Commit 30855137 authored Mar 11, 2019 by Kevin Wolf

file-posix: Fix bdrv_open_flags() for snapshot=on

Using a different read-only setting for bs->open_flags than for the
flags to the driver's open function is just inconsistent and a bad idea.
After this patch, the temporary snapshot keeps being opened read-only if
read-only=on,snapshot=on is passed.

If we wanted to change this behaviour to make only the orginal image
file read-only, but the temporary overlay read-write (as the comment in
the removed code suggests), that change would have to be made in
bdrv_temp_snapshot_options() (where the comment suggests otherwise).

Addressing this inconsistency before introducing dynamic auto-read-only
is important because otherwise we would immediately try to reopen the
temporary overlay even though the file is already unlinked.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

parent 69b736e7

block.c

+0 −7

Original line number	Diff line number	Diff line
		@@ -1163,13 +1163,6 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags)
		*/
		open_flags &= ~(BDRV_O_SNAPSHOT \| BDRV_O_NO_BACKING \| BDRV_O_PROTOCOL);

		/*
		* Snapshots should be writable.
		*/
		if (flags & BDRV_O_TEMPORARY) {
		open_flags \|= BDRV_O_RDWR;
		}

		return open_flags;
		}

tests/qemu-iotests/051

+7 −0

Original line number	Diff line number	Diff line
		@@ -356,6 +356,13 @@ $QEMU_IO -c "read -P 0x33 0 4k" "$TEST_IMG" \| _filter_qemu_io
		# Using snapshot=on with a non-existent TMPDIR
		TMPDIR=/nonexistent run_qemu -drive driver=null-co,snapshot=on

		# Using snapshot=on together with read-only=on
		echo "info block" \|
		run_qemu -drive file="$TEST_IMG",snapshot=on,read-only=on,if=none,id=$device_id \|
		_filter_qemu_io \|
		sed -e 's#"/[^"]*/vl\.[A-Za-z0-9]\{6\}"#SNAPSHOT_PATH#g'


		# success, all done
		echo "*** done"
		rm -f $seq.full

tests/qemu-iotests/051.out

+9 −0

Original line number	Diff line number	Diff line
		@@ -458,4 +458,13 @@ read 4096/4096 bytes at offset 0
		Testing: -drive driver=null-co,snapshot=on
		QEMU_PROG: -drive driver=null-co,snapshot=on: Could not get temporary filename: No such file or directory

		Testing: -drive file=TEST_DIR/t.qcow2,snapshot=on,read-only=on,if=none,id=drive0
		QEMU X.Y.Z monitor - type 'help' for more information
		(qemu) info block
		drive0 (NODE_NAME): json:{"backing": {"driver": "qcow2", "file": {"driver": "file", "filename": "TEST_DIR/t.qcow2"}}, "driver": "qcow2", "file": {"driver": "file", "filename": SNAPSHOT_PATH}} (qcow2, read-only)
		Removable device: not locked, tray closed
		Cache mode: writeback, ignore flushes
		Backing file: TEST_DIR/t.qcow2 (chain depth: 1)
		(qemu) quit

		*** done

tests/qemu-iotests/051.pc.out

+9 −0

Original line number	Diff line number	Diff line
		@@ -530,4 +530,13 @@ read 4096/4096 bytes at offset 0
		Testing: -drive driver=null-co,snapshot=on
		QEMU_PROG: -drive driver=null-co,snapshot=on: Could not get temporary filename: No such file or directory

		Testing: -drive file=TEST_DIR/t.qcow2,snapshot=on,read-only=on,if=none,id=drive0
		QEMU X.Y.Z monitor - type 'help' for more information
		(qemu) info block
		drive0 (NODE_NAME): json:{"backing": {"driver": "qcow2", "file": {"driver": "file", "filename": "TEST_DIR/t.qcow2"}}, "driver": "qcow2", "file": {"driver": "file", "filename": SNAPSHOT_PATH}} (qcow2, read-only)
		Removable device: not locked, tray closed
		Cache mode: writeback, ignore flushes
		Backing file: TEST_DIR/t.qcow2 (chain depth: 1)
		(qemu) quit

		*** done