From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55670) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ajubT-0007Xo-35 for qemu-devel@nongnu.org; Sat, 26 Mar 2016 16:14:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ajubS-0008Cu-9x for qemu-devel@nongnu.org; Sat, 26 Mar 2016 16:14:35 -0400 References: <1458325289-17848-1-git-send-email-kwolf@redhat.com> <1458325289-17848-12-git-send-email-kwolf@redhat.com> From: Max Reitz Message-ID: <56F6EDA2.3050907@redhat.com> Date: Sat, 26 Mar 2016 21:14:26 +0100 MIME-Version: 1.0 In-Reply-To: <1458325289-17848-12-git-send-email-kwolf@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="7qSxuwJQcDWRnTbXS3kLBaKhhtEAkVDx6" Subject: Re: [Qemu-devel] [PATCH 11/20] block/qapi: Use blk_enable_write_cache() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --7qSxuwJQcDWRnTbXS3kLBaKhhtEAkVDx6 Content-Type: multipart/mixed; boundary="C0Jik0qIPiKXrAGiRw9PfK4Eat921MhGL" From: Max Reitz To: Kevin Wolf , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org Message-ID: <56F6EDA2.3050907@redhat.com> Subject: Re: [PATCH 11/20] block/qapi: Use blk_enable_write_cache() References: <1458325289-17848-1-git-send-email-kwolf@redhat.com> <1458325289-17848-12-git-send-email-kwolf@redhat.com> In-Reply-To: <1458325289-17848-12-git-send-email-kwolf@redhat.com> --C0Jik0qIPiKXrAGiRw9PfK4Eat921MhGL Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: quoted-printable On 18.03.2016 19:21, Kevin Wolf wrote: > Now that WCE is handled on the BlockBackend level, the flag is > meaningless for BDSes. As the schema requires us to fill the field, > we return an enabled write cache for them. >=20 > Note that this means that querying the BlockBackend name may return > writethrough as the cache information, whereas querying the node-name o= f > the root of that same BlockBackend will return writeback. >=20 > This may appear odd at first, Yeah, intuitively I'd think that a BDS shares the writeback mode of the BB at the tree root, but... > but it actually makes sense because it > correctly repesents the layer that implements the WCE handling. =2E..when you actually access the BDS directly, i.e., not through the whole tree and the BB at its root, then you will indeed get WB behavior. > This > becomes more apparent when you consider nodes that are the root node of= > multiple BlockBackends, where each BB can have its own WCE setting. True. >=20 > Signed-off-by: Kevin Wolf > --- > block.c | 2 +- > block/qapi.c | 7 +++--- > include/block/qapi.h | 3 ++- > tests/qemu-iotests/142 | 7 +++++- > tests/qemu-iotests/142.out | 57 ++++++++++++++++++++++++++++++++++++++= -------- > 5 files changed, 60 insertions(+), 16 deletions(-) Reviewed-by: Max Reitz --C0Jik0qIPiKXrAGiRw9PfK4Eat921MhGL-- --7qSxuwJQcDWRnTbXS3kLBaKhhtEAkVDx6 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJW9u2iAAoJEDuxQgLoOKytpp4H/18htSxzI+xc+SPLJGf3P073 6JR89uXlljdlWP+r0tuhbdWOVWXiWdr3/j6HSak9xhg6zk+ckIQRF2uAvta0UJkG 47RHPEw4RAw6SajmnILOaUVRrFKKCLwZOZZgPqPxh+4COKDEJXHAUTsiCrsU7pJf PMmMz+nb4FUo1+X+zL7N8tmKe4voT60PctBh+4WLEXnmDk9Xcw1iBdsRx6W2cdcQ HrV6O1ZwLLSUx07mscdqGV2u8lPw/dkknzu4uFXqXwvtjY6nVnvaHMXJJw/6JxhU KXOJWJlgMUfC69hwYlg70o0QB6cn/va1HLWVcqywnl0aWjDZG005Nwx4cmSOWoE= =NWBs -----END PGP SIGNATURE----- --7qSxuwJQcDWRnTbXS3kLBaKhhtEAkVDx6--