Merge remote-tracking branch 'remotes/aperard/tags/pull-xen-20200407' into staging

Xen queue for QEMU 5.0

- Fix for xen-block.
- A fix for a Coverity false positive in xen-usb.
- Update MAINTAINERS to add xen-usb.c to Xen section.

# gpg: Signature made Tue 07 Apr 2020 16:21:16 BST
# gpg:                using RSA key F80C006308E22CFD8A92E7980CF5572FD7FB55AF
# gpg:                issuer "anthony.perard@citrix.com"
# gpg: Good signature from "Anthony PERARD <anthony.perard@gmail.com>" [marginal]
# gpg:                 aka "Anthony PERARD <anthony.perard@citrix.com>" [marginal]
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: 5379 2F71 024C 600F 778A  7161 D8D5 7199 DF83 42C8
#      Subkey fingerprint: F80C 0063 08E2 2CFD 8A92  E798 0CF5 572F D7FB 55AF

* remotes/aperard/tags/pull-xen-20200407:
  MAINTAINERS: Add xen-usb.c to Xen section
  xen-block: Fix uninitialized variable
  hw/usb/xen-usb.c: Pass struct usbback_req* to usbback_packet_complete()

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/block/backup.c b/block/backup.c
index 7430ca5..a7a7dca 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -126,11 +126,7 @@
 static void backup_clean(Job *job)
 {
     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
-    AioContext *aio_context = bdrv_get_aio_context(s->backup_top);
-
-    aio_context_acquire(aio_context);
     bdrv_backup_top_drop(s->backup_top);
-    aio_context_release(aio_context);
 }
 
 void backup_do_checkpoint(BlockJob *job, Error **errp)
diff --git a/block/block-backend.c b/block/block-backend.c
index 8b8f2a8..38ae413 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1140,16 +1140,22 @@
     return 0;
 }
 
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
 static void coroutine_fn blk_wait_while_drained(BlockBackend *blk)
 {
+    assert(blk->in_flight > 0);
+
     if (blk->quiesce_counter && !blk->disable_request_queuing) {
+        blk_dec_in_flight(blk);
         qemu_co_queue_wait(&blk->queued_requests, NULL);
+        blk_inc_in_flight(blk);
     }
 }
 
-int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
-                               unsigned int bytes, QEMUIOVector *qiov,
-                               BdrvRequestFlags flags)
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_preadv(BlockBackend *blk, int64_t offset, unsigned int bytes,
+              QEMUIOVector *qiov, BdrvRequestFlags flags)
 {
     int ret;
     BlockDriverState *bs;
@@ -1178,10 +1184,24 @@
     return ret;
 }
 
-int coroutine_fn blk_co_pwritev_part(BlockBackend *blk, int64_t offset,
-                                     unsigned int bytes,
-                                     QEMUIOVector *qiov, size_t qiov_offset,
-                                     BdrvRequestFlags flags)
+int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
+                               unsigned int bytes, QEMUIOVector *qiov,
+                               BdrvRequestFlags flags)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_preadv(blk, offset, bytes, qiov, flags);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_pwritev_part(BlockBackend *blk, int64_t offset, unsigned int bytes,
+                    QEMUIOVector *qiov, size_t qiov_offset,
+                    BdrvRequestFlags flags)
 {
     int ret;
     BlockDriverState *bs;
@@ -1214,6 +1234,20 @@
     return ret;
 }
 
+int coroutine_fn blk_co_pwritev_part(BlockBackend *blk, int64_t offset,
+                                     unsigned int bytes,
+                                     QEMUIOVector *qiov, size_t qiov_offset,
+                                     BdrvRequestFlags flags)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_pwritev_part(blk, offset, bytes, qiov, qiov_offset, flags);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
 int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
                                 unsigned int bytes, QEMUIOVector *qiov,
                                 BdrvRequestFlags flags)
@@ -1234,7 +1268,7 @@
     BlkRwCo *rwco = opaque;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, qiov->size,
+    rwco->ret = blk_do_preadv(rwco->blk, rwco->offset, qiov->size,
                               qiov, rwco->flags);
     aio_wait_kick();
 }
@@ -1244,8 +1278,8 @@
     BlkRwCo *rwco = opaque;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, qiov->size,
-                               qiov, rwco->flags);
+    rwco->ret = blk_do_pwritev_part(rwco->blk, rwco->offset, qiov->size,
+                                    qiov, 0, rwco->flags);
     aio_wait_kick();
 }
 
@@ -1262,6 +1296,7 @@
         .ret    = NOT_DONE,
     };
 
+    blk_inc_in_flight(blk);
     if (qemu_in_coroutine()) {
         /* Fast-path if already in coroutine context */
         co_entry(&rwco);
@@ -1270,6 +1305,7 @@
         bdrv_coroutine_enter(blk_bs(blk), co);
         BDRV_POLL_WHILE(blk_bs(blk), rwco.ret == NOT_DONE);
     }
+    blk_dec_in_flight(blk);
 
     return rwco.ret;
 }
@@ -1387,14 +1423,8 @@
     BlkRwCo *rwco = &acb->rwco;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    if (rwco->blk->quiesce_counter) {
-        blk_dec_in_flight(rwco->blk);
-        blk_wait_while_drained(rwco->blk);
-        blk_inc_in_flight(rwco->blk);
-    }
-
     assert(qiov->size == acb->bytes);
-    rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, acb->bytes,
+    rwco->ret = blk_do_preadv(rwco->blk, rwco->offset, acb->bytes,
                               qiov, rwco->flags);
     blk_aio_complete(acb);
 }
@@ -1405,15 +1435,9 @@
     BlkRwCo *rwco = &acb->rwco;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    if (rwco->blk->quiesce_counter) {
-        blk_dec_in_flight(rwco->blk);
-        blk_wait_while_drained(rwco->blk);
-        blk_inc_in_flight(rwco->blk);
-    }
-
     assert(!qiov || qiov->size == acb->bytes);
-    rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, acb->bytes,
-                               qiov, rwco->flags);
+    rwco->ret = blk_do_pwritev_part(rwco->blk, rwco->offset, acb->bytes,
+                                    qiov, 0, rwco->flags);
     blk_aio_complete(acb);
 }
 
@@ -1488,38 +1512,6 @@
                         blk_aio_write_entry, flags, cb, opaque);
 }
 
-static void blk_aio_flush_entry(void *opaque)
-{
-    BlkAioEmAIOCB *acb = opaque;
-    BlkRwCo *rwco = &acb->rwco;
-
-    rwco->ret = blk_co_flush(rwco->blk);
-    blk_aio_complete(acb);
-}
-
-BlockAIOCB *blk_aio_flush(BlockBackend *blk,
-                          BlockCompletionFunc *cb, void *opaque)
-{
-    return blk_aio_prwv(blk, 0, 0, NULL, blk_aio_flush_entry, 0, cb, opaque);
-}
-
-static void blk_aio_pdiscard_entry(void *opaque)
-{
-    BlkAioEmAIOCB *acb = opaque;
-    BlkRwCo *rwco = &acb->rwco;
-
-    rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, acb->bytes);
-    blk_aio_complete(acb);
-}
-
-BlockAIOCB *blk_aio_pdiscard(BlockBackend *blk,
-                             int64_t offset, int bytes,
-                             BlockCompletionFunc *cb, void *opaque)
-{
-    return blk_aio_prwv(blk, offset, bytes, NULL, blk_aio_pdiscard_entry, 0,
-                        cb, opaque);
-}
-
 void blk_aio_cancel(BlockAIOCB *acb)
 {
     bdrv_aio_cancel(acb);
@@ -1530,7 +1522,9 @@
     bdrv_aio_cancel_async(acb);
 }
 
-int blk_co_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
 {
     blk_wait_while_drained(blk);
 
@@ -1546,8 +1540,7 @@
     BlkRwCo *rwco = opaque;
     QEMUIOVector *qiov = rwco->iobuf;
 
-    rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset,
-                             qiov->iov[0].iov_base);
+    rwco->ret = blk_do_ioctl(rwco->blk, rwco->offset, qiov->iov[0].iov_base);
     aio_wait_kick();
 }
 
@@ -1561,7 +1554,7 @@
     BlkAioEmAIOCB *acb = opaque;
     BlkRwCo *rwco = &acb->rwco;
 
-    rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset, rwco->iobuf);
+    rwco->ret = blk_do_ioctl(rwco->blk, rwco->offset, rwco->iobuf);
 
     blk_aio_complete(acb);
 }
@@ -1572,7 +1565,9 @@
     return blk_aio_prwv(blk, req, 0, buf, blk_aio_ioctl_entry, 0, cb, opaque);
 }
 
-int blk_co_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn
+blk_do_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
 {
     int ret;
 
@@ -1586,7 +1581,50 @@
     return bdrv_co_pdiscard(blk->root, offset, bytes);
 }
 
-int blk_co_flush(BlockBackend *blk)
+static void blk_aio_pdiscard_entry(void *opaque)
+{
+    BlkAioEmAIOCB *acb = opaque;
+    BlkRwCo *rwco = &acb->rwco;
+
+    rwco->ret = blk_do_pdiscard(rwco->blk, rwco->offset, acb->bytes);
+    blk_aio_complete(acb);
+}
+
+BlockAIOCB *blk_aio_pdiscard(BlockBackend *blk,
+                             int64_t offset, int bytes,
+                             BlockCompletionFunc *cb, void *opaque)
+{
+    return blk_aio_prwv(blk, offset, bytes, NULL, blk_aio_pdiscard_entry, 0,
+                        cb, opaque);
+}
+
+int coroutine_fn blk_co_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_pdiscard(blk, offset, bytes);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
+static void blk_pdiscard_entry(void *opaque)
+{
+    BlkRwCo *rwco = opaque;
+    QEMUIOVector *qiov = rwco->iobuf;
+
+    rwco->ret = blk_do_pdiscard(rwco->blk, rwco->offset, qiov->size);
+    aio_wait_kick();
+}
+
+int blk_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
+{
+    return blk_prw(blk, offset, NULL, bytes, blk_pdiscard_entry, 0);
+}
+
+/* To be called between exactly one pair of blk_inc/dec_in_flight() */
+static int coroutine_fn blk_do_flush(BlockBackend *blk)
 {
     blk_wait_while_drained(blk);
 
@@ -1597,10 +1635,36 @@
     return bdrv_co_flush(blk_bs(blk));
 }
 
+static void blk_aio_flush_entry(void *opaque)
+{
+    BlkAioEmAIOCB *acb = opaque;
+    BlkRwCo *rwco = &acb->rwco;
+
+    rwco->ret = blk_do_flush(rwco->blk);
+    blk_aio_complete(acb);
+}
+
+BlockAIOCB *blk_aio_flush(BlockBackend *blk,
+                          BlockCompletionFunc *cb, void *opaque)
+{
+    return blk_aio_prwv(blk, 0, 0, NULL, blk_aio_flush_entry, 0, cb, opaque);
+}
+
+int coroutine_fn blk_co_flush(BlockBackend *blk)
+{
+    int ret;
+
+    blk_inc_in_flight(blk);
+    ret = blk_do_flush(blk);
+    blk_dec_in_flight(blk);
+
+    return ret;
+}
+
 static void blk_flush_entry(void *opaque)
 {
     BlkRwCo *rwco = opaque;
-    rwco->ret = blk_co_flush(rwco->blk);
+    rwco->ret = blk_do_flush(rwco->blk);
     aio_wait_kick();
 }
 
@@ -2083,20 +2147,6 @@
     return bdrv_truncate(blk->root, offset, exact, prealloc, errp);
 }
 
-static void blk_pdiscard_entry(void *opaque)
-{
-    BlkRwCo *rwco = opaque;
-    QEMUIOVector *qiov = rwco->iobuf;
-
-    rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, qiov->size);
-    aio_wait_kick();
-}
-
-int blk_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
-{
-    return blk_prw(blk, offset, NULL, bytes, blk_pdiscard_entry, 0);
-}
-
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
                      int64_t pos, int size)
 {
diff --git a/block/qcow2.c b/block/qcow2.c
index 2bb536b..b524b0c 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3784,6 +3784,12 @@
     int ret;
     BDRVQcow2State *s = bs->opaque;
 
+    /* If the image does not support QCOW_OFLAG_ZERO then discarding
+     * clusters could expose stale data from the backing file. */
+    if (s->qcow_version < 3 && bs->backing) {
+        return -ENOTSUP;
+    }
+
     if (!QEMU_IS_ALIGNED(offset | bytes, s->cluster_size)) {
         assert(bytes < s->cluster_size);
         /* Ignore partial clusters, except for the special case of the
@@ -4349,6 +4355,11 @@
         return -EINVAL;
     }
 
+    if (offset_into_cluster(s, bytes) &&
+        (offset + bytes) != (bs->total_sectors << BDRV_SECTOR_BITS)) {
+        return -EINVAL;
+    }
+
     while (bytes && aio_task_pool_status(aio) == 0) {
         uint64_t chunk_size = MIN(bytes, s->cluster_size);
 
diff --git a/block/replication.c b/block/replication.c
index 413d954..da013c2 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -144,12 +144,15 @@
 static void replication_close(BlockDriverState *bs)
 {
     BDRVReplicationState *s = bs->opaque;
+    Job *commit_job;
 
     if (s->stage == BLOCK_REPLICATION_RUNNING) {
         replication_stop(s->rs, false, NULL);
     }
     if (s->stage == BLOCK_REPLICATION_FAILOVER) {
-        job_cancel_sync(&s->commit_job->job);
+        commit_job = &s->commit_job->job;
+        assert(commit_job->aio_context == qemu_get_current_aio_context());
+        job_cancel_sync(commit_job);
     }
 
     if (s->mode == REPLICATION_MODE_SECONDARY) {
diff --git a/block/vpc.c b/block/vpc.c
index 6df75e2..d8141b5 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -835,7 +835,7 @@
 
     /* Write the footer (twice: at the beginning and at the end) */
     block_size = 0x200000;
-    num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);
+    num_bat_entries = DIV_ROUND_UP(total_sectors, block_size / 512);
 
     ret = blk_pwrite(blk, offset, buf, HEADER_SIZE, 0);
     if (ret < 0) {
diff --git a/blockdev.c b/blockdev.c
index fa8630c..5faddaa 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3612,7 +3612,16 @@
     }
 
     trace_qmp_block_job_finalize(job);
+    job_ref(&job->job);
     job_finalize(&job->job, errp);
+
+    /*
+     * Job's context might have changed via job_finalize (and job_txn_apply
+     * automatically acquires the new one), so make sure we release the correct
+     * one.
+     */
+    aio_context = blk_get_aio_context(job->blk);
+    job_unref(&job->job);
     aio_context_release(aio_context);
 }
 
diff --git a/hw/block/dataplane/xen-block.c b/hw/block/dataplane/xen-block.c
index 288a87a..5f8f157 100644
--- a/hw/block/dataplane/xen-block.c
+++ b/hw/block/dataplane/xen-block.c
@@ -64,6 +64,8 @@
     AioContext *ctx;
 };
 
+static int xen_block_send_response(XenBlockRequest *request);
+
 static void reset_request(XenBlockRequest *request)
 {
     memset(&request->req, 0, sizeof(request->req));
@@ -115,23 +117,26 @@
     return request;
 }
 
-static void xen_block_finish_request(XenBlockRequest *request)
+static void xen_block_complete_request(XenBlockRequest *request)
 {
     XenBlockDataPlane *dataplane = request->dataplane;
 
+    if (xen_block_send_response(request)) {
+        Error *local_err = NULL;
+
+        xen_device_notify_event_channel(dataplane->xendev,
+                                        dataplane->event_channel,
+                                        &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+        }
+    }
+
     QLIST_REMOVE(request, list);
     dataplane->requests_inflight--;
-}
-
-static void xen_block_release_request(XenBlockRequest *request)
-{
-    XenBlockDataPlane *dataplane = request->dataplane;
-
-    QLIST_REMOVE(request, list);
     reset_request(request);
     request->dataplane = dataplane;
     QLIST_INSERT_HEAD(&dataplane->freelist, request, list);
-    dataplane->requests_inflight--;
 }
 
 /*
@@ -246,7 +251,6 @@
 }
 
 static int xen_block_do_aio(XenBlockRequest *request);
-static int xen_block_send_response(XenBlockRequest *request);
 
 static void xen_block_complete_aio(void *opaque, int ret)
 {
@@ -286,7 +290,6 @@
     }
 
     request->status = request->aio_errors ? BLKIF_RSP_ERROR : BLKIF_RSP_OKAY;
-    xen_block_finish_request(request);
 
     switch (request->req.operation) {
     case BLKIF_OP_WRITE:
@@ -306,17 +309,8 @@
     default:
         break;
     }
-    if (xen_block_send_response(request)) {
-        Error *local_err = NULL;
 
-        xen_device_notify_event_channel(dataplane->xendev,
-                                        dataplane->event_channel,
-                                        &local_err);
-        if (local_err) {
-            error_report_err(local_err);
-        }
-    }
-    xen_block_release_request(request);
+    xen_block_complete_request(request);
 
     if (dataplane->more_work) {
         qemu_bh_schedule(dataplane->bh);
@@ -420,8 +414,8 @@
     return 0;
 
 err:
-    xen_block_finish_request(request);
     request->status = BLKIF_RSP_ERROR;
+    xen_block_complete_request(request);
     return -1;
 }
 
@@ -575,17 +569,7 @@
                 break;
             };
 
-            if (xen_block_send_response(request)) {
-                Error *local_err = NULL;
-
-                xen_device_notify_event_channel(dataplane->xendev,
-                                                dataplane->event_channel,
-                                                &local_err);
-                if (local_err) {
-                    error_report_err(local_err);
-                }
-            }
-            xen_block_release_request(request);
+            xen_block_complete_request(request);
             continue;
         }
 
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index b198dec..9bbdbd6 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -171,7 +171,6 @@
                              BlockCompletionFunc *cb, void *opaque);
 void blk_aio_cancel(BlockAIOCB *acb);
 void blk_aio_cancel_async(BlockAIOCB *acb);
-int blk_co_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
                           BlockCompletionFunc *cb, void *opaque);
diff --git a/job-qmp.c b/job-qmp.c
index fecc939..f9a5883 100644
--- a/job-qmp.c
+++ b/job-qmp.c
@@ -114,7 +114,16 @@
     }
 
     trace_qmp_job_finalize(job);
+    job_ref(job);
     job_finalize(job, errp);
+
+    /*
+     * Job's context might have changed via job_finalize (and job_txn_apply
+     * automatically acquires the new one), so make sure we release the correct
+     * one.
+     */
+    aio_context = job->aio_context;
+    job_unref(job);
     aio_context_release(aio_context);
 }
 
diff --git a/job.c b/job.c
index 134a07b..53be57a 100644
--- a/job.c
+++ b/job.c
@@ -136,17 +136,38 @@
     }
 }
 
-static int job_txn_apply(JobTxn *txn, int fn(Job *))
+static int job_txn_apply(Job *job, int fn(Job *))
 {
-    Job *job, *next;
+    AioContext *inner_ctx;
+    Job *other_job, *next;
+    JobTxn *txn = job->txn;
     int rc = 0;
 
-    QLIST_FOREACH_SAFE(job, &txn->jobs, txn_list, next) {
-        rc = fn(job);
+    /*
+     * Similar to job_completed_txn_abort, we take each job's lock before
+     * applying fn, but since we assume that outer_ctx is held by the caller,
+     * we need to release it here to avoid holding the lock twice - which would
+     * break AIO_WAIT_WHILE from within fn.
+     */
+    job_ref(job);
+    aio_context_release(job->aio_context);
+
+    QLIST_FOREACH_SAFE(other_job, &txn->jobs, txn_list, next) {
+        inner_ctx = other_job->aio_context;
+        aio_context_acquire(inner_ctx);
+        rc = fn(other_job);
+        aio_context_release(inner_ctx);
         if (rc) {
             break;
         }
     }
+
+    /*
+     * Note that job->aio_context might have been changed by calling fn, so we
+     * can't use a local variable to cache it.
+     */
+    aio_context_acquire(job->aio_context);
+    job_unref(job);
     return rc;
 }
 
@@ -774,11 +795,11 @@
     assert(job && job->txn);
 
     /* prepare the transaction to complete */
-    rc = job_txn_apply(job->txn, job_prepare);
+    rc = job_txn_apply(job, job_prepare);
     if (rc) {
         job_completed_txn_abort(job);
     } else {
-        job_txn_apply(job->txn, job_finalize_single);
+        job_txn_apply(job, job_finalize_single);
     }
 }
 
@@ -824,10 +845,10 @@
         assert(other_job->ret == 0);
     }
 
-    job_txn_apply(txn, job_transition_to_pending);
+    job_txn_apply(job, job_transition_to_pending);
 
     /* If no jobs need manual finalization, automatically do so */
-    if (job_txn_apply(txn, job_needs_finalize) == 0) {
+    if (job_txn_apply(job, job_needs_finalize) == 0) {
         job_do_finalize(job);
     }
 }
@@ -849,9 +870,10 @@
 static void job_exit(void *opaque)
 {
     Job *job = (Job *)opaque;
-    AioContext *ctx = job->aio_context;
+    AioContext *ctx;
 
-    aio_context_acquire(ctx);
+    job_ref(job);
+    aio_context_acquire(job->aio_context);
 
     /* This is a lie, we're not quiescent, but still doing the completion
      * callbacks. However, completion callbacks tend to involve operations that
@@ -862,6 +884,14 @@
 
     job_completed(job);
 
+    /*
+     * Note that calling job_completed can move the job to a different
+     * aio_context, so we cannot cache from above. job_txn_apply takes care of
+     * acquiring the new lock, and we ref/unref to avoid job_completed freeing
+     * the job underneath us.
+     */
+    ctx = job->aio_context;
+    job_unref(job);
     aio_context_release(ctx);
 }
 
diff --git a/qemu-img.c b/qemu-img.c
index b167376..821cbf6 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1924,8 +1924,8 @@
         if (status == BLK_DATA && !copy_range) {
             ret = convert_co_read(s, sector_num, n, buf);
             if (ret < 0) {
-                error_report("error while reading sector %" PRId64
-                             ": %s", sector_num, strerror(-ret));
+                error_report("error while reading at byte %lld: %s",
+                             sector_num * BDRV_SECTOR_SIZE, strerror(-ret));
                 s->ret = ret;
             }
         } else if (!s->min_sparse && status == BLK_ZERO) {
@@ -1953,8 +1953,8 @@
                 ret = convert_co_write(s, sector_num, n, buf, status);
             }
             if (ret < 0) {
-                error_report("error while writing sector %" PRId64
-                             ": %s", sector_num, strerror(-ret));
+                error_report("error while writing at byte %lld: %s",
+                             sector_num * BDRV_SECTOR_SIZE, strerror(-ret));
                 s->ret = ret;
             }
         }
diff --git a/qobject/json-streamer.c b/qobject/json-streamer.c
index 47dd7ea..b93d97b 100644
--- a/qobject/json-streamer.c
+++ b/qobject/json-streamer.c
@@ -85,7 +85,7 @@
     g_queue_push_tail(&parser->tokens, token);
 
     if ((parser->brace_count > 0 || parser->bracket_count > 0)
-        && parser->bracket_count >= 0 && parser->bracket_count >= 0) {
+        && parser->brace_count >= 0 && parser->bracket_count >= 0) {
         return;
     }
 
diff --git a/tests/qemu-iotests/046 b/tests/qemu-iotests/046
index a066eec..ecbe5fc 100755
--- a/tests/qemu-iotests/046
+++ b/tests/qemu-iotests/046
@@ -193,8 +193,8 @@
 verify_io()
 {
     if ($QEMU_IMG info -U -f "$IMGFMT" "$TEST_IMG" | grep "compat: 0.10" > /dev/null); then
-        # For v2 images, discarded clusters are read from the backing file
-        # Keep the variable empty so that the backing file value can be used as
+        # In v2 images clusters are not discarded when there is a backing file.
+        # Keep the variable empty so that the previous value can be used as
         # the default below
         discarded=
     else
@@ -230,14 +230,16 @@
     echo read -P 70 0x78000 0x6000
     echo read -P 7  0x7e000 0x2000
 
-    echo read -P ${discarded:-8} 0x80000 0x6000
+    echo read -P ${discarded:-89} 0x80000 0x1000
+    echo read -P ${discarded:-8} 0x81000 0x5000
     echo read -P 80 0x86000 0x2000
     echo read -P ${discarded:-8} 0x88000 0x2000
     echo read -P 81 0x8a000 0xe000
     echo read -P 90 0x98000 0x6000
     echo read -P 9  0x9e000 0x2000
 
-    echo read -P ${discarded:-10} 0xa0000 0x6000
+    echo read -P ${discarded:-109} 0xa0000 0x1000
+    echo read -P ${discarded:-10} 0xa1000 0x5000
     echo read -P 100 0xa6000 0x2000
     echo read -P ${discarded:-10} 0xa8000 0x2000
     echo read -P 101 0xaa000 0xe000
diff --git a/tests/qemu-iotests/046.out b/tests/qemu-iotests/046.out
index ca2c740..7078304 100644
--- a/tests/qemu-iotests/046.out
+++ b/tests/qemu-iotests/046.out
@@ -187,8 +187,10 @@
 24 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 8192/8192 bytes at offset 516096
 8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 24576/24576 bytes at offset 524288
-24 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 524288
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 20480/20480 bytes at offset 528384
+20 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 8192/8192 bytes at offset 548864
 8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 8192/8192 bytes at offset 557056
@@ -199,8 +201,10 @@
 24 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 8192/8192 bytes at offset 647168
 8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-read 24576/24576 bytes at offset 655360
-24 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 655360
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 20480/20480 bytes at offset 659456
+20 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 8192/8192 bytes at offset 679936
 8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 8192/8192 bytes at offset 688128
diff --git a/tests/qemu-iotests/060 b/tests/qemu-iotests/060
index 043f129..32c0ecc 100755
--- a/tests/qemu-iotests/060
+++ b/tests/qemu-iotests/060
@@ -160,18 +160,16 @@
 
 $QEMU_IO -c 'write 0k 64k' "$BACKING_IMG" | _filter_qemu_io
 
-# compat=0.10 is required in order to make the following discard actually
-# unallocate the sector rather than make it a zero sector - we want COW, after
-# all.
-_make_test_img -o 'compat=0.10' -b "$BACKING_IMG" 1G
+_make_test_img -b "$BACKING_IMG" 1G
 # Write two clusters, the second one enforces creation of an L2 table after
 # the first data cluster.
 $QEMU_IO -c 'write 0k 64k' -c 'write 512M 64k' "$TEST_IMG" | _filter_qemu_io
-# Discard the first cluster. This cluster will soon enough be reallocated and
+# Free the first cluster. This cluster will soon enough be reallocated and
 # used for COW.
-$QEMU_IO -c 'discard 0k 64k' "$TEST_IMG" | _filter_qemu_io
+poke_file "$TEST_IMG" "$l2_offset" "\x00\x00\x00\x00\x00\x00\x00\x00"
+poke_file "$TEST_IMG" "$(($rb_offset+10))" "\x00\x00"
 # Now, corrupt the image by marking the second L2 table cluster as free.
-poke_file "$TEST_IMG" '131084' "\x00\x00" # 0x2000c
+poke_file "$TEST_IMG" "$(($rb_offset+12))" "\x00\x00"
 # Start a write operation requiring COW on the image stopping it right before
 # doing the read; then, trigger the corruption prevention by writing anything to
 # any unallocated cluster, leading to an attempt to overwrite the second L2
diff --git a/tests/qemu-iotests/060.out b/tests/qemu-iotests/060.out
index d27692a..09caaea 100644
--- a/tests/qemu-iotests/060.out
+++ b/tests/qemu-iotests/060.out
@@ -105,8 +105,6 @@
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 536870912
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-discard 65536/65536 bytes at offset 0
-64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qcow2: Marking image as corrupt: Preventing invalid write on metadata (overlaps with active L2 table); further corruption events will be suppressed
 blkdebug: Suspended request '0'
 write failed: Input/output error
diff --git a/tests/qemu-iotests/177 b/tests/qemu-iotests/177
index 752d29f..eadc2c7 100755
--- a/tests/qemu-iotests/177
+++ b/tests/qemu-iotests/177
@@ -89,8 +89,9 @@
 {
     if ($QEMU_IMG info -f "$IMGFMT" "$TEST_IMG" |
 	    grep "compat: 0.10" > /dev/null); then
-        # For v2 images, discarded clusters are read from the backing file
-        discarded=11
+        # In v2 images clusters are not discarded when there is a backing file
+        # so the previous value is read
+        discarded=22
     else
         # Discarded clusters are zeroed for v3 or later
         discarded=0
diff --git a/tests/qemu-iotests/244.out b/tests/qemu-iotests/244.out
index e6f4dc7..56329de 100644
--- a/tests/qemu-iotests/244.out
+++ b/tests/qemu-iotests/244.out
@@ -33,7 +33,7 @@
 Formatting 'TEST_DIR/t.IMGFMT.src', fmt=IMGFMT size=67108864
 wrote 1048576/1048576 bytes at offset 0
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-qemu-img: error while writing sector 0: Operation not supported
+qemu-img: error while writing at byte 0: Operation not supported
 
 Convert uncompressed, then write compressed data manually:
 Images are identical.
diff --git a/tests/qemu-iotests/290 b/tests/qemu-iotests/290
new file mode 100755
index 0000000..776b65e
--- /dev/null
+++ b/tests/qemu-iotests/290
@@ -0,0 +1,97 @@
+#!/usr/bin/env bash
+#
+# Test how 'qemu-io -c discard' behaves on v2 and v3 qcow2 images
+#
+# Copyright (C) 2020 Igalia, S.L.
+# Author: Alberto Garcia <berto@igalia.com>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=berto@igalia.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+status=1    # failure is the default!
+
+_cleanup()
+{
+    _cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow2
+_supported_proto file
+_supported_os Linux
+_unsupported_imgopts 'compat=0.10' refcount_bits data_file
+
+echo
+echo "### Test 'qemu-io -c discard' on a QCOW2 image without a backing file"
+echo
+for qcow2_compat in 0.10 1.1; do
+    echo "# Create an image with compat=$qcow2_compat without a backing file"
+    _make_test_img -o "compat=$qcow2_compat" 128k
+
+    echo "# Fill all clusters with data and then discard them"
+    $QEMU_IO -c 'write -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
+    $QEMU_IO -c 'discard 0 128k' "$TEST_IMG" | _filter_qemu_io
+
+    echo "# Read the data from the discarded clusters"
+    $QEMU_IO -c 'read -P 0x00 0 128k' "$TEST_IMG" | _filter_qemu_io
+
+    echo "# Output of qemu-img map"
+    $QEMU_IMG map "$TEST_IMG" | _filter_testdir
+done
+
+echo
+echo "### Test 'qemu-io -c discard' on a QCOW2 image with a backing file"
+echo
+
+echo "# Create a backing image and fill it with data"
+BACKING_IMG="$TEST_IMG.base"
+TEST_IMG="$BACKING_IMG" _make_test_img 128k
+$QEMU_IO -c 'write -P 0xff 0 128k' "$BACKING_IMG" | _filter_qemu_io
+
+for qcow2_compat in 0.10 1.1; do
+    echo "# Create an image with compat=$qcow2_compat and a backing file"
+    _make_test_img -o "compat=$qcow2_compat" -b "$BACKING_IMG"
+
+    echo "# Fill all clusters with data and then discard them"
+    $QEMU_IO -c 'write -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
+    $QEMU_IO -c 'discard 0 128k' "$TEST_IMG" | _filter_qemu_io
+
+    echo "# Read the data from the discarded clusters"
+    if [ "$qcow2_compat" = "1.1" ]; then
+        # In qcow2 v3 clusters are zeroed (with QCOW_OFLAG_ZERO)
+        $QEMU_IO -c 'read -P 0x00 0 128k' "$TEST_IMG" | _filter_qemu_io
+    else
+        # In qcow2 v2 if there's a backing image we cannot zero the clusters
+        # without exposing the backing file data so discard does nothing
+        $QEMU_IO -c 'read -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
+    fi
+
+    echo "# Output of qemu-img map"
+    $QEMU_IMG map "$TEST_IMG" | _filter_testdir
+done
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/290.out b/tests/qemu-iotests/290.out
new file mode 100644
index 0000000..d2259c8
--- /dev/null
+++ b/tests/qemu-iotests/290.out
@@ -0,0 +1,61 @@
+QA output created by 290
+
+### Test 'qemu-io -c discard' on a QCOW2 image without a backing file
+
+# Create an image with compat=0.10 without a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Output of qemu-img map
+Offset          Length          Mapped to       File
+# Create an image with compat=1.1 without a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Output of qemu-img map
+Offset          Length          Mapped to       File
+
+### Test 'qemu-io -c discard' on a QCOW2 image with a backing file
+
+# Create a backing image and fill it with data
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=131072
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Create an image with compat=0.10 and a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.base
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Output of qemu-img map
+Offset          Length          Mapped to       File
+0               0x20000         0x50000         TEST_DIR/t.qcow2
+# Create an image with compat=1.1 and a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.base
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Output of qemu-img map
+Offset          Length          Mapped to       File
+*** done
diff --git a/tests/qemu-iotests/common.pattern b/tests/qemu-iotests/common.pattern
index 4f5e5bc..4caa5de 100644
--- a/tests/qemu-iotests/common.pattern
+++ b/tests/qemu-iotests/common.pattern
@@ -23,7 +23,7 @@
     local count=$4
 
     for ((i=1;i<=$count;i++)); do
-        echo alloc $(( start + (i - 1) * step )) $size
+        echo "alloc $(( start + (i - 1) * step )) $size"
     done
 }
 
@@ -39,9 +39,9 @@
     local count=$5
     local pattern=$6
 
-    echo === IO: pattern $pattern >&2
+    echo "=== IO: pattern $pattern" >&2
     for ((i=1;i<=$count;i++)); do
-        echo $op -P $pattern $(( start + (i - 1) * step )) $size
+        echo "$op -P $pattern $(( start + (i - 1) * step )) $size"
     done
 }
 
@@ -110,31 +110,31 @@
     #        free - free - compressed
 
     # Write the clusters to be compressed
-    echo === Clusters to be compressed [1]
+    echo '=== Clusters to be compressed [1]'
     io_pattern writev $((offset + 4 * $cluster_size)) $cluster_size $((9 * $cluster_size)) $num 165
-    echo === Clusters to be compressed [2]
+    echo '=== Clusters to be compressed [2]'
     io_pattern writev $((offset + 5 * $cluster_size)) $cluster_size $((9 * $cluster_size)) $num 165
-    echo === Clusters to be compressed [3]
+    echo '=== Clusters to be compressed [3]'
     io_pattern writev $((offset + 8 * $cluster_size)) $cluster_size $((9 * $cluster_size)) $num 165
 
     mv "$TEST_IMG" "$TEST_IMG.orig"
     $QEMU_IMG convert -f $IMGFMT -O $IMGFMT -c "$TEST_IMG.orig" "$TEST_IMG"
 
     # Write the used clusters
-    echo === Used clusters [1]
+    echo '=== Used clusters [1]'
     io_pattern writev $((offset + 0 * $cluster_size)) $cluster_size $((9 * $cluster_size)) $num 165
-    echo === Used clusters [2]
+    echo '=== Used clusters [2]'
     io_pattern writev $((offset + 1 * $cluster_size)) $cluster_size $((9 * $cluster_size)) $num 165
-    echo === Used clusters [3]
+    echo '=== Used clusters [3]'
     io_pattern writev $((offset + 3 * $cluster_size)) $cluster_size $((9 * $cluster_size)) $num 165
 
     # Read them
-    echo === Read used/compressed clusters
+    echo '=== Read used/compressed clusters'
     io_pattern readv $((offset + 0 * $cluster_size)) $((2 * $cluster_size)) $((9 * $cluster_size)) $num 165
     io_pattern readv $((offset + 3 * $cluster_size)) $((3 * $cluster_size)) $((9 * $cluster_size)) $num 165
     io_pattern readv $((offset + 8 * $cluster_size)) $((1 * $cluster_size)) $((9 * $cluster_size)) $num 165
 
-    echo === Read zeros
+    echo '=== Read zeros'
     io_zero readv $((offset + 2 * $cluster_size)) $((1 * $cluster_size)) $((9 * $cluster_size)) $num
     io_zero readv $((offset + 6 * $cluster_size)) $((2 * $cluster_size)) $((9 * $cluster_size)) $num
 }
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 79c6dfc..435dccd 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -296,3 +296,4 @@
 286 rw quick
 288 quick
 289 rw quick
+290 rw auto quick
diff --git a/tests/test-blockjob.c b/tests/test-blockjob.c
index 4eeb184..7519847 100644
--- a/tests/test-blockjob.c
+++ b/tests/test-blockjob.c
@@ -367,7 +367,9 @@
     aio_poll(qemu_get_aio_context(), true);
     assert(job->status == JOB_STATUS_PENDING);
 
+    aio_context_acquire(job->aio_context);
     job_finalize(job, &error_abort);
+    aio_context_release(job->aio_context);
     assert(job->status == JOB_STATUS_CONCLUDED);
 
     cancel_common(s);