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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744915321; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=csqy0lFVvHPMOE3Y+BWOfgNJuQqp7DKuYy228mUVHtk=; b=W1PmD6xhti+LISvhoukRv0/ZLVnd5gTTuaiCaa4154rKRoCs5zd4Fma7G+w2qtRuybVcS9 f8N6z4IHywrgWET9UL43oGMtsDyAIP9056ry9tDp61yIeIpz4QFEhxIKOZDeBcN0A1DOUT FKdgmxjPctzFRRRujgY8RlN7SfQ6sb4= X-MC-Unique: -3VsHMIcOe2j8rvNlqrr-A-1 X-Mimecast-MFC-AGG-ID: -3VsHMIcOe2j8rvNlqrr-A_1744915316 From: Eric Blake To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, vsementsov@yandex-team.ru, Stefan Hajnoczi , Fam Zheng , Kevin Wolf , Hanna Reitz Subject: [PATCH v2 03/11] block: Let bdrv_co_is_zero_fast consolidate adjacent extents Date: Thu, 17 Apr 2025 13:39:08 -0500 Message-ID: <20250417184133.105746-16-eblake@redhat.com> In-Reply-To: <20250417184133.105746-13-eblake@redhat.com> References: <20250417184133.105746-13-eblake@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" Some BDS drivers have a cap on how much block status they can supply in one query (for example, NBD talking to an older server cannot inspect more than 4G per query; and qcow2 tends to cap its answers rather than cross a cluster boundary of an L1 table). Although the existing callers of bdrv_co_is_zero_fast are not passing in that large of a 'bytes' parameter, an upcoming caller wants to query the entire image at once, and will thus benefit from being able to treat adjacent zero regions in a coalesced manner, rather than claiming the region is non-zero merely because pnum was truncated and didn't match the incoming bytes. While refactoring this into a loop, note that there is no need to assign pnum prior to calling bdrv_co_common_block_status_above() (it is guaranteed to be assigned deeper in the callstack). Signed-off-by: Eric Blake Reviewed-by: Stefan Hajnoczi --- block/io.c | 27 +++++++++++++++------------ 1 file changed, 15 insertions(+), 12 deletions(-) diff --git a/block/io.c b/block/io.c index 73c96084e62..6ef78070915 100644 --- a/block/io.c +++ b/block/io.c @@ -2757,22 +2757,25 @@ int coroutine_fn bdrv_co_is_zero_fast(BlockDriverSt= ate *bs, int64_t offset, int64_t bytes) { int ret; - int64_t pnum =3D bytes; + int64_t pnum; IO_CODE(); - if (!bytes) { - return 1; + while (bytes) { + ret =3D bdrv_co_common_block_status_above(bs, NULL, false, + BDRV_BSTAT_ZERO, offset, b= ytes, + &pnum, NULL, NULL, NULL); + + if (ret < 0) { + return ret; + } + if (!(ret & BDRV_BLOCK_ZERO)) { + return 0; + } + offset +=3D pnum; + bytes -=3D pnum; } - ret =3D bdrv_co_common_block_status_above(bs, NULL, false, BDRV_BSTAT_= ZERO, - offset, bytes, &pnum, NULL, NU= LL, - NULL); - - if (ret < 0) { - return ret; - } - - return (pnum =3D=3D bytes) && (ret & BDRV_BLOCK_ZERO); + return 1; } int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t offset, --=20 2.49.0