From nobody Mon Apr 6 18:55:59 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=quarantine dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1773848033; cv=none; d=zohomail.com; s=zohoarc; b=JuMfGfU/WRx9bnqiWrkM1xMjRuPOfBkU0Wr3wgzS/decxo97i/pA4hqedmBCTXL3Iym/gzSLAieqbt2G92PwLNjOqBq8XKpRp8wVik6oBSRjnGYaysCgnPxWLX0VPe3pRW8DEBytoH7daTJ07X75FaF7DbB/AGsu7I4CU7QzhyA= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1773848033; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=uAiGkojcHQ/1SSiJjKjsQUYUlQYXvjhlE4iBA6dpRbk=; b=NE5qQGRdvlTZwN278PVXtWbFYAQAYHB0XjwMc6Ihx9BBXcdww8XC0f/GYEBMgX1WgDR6aiM2dSvsj4U9xyolRe2tj3MjhHCYdLyr8rqqPhxIm6uToAEsB6uPpqtWD9oXwr8EK472HbSmVKFQyz1NdjxI1Pof1HwmT01y48wrvpg= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=quarantine dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1773848033670721.4448551551956; Wed, 18 Mar 2026 08:33:53 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w2ssv-0002Z2-Ll; Wed, 18 Mar 2026 11:32:37 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1w2ssn-0002WH-Eb for qemu-devel@nongnu.org; Wed, 18 Mar 2026 11:32:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1w2ssj-0000OM-EQ for qemu-devel@nongnu.org; Wed, 18 Mar 2026 11:32:28 -0400 Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-344-T2ZuqBELNHOOk7bbtN06QA-1; Wed, 18 Mar 2026 11:32:22 -0400 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4839fc4cef6so12317965e9.0 for ; Wed, 18 Mar 2026 08:32:22 -0700 (PDT) Received: from localhost (p200300cfd737d03304b9bf783d26f60b.dip0.t-ipconnect.de. [2003:cf:d737:d033:4b9:bf78:3d26:f60b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4856eaffbbdsm147563775e9.15.2026.03.18.08.32.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 08:32:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1773847944; 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=uAiGkojcHQ/1SSiJjKjsQUYUlQYXvjhlE4iBA6dpRbk=; b=fUT0Fs+NCLZDP1RUMnyzrPZMrtb0VxZCjcENdBL5TTX66WlyPQywkLcHKbhFDdjWd6ofUO 4kS4JVfk4gfYBbqov5L/9oYv6mGVEyQyI0j6Qemsl6MqYzSHc7Q67Mm3PEJh8jDidUJ0W9 uYdXhoqtAVRK/B74pKQxtZykOR2qRhg= X-MC-Unique: T2ZuqBELNHOOk7bbtN06QA-1 X-Mimecast-MFC-AGG-ID: T2ZuqBELNHOOk7bbtN06QA_1773847941 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1773847941; x=1774452741; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=uAiGkojcHQ/1SSiJjKjsQUYUlQYXvjhlE4iBA6dpRbk=; b=kXmW3niei62ykpPW9pmcjIRdDsMd4l8uqOFFGKjnEVFoSecifcRNXHxFC116ngJeeM qWHaMDgxyPOwSW92V91Xo+xo+vVO/JOor42QvU5keJ8OOpPWseYpV8kRzwpdeQA35Zpn LB54oxqrxyKQB3p4duD42kRAhSN2KSa3l+Qs1qMpFgTvey/Dd9e5CtuLtAvx9ewQhmId P1hJyHi3k9hjjnYDZmtwVtwWQgMyKQSz1Y6chKQL5gPS5mp+Ix/MiMdZusNEkcRugiI/ 1yK/ldAQhOBjrhWyV3EOvOBW4VbbsnqnSrw7vEYmD9c4QUqtBIzp+qmAwOmyxL0QcwJU ZqEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773847941; x=1774452741; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=uAiGkojcHQ/1SSiJjKjsQUYUlQYXvjhlE4iBA6dpRbk=; b=npOp5HBIwhClupTbNq4T4szpbM1ApO7t5GGdzK3dlUzGDiDw2jtr19GQT/jV5iH805 cJQWY9jFdmpoTjaebbk7SEuiHopS7Ij599vfNxAVCTx+nGp379qVamWslFp5PzZPSIWS QzudORzeUBQVWYx3VViNuDl/P1Yr0ZI7C2ZYkvbHmTyb3H8mHzHv03pfAIZpTcM7Qk1S RcLyXzyVFK7qVh/9u5uqjFeQnyguGdIaqdrBGWaTaftma6ZiHTc01bN10OOO05wPQtsd zbygCx4PQRfChz1EzGyGDofeyjfRbVH6+v46tqhTHRTz/avUbpwFd7o9uJZ0EA3kxxxn hPEw== X-Gm-Message-State: AOJu0YyOncJWdDFsM8il98vAQRvQfgcjzwvpoFftqy83qgrt2e0C5XJE hNkSXMQX8FJ5PZGBc34X3m6trY4pJWlt5gN6f3/AHC2gzjNxNlabVQsveqW210fMqruPigasE07 4O/enc9UzCgdj4gzX2x2GP4XfNYlKcGPq6csxiO7f7lG1zvgR0QeId5JU X-Gm-Gg: ATEYQzzVYN05rpAy9zuNZBIk8psNr7Dwlt5Jaw2pSIYrn+nE62OWb+l8UcOub1sEcfh e/0jrBiaFXMF+yLbczxzzwFzJp6i6I1SYYhG1MynLM4TShftZduns8VyAqLW+KH4Ug6Lg/lU5kG i4sMg5Xy3oJr0qG+ZDgpECclRfH/PRM4R3XuzeGo/VCT56kq1FJzg0p05s4LZ42FoIhp9Yc4YIM 1Qx9N3do1z9uwlM/FtGdiZ5OGJxU5MTLMCjU8t0ZMCuoazt6bKT+IAj4zs20CYK7k7Zu3V+hZqk /w/rT4bq3ABIk880HPPos1OwI2WtzbQCMAwXhmNhVA3/0/oWxKkY4bJtxe3Y6RHyP1IeATVeE3x xjjEc7bA9PYLbLL5JhCCLyy+zz4w/oVwtkWHPLy/Uq+hP3HAdOPLJEbJOvPYr4kijfJTTv+h7N1 em+ws= X-Received: by 2002:a05:600c:848d:b0:485:3989:b3e4 with SMTP id 5b1f17b1804b1-486f8b219e0mr519305e9.6.1773847941238; Wed, 18 Mar 2026 08:32:21 -0700 (PDT) X-Received: by 2002:a05:600c:848d:b0:485:3989:b3e4 with SMTP id 5b1f17b1804b1-486f8b219e0mr518775e9.6.1773847940636; Wed, 18 Mar 2026 08:32:20 -0700 (PDT) From: Hanna Czenczek To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Hanna Czenczek , Kevin Wolf , Julia Suvorova , Aarushi Mehta , Stefan Hajnoczi , Stefano Garzarella Subject: [PATCH for-11.0 2/3] linux-aio: Resubmit tails of short reads/writes Date: Wed, 18 Mar 2026 16:32:04 +0100 Message-ID: <20260318153206.171494-3-hreitz@redhat.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260318153206.171494-1-hreitz@redhat.com> References: <20260318153206.171494-1-hreitz@redhat.com> MIME-Version: 1.0 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=170.10.133.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.819, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.903, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1773848036149158500 Content-Type: text/plain; charset="utf-8" Short reads/writes can happen. One way to reproduce them is via our FUSE export, with the following diff applied (%s/escaped // to apply -- if you put plain diffs in commit messages, git-am will apply them, and I would rather avoid breaking FUSE accidentally via this patch): escaped diff --git a/block/export/fuse.c b/block/export/fuse.c escaped index a2a478d293..67dc50a412 100644 escaped --- a/block/export/fuse.c escaped +++ b/block/export/fuse.c @@ -828,7 +828,7 @@ static ssize_t coroutine_fn GRAPH_RDLOCK fuse_co_init(FuseExport *exp, struct fuse_init_out *out, const struct fuse_init_in_compat *in) { - const uint32_t supported_flags =3D FUSE_ASYNC_READ | FUSE_ASYNC_DIO; + const uint32_t supported_flags =3D FUSE_ASYNC_READ; if (in->major !=3D 7) { error_report("FUSE major version mismatch: We have 7, but kernel h= as %" @@ -1060,6 +1060,8 @@ fuse_co_read(FuseExport *exp, void **bufptr, uint64_t= offset, uint32_t size) void *buf; int ret; + size =3D MIN(size, 4096); + /* Limited by max_read, should not happen */ if (size > FUSE_MAX_READ_BYTES) { return -EINVAL; @@ -1110,6 +1112,8 @@ fuse_co_write(FuseExport *exp, struct fuse_write_out = *out, int64_t blk_len; int ret; + size =3D MIN(size, 4096); + QEMU_BUILD_BUG_ON(FUSE_MAX_WRITE_BYTES > BDRV_REQUEST_MAX_BYTES); /* Limited by max_write, should not happen */ if (size > FUSE_MAX_WRITE_BYTES) { Then: $ ./qemu-img create -f raw test.raw 8k Formatting 'test.raw', fmt=3Draw size=3D8192 $ ./qemu-io -f raw -c 'write -P 42 0 8k' test.raw wrote 8192/8192 bytes at offset 0 8 KiB, 1 ops; 00.00 sec (64.804 MiB/sec and 8294.9003 ops/sec) $ hexdump -C test.raw 00000000 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a |**************= **| * 00002000 With aio=3Dthreads, short I/O works: $ storage-daemon/qemu-storage-daemon \ --blockdev file,node-name=3Dtest,filename=3Dtest.raw \ --export fuse,id=3Dexp,node-name=3Dtest,mountpoint=3Dtest.raw,writable= =3Dtrue Other shell: $ ./qemu-io --image-opts -c 'read -P 42 0 8k' \ driver=3Dfile,filename=3Dtest.raw,cache.direct=3Don,aio=3Dthreads read 8192/8192 bytes at offset 0 8 KiB, 1 ops; 00.00 sec (36.563 MiB/sec and 4680.0923 ops/sec) $ ./qemu-io --image-opts -c 'write -P 23 0 8k' \ driver=3Dfile,filename=3Dtest.raw,cache.direct=3Don,aio=3Dthreads wrote 8192/8192 bytes at offset 0 8 KiB, 1 ops; 00.00 sec (35.995 MiB/sec and 4607.2970 ops/sec) $ hexdump -C test.raw 00000000 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 |..............= ..| * 00002000 But with aio=3Dnative, it does not: $ ./qemu-io --image-opts -c 'read -P 23 0 8k' \ driver=3Dfile,filename=3Dtest.raw,cache.direct=3Don,aio=3Dnative Pattern verification failed at offset 0, 8192 bytes read 8192/8192 bytes at offset 0 8 KiB, 1 ops; 00.00 sec (86.155 MiB/sec and 11027.7900 ops/sec) $ ./qemu-io --image-opts -c 'write -P 42 0 8k' \ driver=3Dfile,filename=3Dtest.raw,cache.direct=3Don,aio=3Dnative write failed: No space left on device $ hexdump -C test.raw 00000000 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a 2a |**************= **| * 00001000 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 |..............= ..| * 00002000 This patch fixes that. Signed-off-by: Hanna Czenczek Reviewed-by: Kevin Wolf --- block/linux-aio.c | 61 ++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 53 insertions(+), 8 deletions(-) diff --git a/block/linux-aio.c b/block/linux-aio.c index 1f25339dc9..01621d4794 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -46,6 +46,10 @@ struct qemu_laiocb { size_t nbytes; QEMUIOVector *qiov; =20 + /* For handling short reads/writes */ + size_t total_done; + QEMUIOVector resubmit_qiov; + int type; BdrvRequestFlags flags; uint64_t dev_max_batch; @@ -73,28 +77,61 @@ struct LinuxAioState { }; =20 static void ioq_submit(LinuxAioState *s); +static int laio_do_submit(struct qemu_laiocb *laiocb); =20 static inline ssize_t io_event_ret(struct io_event *ev) { return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res); } =20 +/** + * Retry tail of short requests. + */ +static int laio_resubmit_short_io(struct qemu_laiocb *laiocb, size_t done) +{ + QEMUIOVector *resubmit_qiov =3D &laiocb->resubmit_qiov; + + laiocb->total_done +=3D done; + + if (!resubmit_qiov->iov) { + qemu_iovec_init(resubmit_qiov, laiocb->qiov->niov); + } else { + qemu_iovec_reset(resubmit_qiov); + } + qemu_iovec_concat(resubmit_qiov, laiocb->qiov, + laiocb->total_done, laiocb->nbytes - laiocb->total_d= one); + + return laio_do_submit(laiocb); +} + /* * Completes an AIO request. */ static void qemu_laio_process_completion(struct qemu_laiocb *laiocb) { - int ret; + ssize_t ret; =20 ret =3D laiocb->ret; if (ret !=3D -ECANCELED) { - if (ret =3D=3D laiocb->nbytes) { + if (ret =3D=3D laiocb->nbytes - laiocb->total_done) { ret =3D 0; + } else if (ret > 0 && (laiocb->type =3D=3D QEMU_AIO_READ || + laiocb->type =3D=3D QEMU_AIO_WRITE)) { + ret =3D laio_resubmit_short_io(laiocb, ret); + if (!ret) { + return; + } } else if (ret >=3D 0) { - /* Short reads mean EOF, pad with zeros. */ + /* + * For normal reads and writes, we only get here if ret =3D=3D= 0, which + * means EOF for reads and ENOSPC for writes. + * For zone-append, we get here with any ret >=3D 0, which we = just + * treat as ENOSPC, too (safer than resubmitting, probably, bu= t not + * 100 % clear). + */ if (laiocb->type =3D=3D QEMU_AIO_READ) { - qemu_iovec_memset(laiocb->qiov, ret, 0, - laiocb->qiov->size - ret); + qemu_iovec_memset(laiocb->qiov, laiocb->total_done, 0, + laiocb->qiov->size - laiocb->total_done); } else { ret =3D -ENOSPC; } @@ -102,6 +139,7 @@ static void qemu_laio_process_completion(struct qemu_la= iocb *laiocb) } =20 laiocb->ret =3D ret; + qemu_iovec_destroy(&laiocb->resubmit_qiov); =20 /* * If the coroutine is already entered it must be in ioq_submit() and @@ -380,23 +418,30 @@ static int laio_do_submit(struct qemu_laiocb *laiocb) int fd =3D laiocb->fd; off_t offset =3D laiocb->offset; =20 + if (laiocb->resubmit_qiov.iov) { + qiov =3D &laiocb->resubmit_qiov; + } + switch (laiocb->type) { case QEMU_AIO_WRITE: #ifdef HAVE_IO_PREP_PWRITEV2 { int laio_flags =3D (laiocb->flags & BDRV_REQ_FUA) ? RWF_DSYNC : 0; - io_prep_pwritev2(iocbs, fd, qiov->iov, qiov->niov, offset, laio_fl= ags); + io_prep_pwritev2(iocbs, fd, qiov->iov, qiov->niov, + offset + laiocb->total_done, laio_flags); } #else assert(laiocb->flags =3D=3D 0); - io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset); + io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, + offset + laiocb->total_done); #endif break; case QEMU_AIO_ZONE_APPEND: io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset); break; case QEMU_AIO_READ: - io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset); + io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, + offset + laiocb->total_done); break; case QEMU_AIO_FLUSH: io_prep_fdsync(iocbs, fd); --=20 2.53.0