[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-block] [PULL 57/76] block: Add bitmap successors
From: |
Kevin Wolf |
Subject: |
[Qemu-block] [PULL 57/76] block: Add bitmap successors |
Date: |
Tue, 28 Apr 2015 17:00:39 +0200 |
From: John Snow <address@hidden>
A bitmap successor is an anonymous BdrvDirtyBitmap that is intended to
be created just prior to a sensitive operation (e.g. Incremental Backup)
that can either succeed or fail, but during the course of which we still
want a bitmap tracking writes.
On creating a successor, we "freeze" the parent bitmap which prevents
its deletion, enabling, anonymization, or creating a bitmap with the
same name.
On success, the parent bitmap can "abdicate" responsibility to the
successor, which will inherit its name. The successor will have been
tracking writes during the course of the backup operation. The parent
will be safely deleted.
On failure, we can "reclaim" the successor from the parent, unifying
them such that the resulting bitmap describes all writes occurring since
the last successful backup, for instance. Reclamation will thaw the
parent, but not explicitly re-enable it.
BdrvDirtyBitmap operations that target a single bitmap are protected
by assertions that the bitmap is not frozen and/or disabled.
BdrvDirtyBitmap operations that target a group of bitmaps, such as
bdrv_{set,reset}_dirty will ignore frozen/disabled drives with a
conditional instead.
Internal functions that enable/disable dirty bitmaps have assertions
added to them to prevent modifying frozen bitmaps.
Signed-off-by: John Snow <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Message-id: address@hidden
Signed-off-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
block.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++++-
blockdev.c | 7 ++++
include/block/block.h | 10 +++++
qapi/block-core.json | 1 +
4 files changed, 121 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index 0e63524..dffa9de 100644
--- a/block.c
+++ b/block.c
@@ -52,8 +52,17 @@
#include <windows.h>
#endif
+/**
+ * A BdrvDirtyBitmap can be in three possible states:
+ * (1) successor is NULL and disabled is false: full r/w mode
+ * (2) successor is NULL and disabled is true: read only mode ("disabled")
+ * (3) successor is set: frozen mode.
+ * A frozen bitmap cannot be renamed, deleted, anonymized, cleared, set,
+ * or enabled. A frozen bitmap can only abdicate() or reclaim().
+ */
struct BdrvDirtyBitmap {
HBitmap *bitmap;
+ BdrvDirtyBitmap *successor;
char *name;
bool disabled;
QLIST_ENTRY(BdrvDirtyBitmap) list;
@@ -5518,6 +5527,7 @@ BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState
*bs, const char *name)
void bdrv_dirty_bitmap_make_anon(BlockDriverState *bs, BdrvDirtyBitmap *bitmap)
{
+ assert(!bdrv_dirty_bitmap_frozen(bitmap));
g_free(bitmap->name);
bitmap->name = NULL;
}
@@ -5553,9 +5563,98 @@ BdrvDirtyBitmap
*bdrv_create_dirty_bitmap(BlockDriverState *bs,
return bitmap;
}
+bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap)
+{
+ return bitmap->successor;
+}
+
bool bdrv_dirty_bitmap_enabled(BdrvDirtyBitmap *bitmap)
{
- return !bitmap->disabled;
+ return !(bitmap->disabled || bitmap->successor);
+}
+
+/**
+ * Create a successor bitmap destined to replace this bitmap after an
operation.
+ * Requires that the bitmap is not frozen and has no successor.
+ */
+int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
+ BdrvDirtyBitmap *bitmap, Error **errp)
+{
+ uint64_t granularity;
+ BdrvDirtyBitmap *child;
+
+ if (bdrv_dirty_bitmap_frozen(bitmap)) {
+ error_setg(errp, "Cannot create a successor for a bitmap that is "
+ "currently frozen");
+ return -1;
+ }
+ assert(!bitmap->successor);
+
+ /* Create an anonymous successor */
+ granularity = bdrv_dirty_bitmap_granularity(bitmap);
+ child = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
+ if (!child) {
+ return -1;
+ }
+
+ /* Successor will be on or off based on our current state. */
+ child->disabled = bitmap->disabled;
+
+ /* Install the successor and freeze the parent */
+ bitmap->successor = child;
+ return 0;
+}
+
+/**
+ * For a bitmap with a successor, yield our name to the successor,
+ * delete the old bitmap, and return a handle to the new bitmap.
+ */
+BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
+ BdrvDirtyBitmap *bitmap,
+ Error **errp)
+{
+ char *name;
+ BdrvDirtyBitmap *successor = bitmap->successor;
+
+ if (successor == NULL) {
+ error_setg(errp, "Cannot relinquish control if "
+ "there's no successor present");
+ return NULL;
+ }
+
+ name = bitmap->name;
+ bitmap->name = NULL;
+ successor->name = name;
+ bitmap->successor = NULL;
+ bdrv_release_dirty_bitmap(bs, bitmap);
+
+ return successor;
+}
+
+/**
+ * In cases of failure where we can no longer safely delete the parent,
+ * we may wish to re-join the parent and child/successor.
+ * The merged parent will be un-frozen, but not explicitly re-enabled.
+ */
+BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState *bs,
+ BdrvDirtyBitmap *parent,
+ Error **errp)
+{
+ BdrvDirtyBitmap *successor = parent->successor;
+
+ if (!successor) {
+ error_setg(errp, "Cannot reclaim a successor when none is present");
+ return NULL;
+ }
+
+ if (!hbitmap_merge(parent->bitmap, successor->bitmap)) {
+ error_setg(errp, "Merging of parent and successor bitmap failed");
+ return NULL;
+ }
+ bdrv_release_dirty_bitmap(bs, successor);
+ parent->successor = NULL;
+
+ return parent;
}
void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap)
@@ -5563,6 +5662,7 @@ void bdrv_release_dirty_bitmap(BlockDriverState *bs,
BdrvDirtyBitmap *bitmap)
BdrvDirtyBitmap *bm, *next;
QLIST_FOREACH_SAFE(bm, &bs->dirty_bitmaps, list, next) {
if (bm == bitmap) {
+ assert(!bdrv_dirty_bitmap_frozen(bm));
QLIST_REMOVE(bitmap, list);
hbitmap_free(bitmap->bitmap);
g_free(bitmap->name);
@@ -5574,11 +5674,13 @@ void bdrv_release_dirty_bitmap(BlockDriverState *bs,
BdrvDirtyBitmap *bitmap)
void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
{
+ assert(!bdrv_dirty_bitmap_frozen(bitmap));
bitmap->disabled = true;
}
void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
{
+ assert(!bdrv_dirty_bitmap_frozen(bitmap));
bitmap->disabled = false;
}
diff --git a/blockdev.c b/blockdev.c
index 5dde1e8..e8b712e 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2065,9 +2065,16 @@ void qmp_block_dirty_bitmap_remove(const char *node,
const char *name,
return;
}
+ if (bdrv_dirty_bitmap_frozen(bitmap)) {
+ error_setg(errp,
+ "Bitmap '%s' is currently frozen and cannot be removed",
+ name);
+ goto out;
+ }
bdrv_dirty_bitmap_make_anon(bs, bitmap);
bdrv_release_dirty_bitmap(bs, bitmap);
+ out:
aio_context_release(aio_context);
}
diff --git a/include/block/block.h b/include/block/block.h
index 5d131f0..1635c22 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -454,6 +454,15 @@ BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState
*bs,
uint32_t granularity,
const char *name,
Error **errp);
+int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
+ BdrvDirtyBitmap *bitmap,
+ Error **errp);
+BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
+ BdrvDirtyBitmap *bitmap,
+ Error **errp);
+BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState *bs,
+ BdrvDirtyBitmap *bitmap,
+ Error **errp);
BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState *bs,
const char *name);
void bdrv_dirty_bitmap_make_anon(BlockDriverState *bs, BdrvDirtyBitmap
*bitmap);
@@ -464,6 +473,7 @@ BlockDirtyInfoList
*bdrv_query_dirty_bitmaps(BlockDriverState *bs);
uint32_t bdrv_get_default_bitmap_granularity(BlockDriverState *bs);
uint32_t bdrv_dirty_bitmap_granularity(BdrvDirtyBitmap *bitmap);
bool bdrv_dirty_bitmap_enabled(BdrvDirtyBitmap *bitmap);
+bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap);
int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap, int64_t
sector);
void bdrv_set_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
int64_t cur_sector, int nr_sectors);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 6237f9d..f3b92d8 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1008,6 +1008,7 @@
# Returns: nothing on success
# If @node is not a valid block device or node, DeviceNotFound
# If @name is not found, GenericError with an explanation
+# if @name is frozen by an operation, GenericError
#
# Since 2.4
##
--
1.8.3.1
- [Qemu-block] [PULL 47/76] block/iscsi: bump year in copyright notice, (continued)
- [Qemu-block] [PULL 47/76] block/iscsi: bump year in copyright notice, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 48/76] block/iscsi: use the allocationmap also if cache.direct=on, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 49/76] docs: incremental backup documentation, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 50/76] qapi: Add optional field "name" to block dirty bitmap, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 51/76] qmp: Ensure consistent granularity type, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 52/76] qmp: Add block-dirty-bitmap-add and block-dirty-bitmap-remove, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 53/76] block: Introduce bdrv_dirty_bitmap_granularity(), Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 54/76] hbitmap: cache array lengths, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 55/76] hbitmap: add hbitmap_merge, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 56/76] block: Add bitmap disabled status, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 57/76] block: Add bitmap successors,
Kevin Wolf <=
- [Qemu-block] [PULL 58/76] qmp: Add support of "dirty-bitmap" sync mode for drive-backup, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 59/76] qmp: add block-dirty-bitmap-clear, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 60/76] qmp: Add dirty bitmap status field in query-block, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 61/76] block: add BdrvDirtyBitmap documentation, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 62/76] block: Ensure consistent bitmap function prototypes, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 64/76] hbitmap: truncate tests, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 63/76] block: Resize bitmaps on bdrv_truncate, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 65/76] iotests: add invalid input incremental backup tests, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 68/76] iotests: add incremental backup failure recovery test, Kevin Wolf, 2015/04/28
- [Qemu-block] [PULL 67/76] iotests: add simple incremental backup case, Kevin Wolf, 2015/04/28