From: Zhang Yi yi.zhang@huawei.com
hulk inclusion category: bugfix bugzilla: 186882, https://gitee.com/openeuler/kernel/issues/I5C3AI
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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 Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- 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 867362f45cf6..98cfa73cb165 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -564,13 +564,13 @@ 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,