jbd2: Add sanity check for attempts to start handle during umount
An attempt to modify the file system during the call to
jbd2_destroy_journal() can lead to a system lockup. So add some
checking to make it much more obvious when this happens to and to
determine where the offending code is located.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 5247e7f..524800d 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -299,6 +299,16 @@
transaction->t_chp_stats.cs_forced_to_close++;
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
+ if (unlikely(journal->j_flags & JBD2_UNMOUNT))
+ /*
+ * The journal thread is dead; so starting and
+ * waiting for a commit to finish will cause
+ * us to wait for a _very_ long time.
+ */
+ printk(KERN_ERR "JBD2: %s: "
+ "Waiting for Godot: block %llu\n",
+ journal->j_devname,
+ (unsigned long long) bh->b_blocknr);
jbd2_log_start_commit(journal, tid);
jbd2_log_wait_commit(journal, tid);
ret = 1;