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From bff9b33a3c4e0757c1e779ebedbffa391d926ecb Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Mon, 4 Nov 2013 22:31:52 +0100
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Subject: [PATCH 01/87] block: drop bs_snapshots global variable
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <1383604354-12743-2-git-send-email-mreitz@redhat.com>
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Patchwork-id: 55301
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O-Subject: [RHEL-7.0 qemu-kvm PATCH 01/43] block: drop bs_snapshots global variable
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Bugzilla: 1026524
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Stefan Hajnoczi <stefanha@redhat.com>
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BZ: 1026524
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The bs_snapshots global variable points to the BlockDriverState which
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will be used to save vmstate.  This is really a savevm.c concept but was
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moved into block.c:bdrv_snapshots() when it became clear that hotplug
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could result in a dangling pointer.
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While auditing the block layer's global state I came upon bs_snapshots
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and realized that a variable is not necessary here.  Simply find the
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first BlockDriverState capable of internal snapshots each time this is
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needed.
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The behavior of bdrv_snapshots() is preserved across hotplug because new
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drives are always appended to the bdrv_states list.  This means that
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calling the new find_vmstate_bs() function is idempotent - it returns
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the same BlockDriverState unless it was hot-unplugged.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
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Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 29d782710f87f01991bfc85cd9bef7d15280a5e2)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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---
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 block.c               | 28 ----------------------------
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 include/block/block.h |  1 -
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 savevm.c              | 19 +++++++++++++++----
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 3 files changed, 15 insertions(+), 33 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 block.c               |   28 ----------------------------
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 include/block/block.h |    1 -
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 savevm.c              |   19 +++++++++++++++----
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 3 files changed, 15 insertions(+), 33 deletions(-)
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diff --git a/block.c b/block.c
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index fdff92f..84a3a8d 100644
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--- a/block.c
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+++ b/block.c
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@@ -99,9 +99,6 @@ static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
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 static QLIST_HEAD(, BlockDriver) bdrv_drivers =
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     QLIST_HEAD_INITIALIZER(bdrv_drivers);
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-/* The device to use for VM snapshots */
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-static BlockDriverState *bs_snapshots;
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-
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 /* If non-zero, use only whitelisted block drivers */
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 static int use_bdrv_whitelist;
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@@ -1384,9 +1381,6 @@ void bdrv_close(BlockDriverState *bs)
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     notifier_list_notify(&bs->close_notifiers, bs);
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     if (bs->drv) {
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-        if (bs == bs_snapshots) {
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-            bs_snapshots = NULL;
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-        }
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         if (bs->backing_hd) {
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             bdrv_delete(bs->backing_hd);
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             bs->backing_hd = NULL;
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@@ -1619,7 +1613,6 @@ void bdrv_delete(BlockDriverState *bs)
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     bdrv_close(bs);
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-    assert(bs != bs_snapshots);
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     g_free(bs);
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 }
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@@ -1663,9 +1656,6 @@ void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,
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 {
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     bs->dev_ops = ops;
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     bs->dev_opaque = opaque;
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-    if (bdrv_dev_has_removable_media(bs) && bs == bs_snapshots) {
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-        bs_snapshots = NULL;
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-    }
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 }
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 void bdrv_emit_qmp_error_event(const BlockDriverState *bdrv,
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@@ -3493,24 +3483,6 @@ int bdrv_is_snapshot(BlockDriverState *bs)
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     return !!(bs->open_flags & BDRV_O_SNAPSHOT);
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 }
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-BlockDriverState *bdrv_snapshots(void)
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-{
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-    BlockDriverState *bs;
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-
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-    if (bs_snapshots) {
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-        return bs_snapshots;
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-    }
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-
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-    bs = NULL;
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-    while ((bs = bdrv_next(bs))) {
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-        if (bdrv_can_snapshot(bs)) {
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-            bs_snapshots = bs;
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-            return bs;
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-        }
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-    }
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-    return NULL;
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-}
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-
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 int bdrv_snapshot_create(BlockDriverState *bs,
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                          QEMUSnapshotInfo *sn_info)
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 {
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diff --git a/include/block/block.h b/include/block/block.h
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index bc1f5f6..3b3f40e 100644
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--- a/include/block/block.h
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+++ b/include/block/block.h
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@@ -362,7 +362,6 @@ BlockInfo *bdrv_query_info(BlockDriverState *s);
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 BlockStats *bdrv_query_stats(const BlockDriverState *bs);
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 int bdrv_can_snapshot(BlockDriverState *bs);
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 int bdrv_is_snapshot(BlockDriverState *bs);
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-BlockDriverState *bdrv_snapshots(void);
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 int bdrv_snapshot_create(BlockDriverState *bs,
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                          QEMUSnapshotInfo *sn_info);
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 int bdrv_snapshot_goto(BlockDriverState *bs,
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diff --git a/savevm.c b/savevm.c
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index 1ed7f05..d9f3787 100644
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--- a/savevm.c
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+++ b/savevm.c
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@@ -2262,6 +2262,17 @@ out:
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     return ret;
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 }
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+static BlockDriverState *find_vmstate_bs(void)
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+{
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+    BlockDriverState *bs = NULL;
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+    while ((bs = bdrv_next(bs))) {
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+        if (bdrv_can_snapshot(bs)) {
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+            return bs;
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+        }
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+    }
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+    return NULL;
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+}
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+
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 static int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
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                               const char *name)
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 {
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@@ -2338,7 +2349,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
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         }
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     }
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-    bs = bdrv_snapshots();
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+    bs = find_vmstate_bs();
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     if (!bs) {
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         monitor_printf(mon, "No block device can accept snapshots\n");
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         return;
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@@ -2440,7 +2451,7 @@ int load_vmstate(const char *name)
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     QEMUFile *f;
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     int ret;
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-    bs_vm_state = bdrv_snapshots();
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+    bs_vm_state = find_vmstate_bs();
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     if (!bs_vm_state) {
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         error_report("No block device supports snapshots");
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         return -ENOTSUP;
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@@ -2519,7 +2530,7 @@ void do_delvm(Monitor *mon, const QDict *qdict)
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     int ret;
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     const char *name = qdict_get_str(qdict, "name");
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-    bs = bdrv_snapshots();
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+    bs = find_vmstate_bs();
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     if (!bs) {
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         monitor_printf(mon, "No block device supports snapshots\n");
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         return;
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@@ -2551,7 +2562,7 @@ void do_info_snapshots(Monitor *mon, const QDict *qdict)
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     int *available_snapshots;
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     char buf[256];
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-    bs = bdrv_snapshots();
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+    bs = find_vmstate_bs();
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     if (!bs) {
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         monitor_printf(mon, "No available block device supports snapshots\n");
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         return;
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-- 
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1.7.1
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