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bh=c24n6h4cZyn1238lp8INnIalpufCghBolGU2T98Z3MA=; b=av4ny38gIJqvwDT1txTQokg8sJVjyAtUzFaO344PcPOy14pIjlTdBtxBq/cCZgDXn1vLlt 2KOvLiQ08mu24100bJWdyvmMWZP/UpLNU9+Ey6wg9vW7W5Rkjdwci296iA/Y7br2TCbsTL 4+7HF15ooXD4E30D+JltuPcAcUA/pbk= X-MC-Unique: ocn7J748O26i7xOx8RDGrw-1 From: Emanuele Giuseppe Esposito To: qemu-block@nongnu.org Cc: Kevin Wolf , Hanna Reitz , Ninad Palsule , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, Emanuele Giuseppe Esposito Subject: [PATCH] block/file-posix: don't use functions calling AIO_WAIT_WHILE in worker threads Date: Thu, 9 Feb 2023 10:45:22 -0500 Message-Id: <20230209154522.1164401-1-eesposit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 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=eesposit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: 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: 1675957591921100001 Content-Type: text/plain; charset="utf-8" When calling bdrv_getlength() in handle_aiocb_write_zeroes(), the function creates a new coroutine and then waits that it finishes using AIO_WAIT_WHILE. The problem is that this function could also run in a worker thread, that has a different AioContext from main loop and iothreads, therefore in AIO_WAIT_WHILE we will have in_aio_context_home_thread(ctx) =3D=3D false and therefore assert(qemu_get_current_aio_context() =3D=3D qemu_get_aio_context()); in the else branch will fail, crashing QEMU. Aside from that, bdrv_getlength() is wrong also conceptually, because it reads the BDS graph from another thread and is not protected by any lock. Replace it with raw_co_getlength, that doesn't create a coroutine and doesn't read the BDS graph. Signed-off-by: Emanuele Giuseppe Esposito Reported-by: Ninad Palsule Suggested-by: Kevin Wolf --- block/file-posix.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/file-posix.c b/block/file-posix.c index d3073a7caa..9a99111f45 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1738,7 +1738,7 @@ static int handle_aiocb_write_zeroes(void *opaque) #ifdef CONFIG_FALLOCATE /* Last resort: we are trying to extend the file with zeroed data. This * can be done via fallocate(fd, 0) */ - len =3D bdrv_getlength(aiocb->bs); + len =3D raw_co_getlength(aiocb->bs); if (s->has_fallocate && len >=3D 0 && aiocb->aio_offset >=3D len) { int ret =3D do_fallocate(s->fd, 0, aiocb->aio_offset, aiocb->aio_n= bytes); if (ret =3D=3D 0 || ret !=3D -ENOTSUP) { --=20 2.39.1