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    Subject[PATCH 3.11 111/208] jbd2: don't BUG but return ENOSPC if a handle runs out of space
    Date
    3.11.10.3 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Theodore Ts'o <tytso@mit.edu>

    commit f6c07cad081ba222d63623d913aafba5586c1d2c upstream.

    If a handle runs out of space, we currently stop the kernel with a BUG
    in jbd2_journal_dirty_metadata(). This makes it hard to figure out
    what might be going on. So return an error of ENOSPC, so we can let
    the file system layer figure out what is going on, to make it more
    likely we can get useful debugging information). This should make it
    easier to debug problems such as the one which was reported by:

    https://bugzilla.kernel.org/show_bug.cgi?id=44731

    The only two callers of this function are ext4_handle_dirty_metadata()
    and ocfs2_journal_dirty(). The ocfs2 function will trigger a
    BUG_ON(), which means there will be no change in behavior. The ext4
    function will call ext4_error_inode() which will print the useful
    debugging information and then handle the situation using ext4's error
    handling mechanisms (i.e., which might mean halting the kernel or
    remounting the file system read-only).

    Also, since both file systems already call WARN_ON(), drop the WARN_ON
    from jbd2_journal_dirty_metadata() to avoid two stack traces from
    being displayed.

    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Cc: ocfs2-devel@oss.oracle.com
    Acked-by: Joel Becker <jlbec@evilplan.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    fs/jbd2/transaction.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
    index 7aa9a32..b0b74e5 100644
    --- a/fs/jbd2/transaction.c
    +++ b/fs/jbd2/transaction.c
    @@ -1290,7 +1290,10 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
    * once a transaction -bzzz
    */
    jh->b_modified = 1;
    - J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
    + if (handle->h_buffer_credits <= 0) {
    + ret = -ENOSPC;
    + goto out_unlock_bh;
    + }
    handle->h_buffer_credits--;
    }

    @@ -1373,7 +1376,6 @@ out_unlock_bh:
    jbd2_journal_put_journal_head(jh);
    out:
    JBUFFER_TRACE(jh, "exit");
    - WARN_ON(ret); /* All errors are bugs, so dump the stack */
    return ret;
    }

    --
    1.8.3.2


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