[Qemu-devel] [PATCH] block: Close a BlockDriverState completely even when bs->drv is NULL

* [Qemu-devel] [PATCH] block: Close a BlockDriverState completely even when bs->drv is NULL
@ 2017-11-06 14:53 Alberto Garcia
  2017-11-07 22:29 ` Eric Blake
                   ` (3 more replies)
  0 siblings, 4 replies; 8+ messages in thread
From: Alberto Garcia @ 2017-11-06 14:53 UTC (permalink / raw)
  To: qemu-devel; +Cc: Alberto Garcia, qemu-block, Max Reitz, Kevin Wolf

bdrv_close() skips much of its logic when bs->drv is NULL. This is
fine when we're closing a BlockDriverState that has just been created
(because e.g the initialization process failed), but it's not enough
in other cases.

For example, when a valid qcow2 image is found to be corrupted then
QEMU marks it as such in the file header and then sets bs->drv to
NULL in order to make the BlockDriverState unusable. When that BDS is
later closed then many of its data structures are not freed (leaking
their memory) and none of its children are detached. This results in
bdrv_close_all() failing to close all BDSs and making this assertion
fail when QEMU is being shut down:

   bdrv_close_all: Assertion `QTAILQ_EMPTY(&all_bdrv_states)' failed.

This patch makes bdrv_close() do the full uninitialization process
in all cases. This fixes the problem with corrupted images and still
works fine with freshly created BDSs.

Signed-off-by: Alberto Garcia <berto@igalia.com>
---
 block.c                    | 57 +++++++++++++++++++++++-----------------------
 tests/qemu-iotests/060     | 13 +++++++++++
 tests/qemu-iotests/060.out | 12 ++++++++++
 3 files changed, 53 insertions(+), 29 deletions(-)

diff --git a/block.c b/block.c
index 684cb018da..389a6edad2 100644
--- a/block.c
+++ b/block.c
@@ -3179,6 +3179,7 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state)
 static void bdrv_close(BlockDriverState *bs)
 {
     BdrvAioNotifier *ban, *ban_next;
+    BdrvChild *child, *next;
 
     assert(!bs->job);
     assert(!bs->refcnt);
@@ -3188,43 +3189,41 @@ static void bdrv_close(BlockDriverState *bs)
     bdrv_drain(bs); /* in case flush left pending I/O */
 
     if (bs->drv) {
-        BdrvChild *child, *next;
-
         bs->drv->bdrv_close(bs);
         bs->drv = NULL;
+    }
 
-        bdrv_set_backing_hd(bs, NULL, &error_abort);
+    bdrv_set_backing_hd(bs, NULL, &error_abort);
 
-        if (bs->file != NULL) {
-            bdrv_unref_child(bs, bs->file);
-            bs->file = NULL;
-        }
+    if (bs->file != NULL) {
+        bdrv_unref_child(bs, bs->file);
+        bs->file = NULL;
+    }
 
-        QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
-            /* TODO Remove bdrv_unref() from drivers' close function and use
-             * bdrv_unref_child() here */
-            if (child->bs->inherits_from == bs) {
-                child->bs->inherits_from = NULL;
-            }
-            bdrv_detach_child(child);
+    QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
+        /* TODO Remove bdrv_unref() from drivers' close function and use
+         * bdrv_unref_child() here */
+        if (child->bs->inherits_from == bs) {
+            child->bs->inherits_from = NULL;
         }
-
-        g_free(bs->opaque);
-        bs->opaque = NULL;
-        atomic_set(&bs->copy_on_read, 0);
-        bs->backing_file[0] = '\0';
-        bs->backing_format[0] = '\0';
-        bs->total_sectors = 0;
-        bs->encrypted = false;
-        bs->sg = false;
-        QDECREF(bs->options);
-        QDECREF(bs->explicit_options);
-        bs->options = NULL;
-        bs->explicit_options = NULL;
-        QDECREF(bs->full_open_options);
-        bs->full_open_options = NULL;
+        bdrv_detach_child(child);
     }
 
+    g_free(bs->opaque);
+    bs->opaque = NULL;
+    atomic_set(&bs->copy_on_read, 0);
+    bs->backing_file[0] = '\0';
+    bs->backing_format[0] = '\0';
+    bs->total_sectors = 0;
+    bs->encrypted = false;
+    bs->sg = false;
+    QDECREF(bs->options);
+    QDECREF(bs->explicit_options);
+    bs->options = NULL;
+    bs->explicit_options = NULL;
+    QDECREF(bs->full_open_options);
+    bs->full_open_options = NULL;
+
     bdrv_release_named_dirty_bitmaps(bs);
     assert(QLIST_EMPTY(&bs->dirty_bitmaps));
 
diff --git a/tests/qemu-iotests/060 b/tests/qemu-iotests/060
index 66a8fa4aea..1cebe4c775 100755
--- a/tests/qemu-iotests/060
+++ b/tests/qemu-iotests/060
@@ -291,6 +291,19 @@ _make_test_img 64M
 poke_file "$TEST_IMG" "48"                "\x00\x00\x00\x00\x00\x00\x00\x00"
 $QEMU_IO -c "write 0 64k" "$TEST_IMG" | _filter_qemu_io
 
+echo
+echo "=== Testing the QEMU shutdown with a corrupted image ==="
+echo
+_make_test_img 64M
+poke_file "$TEST_IMG" "$rt_offset"        "\x00\x00\x00\x00\x00\x00\x00\x00"
+echo "{'execute': 'qmp_capabilities'}
+      {'execute': 'human-monitor-command',
+       'arguments': {'command-line': 'qemu-io drive \"write 0 512\"'}}
+      {'execute': 'quit'}" \
+    | $QEMU -qmp stdio -nographic -nodefaults \
+            -drive if=none,node-name=drive,file="$TEST_IMG",driver=qcow2 \
+    | _filter_qmp | _filter_qemu_io
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
diff --git a/tests/qemu-iotests/060.out b/tests/qemu-iotests/060.out
index cfd78f87a9..a5093fab8e 100644
--- a/tests/qemu-iotests/060.out
+++ b/tests/qemu-iotests/060.out
@@ -220,4 +220,16 @@ can't open device TEST_DIR/t.IMGFMT: Image does not contain a reference count ta
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 qcow2: Marking image as corrupt: Preventing invalid allocation of L2 table at offset 0; further corruption events will be suppressed
 write failed: Input/output error
+
+=== Testing the QEMU shutdown with a corrupted image ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+qcow2: Marking image as corrupt: Preventing invalid write on metadata (overlaps with refcount table); further corruption events will be suppressed
+QMP_VERSION
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_IMAGE_CORRUPTED", "data": {"device": "none0", "msg": "Preventing invalid write on metadata (overlaps with refcount table)", "offset": 65536, "node-name": "drive", "fatal": true, "size": 65536}}
+write failed: Input/output error
+{"return": ""}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false}}
 *** done
-- 
2.11.0

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