From ad64bca4d6cc7a258a546112b9494e6bfdf6cfbe Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Wed, 3 Apr 2019 22:42:51 +0200
Subject: [PATCH 156/163] block/qcow2-bitmap: Allow resizes with persistent
 bitmaps

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20190403224253.5251-4-jsnow@redhat.com>
Patchwork-id: 85433
O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 3/5] block/qcow2-bitmap: Allow resizes with persistent bitmaps
Bugzilla: 1666884
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Sergio Lopez Pascual <slp@redhat.com>

Since we now load all bitmaps into memory anyway, we can just truncate
them in-memory and then flush them back to disk. Just in case, we will
still check and enforce that this shortcut is valid -- i.e. that any
bitmap described on-disk is indeed in-memory and can be modified.

If there are any inconsistent bitmaps, we refuse to allow the truncate
as we do not actually load these bitmaps into memory, and it isn't safe
or reasonable to attempt to truncate corrupted data.

Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190311185147.52309-4-vsementsov@virtuozzo.com
  [vsementsov: drop bitmap flushing, fix block comments style]
Signed-off-by: John Snow <jsnow@redhat.com>
(cherry picked from commit d19c6b36ffe09cec7ce7ac6a3e979bfe923ebba9)
Signed-off-by: John Snow <jsnow@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/qcow2-bitmap.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 block/qcow2.c        |  4 +---
 block/qcow2.h        |  1 +
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index fe4a6a2..3150855 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -1176,6 +1176,52 @@ int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp)
     return qcow2_reopen_bitmaps_rw_hint(bs, NULL, errp);
 }
 
+/* Checks to see if it's safe to resize bitmaps */
+int qcow2_truncate_bitmaps_check(BlockDriverState *bs, Error **errp)
+{
+    BDRVQcow2State *s = bs->opaque;
+    Qcow2BitmapList *bm_list;
+    Qcow2Bitmap *bm;
+    int ret = 0;
+
+    if (s->nb_bitmaps == 0) {
+        return 0;
+    }
+
+    bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
+                               s->bitmap_directory_size, errp);
+    if (bm_list == NULL) {
+        return -EINVAL;
+    }
+
+    QSIMPLEQ_FOREACH(bm, bm_list, entry) {
+        BdrvDirtyBitmap *bitmap = bdrv_find_dirty_bitmap(bs, bm->name);
+        if (bitmap == NULL) {
+            /*
+             * We rely on all bitmaps being in-memory to be able to resize them,
+             * Otherwise, we'd need to resize them on disk explicitly
+             */
+            error_setg(errp, "Cannot resize qcow2 with persistent bitmaps that "
+                       "were not loaded into memory");
+            ret = -ENOTSUP;
+            goto out;
+        }
+
+        /*
+         * The checks against readonly and busy are redundant, but certainly
+         * do no harm. checks against inconsistent are crucial:
+         */
+        if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_DEFAULT, errp)) {
+            ret = -ENOTSUP;
+            goto out;
+        }
+    }
+
+out:
+    bitmap_list_free(bm_list);
+    return ret;
+}
+
 /* store_bitmap_data()
  * Store bitmap to image, filling bitmap table accordingly.
  */
diff --git a/block/qcow2.c b/block/qcow2.c
index 21f7556..b137480 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3487,9 +3487,7 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
     }
 
     /* cannot proceed if image has bitmaps */
-    if (s->nb_bitmaps) {
-        /* TODO: resize bitmaps in the image */
-        error_setg(errp, "Can't resize an image which has bitmaps");
+    if (qcow2_truncate_bitmaps_check(bs, errp)) {
         ret = -ENOTSUP;
         goto fail;
     }
diff --git a/block/qcow2.h b/block/qcow2.h
index 2633e33..3b1b972 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -681,6 +681,7 @@ Qcow2BitmapInfoList *qcow2_get_bitmap_info_list(BlockDriverState *bs,
 int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs, bool *header_updated,
                                  Error **errp);
 int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp);
+int qcow2_truncate_bitmaps_check(BlockDriverState *bs, Error **errp);
 void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp);
 int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp);
 bool qcow2_can_store_new_dirty_bitmap(BlockDriverState *bs,
-- 
1.8.3.1