From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39073) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c7PX9-0003fr-9P for qemu-devel@nongnu.org; Thu, 17 Nov 2016 11:27:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c7PX8-0007Xv-5h for qemu-devel@nongnu.org; Thu, 17 Nov 2016 11:27:31 -0500 Date: Thu, 17 Nov 2016 17:27:19 +0100 From: Olaf Hering Message-ID: <20161117162719.GA18909@aepfle.de> References: <1459513321-3776-1-git-send-email-olaf@aepfle.de> <56FEAD92.5010802@redhat.com> <20160401174953.GD22458@aepfle.de> <7bcb7f33-5fb1-20d8-e92f-3b913b54e53b@redhat.com> <20161117135409.GA31152@aepfle.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="GvXjxJ+pjyke8COw" Content-Disposition: inline In-Reply-To: <20161117135409.GA31152@aepfle.de> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH] block: split large discard requests from block frontend List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: Kevin Wolf , Stefan Hajnoczi , qemu-devel@nongnu.org, qemu-block@nongnu.org --GvXjxJ+pjyke8COw Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Nov 17, Olaf Hering wrote: > Looking at current master, BLKIF_OP_DISCARD is indeed broken. The values > passed from the guest are u64 and get stashed into signed values. I will > add a loop to repeatedly call blk_aio_pdiscard with small chunks of > BDRV_REQUEST_MAX_SECTORS. I have not compile tested the change below, but thats the way how I would deal with it: diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c index 3a7dc19..5962c4b 100644 --- a/hw/block/xen_disk.c +++ b/hw/block/xen_disk.c @@ -660,6 +660,38 @@ static void qemu_aio_complete(void *opaque, int ret) qemu_bh_schedule(ioreq->blkdev->bh); } =20 +static bool blk_split_discard(struct ioreq *ioreq, blkif_sector_t sector_n= umber, uint64_t nr_sectors) +{ + struct XenBlkDev *blkdev =3D ioreq->blkdev; + int64_t byte_offset; + int bytes; + uint64_t byte_limit =3D INT64_MAX + INT_MAX; + uint64_t sec_start =3D sector_number; + uint64_t sec_count =3D nr_sectors; + uint64_t byte_remaining; + uint64_t limit =3D BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS; + + /* Wrap around? */ + if ((sec_start + sec_count) < sec_count) + return false; + /* Overflowing byte limit? */ + if ((sec_start + sec_count) > (byte_limit >> BDRV_SECTOR_BITS)) + return false; + + byte_offset =3D sec_start << BDRV_SECTOR_BITS; + byte_remaining =3D sec_count << BDRV_SECTOR_BITS; + do { + bytes =3D byte_remaining > limit ? limit : byte_remaining; + ioreq->aio_inflight++; + blk_aio_pdiscard(blkdev->blk, byte_offset, bytes, + qemu_aio_complete, ioreq); + byte_remaining -=3D bytes; + byte_offset +=3D bytes; + } while (byte_remaining > 0); + + return true; +} + static int ioreq_runio_qemu_aio(struct ioreq *ioreq) { struct XenBlkDev *blkdev =3D ioreq->blkdev; @@ -708,12 +740,9 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq) break; case BLKIF_OP_DISCARD: { - struct blkif_request_discard *discard_req =3D (void *)&ioreq->req; - ioreq->aio_inflight++; - blk_aio_pdiscard(blkdev->blk, - discard_req->sector_number << BDRV_SECTOR_BITS, - discard_req->nr_sectors << BDRV_SECTOR_BITS, - qemu_aio_complete, ioreq); + struct blkif_request_discard *req =3D (void *)&ioreq->req; + if (blk_split_discard(ioreq, req->sector_number, req->nr_sectors)) + goto err; break; } default: Olaf --GvXjxJ+pjyke8COw Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iEYEARECAAYFAlgt2mcACgkQXUKg+qaYNn5cFACgjIFhQl5d8V/FFxKv9sc9Sj0o cm4AoNlE55oYb+5aWMNSnp+4gsDMjQ3H =yHB1 -----END PGP SIGNATURE----- --GvXjxJ+pjyke8COw--