dm mpath: make it easier to detect unintended I/O request flushes

I/O errors triggered by multipathd incorrectly not enabling the no-flush
flag for DM_DEVICE_SUSPEND or DM_DEVICE_RESUME are hard to debug.  Add
more logging to make it easier to debug this.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

2 files changed, 23 insertions, 4 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index cc529537c8ce..fd7cdc4ce2a5 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -442,6 +442,23 @@ failed:
 }
 
 /*
+ * dm_report_EIO() is a macro instead of a function to make pr_debug()
+ * report the function name and line number of the function from which
+ * it has been invoked.
+ */
+#define dm_report_EIO(m)                                                \
+({                                                                      \
+        struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
+                                                                        \
+        pr_debug("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d\n", \
+                 dm_device_name(md),                                    \
+                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),        \
+                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags),  \
+                 dm_noflush_suspending((m)->ti));                       \
+        -EIO;                                                           \
+})
+
+/*
  * Map cloned requests (request-based multipath)
  */
 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
@@ -464,7 +481,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
         if (!pgpath) {
                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
                         return DM_MAPIO_DELAY_REQUEUE;
-                return -EIO;    /* Failed */
+                return dm_report_EIO(m);        /* Failed */
         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
                 if (pg_init_all_paths(m))
@@ -541,7 +558,7 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_m
         if (!pgpath) {
                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
                         return DM_MAPIO_REQUEUE;
-                return -EIO;
+                return dm_report_EIO(m);
         }
 
         mpio->pgpath = pgpath;
@@ -1476,7 +1493,7 @@ static int do_end_io(struct multipath *m, struct request *clone,
 
         if (atomic_read(&m->nr_valid_paths) == 0 &&
             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
-                r = -EIO;
+                r = dm_report_EIO(m);
 
         return r;
 }
@@ -1519,7 +1536,7 @@ static int do_end_io_bio(struct multipath *m, struct bio *clone,
 
         if (atomic_read(&m->nr_valid_paths) == 0 &&
             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
-                return -EIO;
+                return dm_report_EIO(m);
 
         /* Queue for the daemon to resubmit */
         dm_bio_restore(get_bio_details_from_bio(clone), clone);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 45660246e8f5..dbfaf6dde657 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2169,6 +2169,8 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
          */
         if (noflush)
                 set_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
+        else
+                pr_debug("%s: suspending with flush\n", dm_device_name(md));
 
         /*
          * This gets reverted if there's an error later and the targets