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bh=fSzpbwFqcetssAHV7O9Qdmxy1jcL+ITFbiKVQpjaoHo=; b=JR2C35Qf4i2ywxhJySU1ISu2QG/UM98NaaZHo9ZAdZN6bJAQWqoxG03yqAWiuLILJ1mfzQ FpeI3GrBN5GoZvKAmTcXDu06z2cP5vIi90IEhbBAiqdy1EXwih1zuQVJ7oL1FIQJY3kCoS MT0Q81aCJVgd7TEWPpcsvkNKvPrVOqU= X-MC-Unique: NyWkPPTyNHKQf5K4sLl5Fg-1 From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PATCH v6 04/10] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate Date: Thu, 23 Apr 2020 17:01:21 +0200 Message-Id: <20200423150127.142609-5-kwolf@redhat.com> In-Reply-To: <20200423150127.142609-1-kwolf@redhat.com> References: <20200423150127.142609-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=205.139.110.61; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/23 03:23:21 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: kwolf@redhat.com, vsementsov@virtuozzo.com, berto@igalia.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling qcow2_cluster_zeroize() with flags=3D0 does the right thing: It doesn't undo any previous preallocation, but just adds the zero flag to all relevant L2 entries. If an external data file is in use, a write_zeroes request to the data file is made instead. Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Reviewed-by: Eric Blake --- block/qcow2-cluster.c | 2 +- block/qcow2.c | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+), 1 deletion(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 17f1363279..4b5fc8c4a7 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1795,7 +1795,7 @@ int qcow2_cluster_zeroize(BlockDriverState *bs, uint6= 4_t offset, /* Caller must pass aligned values, except at image end */ assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || - end_offset =3D=3D bs->total_sectors << BDRV_SECTOR_BITS); + end_offset >=3D bs->total_sectors << BDRV_SECTOR_BITS); =20 /* The zero flag is only supported by version 3 and newer */ if (s->qcow_version < 3) { diff --git a/block/qcow2.c b/block/qcow2.c index 9cfbdfc939..ad621fe404 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1726,6 +1726,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverStat= e *bs, QDict *options, =20 bs->supported_zero_flags =3D header.version >=3D 3 ? BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK := 0; + bs->supported_truncate_flags =3D BDRV_REQ_ZERO_WRITE; =20 /* Repair image if dirty */ if (!(flags & (BDRV_O_CHECK | BDRV_O_INACTIVE)) && !bs->read_only && @@ -4214,6 +4215,38 @@ static int coroutine_fn qcow2_co_truncate(BlockDrive= rState *bs, int64_t offset, g_assert_not_reached(); } =20 + if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) { + uint64_t zero_start =3D QEMU_ALIGN_UP(old_length, s->cluster_size); + + /* + * Use zero clusters as much as we can. qcow2_cluster_zeroize() + * requires a cluster-aligned start. The end may be unaligned if i= t is + * at the end of the image (which it is here). + */ + ret =3D qcow2_cluster_zeroize(bs, zero_start, offset - zero_start,= 0); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to zero out new clusters"= ); + goto fail; + } + + /* Write explicit zeros for the unaligned head */ + if (zero_start > old_length) { + uint8_t *buf =3D qemu_blockalign0(bs, s->cluster_size); + QEMUIOVector qiov; + qemu_iovec_init_buf(&qiov, buf, zero_start - old_length); + + qemu_co_mutex_unlock(&s->lock); + ret =3D qcow2_co_pwritev_part(bs, old_length, qiov.size, &qiov= , 0, 0); + qemu_co_mutex_lock(&s->lock); + + qemu_vfree(buf); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed to zero out the new a= rea"); + goto fail; + } + } + } + if (prealloc !=3D PREALLOC_MODE_OFF) { /* Flush metadata before actually changing the image size */ ret =3D qcow2_write_caches(bs); --=20 2.25.3