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Mon, 27 Apr 2020 10:00:28 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-114-29.ams2.redhat.com [10.36.114.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8E17B5C1D6; Mon, 27 Apr 2020 10:00:12 +0000 (UTC) Subject: Re: [PATCH v3 1/3] block: Add blk_new_with_bs() helper To: Eric Blake , qemu-devel@nongnu.org References: <20200424190903.522087-1-eblake@redhat.com> <20200424190903.522087-2-eblake@redhat.com> From: Max Reitz 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, 27 Apr 2020 12:00:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200424190903.522087-2-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="xEhqSYEW8v88T08h11wOrhpB6WnrQnVsQ" Received-SPF: pass client-ip=205.139.110.120; envelope-from=mreitz@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/27 01:12:26 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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: Kevin Wolf , Fam Zheng , "open list:Sheepdog" , qemu-block@nongnu.org, Jeff Cody , Stefan Weil , Markus Armbruster , stefanha@redhat.com, Liu Yuan , "Denis V. Lunev" , John Snow 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) --xEhqSYEW8v88T08h11wOrhpB6WnrQnVsQ Content-Type: multipart/mixed; boundary="WxyYo912wrh8eXyU9mtlMnuwoO7xchuxq" --WxyYo912wrh8eXyU9mtlMnuwoO7xchuxq Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 24.04.20 21:09, Eric Blake wrote: > There are several callers that need to create a new block backend from > an existing BDS; make the task slightly easier with a common helper > routine. >=20 > Suggested-by: Max Reitz > Signed-off-by: Eric Blake > --- > include/sysemu/block-backend.h | 2 ++ > block/block-backend.c | 23 +++++++++++++++++++++++ > block/crypto.c | 10 ++++------ > block/parallels.c | 8 ++++---- > block/qcow.c | 8 ++++---- > block/qcow2.c | 18 ++++++++---------- > block/qed.c | 9 ++++----- > block/sheepdog.c | 11 +++++------ > block/vdi.c | 8 ++++---- > block/vhdx.c | 9 ++++----- > block/vmdk.c | 9 ++++----- > block/vpc.c | 8 ++++---- > blockdev.c | 8 +++----- > blockjob.c | 7 ++----- > 14 files changed, 75 insertions(+), 63 deletions(-) [...] > diff --git a/block/crypto.c b/block/crypto.c > index d577f89659fa..a4d77f07fe8c 100644 > --- a/block/crypto.c > +++ b/block/crypto.c > @@ -256,16 +256,14 @@ static int block_crypto_co_create_generic(BlockDriv= erState *bs, > PreallocMode prealloc, > Error **errp) > { > - int ret; > + int ret =3D -EPERM; I=E2=80=99m not sure I=E2=80=99m a fan of this, because I feel like it make= s the code harder to read, due to having to look in three places (here, around the blk_new_with_bs() call, and under the cleanup label) instead of in two (not here) to verify that the error handling code is correct. There=E2=80=99s also the fact that this is not really a default return valu= e, but one very specific error code for if one very specific function call fails. I suppose it comes down to whether one considers LoC a complexity problem. (I don=E2=80=99t, necessarily.) (Also I realize it seems rather common in the kernel to set error return variables before the function call, but I think the more common pattern in qemu is to set it in the error path.) [...] > diff --git a/block/qed.c b/block/qed.c > index 1af9b3cb1db1..7a31495d293b 100644 > --- a/block/qed.c > +++ b/block/qed.c > @@ -610,7 +610,7 @@ static int coroutine_fn bdrv_qed_co_create(BlockdevCr= eateOptions *opts, > QEDHeader le_header; > uint8_t *l1_table =3D NULL; > size_t l1_size; > - int ret =3D 0; > + int ret =3D -EPERM; (Same here; well, especially here, because there is so much other code between the initialization and the =E2=80=9Cgoto out=E2=80=9D this is for) [...] > diff --git a/block/sheepdog.c b/block/sheepdog.c > index 59f7ebb1710f..2b53cd950d20 100644 > --- a/block/sheepdog.c > +++ b/block/sheepdog.c > @@ -1801,14 +1801,13 @@ static int sd_prealloc(BlockDriverState *bs, int6= 4_t old_size, int64_t new_size, > uint32_t idx, max_idx; > uint32_t object_size; > void *buf =3D NULL; > - int ret; > + int ret =3D -EPERM; (and here) [...] > diff --git a/block/vhdx.c b/block/vhdx.c > index 33e57cd6567a..bdf5d05cc018 100644 > --- a/block/vhdx.c > +++ b/block/vhdx.c > @@ -1891,7 +1891,7 @@ static int coroutine_fn vhdx_co_create(BlockdevCrea= teOptions *opts, > BlockBackend *blk =3D NULL; > BlockDriverState *bs =3D NULL; >=20 > - int ret =3D 0; > + int ret =3D -EPERM; (and again especially here) But it does look like you got all cases covered this time. 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