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From 41d6c207c482093df8669f7cdcdb49bb25dba741 Mon Sep 17 00:00:00 2001
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From: Eric Blake <eblake@redhat.com>
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Date: Tue, 2 Jun 2020 02:34:12 +0100
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Subject: [PATCH 07/26] block: Make it easier to learn which BDS support
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 bitmaps
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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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RH-Author: Eric Blake <eblake@redhat.com>
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Message-id: <20200602023420.2133649-5-eblake@redhat.com>
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Patchwork-id: 97071
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O-Subject: [RHEL-AV-8.2.1 qemu-kvm PATCH 04/12] block: Make it easier to learn which BDS support bitmaps
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Bugzilla: 1779893 1779904
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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Upcoming patches will enhance bitmap support in qemu-img, but in doing
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so, it turns out to be nice to suppress output when persistent bitmaps
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make no sense (such as on a qcow2 v2 image).  Add a hook to make this
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easier to query.
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This patch adds a new callback .bdrv_supports_persistent_dirty_bitmap,
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rather than trying to shoehorn the answer in via existing callbacks.
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In particular, while it might have been possible to overload
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.bdrv_co_can_store_new_dirty_bitmap to special-case a NULL input to
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answer whether any persistent bitmaps are supported, that is at odds
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with whether a particular bitmap can be stored (for example, even on
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an image that supports persistent bitmaps but has currently filled up
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the maximum number of bitmaps, attempts to store another one should
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fail); and the new functionality doesn't require coroutine safety.
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Similarly, we could have added one more piece of information to
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.bdrv_get_info, but then again, most callers to that function tend to
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already discard extraneous information, and making it a catch-all
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rather than a series of dedicated scalar queries hasn't really
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simplified life.
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In the future, when we improve the ability to look up bitmaps through
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a filter, we will probably also want to teach the block layer to
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automatically let filters pass this request on through.
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Signed-off-by: Eric Blake <eblake@redhat.com>
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Message-Id: <20200513011648.166876-4-eblake@redhat.com>
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Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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(cherry picked from commit ef893b5c84f3199d777e33966dc28839f71b1a5c)
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Signed-off-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 block/dirty-bitmap.c         | 9 +++++++++
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 block/qcow2-bitmap.c         | 7 +++++++
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 block/qcow2.c                | 2 ++
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 block/qcow2.h                | 1 +
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 include/block/block_int.h    | 1 +
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 include/block/dirty-bitmap.h | 1 +
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 6 files changed, 21 insertions(+)
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diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
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index 7039e82..2f96acc 100644
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--- a/block/dirty-bitmap.c
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+++ b/block/dirty-bitmap.c
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@@ -478,6 +478,15 @@ int bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name,
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     }
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 }
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+bool
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+bdrv_supports_persistent_dirty_bitmap(BlockDriverState *bs)
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+{
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+    if (bs->drv && bs->drv->bdrv_supports_persistent_dirty_bitmap) {
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+        return bs->drv->bdrv_supports_persistent_dirty_bitmap(bs);
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+    }
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+    return false;
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+}
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+
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 static bool coroutine_fn
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 bdrv_co_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
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                                    uint32_t granularity, Error **errp)
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diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
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index c6c8ebb..cbac905 100644
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--- a/block/qcow2-bitmap.c
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+++ b/block/qcow2-bitmap.c
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@@ -1759,3 +1759,10 @@ fail:
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                   name, bdrv_get_device_or_node_name(bs));
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     return false;
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 }
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+
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+bool qcow2_supports_persistent_dirty_bitmap(BlockDriverState *bs)
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+{
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+    BDRVQcow2State *s = bs->opaque;
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+
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+    return s->qcow_version >= 3;
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+}
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diff --git a/block/qcow2.c b/block/qcow2.c
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index af0ad4a..36b0f7d 100644
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--- a/block/qcow2.c
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+++ b/block/qcow2.c
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@@ -5551,6 +5551,8 @@ BlockDriver bdrv_qcow2 = {
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     .bdrv_detach_aio_context  = qcow2_detach_aio_context,
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     .bdrv_attach_aio_context  = qcow2_attach_aio_context,
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+    .bdrv_supports_persistent_dirty_bitmap =
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+            qcow2_supports_persistent_dirty_bitmap,
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     .bdrv_co_can_store_new_dirty_bitmap = qcow2_co_can_store_new_dirty_bitmap,
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     .bdrv_co_remove_persistent_dirty_bitmap =
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             qcow2_co_remove_persistent_dirty_bitmap,
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diff --git a/block/qcow2.h b/block/qcow2.h
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index 0942126..ceb1ceb 100644
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--- a/block/qcow2.h
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+++ b/block/qcow2.h
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@@ -767,6 +767,7 @@ bool qcow2_co_can_store_new_dirty_bitmap(BlockDriverState *bs,
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 int qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs,
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                                             const char *name,
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                                             Error **errp);
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+bool qcow2_supports_persistent_dirty_bitmap(BlockDriverState *bs);
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 ssize_t coroutine_fn
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 qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size,
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diff --git a/include/block/block_int.h b/include/block/block_int.h
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index 562dca1..cc18e8d 100644
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--- a/include/block/block_int.h
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+++ b/include/block/block_int.h
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@@ -568,6 +568,7 @@ struct BlockDriver {
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                              uint64_t parent_perm, uint64_t parent_shared,
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                              uint64_t *nperm, uint64_t *nshared);
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+    bool (*bdrv_supports_persistent_dirty_bitmap)(BlockDriverState *bs);
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     bool (*bdrv_co_can_store_new_dirty_bitmap)(BlockDriverState *bs,
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                                                const char *name,
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                                                uint32_t granularity,
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diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
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index e2b20ec..f6e9a38 100644
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--- a/include/block/dirty-bitmap.h
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+++ b/include/block/dirty-bitmap.h
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@@ -16,6 +16,7 @@ typedef enum BitmapCheckFlags {
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 #define BDRV_BITMAP_MAX_NAME_SIZE 1023
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+bool bdrv_supports_persistent_dirty_bitmap(BlockDriverState *bs);
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 BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
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                                           uint32_t granularity,
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                                           const char *name,
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-- 
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1.8.3.1
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