Revert "dm mirror: use all available legs on multiple failures"

This reverts commit 12a7cf5ba6c776a2621d8972c7d42e8d3d959d20.

This commit apparently attempted to fix an issue that didn't really
exist, furthermore: this commit is the source of deadlocks and crashes
seen in multiple cases related to failing the primary mirror dev while
syncing.

Reported-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index e61c45047c25..4da8858856fb 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -145,6 +145,7 @@ static void dispatch_bios(void *context, struct bio_list *bio_list)
 
 struct dm_raid1_bio_record {
         struct mirror *m;
+        /* if details->bi_bdev == NULL, details were not saved */
         struct dm_bio_details details;
         region_t write_region;
 };
@@ -1198,6 +1199,8 @@ static int mirror_map(struct dm_target *ti, struct bio *bio)
         struct dm_raid1_bio_record *bio_record =
           dm_per_bio_data(bio, sizeof(struct dm_raid1_bio_record));
 
+        bio_record->details.bi_bdev = NULL;
+
         if (rw == WRITE) {
                 /* Save region for mirror_end_io() handler */
                 bio_record->write_region = dm_rh_bio_to_region(ms->rh, bio);
@@ -1256,12 +1259,22 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
         }
 
         if (error == -EOPNOTSUPP)
-                return error;
+                goto out;
 
         if ((error == -EWOULDBLOCK) && (bio->bi_opf & REQ_RAHEAD))
-                return error;
+                goto out;
 
         if (unlikely(error)) {
+                if (!bio_record->details.bi_bdev) {
+                        /*
+                         * There wasn't enough memory to record necessary
+                         * information for a retry or there was no other
+                         * mirror in-sync.
+                         */
+                        DMERR_LIMIT("Mirror read failed.");
+                        return -EIO;
+                }
+
                 m = bio_record->m;
 
                 DMERR("Mirror read failed from %s. Trying alternative device.",
@@ -1277,6 +1290,7 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
                         bd = &bio_record->details;
 
                         dm_bio_restore(bd, bio);
+                        bio_record->details.bi_bdev = NULL;
                         bio->bi_error = 0;
 
                         queue_bio(ms, bio, rw);
@@ -1285,6 +1299,9 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
                 DMERR("All replicated volumes dead, failing I/O");
         }
 
+out:
+        bio_record->details.bi_bdev = NULL;
+
         return error;
 }