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From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, eblake@redhat.com, armbru@redhat.com,
	xiechanglong.d@gmail.com, wencongyang2@huawei.com,
	vsementsov@virtuozzo.com, jsnow@redhat.com, mreitz@redhat.com,
	kwolf@redhat.com
Subject: [PATCH v2 2/6] block/copy-before-write: require BLK_PERM_WRITE_UNCHANGED for fleecing
Date: Wed, 21 Jul 2021 17:04:20 +0300	[thread overview]
Message-ID: <20210721140424.163701-3-vsementsov@virtuozzo.com> (raw)
In-Reply-To: <20210721140424.163701-1-vsementsov@virtuozzo.com>

Now block-copy detects fleecing scheme and do write-unchanged
operations if detected. So, let's require appropriate permissions.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/copy-before-write.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index 2cd68b480a..808e8707ed 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -113,6 +113,14 @@ static void cbw_refresh_filename(BlockDriverState *bs)
             bs->file->bs->filename);
 }
 
+static bool cbw_is_fleecing(BlockDriverState *bs)
+{
+    BDRVCopyBeforeWriteState *s = bs->opaque;
+
+    return bs->file && s->target &&
+        bdrv_skip_filters(bs) == bdrv_backing_chain_next(s->target->bs);
+}
+
 static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
                            BdrvChildRole role,
                            BlockReopenQueue *reopen_queue,
@@ -129,7 +137,8 @@ static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
          * only upfront.
          */
         *nshared = BLK_PERM_ALL & ~BLK_PERM_RESIZE;
-        *nperm = BLK_PERM_WRITE;
+        *nperm =
+            cbw_is_fleecing(bs) ? BLK_PERM_WRITE_UNCHANGED : BLK_PERM_WRITE;
     } else {
         /* Source child */
         bdrv_default_perms(bs, c, role, reopen_queue,
-- 
2.29.2



  parent reply	other threads:[~2021-07-21 14:07 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21 14:04 [PATCH v2 for-6.2 0/6] push backup with fleecing Vladimir Sementsov-Ogievskiy
2021-07-21 14:04 ` [PATCH v2 1/6] block/block-copy: use write-unchanged for fleecing scheme Vladimir Sementsov-Ogievskiy
2021-07-21 14:04 ` Vladimir Sementsov-Ogievskiy [this message]
2021-07-21 14:04 ` [PATCH v2 3/6] block: share writes on backing child of fleecing node Vladimir Sementsov-Ogievskiy
2021-07-21 14:04 ` [PATCH v2 4/6] block: blk_root(): return non-const pointer Vladimir Sementsov-Ogievskiy
2021-07-21 14:04 ` [PATCH v2 5/6] qapi: backup: add immutable-source paramter Vladimir Sementsov-Ogievskiy
2021-07-21 14:04 ` [PATCH v2 6/6] iotests/image-fleecing: test push backup with fleecing Vladimir Sementsov-Ogievskiy
2021-08-04 10:03 ` [PATCH v2 for-6.2 0/6] " Vladimir Sementsov-Ogievskiy

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