From patchwork Mon Feb 27 03:28:09 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Xiubo Li X-Patchwork-Id: 657170 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 D3C7AC64ED6 for ; Mon, 27 Feb 2023 03:37:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230218AbjB0DhH (ORCPT ); Sun, 26 Feb 2023 22:37:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230492AbjB0DhE (ORCPT ); Sun, 26 Feb 2023 22:37:04 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D65E11E8D for ; Sun, 26 Feb 2023 19:36:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677468915; 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=G94oRvHjL3Co0cHnwuIxM5CwftRB1MWIBEmdKPLLu6U=; b=gxJyVyiz0zEkVq1LqauWlXT89JvLi4gwKhn3ZyJLTiUs25QIQSGrMTD2JbH+qpidegCsQV 2ni7nu6VJHKFmmqNRUEES3aEFe55iDcf+fd5Md2blXeDyaYixfkBRlpzgepjOSrffr4M5b bxzYy+X9GWAnPxgNCGEYgpf30owCIgs= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-399-r6hinnfRMJKvSTQ6h5OZuQ-1; Sun, 26 Feb 2023 22:32:03 -0500 X-MC-Unique: r6hinnfRMJKvSTQ6h5OZuQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AF252857A93; Mon, 27 Feb 2023 03:32:02 +0000 (UTC) Received: from lxbceph1.gsslab.pek2.redhat.com (unknown [10.72.47.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id DFEA41731B; Mon, 27 Feb 2023 03:31:59 +0000 (UTC) From: xiubli@redhat.com To: idryomov@gmail.com, ceph-devel@vger.kernel.org Cc: jlayton@kernel.org, lhenriques@suse.de, vshankar@redhat.com, mchangir@redhat.com, Xiubo Li Subject: [PATCH v16 64/68] ceph: update documentation regarding snapshot naming limitations Date: Mon, 27 Feb 2023 11:28:09 +0800 Message-Id: <20230227032813.337906-65-xiubli@redhat.com> In-Reply-To: <20230227032813.337906-1-xiubli@redhat.com> References: <20230227032813.337906-1-xiubli@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org From: Luís Henriques Signed-off-by: Luís Henriques Reviewed-by: Xiubo Li Signed-off-by: Jeff Layton --- Documentation/filesystems/ceph.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Documentation/filesystems/ceph.rst b/Documentation/filesystems/ceph.rst index 76ce938e7024..085f309ece60 100644 --- a/Documentation/filesystems/ceph.rst +++ b/Documentation/filesystems/ceph.rst @@ -57,6 +57,16 @@ a snapshot on any subdirectory (and its nested contents) in the system. Snapshot creation and deletion are as simple as 'mkdir .snap/foo' and 'rmdir .snap/foo'. +Snapshot names have two limitations: + +* They can not start with an underscore ('_'), as these names are reserved + for internal usage by the MDS. +* They can not exceed 240 characters in size. This is because the MDS makes + use of long snapshot names internally, which follow the format: + `__`. Since filenames in general can't have + more than 255 characters, and `` takes 13 characters, the long + snapshot names can take as much as 255 - 1 - 1 - 13 = 240. + Ceph also provides some recursive accounting on directories for nested files and bytes. That is, a 'getfattr -d foo' on any directory in the system will reveal the total number of nested regular files and