Add tracing for when we actually wait for writeback.

This helps track deadlock bugs, just like the similar code
in lafs_iolock_block.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/io.c b/io.c
index c7734aab71125261522dfd784c798d2a17ce02d2..5fafb999c1713e1846c7c3073b9e3f922962c68d 100644 (file)
--- a/io.c
+++ b/io.c
@@ -373,6 +373,11 @@ static void wait_writeback(struct block *b)
 {
        if (test_bit(B_Writeback, &b->flags)) {
                DEFINE_WAIT(wq);
+#ifdef DEBUG_IOLOCK
+               printk("writeback wait for %s:%d: %s\n",
+                      b->iolock_file, b->iolock_line,
+                      strblk(b));
+#endif
                lafs_trigger_flush(b);
                for (;;) {
                        prepare_to_wait(&block_wait, &wq, TASK_UNINTERRUPTIBLE);