_io_end() and lead to subtract j_reserved_credits twice from commit_transaction->t_outstanding_credits, finally the t_outstanding_credits is mistakenly smaller than t_nr_buffers and trigger assert.
kjournald2 kworker
jbd2_journal_commit_transaction() write_unlock(&journal->j_state_lock); atomic_sub(j_reserved_credits, t_outstanding_credits); //sub once
jbd2_journal_start_reserved() start_this_handle() //detect aborted journal jbd2_journal_free_reserved() //get running transaction read_lock(&journal->j_state_lock) __jbd2_journal_unreserve_handle() atomic_sub(j_reserved_credits, t_outstanding_credits); //sub again read_unlock(&journal->j_state_lock);
journal->j_running_transaction = NULL; J_ASSERT(t_nr_buffers <= t_outstanding_credits) //bomb!!!
Fix this issue by using journal->j_state_lock to protect the subtraction in jbd2_journal_commit_transaction().
Fixes: 96f1e0974575 ("jbd2: avoid long hold times of j_state_lock while committing a transaction") Signed-off-by: Zhang Yi yi.zhang@huawei.com Reviewed-by: Jan Kara jack@suse.cz Link: https://lore.kernel.org/r/20220611130426.2013258-1-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Sasha Levin sashal@kernel.org --- fs/jbd2/commit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index ac7f067b7bdd..f306b52b8e0b 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -551,13 +551,13 @@ void jbd2_journal_commit_transaction(journal_t *journal) */ jbd2_journal_switch_revoke_table(journal);
+ write_lock(&journal->j_state_lock); /* * Reserved credits cannot be claimed anymore, free them */ atomic_sub(atomic_read(&journal->j_reserved_credits), &commit_transaction->t_outstanding_credits);
- write_lock(&journal->j_state_lock); trace_jbd2_commit_flushing(journal, commit_transaction); stats.run.rs_flushing = jiffies; stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,