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Re: [PATCH 01/22] blockdev: Allow external snapshots everywhere

From: Vladimir Sementsov-Ogievskiy
Subject: Re: [PATCH 01/22] blockdev: Allow external snapshots everywhere
Date: Wed, 25 Sep 2019 11:45:24 +0000

20.09.2019 18:27, Max Reitz wrote:
> There is no good reason why we would allow external snapshots only on
> the first non-filter node in a chain.  Parent BDSs should not care
> whether their child is replaced by a snapshot.  (If they do care, they
> should announce that via freezing the chain, which is checked in
> bdrv_append() through bdrv_set_backing_hd().)
> Before we had bdrv_is_first_non_filter() here (since 212a5a8f095), there
> was a special function bdrv_check_ext_snapshot() that allowed snapshots
> by default, but block drivers could override this.  Only blkverify did
> so, however.
> It is not clear to me why blkverify would do so; maybe just so that the
> testee block driver would not be replaced.  The introducing commit
> f6186f49e2c does not explain why.  Maybe because 08b24cfe376 would have
> been the correct solution?  (Which adds a .supports_backing check.)
> Signed-off-by: Max Reitz<address@hidden>

Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>

Best regards,

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