From patchwork Fri Aug 13 01:45:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 12434499 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E2E1C432BE for ; Fri, 13 Aug 2021 01:45:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2EC46610CC for ; Fri, 13 Aug 2021 01:45:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238288AbhHMBqK (ORCPT ); Thu, 12 Aug 2021 21:46:10 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:47116 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238266AbhHMBqJ (ORCPT ); Thu, 12 Aug 2021 21:46:09 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id CB45F1FF80; Fri, 13 Aug 2021 01:45:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1628819142; h=from:from:reply-to: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=LamDGYFppAFdL7WCvYoQSTIDfJ7v5NOZ+rmKtnq+i8o=; b=ApNf9lb0Q7HdntXHacOQkOGQ6oxP2VJSVLUgv8JqWyY124KVBpb/BNVeIFlY934SZ5w9mO VYHg2stE4hINYwm9bH3C0TPkq2apKhKCUAo9ld4owkRzFcSHdH5xfL/pr4fU7tNsnSHhxi davfFx52nHTYCzSm3sfjlUJI+QA+tZI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1628819142; h=from:from:reply-to: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=LamDGYFppAFdL7WCvYoQSTIDfJ7v5NOZ+rmKtnq+i8o=; b=auLJcE/GO4pW3gWrYHGNqNuOeSqcgRU5a5HQnGqpFj2lGLJhXsvARY6SDS/oQmRHrej/On mZRsHneH0bhQufDw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id E2F9113BB4; Fri, 13 Aug 2021 01:45:39 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id POzTJ8POFWEWIAAAMHmgww (envelope-from ); Fri, 13 Aug 2021 01:45:39 +0000 MIME-Version: 1.0 From: "NeilBrown" To: "Christoph Hellwig" , "Josef Bacik" , "J. Bruce Fields" , "Chuck Lever" , "Chris Mason" , "David Sterba" , "Alexander Viro" Cc: linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-btrfs@vger.kernel.org Subject: [PATCH] VFS/BTRFS/NFSD: provide more unique inode number for btrfs export In-reply-to: <162742539595.32498.13687924366155737575.stgit@noble.brown> References: <162742539595.32498.13687924366155737575.stgit@noble.brown> Date: Fri, 13 Aug 2021 11:45:36 +1000 Message-id: <162881913686.1695.12479588032010502384@noble.neil.brown.name> Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [[This patch is a minimal patch which addresses the current problems with nfsd and btrfs, in a way which I think is most supportable, least surprising, and least likely to impact any future attempts to more completely fix the btrfs file-identify problem]] BTRFS does not provide unique inode numbers across a filesystem. It *does* provide unique inode numbers with a subvolume and uses synthetic device numbers for different subvolumes to ensure uniqueness for device+inode. nfsd cannot use these varying device numbers. If nfsd were to synthesise different stable filesystem ids to give to the client, that would cause subvolumes to appear in the mount table on the client, even though they don't appear in the mount table on the server. Also, NFSv3 doesn't support changing the filesystem id without a new explicit mount on the client (this is partially supported in practice, but violates the protocol specification). So currently, the roots of all subvolumes report the same inode number in the same filesystem to NFS clients and tools like 'find' notice that a directory has the same identity as an ancestor, and so refuse to enter that directory. This patch allows btrfs (or any filesystem) to provide a 64bit number that can be xored with the inode number to make the number more unique. Rather than the client being certain to see duplicates, with this patch it is possible but extremely rare. The number than btrfs provides is a swab64() version of the subvolume identifier. This has most entropy in the high bits (the low bits of the subvolume identifer), while the inoe has most entropy in the low bits. The result will always be unique within a subvolume, and will almost always be unique across the filesystem. Signed-off-by: NeilBrown Acked-by: Josef Bacik --- fs/btrfs/inode.c | 4 ++++ fs/nfsd/nfs3xdr.c | 17 ++++++++++++++++- fs/nfsd/nfs4xdr.c | 9 ++++++++- fs/nfsd/xdr3.h | 2 ++ include/linux/stat.h | 17 +++++++++++++++++ 5 files changed, 47 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 0117d867ecf8..989fdf2032d5 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -9195,6 +9195,10 @@ static int btrfs_getattr(struct user_namespace *mnt_userns, generic_fillattr(&init_user_ns, inode, stat); stat->dev = BTRFS_I(inode)->root->anon_dev; + if (BTRFS_I(inode)->root->root_key.objectid != BTRFS_FS_TREE_OBJECTID) + stat->ino_uniquifier = + swab64(BTRFS_I(inode)->root->root_key.objectid); + spin_lock(&BTRFS_I(inode)->lock); delalloc_bytes = BTRFS_I(inode)->new_delalloc_bytes; inode_bytes = inode_get_bytes(inode); diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c index 0a5ebc52e6a9..669e2437362a 100644 --- a/fs/nfsd/nfs3xdr.c +++ b/fs/nfsd/nfs3xdr.c @@ -340,6 +340,7 @@ svcxdr_encode_fattr3(struct svc_rqst *rqstp, struct xdr_stream *xdr, { struct user_namespace *userns = nfsd_user_namespace(rqstp); __be32 *p; + u64 ino; u64 fsid; p = xdr_reserve_space(xdr, XDR_UNIT * 21); @@ -377,7 +378,10 @@ svcxdr_encode_fattr3(struct svc_rqst *rqstp, struct xdr_stream *xdr, p = xdr_encode_hyper(p, fsid); /* fileid */ - p = xdr_encode_hyper(p, stat->ino); + ino = stat->ino; + if (stat->ino_uniquifier && stat->ino_uniquifier != ino) + ino ^= stat->ino_uniquifier; + p = xdr_encode_hyper(p, ino); p = encode_nfstime3(p, &stat->atime); p = encode_nfstime3(p, &stat->mtime); @@ -1151,6 +1155,17 @@ svcxdr_encode_entry3_common(struct nfsd3_readdirres *resp, const char *name, if (xdr_stream_encode_item_present(xdr) < 0) return false; /* fileid */ + if (!resp->dir_have_uniquifier) { + struct kstat stat; + if (fh_getattr(&resp->fh, &stat) == nfs_ok) + resp->dir_ino_uniquifier = stat.ino_uniquifier; + else + resp->dir_ino_uniquifier = 0; + resp->dir_have_uniquifier = 1; + } + if (resp->dir_ino_uniquifier && + resp->dir_ino_uniquifier != ino) + ino ^= resp->dir_ino_uniquifier; if (xdr_stream_encode_u64(xdr, ino) < 0) return false; /* name */ diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 7abeccb975b2..ddccf849c29c 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -3114,10 +3114,14 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp, fhp->fh_handle.fh_size); } if (bmval0 & FATTR4_WORD0_FILEID) { + u64 ino = stat.ino; + if (stat.ino_uniquifier && + stat.ino_uniquifier != stat.ino) + ino ^= stat.ino_uniquifier; p = xdr_reserve_space(xdr, 8); if (!p) goto out_resource; - p = xdr_encode_hyper(p, stat.ino); + p = xdr_encode_hyper(p, ino); } if (bmval0 & FATTR4_WORD0_FILES_AVAIL) { p = xdr_reserve_space(xdr, 8); @@ -3285,6 +3289,9 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp, if (err) goto out_nfserr; ino = parent_stat.ino; + if (parent_stat.ino_uniquifier && + parent_stat.ino_uniquifier != ino) + ino ^= parent_stat.ino_uniquifier; } p = xdr_encode_hyper(p, ino); } diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h index 933008382bbe..b4f9f3c71f72 100644 --- a/fs/nfsd/xdr3.h +++ b/fs/nfsd/xdr3.h @@ -179,6 +179,8 @@ struct nfsd3_readdirres { struct xdr_buf dirlist; struct svc_fh scratch; struct readdir_cd common; + u64 dir_ino_uniquifier; + int dir_have_uniquifier; unsigned int cookie_offset; struct svc_rqst * rqstp; diff --git a/include/linux/stat.h b/include/linux/stat.h index fff27e603814..a5188f42ed81 100644 --- a/include/linux/stat.h +++ b/include/linux/stat.h @@ -46,6 +46,23 @@ struct kstat { struct timespec64 btime; /* File creation time */ u64 blocks; u64 mnt_id; + /* + * BTRFS does not provide unique inode numbers within a filesystem, + * depending on a synthetic 'dev' to provide uniqueness. + * NFSd cannot make use of this 'dev' number so clients often see + * duplicate inode numbers. + * For BTRFS, 'ino' is unlikely to use the high bits. It puts + * another number in ino_uniquifier which: + * - has most entropy in the high bits + * - is different precisely when 'dev' is different + * - is stable across unmount/remount + * NFSd can xor this with 'ino' to get a substantially more unique + * number for reporting to the client. + * The ino_uniquifier for a directory can reasonably be applied + * to inode numbers reported by the readdir filldir callback. + * It is NOT currently exported to user-space. + */ + u64 ino_uniquifier; }; #endif