From bff9b33a3c4e0757c1e779ebedbffa391d926ecb Mon Sep 17 00:00:00 2001

From: Max Reitz <mreitz@redhat.com>

Date: Mon, 4 Nov 2013 22:31:52 +0100

Subject: [PATCH 01/87] block: drop bs_snapshots global variable

RH-Author: Max Reitz <mreitz@redhat.com>

Message-id: <1383604354-12743-2-git-send-email-mreitz@redhat.com>

Patchwork-id: 55301

O-Subject: [RHEL-7.0 qemu-kvm PATCH 01/43] block: drop bs_snapshots global variable

Bugzilla: 1026524

RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

RH-Acked-by: Fam Zheng <famz@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

From: Stefan Hajnoczi <stefanha@redhat.com>

BZ: 1026524

The bs_snapshots global variable points to the BlockDriverState which

will be used to save vmstate.  This is really a savevm.c concept but was

moved into block.c:bdrv_snapshots() when it became clear that hotplug

could result in a dangling pointer.

While auditing the block layer's global state I came upon bs_snapshots

and realized that a variable is not necessary here.  Simply find the

first BlockDriverState capable of internal snapshots each time this is

needed.

The behavior of bdrv_snapshots() is preserved across hotplug because new

drives are always appended to the bdrv_states list.  This means that

calling the new find_vmstate_bs() function is idempotent - it returns

the same BlockDriverState unless it was hot-unplugged.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Reviewed-by: Eric Blake <eblake@redhat.com>

Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

(cherry picked from commit 29d782710f87f01991bfc85cd9bef7d15280a5e2)

Signed-off-by: Max Reitz <mreitz@redhat.com>

---

 block.c               | 28 ----------------------------

 include/block/block.h |  1 -

 savevm.c              | 19 +++++++++++++++----

 3 files changed, 15 insertions(+), 33 deletions(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 block.c               |   28 ----------------------------

 include/block/block.h |    1 -

 savevm.c              |   19 +++++++++++++++----

 3 files changed, 15 insertions(+), 33 deletions(-)

diff --git a/block.c b/block.c

index fdff92f..84a3a8d 100644

--- a/block.c

+++ b/block.c

@@ -99,9 +99,6 @@ static QTAILQ_HEAD(, BlockDriverState) bdrv_states =

 static QLIST_HEAD(, BlockDriver) bdrv_drivers =

     QLIST_HEAD_INITIALIZER(bdrv_drivers);

-/* The device to use for VM snapshots */

-static BlockDriverState *bs_snapshots;

-

 /* If non-zero, use only whitelisted block drivers */

 static int use_bdrv_whitelist;

@@ -1384,9 +1381,6 @@ void bdrv_close(BlockDriverState *bs)

     notifier_list_notify(&bs->close_notifiers, bs);

     if (bs->drv) {

-        if (bs == bs_snapshots) {

-            bs_snapshots = NULL;

-        }

         if (bs->backing_hd) {

             bdrv_delete(bs->backing_hd);

             bs->backing_hd = NULL;

@@ -1619,7 +1613,6 @@ void bdrv_delete(BlockDriverState *bs)

     bdrv_close(bs);

-    assert(bs != bs_snapshots);

     g_free(bs);

 }

@@ -1663,9 +1656,6 @@ void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,

 {

     bs->dev_ops = ops;

     bs->dev_opaque = opaque;

-    if (bdrv_dev_has_removable_media(bs) && bs == bs_snapshots) {

-        bs_snapshots = NULL;

-    }

 }

 void bdrv_emit_qmp_error_event(const BlockDriverState *bdrv,

@@ -3493,24 +3483,6 @@ int bdrv_is_snapshot(BlockDriverState *bs)

     return !!(bs->open_flags & BDRV_O_SNAPSHOT);

 }

-BlockDriverState *bdrv_snapshots(void)

-{

-    BlockDriverState *bs;

-

-    if (bs_snapshots) {

-        return bs_snapshots;

-    }

-

-    bs = NULL;

-    while ((bs = bdrv_next(bs))) {

-        if (bdrv_can_snapshot(bs)) {

-            bs_snapshots = bs;

-            return bs;

-        }

-    }

-    return NULL;

-}

-

 int bdrv_snapshot_create(BlockDriverState *bs,

                          QEMUSnapshotInfo *sn_info)

 {

diff --git a/include/block/block.h b/include/block/block.h

index bc1f5f6..3b3f40e 100644

--- a/include/block/block.h

+++ b/include/block/block.h

@@ -362,7 +362,6 @@ BlockInfo *bdrv_query_info(BlockDriverState *s);

 BlockStats *bdrv_query_stats(const BlockDriverState *bs);

 int bdrv_can_snapshot(BlockDriverState *bs);

 int bdrv_is_snapshot(BlockDriverState *bs);

-BlockDriverState *bdrv_snapshots(void);

 int bdrv_snapshot_create(BlockDriverState *bs,

                          QEMUSnapshotInfo *sn_info);

 int bdrv_snapshot_goto(BlockDriverState *bs,

diff --git a/savevm.c b/savevm.c

index 1ed7f05..d9f3787 100644

--- a/savevm.c

+++ b/savevm.c

@@ -2262,6 +2262,17 @@ out:

     return ret;

 }

+static BlockDriverState *find_vmstate_bs(void)

+{

+    BlockDriverState *bs = NULL;

+    while ((bs = bdrv_next(bs))) {

+        if (bdrv_can_snapshot(bs)) {

+            return bs;

+        }

+    }

+    return NULL;

+}

+

 static int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,

                               const char *name)

 {

@@ -2338,7 +2349,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)

         }

     }

-    bs = bdrv_snapshots();

+    bs = find_vmstate_bs();

     if (!bs) {

         monitor_printf(mon, "No block device can accept snapshots\n");

         return;

@@ -2440,7 +2451,7 @@ int load_vmstate(const char *name)

     QEMUFile *f;

     int ret;

-    bs_vm_state = bdrv_snapshots();

+    bs_vm_state = find_vmstate_bs();

     if (!bs_vm_state) {

         error_report("No block device supports snapshots");

         return -ENOTSUP;

@@ -2519,7 +2530,7 @@ void do_delvm(Monitor *mon, const QDict *qdict)

     int ret;

     const char *name = qdict_get_str(qdict, "name");

-    bs = bdrv_snapshots();

+    bs = find_vmstate_bs();

     if (!bs) {

         monitor_printf(mon, "No block device supports snapshots\n");

         return;

@@ -2551,7 +2562,7 @@ void do_info_snapshots(Monitor *mon, const QDict *qdict)

     int *available_snapshots;

     char buf[256];

-    bs = bdrv_snapshots();

+    bs = find_vmstate_bs();

     if (!bs) {

         monitor_printf(mon, "No available block device supports snapshots\n");

         return;

-- 

1.7.1