qcow2: Fix copy_sectors() with VM state

bs->total_sectors is not the highest possible sector number that could
be involved in a copy on write operation: VM state is after the end of
the virtual disk. This resulted in wrong values for the number of
sectors to be copied (n).

The code that checks for the end of the image isn't required any more
because the code hasn't been calling the block layer's bdrv_read() for a
long time; instead, it directly calls qcow2_readv(), which doesn't error
out on VM state sector numbers.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/qcow2-cluster.c

@@ -359,15 +359,6 @@ static int coroutine_fn copy_sectors(BlockDriverState *bs,
     struct iovec iov;
     int n, ret;
 
-    /*
-     * If this is the last cluster and it is only partially used, we must only
-     * copy until the end of the image, or bdrv_check_request will fail for the
-     * bdrv_read/write calls below.
-     */
-    if (start_sect + n_end > bs->total_sectors) {
-        n_end = bs->total_sectors - start_sect;
-    }
-
     n = n_end - n_start;
     if (n <= 0) {
         return 0;

tests/qemu-iotests/029

 #!/bin/bash
 #
-# Test loading internal snapshots where the L1 table of the snapshot
-# is smaller than the current L1 table.
+# qcow2 internal snapshots/VM state tests
 #
 # Copyright (C) 2011 Red Hat, Inc.
 #
@@ -45,6 +44,11 @@ _supported_fmt qcow2
 _supported_proto generic
 _supported_os Linux
 
+echo
+echo Test loading internal snapshots where the L1 table of the snapshot
+echo is smaller than the current L1 table.
+echo
+
 CLUSTER_SIZE=65536
 _make_test_img 64M
 $QEMU_IMG snapshot -c foo "$TEST_IMG"
@@ -59,6 +63,20 @@ $QEMU_IO -c 'write -b 0 4M' "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG snapshot -a foo "$TEST_IMG"
 _check_test_img
 
+
+echo
+echo Try using a huge VM state
+echo
+
+CLUSTER_SIZE=65536
+_make_test_img 64M
+{ $QEMU_IO -c "write -b -P 0x11 1T 4k" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+{ $QEMU_IMG snapshot -c foo $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+{ $QEMU_IMG snapshot -a foo $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+{ $QEMU_IO -c "read -b -P 0x11 1T 4k" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+_check_test_img
+
+
 # success, all done
 echo "*** done"
 rm -f $seq.full

tests/qemu-iotests/029.out

 QA output created by 029
+
+Test loading internal snapshots where the L1 table of the snapshot
+is smaller than the current L1 table.
+
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
 wrote 4096/4096 bytes at offset 0
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
@@ -7,4 +11,13 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=16777216
 wrote 4194304/4194304 bytes at offset 0
 4 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 No errors were found on the image.
+
+Try using a huge VM state
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+wrote 4096/4096 bytes at offset 1099511627776
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 1099511627776
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+No errors were found on the image.
 *** done