From nobody Tue Nov 11 01:39:40 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.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; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com ARC-Seal: i=1; a=rsa-sha256; t=1560876040; cv=none; d=zoho.com; s=zohoarc; b=TtkOSu+/U5NCAKyTQNaG9NVjRjCB7htFY3h0uR5heyuaxkgrdGg+QytJAg5NrJ4TSTVSy3PoOKzMX3ynYBial0LCrk59MF83xw8M2x+JHeMRiGbtHBGlZGcwN/DADZ89i86zATGte6JIpYgWdi7eVSZLrzzZnU8D1QhARWlghGY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1560876040; h=Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=lj9349eOQeNx+/H/iLKWW/YH/MC7dXsKy3cD19aYRSg=; b=gBT6IYM42LtlHhH/RI5yJ7rHmhFx5CxyE4jd3xQhl+qF4tYBKLoLBImSvc4gE2heQNvfNp3dY1OIoKnIeFheUmY34PAf1Ta9WQrenkHbFgxMLvV5Q9wP68egLdn9IQ2mFrdADZ/w1r9m852siBM1ZH7/RVOyqbynUzv4F5GR75Y= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1560876040968132.09777253318964; Tue, 18 Jun 2019 09:40:40 -0700 (PDT) Received: from localhost ([::1]:59734 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdH9z-0002Wp-RD for importer@patchew.org; Tue, 18 Jun 2019 12:40:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34201) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdGFe-0007QF-5m for qemu-devel@nongnu.org; Tue, 18 Jun 2019 11:42:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hdGFX-0005rU-5M for qemu-devel@nongnu.org; Tue, 18 Jun 2019 11:42:22 -0400 Received: from relay.sw.ru ([185.231.240.75]:38512) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hdGFT-0005VY-BY; Tue, 18 Jun 2019 11:42:17 -0400 Received: from [10.94.3.0] (helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92) (envelope-from ) id 1hdGFH-0002Sc-Jm; Tue, 18 Jun 2019 18:42:03 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-devel@nongnu.org, qemu-block@nongnu.org Date: Tue, 18 Jun 2019 18:42:00 +0300 Message-Id: <20190618154202.89107-2-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20190618154202.89107-1-vsementsov@virtuozzo.com> References: <20190618154202.89107-1-vsementsov@virtuozzo.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 185.231.240.75 Subject: [Qemu-devel] [PATCH v2 1/3] block: implement BDRV_REQ_PREFETCH 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, fam@euphon.net, vsementsov@virtuozzo.com, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org, jsnow@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Do effective copy-on-read request when we don't need data actually. It will be used for block-stream and NBD_CMD_CACHE. Signed-off-by: Vladimir Sementsov-Ogievskiy --- include/block/block.h | 8 +++++++- block/io.c | 18 ++++++++++++------ 2 files changed, 19 insertions(+), 7 deletions(-) diff --git a/include/block/block.h b/include/block/block.h index f9415ed740..a063ee135b 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -88,8 +88,14 @@ typedef enum { * fallback. */ BDRV_REQ_NO_FALLBACK =3D 0x100, =20 + /* + * BDRV_REQ_PREFETCH may be used only together with BDRV_REQ_COPY_ON_R= EAD + * on read request and means that caller don't really need data to be + * written to qiov parameter which may be NULL. + */ + BDRV_REQ_PREFETCH =3D 0x200, /* Mask of valid flags */ - BDRV_REQ_MASK =3D 0x1ff, + BDRV_REQ_MASK =3D 0x3ff, } BdrvRequestFlags; =20 typedef struct BlockSizes { diff --git a/block/io.c b/block/io.c index 9ba1bada36..a232243de3 100644 --- a/block/io.c +++ b/block/io.c @@ -1104,7 +1104,8 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, = uint64_t offset, } =20 static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child, - int64_t offset, unsigned int bytes, QEMUIOVector *qiov) + int64_t offset, unsigned int bytes, QEMUIOVector *qiov, + int flags) { BlockDriverState *bs =3D child->bs; =20 @@ -1215,9 +1216,11 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(Bdr= vChild *child, goto err; } =20 - qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes, - pnum - skip_bytes); - } else { + if (!(flags & BDRV_REQ_PREFETCH)) { + qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_b= ytes, + pnum - skip_bytes); + } + } else if (!(flags & BDRV_REQ_PREFETCH)) { /* Read directly into the destination */ qemu_iovec_init(&local_qiov, qiov->niov); qemu_iovec_concat(&local_qiov, qiov, progress, pnum - skip_byt= es); @@ -1268,7 +1271,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild= *child, * potential fallback support, if we ever implement any read flags * to pass through to drivers. For now, there aren't any * passthrough flags. */ - assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ))); + assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ | + BDRV_REQ_PREFETCH))); =20 /* Handle Copy on Read and associated serialisation */ if (flags & BDRV_REQ_COPY_ON_READ) { @@ -1296,7 +1300,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild= *child, } =20 if (!ret || pnum !=3D bytes) { - ret =3D bdrv_co_do_copy_on_readv(child, offset, bytes, qiov); + ret =3D bdrv_co_do_copy_on_readv(child, offset, bytes, qiov, f= lags); + goto out; + } else if (flags & BDRV_REQ_PREFETCH) { goto out; } } --=20 2.18.0 From nobody Tue Nov 11 01:39:40 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.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; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com ARC-Seal: i=1; a=rsa-sha256; t=1560875099; cv=none; d=zoho.com; s=zohoarc; b=DddYpF2sydoIdymUjXFe2ZXSqB2w40yyATJbtfLjTSopFlaizwSQcBlX1id5ljfSSP8HA2yIO2AsFPDUOKRvnqrs++SnWHXDfRRxGmgFV1teiSQl/cYipPSdglfusbc0CmdQQaPOjtdhlpOpBt9ogPrwGixPw4PagGcQ52ifO4c= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1560875099; h=Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=eEnh/7YypT5sIm7e6f+MfbzStchEyhQQai+JX11gR/o=; b=gm58L+KqFYhd5TlxUq/RBIgj9IzpOXL3IuuHg1FPaF3styKuamr+8Htvk/7E4aZvprUyo4L3bXVLjIYMYSfOqgHZFcqSdlG8k+Rzgl+pNX8XS6Nsuyv7stvwVifiwnszXxcc1D23mhRly5af82aoWEtTXcANWiDJoRZeH0J5K8k= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1560875099914177.14715275450874; Tue, 18 Jun 2019 09:24:59 -0700 (PDT) Received: from localhost ([::1]:59542 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdGui-0003gi-VQ for importer@patchew.org; Tue, 18 Jun 2019 12:24:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34215) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdGFf-0007QI-M5 for qemu-devel@nongnu.org; Tue, 18 Jun 2019 11:42:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hdGFY-0005vE-Ti for qemu-devel@nongnu.org; Tue, 18 Jun 2019 11:42:24 -0400 Received: from relay.sw.ru ([185.231.240.75]:38517) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hdGFT-0005Vb-Bx; Tue, 18 Jun 2019 11:42:17 -0400 Received: from [10.94.3.0] (helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92) (envelope-from ) id 1hdGFH-0002Sc-OG; Tue, 18 Jun 2019 18:42:03 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-devel@nongnu.org, qemu-block@nongnu.org Date: Tue, 18 Jun 2019 18:42:01 +0300 Message-Id: <20190618154202.89107-3-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20190618154202.89107-1-vsementsov@virtuozzo.com> References: <20190618154202.89107-1-vsementsov@virtuozzo.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 185.231.240.75 Subject: [Qemu-devel] [PATCH v2 2/3] block/stream: use BDRV_REQ_PREFETCH 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, fam@euphon.net, vsementsov@virtuozzo.com, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org, jsnow@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" This helps to avoid extra io, allocations and memory copying. Signed-off-by: Vladimir Sementsov-Ogievskiy --- block/stream.c | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-) diff --git a/block/stream.c b/block/stream.c index 1a906fd860..b316bfb290 100644 --- a/block/stream.c +++ b/block/stream.c @@ -22,11 +22,11 @@ =20 enum { /* - * Size of data buffer for populating the image file. This should be = large + * Maximum chunk size to feed it to copy-on-read. This should be large * enough to process multiple clusters in a single call, so that popul= ating * contiguous regions of the image is efficient. */ - STREAM_BUFFER_SIZE =3D 512 * 1024, /* in bytes */ + STREAM_CHUNK =3D 512 * 1024, /* in bytes */ }; =20 typedef struct StreamBlockJob { @@ -39,13 +39,12 @@ typedef struct StreamBlockJob { } StreamBlockJob; =20 static int coroutine_fn stream_populate(BlockBackend *blk, - int64_t offset, uint64_t bytes, - void *buf) + int64_t offset, uint64_t bytes) { assert(bytes < SIZE_MAX); =20 - /* Copy-on-read the unallocated clusters */ - return blk_co_pread(blk, offset, bytes, buf, BDRV_REQ_COPY_ON_READ); + return blk_co_preadv(blk, offset, bytes, NULL, + BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH); } =20 static void stream_abort(Job *job) @@ -117,7 +116,6 @@ static int coroutine_fn stream_run(Job *job, Error **er= rp) int error =3D 0; int ret =3D 0; int64_t n =3D 0; /* bytes */ - void *buf; =20 if (!bs->backing) { goto out; @@ -130,8 +128,6 @@ static int coroutine_fn stream_run(Job *job, Error **er= rp) } job_progress_set_remaining(&s->common.job, len); =20 - buf =3D qemu_blockalign(bs, STREAM_BUFFER_SIZE); - /* Turn on copy-on-read for the whole block device so that guest read * requests help us make progress. Only do this when copying the enti= re * backing chain since the copy-on-read operation does not take base i= nto @@ -154,7 +150,7 @@ static int coroutine_fn stream_run(Job *job, Error **er= rp) =20 copy =3D false; =20 - ret =3D bdrv_is_allocated(bs, offset, STREAM_BUFFER_SIZE, &n); + ret =3D bdrv_is_allocated(bs, offset, STREAM_CHUNK, &n); if (ret =3D=3D 1) { /* Allocated in the top, no need to copy. */ } else if (ret >=3D 0) { @@ -172,7 +168,7 @@ static int coroutine_fn stream_run(Job *job, Error **er= rp) } trace_stream_one_iteration(s, offset, n, ret); if (copy) { - ret =3D stream_populate(blk, offset, n, buf); + ret =3D stream_populate(blk, offset, n); } if (ret < 0) { BlockErrorAction action =3D @@ -206,8 +202,6 @@ static int coroutine_fn stream_run(Job *job, Error **er= rp) /* Do not remove the backing file if an error was there but ignored. = */ ret =3D error; =20 - qemu_vfree(buf); - out: /* Modify backing chain and close BDSes in main loop */ return ret; --=20 2.18.0 From nobody Tue Nov 11 01:39:40 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.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; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com ARC-Seal: i=1; a=rsa-sha256; t=1560876177; cv=none; d=zoho.com; s=zohoarc; b=fuFlrntolvfjknK2A1QfQ/xiAv2Aym1OJnXLawqMBcZz9Ng62qX9o+OvX61Urczno2nfqIM2NdLp+g+eVCNXNVtZnI/58RgktqCt3TJFs5sxDReNNGK8IAxUc2zoLuoe66I/44/ahGI6wClEHhWISOUU2JA76mir8byFUFZOgRQ= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1560876177; h=Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=/BXE+mGcyU67TCjFKEGCHHkC8gpSyrcWqOk6LbdpX5o=; b=l3SwiTgvpQVApgJZrxEvnPWTtEFYCSNXOn5rLXroycKj5jrrqh7atEEV9xiU+0ykXgnTeWmb1WXygIc8/OQ03ofKP8umAsDa3aJm24tZmqF9dbCcIl7Nwp3DUOy1zzak4T9ZrNH/qdMVOfjsOyAoxXswVsm5pi0iSd+AElcmgj4= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1560876177656173.46414913826686; Tue, 18 Jun 2019 09:42:57 -0700 (PDT) Received: from localhost ([::1]:59738 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdHC8-0004JD-IO for importer@patchew.org; Tue, 18 Jun 2019 12:42:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34217) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdGFf-0007QK-M5 for qemu-devel@nongnu.org; Tue, 18 Jun 2019 11:42:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hdGFY-0005vL-US for qemu-devel@nongnu.org; Tue, 18 Jun 2019 11:42:24 -0400 Received: from relay.sw.ru ([185.231.240.75]:38504) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hdGFT-0005VZ-AZ; Tue, 18 Jun 2019 11:42:17 -0400 Received: from [10.94.3.0] (helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92) (envelope-from ) id 1hdGFI-0002Sc-2i; Tue, 18 Jun 2019 18:42:04 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-devel@nongnu.org, qemu-block@nongnu.org Date: Tue, 18 Jun 2019 18:42:02 +0300 Message-Id: <20190618154202.89107-4-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20190618154202.89107-1-vsementsov@virtuozzo.com> References: <20190618154202.89107-1-vsementsov@virtuozzo.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 185.231.240.75 Subject: [Qemu-devel] [PATCH v2 3/3] nbd: improve CMD_CACHE: use blk_co_pcache 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, fam@euphon.net, vsementsov@virtuozzo.com, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org, jsnow@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" This helps to avoid extra io, allocations and memory copying. We assume here that CMD_CACHE is always used with copy-on-read, as otherwise it's a noop. Signed-off-by: Vladimir Sementsov-Ogievskiy --- nbd/server.c | 43 +++++++++++++++++++++++++++++++++++-------- 1 file changed, 35 insertions(+), 8 deletions(-) diff --git a/nbd/server.c b/nbd/server.c index aeca3893fe..6048257872 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -2101,12 +2101,15 @@ static int nbd_co_receive_request(NBDRequestData *r= eq, NBDRequest *request, return -EINVAL; } =20 - req->data =3D blk_try_blockalign(client->exp->blk, request->len); - if (req->data =3D=3D NULL) { - error_setg(errp, "No memory"); - return -ENOMEM; + if (request->type !=3D NBD_CMD_CACHE) { + req->data =3D blk_try_blockalign(client->exp->blk, request->le= n); + if (req->data =3D=3D NULL) { + error_setg(errp, "No memory"); + return -ENOMEM; + } } } + if (request->type =3D=3D NBD_CMD_WRITE) { if (nbd_read(client->ioc, req->data, request->len, "CMD_WRITE data= ", errp) < 0) @@ -2191,7 +2194,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *cl= ient, NBDRequest *request, int ret; NBDExport *exp =3D client->exp; =20 - assert(request->type =3D=3D NBD_CMD_READ || request->type =3D=3D NBD_C= MD_CACHE); + assert(request->type =3D=3D NBD_CMD_READ); =20 /* XXX: NBD Protocol only documents use of FUA with WRITE */ if (request->flags & NBD_CMD_FLAG_FUA) { @@ -2203,7 +2206,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *cl= ient, NBDRequest *request, } =20 if (client->structured_reply && !(request->flags & NBD_CMD_FLAG_DF) && - request->len && request->type !=3D NBD_CMD_CACHE) + request->len) { return nbd_co_send_sparse_read(client, request->handle, request->f= rom, data, request->len, errp); @@ -2211,7 +2214,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *cl= ient, NBDRequest *request, =20 ret =3D blk_pread(exp->blk, request->from + exp->dev_offset, data, request->len); - if (ret < 0 || request->type =3D=3D NBD_CMD_CACHE) { + if (ret < 0) { return nbd_send_generic_reply(client, request->handle, ret, "reading from file failed", errp); } @@ -2230,6 +2233,28 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *c= lient, NBDRequest *request, } } =20 +/* + * nbd_do_cmd_cache + * + * Handle NBD_CMD_CACHE request. + * Return -errno if sending fails. Other errors are reported directly to t= he + * client as an error reply. + */ +static coroutine_fn int nbd_do_cmd_cache(NBDClient *client, NBDRequest *re= quest, + Error **errp) +{ + int ret; + NBDExport *exp =3D client->exp; + + assert(request->type =3D=3D NBD_CMD_CACHE); + + ret =3D blk_co_preadv(exp->blk, request->from + exp->dev_offset, reque= st->len, + NULL, BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH); + + return nbd_send_generic_reply(client, request->handle, ret, + "caching data failed", errp); +} + /* Handle NBD request. * Return -errno if sending fails. Other errors are reported directly to t= he * client as an error reply. */ @@ -2243,8 +2268,10 @@ static coroutine_fn int nbd_handle_request(NBDClient= *client, char *msg; =20 switch (request->type) { - case NBD_CMD_READ: case NBD_CMD_CACHE: + return nbd_do_cmd_cache(client, request, errp); + + case NBD_CMD_READ: return nbd_do_cmd_read(client, request, data, errp); =20 case NBD_CMD_WRITE: --=20 2.18.0