Fix negative zio->io_error which must be positive.

All the upper layers of zfs expect zio->io_error to be positive.  I was
careful but I missed one instance in vdev_disk_physio_completion() which
could return a negative error.  To ensure all cases are always caught I
had additionally added an ASSERT() to check this before zio_interpret().

Finally, as a debugging aid when zfs is build with --enable-debug all
errors from the backing block devices will be reported to the console
with an error message like this:

	ZFS: zio error=5 type=1 offset=4217856 size=8192 flags=60440

diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index 6b410b1..9ae8fbc 100644 (file)
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -91,6 +91,17 @@ bdev_capacity(struct block_device *bdev)
        return get_capacity(bdev->bd_disk);
 }
 
+static void
+vdev_disk_error(zio_t *zio)
+{
+#ifdef ZFS_DEBUG
+       printk("ZFS: zio error=%d type=%d offset=%llu "
+           "size=%llu flags=%x\n", zio->io_error, zio->io_type,
+           (u_longlong_t)zio->io_offset, (u_longlong_t)zio->io_size,
+           zio->io_flags);
+#endif
+}
+
 static int
 vdev_disk_open(vdev_t *v, uint64_t *psize, uint64_t *ashift)
 {
@@ -232,6 +243,9 @@ vdev_disk_dio_put(dio_request_t *dr)
 
                if (zio) {
                        zio->io_error = error;
+                       ASSERT3S(zio->io_error, >=, 0);
+                       if (zio->io_error)
+                               vdev_disk_error(zio);
                        zio_interrupt(zio);
                }
        }
@@ -259,10 +273,10 @@ BIO_END_IO_PROTO(vdev_disk_physio_completion, bio, size, error)
 #endif /* HAVE_2ARGS_BIO_END_IO_T */
 
        if (error == 0 && !test_bit(BIO_UPTODATE, &bio->bi_flags))
-               error = EIO;
+               error = -EIO;
 
        if (dr->dr_error == 0)
-               dr->dr_error = error;
+               dr->dr_error = -error;
 
        /* Drop reference aquired by __vdev_disk_physio */
        rc = vdev_disk_dio_put(dr);
@@ -434,6 +448,9 @@ BIO_END_IO_PROTO(vdev_disk_io_flush_completion, bio, size, rc)
                zio->io_vd->vdev_nowritecache = B_TRUE;
 
        bio_put(bio);
+       ASSERT3S(zio->io_error, >=, 0);
+       if (zio->io_error)
+               vdev_disk_error(zio);
        zio_interrupt(zio);
 
        BIO_END_IO_RETURN(0);