98 lines
4.4 KiB
Diff
98 lines
4.4 KiB
Diff
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From 6c139a45537d021f6fd4287bd3c74cba06e6a264 Mon Sep 17 00:00:00 2001
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Message-Id: <6c139a45537d021f6fd4287bd3c74cba06e6a264@dist-git>
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From: Peter Krempa <pkrempa@redhat.com>
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Date: Tue, 23 Jun 2020 12:23:47 +0200
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Subject: [PATCH] qemu: checkpoint: Don't chain bitmaps for checkpoints
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Chaining bitmaps for checkpoints (disabling the active one and creating
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a new) severely overcomplicated all operations in regards to bitmaps.
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Specifically it requires us re-matching the on-disk state to the
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internal metadata and in case of merging during block jobs it makes it
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almost impossible to cover all corner cases.
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Since the checkpoints and incremental backups were not yet enabled,
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let's change the design to keep one bitmap per checkpoint. In case of
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layered snapshots this will be filled in by using dirty-bitmap-populate.
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Finally the main reason for this unnecessary complexity was the fear
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that qemu's performance could degrade. In the end I think that
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addressing the performance issue will be better done in qemu (e.g by
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keeping an internal bitmap updated with changes and merging it
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periodically back to the real bitmaps. QEMU writes out changes to disk
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at shutdown so consistency is not a problem).
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Removing the relationships between bitmaps frees us from complex
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handling and also makes all the surrounding code more robust as one
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broken bitmap doesn't necessarily invalidate whole chains of backups.
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Signed-off-by: Peter Krempa <pkrempa@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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(cherry picked from commit 1f92aa454aa3b04ece9f7479d517bf08ba547f0a)
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https://bugzilla.redhat.com/show_bug.cgi?id=1804593
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Message-Id: <a863b2015f72690ebd90fd518e8163e194909214.1592906423.git.pkrempa@redhat.com>
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Reviewed-by: Ján Tomko <jtomko@redhat.com>
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---
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src/qemu/qemu_checkpoint.c | 21 +--------------------
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1 file changed, 1 insertion(+), 20 deletions(-)
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diff --git a/src/qemu/qemu_checkpoint.c b/src/qemu/qemu_checkpoint.c
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index 34cf122eb3..9762a3eb9d 100644
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--- a/src/qemu/qemu_checkpoint.c
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+++ b/src/qemu/qemu_checkpoint.c
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@@ -460,7 +460,6 @@ qemuCheckpointPrepare(virQEMUDriverPtr driver,
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static int
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qemuCheckpointAddActions(virDomainObjPtr vm,
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virJSONValuePtr actions,
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- virDomainMomentObjPtr old_current,
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virDomainCheckpointDefPtr def)
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{
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size_t i;
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@@ -468,7 +467,6 @@ qemuCheckpointAddActions(virDomainObjPtr vm,
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for (i = 0; i < def->ndisks; i++) {
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virDomainCheckpointDiskDef *chkdisk = &def->disks[i];
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virDomainDiskDefPtr domdisk = virDomainDiskByTarget(vm->def, chkdisk->name);
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- virDomainCheckpointDiskDef *parentchkdisk = NULL;
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/* checkpoint definition validator mandates that the corresponding
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* domdisk should exist */
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@@ -479,23 +477,6 @@ qemuCheckpointAddActions(virDomainObjPtr vm,
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if (qemuMonitorTransactionBitmapAdd(actions, domdisk->src->nodeformat,
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chkdisk->bitmap, true, false, 0) < 0)
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return -1;
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-
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- /* We only want one active bitmap for a disk along the
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- * checkpoint chain, then later differential backups will
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- * merge the bitmaps (only one active) between the bounding
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- * checkpoint and the leaf checkpoint. If the same disks are
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- * involved in each checkpoint, this search terminates in one
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- * iteration; but it is also possible to have to search
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- * further than the immediate parent to find another
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- * checkpoint with a bitmap on the same disk. */
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- if ((parentchkdisk = qemuCheckpointFindActiveDiskInParent(vm, old_current,
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- chkdisk->name))) {
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-
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- if (qemuMonitorTransactionBitmapDisable(actions,
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- domdisk->src->nodeformat,
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- parentchkdisk->bitmap) < 0)
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- return -1;
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- }
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}
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return 0;
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}
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@@ -544,7 +525,7 @@ qemuCheckpointCreateCommon(virQEMUDriverPtr driver,
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tmpactions = virJSONValueNewArray();
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- if (qemuCheckpointAddActions(vm, tmpactions, parent, *def) < 0)
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+ if (qemuCheckpointAddActions(vm, tmpactions, *def) < 0)
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return -1;
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if (!(*chk = virDomainCheckpointAssignDef(vm->checkpoints, *def)))
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--
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2.27.0
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