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[Qemu-devel] [PATCH 02/17] qcow2: No persistent dirty bitmaps for compat
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PATCH 02/17] qcow2: No persistent dirty bitmaps for compat=0.10 |
Date: |
Thu, 23 Nov 2017 03:08:17 +0100 |
Persistent dirty bitmaps require a properly functioning
autoclear_features field, or we cannot track when an unsupporting
program might overwrite them. Therefore, we cannot support them for
compat=0.10 images.
Signed-off-by: Max Reitz <address@hidden>
---
block/qcow2-bitmap.c | 10 ++++++++++
block/qcow2.c | 14 +++++++++++---
2 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index f45e46cfbd..efa10c6663 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -1449,6 +1449,16 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState
*bs,
bool found;
Qcow2BitmapList *bm_list;
+ if (s->qcow_version < 3) {
+ /* Without autoclear_features, we would always have to assume
+ * that a program without persistent dirty bitmap support has
+ * accessed this qcow2 file when opening it, and would thus
+ * have to drop all dirty bitmaps (defeating their purpose).
+ */
+ error_setg(errp, "Cannot store dirty bitmaps in qcow2 v2 files");
+ goto fail;
+ }
+
if (check_constraints_on_bitmap(bs, name, granularity, errp) != 0) {
goto fail;
}
diff --git a/block/qcow2.c b/block/qcow2.c
index 1914a940e5..cabf93e43c 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -302,9 +302,17 @@ static int qcow2_read_extensions(BlockDriverState *bs,
uint64_t start_offset,
}
if (!(s->autoclear_features & QCOW2_AUTOCLEAR_BITMAPS)) {
- warn_report("a program lacking bitmap support "
- "modified this file, so all bitmaps are now "
- "considered inconsistent");
+ if (s->qcow_version < 3) {
+ /* Let's be a bit more specific */
+ warn_report("This qcow2 v2 image contains bitmaps, but "
+ "they may have been modified by a program "
+ "without persistent bitmap support; so now "
+ "they must all be considered inconsistent");
+ } else {
+ warn_report("a program lacking bitmap support "
+ "modified this file, so all bitmaps are now "
+ "considered inconsistent");
+ }
error_printf("Some clusters may be leaked, "
"run 'qemu-img check -r' on the image "
"file to fix.");
--
2.13.6
- [Qemu-devel] [PATCH 00/17] iotests: Fix iotests for weird formats/options, Max Reitz, 2017/11/22
- [Qemu-devel] [PATCH 01/17] block/vmdk: Fix , instead of ; at end of line, Max Reitz, 2017/11/22
- [Qemu-devel] [PATCH 02/17] qcow2: No persistent dirty bitmaps for compat=0.10,
Max Reitz <=
- [Qemu-devel] [PATCH 03/17] block/qcow: Add blkdebug events, Max Reitz, 2017/11/22
- [Qemu-devel] [PATCH 04/17] block/vmdk: Add blkdebug events, Max Reitz, 2017/11/22
- [Qemu-devel] [PATCH 05/17] iotests: Fix _img_info for backslashes, Max Reitz, 2017/11/22
- [Qemu-devel] [PATCH 06/17] iotests: Drop format-specific in _filter_img_info, Max Reitz, 2017/11/22