From patchwork Mon Jan 31 10:43:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Richard Weinberger X-Patchwork-Id: 12730530 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F08EC433EF for ; Mon, 31 Jan 2022 10:44:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358312AbiAaKol convert rfc822-to-8bit (ORCPT ); Mon, 31 Jan 2022 05:44:41 -0500 Received: from lithops.sigma-star.at ([195.201.40.130]:49222 "EHLO lithops.sigma-star.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358302AbiAaKoi (ORCPT ); Mon, 31 Jan 2022 05:44:38 -0500 Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 6B35162DA602; Mon, 31 Jan 2022 11:44:36 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 1fnoSIhD0zBR; Mon, 31 Jan 2022 11:44:35 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id D77AB614E2EF; Mon, 31 Jan 2022 11:44:35 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id BxBA7hyQ9sBy; Mon, 31 Jan 2022 11:44:35 +0100 (CET) Received: from blindfold.corp.sigma-star.at (213-47-184-186.cable.dynamic.surfer.at [213.47.184.186]) by lithops.sigma-star.at (Postfix) with ESMTPSA id 5229562DA602; Mon, 31 Jan 2022 11:44:35 +0100 (CET) From: Richard Weinberger To: linux-nfs@vger.kernel.org Cc: bfields@fieldses.org, luis.turcitu@appsbroker.com, chris.chilvers@appsbroker.com, david.young@appsbroker.com, daire@dneg.com, david.oberhollenzer@sigma-star.at, david@sigma-star.at, goliath@sigma-star.at, trond.myklebust@hammerspace.com, anna.schumaker@netapp.com, Richard Weinberger Subject: [RFC PATCH] mountd: export: Deal with NFS filesystems Date: Mon, 31 Jan 2022 11:43:16 +0100 Message-Id: <20220131104316.10357-1-richard@nod.at> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org When a NFS filesystem is exported usually NFSD refuses to export the filesystem because mountd was unable to provide an UUID and the kernel cannot derive a dev id from the NFS client super block. To deal with this situation, teach uuid_by_path() how to generate an UUID from a NFS filesystem. Using /proc/fs/nfsfs/volumes it is possible to find the NFS fsid from the backend and use it as seed for mountd's UUID mechanism. Signed-off-by: Richard Weinberger --- Hello, This is the userspace side to make cross mounts work for NFS re-exports. The basic idea is that mountd takes the NFS fsid from the backend server and feeds into mountd'd existing UUID mechanism. Getting the NFS fsid is currently a bit clumsy, mountd has to scan /proc/fs/nfsfs/volumes. With the upcoming fsinfo() system call this information could be transferred in a much simpler way. e.g. NFS client stores the fsid in its sb->s_uuid and fsinfo() exposes sb->s_uuid to userspace. This approach works for v3-to-v4 and v4-to-v4 re-exports. v3-to-v3 does *not* work, the reason is that nfs_encode_fh() aborts due to not enough space in the fhandle. I'm still investigating on how to improve this case. Currently I’m toying around with a NFS fsid to export FSID_NUM mappings scheme which are stored to disk. Another possibility is a new fsid type for NFSD, where the raw NFS fsid from the backend server is mirrored. Although such a mirror mode makes local exports impossible. At the end of the day this is something the admin has to decide. I don't think there will be a generic solution which satisfies all needs. Looking forward for your feedback. :-) Thanks, //richard --- support/export/cache.c | 65 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 61 insertions(+), 4 deletions(-) diff --git a/support/export/cache.c b/support/export/cache.c index a5823e92e9f2..053ad86619b8 100644 --- a/support/export/cache.c +++ b/support/export/cache.c @@ -331,6 +331,51 @@ static const unsigned long nonblkid_filesystems[] = { 0 /* last */ }; +static int get_uuid_from_fsid(char *path, char *uuid_str, size_t len) +{ + unsigned int min_dev, maj_dev, min_fsid, maj_fsid; + int rc, n, found = 0, header_seen = 0; + struct stat stb; + FILE *nfsfs_fd; + char line[128]; + + rc = nfsd_path_stat(path, &stb); + if (rc) { + xlog(L_WARNING, "Unable to stat %s", path); + return 0; + } + + nfsfs_fd = fopen("/proc/fs/nfsfs/volumes", "r"); + if (nfsfs_fd == NULL) { + xlog(L_WARNING, "Unable to open nfsfs volume file: %m"); + return 0; + } + + while (fgets(line, sizeof(line), nfsfs_fd) != NULL) { + if (!header_seen) { + header_seen = 1; + continue; + } + n = sscanf(line, "v%*u %*x %*u %u:%u %x:%x %*s", &maj_dev, + &min_dev, &maj_fsid, &min_fsid); + + if (n != 4) { + xlog(L_WARNING, "Unable to parse nfsfs volume line: %d, %s", n, line); + continue; + } + + if (makedev(maj_dev, min_dev) == stb.st_dev) { + found = 1; + snprintf(uuid_str, len, "%08x%08x", maj_fsid, min_fsid); + break; + } + } + + fclose(nfsfs_fd); + + return found; +} + static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid) { /* get a uuid for the filesystem found at 'path'. @@ -362,7 +407,7 @@ static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid) */ struct statfs64 st; char fsid_val[17]; - const char *blkid_val = NULL; + const char *fsuuid_val = NULL; const char *val; int rc; @@ -375,7 +420,19 @@ static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid) break; } if (*bad == 0) - blkid_val = get_uuid_blkdev(path); + fsuuid_val = get_uuid_blkdev(path); + else if (*bad == 0x6969 /* NFS_SUPER_MAGIC */) { + char tmp[17]; + int ret = get_uuid_from_fsid(path, tmp, sizeof(tmp)); + + if (ret < 0) { + xlog(L_WARNING, "Unable to read nfsfs volume file: %i", ret); + } else if (ret == 0) { + xlog(L_WARNING, "Unable to find nfsfs volume entry for %s", path); + } else { + fsuuid_val = tmp; + } + } } if (rc == 0 && @@ -385,8 +442,8 @@ static int uuid_by_path(char *path, int type, size_t uuidlen, char *uuid) else fsid_val[0] = 0; - if (blkid_val && (type--) == 0) - val = blkid_val; + if (fsuuid_val && (type--) == 0) + val = fsuuid_val; else if (fsid_val[0] && (type--) == 0) val = fsid_val; else