diff --git a/block.c b/block.c
index 7e130cc528..5e80336e9f 100644
--- a/block.c
+++ b/block.c
@@ -1271,7 +1271,7 @@ int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp)
     QemuOpts *opts = NULL;
     QDict *snapshot_options;
     BlockDriverState *bs_snapshot;
-    Error *local_err;
+    Error *local_err = NULL;
     int ret;
 
     /* if snapshot, we create a temporary backing file and open it
@@ -1841,9 +1841,9 @@ void bdrv_close(BlockDriverState *bs)
     if (bs->job) {
         block_job_cancel_sync(bs->job);
     }
-    bdrv_drain_all(); /* complete I/O */
+    bdrv_drain(bs); /* complete I/O */
     bdrv_flush(bs);
-    bdrv_drain_all(); /* in case flush left pending I/O */
+    bdrv_drain(bs); /* in case flush left pending I/O */
     notifier_list_notify(&bs->close_notifiers, bs);
 
     if (bs->drv) {
@@ -3906,7 +3906,7 @@ void bdrv_attach_aio_context(BlockDriverState *bs,
 
 void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
 {
-    bdrv_drain_all(); /* ensure there are no in-flight requests */
+    bdrv_drain(bs); /* ensure there are no in-flight requests */
 
     bdrv_detach_aio_context(bs);
 
diff --git a/block/io.c b/block/io.c
index 305e0d952e..d4bc83b33b 100644
--- a/block/io.c
+++ b/block/io.c
@@ -236,12 +236,12 @@ static bool bdrv_requests_pending(BlockDriverState *bs)
 /*
  * Wait for pending requests to complete on a single BlockDriverState subtree
  *
- * See the warning in bdrv_drain_all().  This function can only be called if
- * you are sure nothing can generate I/O because you have op blockers
- * installed.
- *
  * Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState
  * AioContext.
+ *
+ * Only this BlockDriverState's AioContext is run, so in-flight requests must
+ * not depend on events in other AioContexts.  In that case, use
+ * bdrv_drain_all() instead.
  */
 void bdrv_drain(BlockDriverState *bs)
 {
@@ -260,12 +260,6 @@ void bdrv_drain(BlockDriverState *bs)
  *
  * This function does not flush data to disk, use bdrv_flush_all() for that
  * after calling this function.
- *
- * Note that completion of an asynchronous I/O operation can trigger any
- * number of other I/O operations on other devices---for example a coroutine
- * can be arbitrarily complex and a constant flow of I/O can come until the
- * coroutine is complete.  Because of this, it is not possible to have a
- * function to drain a single device's I/O queue.
  */
 void bdrv_drain_all(void)
 {
@@ -288,6 +282,12 @@ void bdrv_drain_all(void)
         }
     }
 
+    /* Note that completion of an asynchronous I/O operation can trigger any
+     * number of other I/O operations on other devices---for example a
+     * coroutine can submit an I/O request to another device in response to
+     * request completion.  Therefore we must keep looping until there was no
+     * more activity rather than simply draining each device independently.
+     */
     while (busy) {
         busy = false;
 
diff --git a/block/mirror.c b/block/mirror.c
index 8888cea952..d409337c4a 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -708,6 +708,8 @@ static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
 
     s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
     if (!s->dirty_bitmap) {
+        g_free(s->replaces);
+        block_job_release(bs);
         return;
     }
     bdrv_set_enable_write_cache(s->target, true);
diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c
index ed92a098c4..53b8afc3d3 100644
--- a/block/qcow2-cache.c
+++ b/block/qcow2-cache.c
@@ -281,9 +281,6 @@ static int qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c,
     i = min_lru_index;
     trace_qcow2_cache_get_replace_entry(qemu_coroutine_self(),
                                         c == s->l2_table_cache, i);
-    if (i < 0) {
-        return i;
-    }
 
     ret = qcow2_cache_entry_flush(bs, c, i);
     if (ret < 0) {
diff --git a/block/raw-posix.c b/block/raw-posix.c
index cbe6574bf4..855febed52 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -2430,7 +2430,8 @@ static int floppy_probe_device(const char *filename)
     struct stat st;
 
     if (strstart(filename, "/dev/fd", NULL) &&
-        !strstart(filename, "/dev/fdset/", NULL)) {
+        !strstart(filename, "/dev/fdset/", NULL) &&
+        !strstart(filename, "/dev/fd/", NULL)) {
         prio = 50;
     }
 
diff --git a/block/snapshot.c b/block/snapshot.c
index 19395ae014..49e143e991 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -239,7 +239,7 @@ int bdrv_snapshot_delete(BlockDriverState *bs,
     }
 
     /* drain all pending i/o before deleting snapshot */
-    bdrv_drain_all();
+    bdrv_drain(bs);
 
     if (drv->bdrv_snapshot_delete) {
         return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
diff --git a/blockjob.c b/blockjob.c
index ec46fad2f1..62bb906634 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -66,10 +66,7 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
 
         block_job_set_speed(job, speed, &local_err);
         if (local_err) {
-            bs->job = NULL;
-            bdrv_op_unblock_all(bs, job->blocker);
-            error_free(job->blocker);
-            g_free(job);
+            block_job_release(bs);
             error_propagate(errp, local_err);
             return NULL;
         }
@@ -77,16 +74,23 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
     return job;
 }
 
+void block_job_release(BlockDriverState *bs)
+{
+    BlockJob *job = bs->job;
+
+    bs->job = NULL;
+    bdrv_op_unblock_all(bs, job->blocker);
+    error_free(job->blocker);
+    g_free(job);
+}
+
 void block_job_completed(BlockJob *job, int ret)
 {
     BlockDriverState *bs = job->bs;
 
     assert(bs->job == job);
     job->cb(job->opaque, ret);
-    bs->job = NULL;
-    bdrv_op_unblock_all(bs, job->blocker);
-    error_free(job->blocker);
-    g_free(job);
+    block_job_release(bs);
 }
 
 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 57d8ef13e2..dd9d5e6aad 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -165,6 +165,14 @@ void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns);
  */
 void block_job_yield(BlockJob *job);
 
+/**
+ * block_job_release:
+ * @bs: The block device.
+ *
+ * Release job resources when an error occurred or job completed.
+ */
+void block_job_release(BlockDriverState *bs);
+
 /**
  * block_job_completed:
  * @job: The job being completed.
diff --git a/migration/block.c b/migration/block.c
index ddb59ccf87..ed865ed23b 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -457,7 +457,7 @@ static int mig_save_device_dirty(QEMUFile *f, BlkMigDevState *bmds,
         blk_mig_lock();
         if (bmds_aio_inflight(bmds, sector)) {
             blk_mig_unlock();
-            bdrv_drain_all();
+            bdrv_drain(bmds->bs);
         } else {
             blk_mig_unlock();
         }