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

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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>
This commit is contained in:
Kevin Wolf 2019-03-11 16:13:16 +01:00
parent 69b736e765
commit 3085513778
4 changed files with 25 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
block.c
View File

@ -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;
}

7
tests/qemu-iotests/051
View File

@ -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

9
tests/qemu-iotests/051.out
View File

@ -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

9
tests/qemu-iotests/051.pc.out
View File

@ -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