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Mon, 9 Sep 2019 08:25:14 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-116-179.ams2.redhat.com [10.36.116.179]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 01E914F85; Mon, 9 Sep 2019 08:25:12 +0000 (UTC) To: Kevin Wolf References: <20190809161407.11920-1-mreitz@redhat.com> <20190809161407.11920-15-mreitz@redhat.com> <20190905140547.GC4911@localhost.localdomain> From: Max Reitz Openpgp: preference=signencrypt Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Mon, 9 Sep 2019 10:25:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190905140547.GC4911@localhost.localdomain> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="qaZx741Ixq2NQeObiucjeYtKMFIrQzbI5" X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.70]); Mon, 09 Sep 2019 08:25:14 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v6 14/42] block: Use CAFs when working with backing chains X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --qaZx741Ixq2NQeObiucjeYtKMFIrQzbI5 Content-Type: multipart/mixed; boundary="wukLIzPDb0O5qhGXw6eNVWOlzg7fJ2Hlx"; protected-headers="v1" From: Max Reitz To: Kevin Wolf Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, Vladimir Sementsov-Ogievskiy Message-ID: Subject: Re: [PATCH v6 14/42] block: Use CAFs when working with backing chains References: <20190809161407.11920-1-mreitz@redhat.com> <20190809161407.11920-15-mreitz@redhat.com> <20190905140547.GC4911@localhost.localdomain> In-Reply-To: <20190905140547.GC4911@localhost.localdomain> --wukLIzPDb0O5qhGXw6eNVWOlzg7fJ2Hlx Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 05.09.19 16:05, Kevin Wolf wrote: > Am 09.08.2019 um 18:13 hat Max Reitz geschrieben: >> Use child access functions when iterating through backing chains so >> filters do not break the chain. >> >> Signed-off-by: Max Reitz >> --- >> block.c | 40 ++++++++++++++++++++++++++++------------ >> 1 file changed, 28 insertions(+), 12 deletions(-) >> >> diff --git a/block.c b/block.c >> index 86b84bea21..42abbaf0ba 100644 >> --- a/block.c >> +++ b/block.c >> @@ -4376,7 +4376,8 @@ int bdrv_change_backing_file(BlockDriverState *b= s, >> } >> =20 >> /* >> - * Finds the image layer in the chain that has 'bs' as its backing fi= le. >> + * Finds the image layer in the chain that has 'bs' (or a filter on >> + * top of it) as its backing file. >> * >> * active is the current topmost image. >> * >> @@ -4388,11 +4389,18 @@ int bdrv_change_backing_file(BlockDriverState = *bs, >> BlockDriverState *bdrv_find_overlay(BlockDriverState *active, >> BlockDriverState *bs) >> { >> - while (active && bs !=3D backing_bs(active)) { >> - active =3D backing_bs(active); >> + bs =3D bdrv_skip_rw_filters(bs); >> + active =3D bdrv_skip_rw_filters(active); >=20 > This does more than the commit message says. In addition to iterating > through filters instead of stopping, it also changes the semantics of > the function to return the next non-filter on top of bs instead of the > next node. Which is to say the overlay. (I think we only ever use =E2=80=9Coverlay=E2=80=9D in the COW sense.) > The block jobs seem to use it only for bdrv_is_allocated_above(), which= > should return the same thing in both cases, so the behaviour stays the > same. qmp_block_commit() will check op blockers on a different node now= , > which could be a fix or a bug, I can't tell offhand. Probably the > blocking doesn't really work anyway. You mean that the op blocker could have been on a block job filter node before? I think that=E2=80=98s pretty much the point of this fix; that t= hat doesn=E2=80=99t make sense. (We didn=E2=80=99t have mirror_top_bs and th= e like at 058223a6e3b.) > All of this should be mentioned in the commit message at least. Maybe > it's also worth splitting in two patches. I don=E2=80=99t know. The function was written when there were no filter= s. This change would have been a no-op then. The fact that it isn=E2=80=99t= to me just means that introducing filters broke it. So I don=E2=80=99t know what I would write. Maybe =E2=80=9Cbdrv_find_ove= rlay() now actually finds the overlay, that is, it will not return a filter node. This is the behavior that all callers expect (because they work on COW backing chains).=E2=80=9D >> + while (active) { >> + BlockDriverState *next =3D bdrv_backing_chain_next(active); >> + if (bs =3D=3D next) { >> + return active; >> + } >> + active =3D next; >> } >> =20 >> - return active; >> + return NULL; >> } >> =20 >> /* Given a BDS, searches for the base layer. */ >> @@ -4544,9 +4552,7 @@ int bdrv_drop_intermediate(BlockDriverState *top= , BlockDriverState *base, >> * other intermediate nodes have been dropped. >> * If 'top' is an implicit node (e.g. "commit_top") we should ski= p >> * it because no one inherits from it. We use explicit_top for th= at. */ >> - while (explicit_top && explicit_top->implicit) { >> - explicit_top =3D backing_bs(explicit_top); >> - } >> + explicit_top =3D bdrv_skip_implicit_filters(explicit_top); >> update_inherits_from =3D bdrv_inherits_from_recursive(base, expli= cit_top); >> =20 >> /* success - we can delete the intermediate states, and link top-= >base */ >> @@ -5014,7 +5020,7 @@ BlockDriverState *bdrv_lookup_bs(const char *dev= ice, >> bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *bas= e) >> { >> while (top && top !=3D base) { >> - top =3D backing_bs(top); >> + top =3D bdrv_filtered_bs(top); >> } >> =20 >> return top !=3D NULL; >> @@ -5253,7 +5259,17 @@ BlockDriverState *bdrv_find_backing_image(Block= DriverState *bs, >> =20 >> is_protocol =3D path_has_protocol(backing_file); >> =20 >> - for (curr_bs =3D bs; curr_bs->backing; curr_bs =3D curr_bs->backi= ng->bs) { >> + /* >> + * Being largely a legacy function, skip any filters here >> + * (because filters do not have normal filenames, so they cannot >> + * match anyway; and allowing json:{} filenames is a bit out of >> + * scope). >> + */ >> + for (curr_bs =3D bdrv_skip_rw_filters(bs); >> + bdrv_filtered_cow_child(curr_bs) !=3D NULL; >> + curr_bs =3D bdrv_backing_chain_next(curr_bs)) >=20 > This could just use bs_below instead of recalculating the node if you > moved the declaration of bs_below to the function scope. Indeed, thanks. Max >> + { >> + BlockDriverState *bs_below =3D bdrv_backing_chain_next(curr_b= s); >> =20 >> /* If either of the filename paths is actually a protocol, th= en >> * compare unmodified paths; otherwise make paths relative */= --wukLIzPDb0O5qhGXw6eNVWOlzg7fJ2Hlx-- --qaZx741Ixq2NQeObiucjeYtKMFIrQzbI5 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl12DGYACgkQ9AfbAGHV z0CcIAgAltyjqIi+iCCUbNH3iDrDeEmgHiqlyMxBLHxm8Iv3rt0tGfozZIYzdSfh IqevqC3xsTIKgA0aLqFMWOu2zM6H8Fzj4ku19WhtzpGvU+GJ7EcgCG/Ez2S5Pkxo V95nPjACMU1odJVun+j6SVRtmljh2qiIoP+ctJFZ6pa61ICSJF+WoZntgbMqrSx5 ihysUWaj+i9JZL5kmeiVbQswhtaPLe1Uv/jiTJhfpZxhq8Xmrwm1bO8DpvIm48m5 kIpZDiXdvvciysOWqiKzY8LukA7x2toCUgOegyiDcNyTNj6yR0xQuMQqeSKDMh1N oKSnd4UNWtaYozpHqtm/jKAszVft6g== =bg3U -----END PGP SIGNATURE----- --qaZx741Ixq2NQeObiucjeYtKMFIrQzbI5--