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    Subject[PATCH AUTOSEL for 4.9 119/190] jbd2: Fix lockdep splat with generic/270 test
    Date
    From: Jan Kara <jack@suse.cz>

    [ Upstream commit c52c47e4b4fbe4284602fc2ccbfc4a4d8dc05b49 ]

    I've hit a lockdep splat with generic/270 test complaining that:

    3216.fsstress.b/3533 is trying to acquire lock:
    (jbd2_handle){++++..}, at: [<ffffffff813152e0>] jbd2_log_wait_commit+0x0/0x150

    but task is already holding lock:
    (jbd2_handle){++++..}, at: [<ffffffff8130bd3b>] start_this_handle+0x35b/0x850

    The underlying problem is that jbd2_journal_force_commit_nested()
    (called from ext4_should_retry_alloc()) may get called while a
    transaction handle is started. In such case it takes care to not wait
    for commit of the running transaction (which would deadlock) but only
    for a commit of a transaction that is already committing (which is safe
    as that doesn't wait for any filesystem locks).

    In fact there are also other callers of jbd2_log_wait_commit() that take
    care to pass tid of a transaction that is already committing and for
    those cases, the lockdep instrumentation is too restrictive and leading
    to false positive reports. Fix the problem by calling
    jbd2_might_wait_for_commit() from jbd2_log_wait_commit() only if the
    transaction isn't already committing.

    Fixes: 1eaa566d368b214d99cbb973647c1b0b8102a9ae
    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    fs/jbd2/journal.c | 15 ++++++++++++++-
    1 file changed, 14 insertions(+), 1 deletion(-)

    diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
    index 7d4b557f1962..047c8ef620fe 100644
    --- a/fs/jbd2/journal.c
    +++ b/fs/jbd2/journal.c
    @@ -691,8 +691,21 @@ int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
    {
    int err = 0;

    - jbd2_might_wait_for_commit(journal);
    read_lock(&journal->j_state_lock);
    +#ifdef CONFIG_PROVE_LOCKING
    + /*
    + * Some callers make sure transaction is already committing and in that
    + * case we cannot block on open handles anymore. So don't warn in that
    + * case.
    + */
    + if (tid_gt(tid, journal->j_commit_sequence) &&
    + (!journal->j_committing_transaction ||
    + journal->j_committing_transaction->t_tid != tid)) {
    + read_unlock(&journal->j_state_lock);
    + jbd2_might_wait_for_commit(journal);
    + read_lock(&journal->j_state_lock);
    + }
    +#endif
    #ifdef CONFIG_JBD2_DEBUG
    if (!tid_geq(journal->j_commit_request, tid)) {
    printk(KERN_ERR
    --
    2.14.1
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