From patchwork Tue Mar 15 10:08:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Schoenebeck X-Patchwork-Id: 12781268 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C6ACAC433F5 for ; Tue, 15 Mar 2022 10:30:13 +0000 (UTC) Received: from localhost ([::1]:55080 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nU4RQ-0006Zq-W2 for qemu-devel@archiver.kernel.org; Tue, 15 Mar 2022 06:30:13 -0400 Received: from eggs.gnu.org ([209.51.188.92]:47216) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nU4Ki-0007aZ-06 for qemu-devel@nongnu.org; Tue, 15 Mar 2022 06:23:16 -0400 Received: from lizzy.crudebyte.com ([91.194.90.13]:57679) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nU4Kg-0004I5-5x for qemu-devel@nongnu.org; Tue, 15 Mar 2022 06:23:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=lizzy; h=Cc:To:Subject:Date:From:References:In-Reply-To: Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Content-ID: Content-Description; bh=a0crYNaDR8bFaHuaYpqJ8FipN3b+gvU/VTrR86DztiI=; b=gyYgM 79e+232gGLMbvffVQMTXYCYTCfVEHar+mupQtlrdAlqBhDE6NDPsFx2Su9iLvlDsc4e+hHdg9mHI2 ptpvJWDiG18a7sjaThTsshWccxuTNk3RgphobOFYSET146uB3LxKiI7EyYzGJqMUeqsGA8aQnP37Y 6bX/y0BXHFcMXwPxhcvd+hKuarCpqW1em4/nRVU7jLlas9+3oFg+n2xzIoEZhrHPVywG4iaK9L9aJ x8O6ikt/CJySOLFUGnL9GH60npJ8MOiXYmRWm2P6HgtAvRZaBkfyCY/K9L4YoelNDhtPa1Ki69CZW Hngz5URD8SW5Ct+STMOIRyjbpqEKA==; Message-Id: In-Reply-To: References: From: Christian Schoenebeck Date: Tue, 15 Mar 2022 11:08:39 +0100 Subject: [PATCH v4 5/7] 9pfs: fix 'Twalk' to only send error if no component walked To: qemu-devel@nongnu.org Cc: Greg Kurz Received-SPF: none client-ip=91.194.90.13; envelope-from=bc73e24258a75dc29458024c7936c8a036c3eac5@lizzy.crudebyte.com; helo=lizzy.crudebyte.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Current implementation of 'Twalk' request handling always sends an 'Rerror' response if any error occured. The 9p2000 protocol spec says though: " If the first element cannot be walked for any reason, Rerror is returned. Otherwise, the walk will return an Rwalk message containing nwqid qids corresponding, in order, to the files that are visited by the nwqid successful elementwise walks; nwqid is therefore either nwname or the index of the first elementwise walk that failed. " http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor33 For that reason we are no longer leaving from an error path in function v9fs_walk(), unless really no path component could be walked successfully or if the request has been interrupted. Local variable 'nwalked' counts and reflects the number of path components successfully processed by background I/O thread, whereas local variable 'name_idx' subsequently counts and reflects the number of path components eventually accepted successfully by 9p server controller portion. New local variable 'any_err' is an aggregate variable reflecting whether any error occurred at all, while already existing variable 'err' only reflects the last error. Despite QIDs being delivered to client in a more relaxed way now, it is important to note though that fid still must remain unaffected if any error occurred. Signed-off-by: Christian Schoenebeck Reviewed-by: Greg Kurz --- hw/9pfs/9p.c | 43 +++++++++++++++++++++++++++---------------- 1 file changed, 27 insertions(+), 16 deletions(-) diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 298f4e6548..e770972a71 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -1766,7 +1766,7 @@ static void coroutine_fn v9fs_walk(void *opaque) { int name_idx, nwalked; g_autofree V9fsQID *qids = NULL; - int i, err = 0; + int i, err = 0, any_err = 0; V9fsPath dpath, path; P9ARRAY_REF(V9fsPath) pathes = NULL; uint16_t nwnames; @@ -1832,19 +1832,20 @@ static void coroutine_fn v9fs_walk(void *opaque) * driver code altogether inside the following block. */ v9fs_co_run_in_worker({ + nwalked = 0; if (v9fs_request_cancelled(pdu)) { - err = -EINTR; + any_err |= err = -EINTR; break; } err = s->ops->lstat(&s->ctx, &dpath, &fidst); if (err < 0) { - err = -errno; + any_err |= err = -errno; break; } stbuf = fidst; - for (nwalked = 0; nwalked < nwnames; nwalked++) { + for (; nwalked < nwnames; nwalked++) { if (v9fs_request_cancelled(pdu)) { - err = -EINTR; + any_err |= err = -EINTR; break; } if (!same_stat_id(&pdu->s->root_st, &stbuf) || @@ -1854,16 +1855,16 @@ static void coroutine_fn v9fs_walk(void *opaque) wnames[nwalked].data, &pathes[nwalked]); if (err < 0) { - err = -errno; + any_err |= err = -errno; break; } if (v9fs_request_cancelled(pdu)) { - err = -EINTR; + any_err |= err = -EINTR; break; } err = s->ops->lstat(&s->ctx, &pathes[nwalked], &stbuf); if (err < 0) { - err = -errno; + any_err |= err = -errno; break; } stbufs[nwalked] = stbuf; @@ -1874,12 +1875,12 @@ static void coroutine_fn v9fs_walk(void *opaque) /* * Handle all the rest of this Twalk request on main thread ... */ - if (err < 0) { + if ((err < 0 && !nwalked) || err == -EINTR) { goto out; } - err = stat_to_qid(pdu, &fidst, &qid); - if (err < 0) { + any_err |= err = stat_to_qid(pdu, &fidst, &qid); + if (err < 0 && !nwalked) { goto out; } stbuf = fidst; @@ -1888,20 +1889,29 @@ static void coroutine_fn v9fs_walk(void *opaque) v9fs_path_copy(&dpath, &fidp->path); v9fs_path_copy(&path, &fidp->path); - for (name_idx = 0; name_idx < nwnames; name_idx++) { + for (name_idx = 0; name_idx < nwalked; name_idx++) { if (!same_stat_id(&pdu->s->root_st, &stbuf) || strcmp("..", wnames[name_idx].data)) { stbuf = stbufs[name_idx]; - err = stat_to_qid(pdu, &stbuf, &qid); + any_err |= err = stat_to_qid(pdu, &stbuf, &qid); if (err < 0) { - goto out; + break; } v9fs_path_copy(&path, &pathes[name_idx]); v9fs_path_copy(&dpath, &path); } memcpy(&qids[name_idx], &qid, sizeof(qid)); } + if (any_err < 0) { + if (!name_idx) { + /* don't send any QIDs, send Rlerror instead */ + goto out; + } else { + /* send QIDs (not Rlerror), but fid MUST remain unaffected */ + goto send_qids; + } + } if (fid == newfid) { if (fidp->fid_type != P9_FID_NONE) { err = -EINVAL; @@ -1919,8 +1929,9 @@ static void coroutine_fn v9fs_walk(void *opaque) newfidp->uid = fidp->uid; v9fs_path_copy(&newfidp->path, &path); } - err = v9fs_walk_marshal(pdu, nwnames, qids); - trace_v9fs_walk_return(pdu->tag, pdu->id, nwnames, qids); +send_qids: + err = v9fs_walk_marshal(pdu, name_idx, qids); + trace_v9fs_walk_return(pdu->tag, pdu->id, name_idx, qids); out: put_fid(pdu, fidp); if (newfidp) {