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[Qemu-block] [PATCH v12 05/16] block: Set "share-rw" flag in drive-backu


From: Fam Zheng
Subject: [Qemu-block] [PATCH v12 05/16] block: Set "share-rw" flag in drive-backup when sync=none
Date: Mon, 23 Jan 2017 20:30:45 +0800

In this case we may open the source's backing image chain multiple
times. Setting share flag means the new open won't try to acquire or
check any lock, once we implement image locking.

Signed-off-by: Fam Zheng <address@hidden>
---
 blockdev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index 245e1e1..c97e97f 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3177,6 +3177,9 @@ static BlockJob *do_drive_backup(DriveBackup *backup, 
BlockJobTxn *txn,
     }
     if (backup->sync == MIRROR_SYNC_MODE_NONE) {
         source = bs;
+        /* FIXME: block layer should really open target with BDRV_O_NO_BACKING
+         * and reuse source's backing chain, if they share one. */
+        flags |= BDRV_O_SHARE_RW;
     }
 
     size = bdrv_getlength(bs);
-- 
2.9.3




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