From patchwork Tue Jun 13 05:24:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Xiubo Li X-Patchwork-Id: 13278024 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 4C33EC7EE29 for ; Tue, 13 Jun 2023 05:36:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240196AbjFMFgE (ORCPT ); Tue, 13 Jun 2023 01:36:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45170 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240181AbjFMFf0 (ORCPT ); Tue, 13 Jun 2023 01:35:26 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C652F294F for ; Mon, 12 Jun 2023 22:31:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1686634286; 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=yOQ5pbAqsLoYpGVWafq0V3DWcaZiJqTd568F6upLExY=; b=CdOY6NwQNuutEDY/zLQGe6qZmxn9sqUaxJpkXdlaJrxutzSIqfBvmznknG+fEzpbMD/enC gPOXGrb1juVNQ73rs1/MNafy54zyhEaZ7Zo7OM9opHsoI6o+rYRZ1Tt7KbhnwRpo2Ckgr6 Sl/6Iuz986WIthZSb5vz6RyZHpKYb7U= 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-520-alXPV3UmN-uGzaEM_JGJ_w-1; Tue, 13 Jun 2023 01:31:22 -0400 X-MC-Unique: alXPV3UmN-uGzaEM_JGJ_w-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 85C5080120A; Tue, 13 Jun 2023 05:31:22 +0000 (UTC) Received: from li-a71a4dcc-35d1-11b2-a85c-951838863c8d.ibm.com.com (ovpn-12-155.pek2.redhat.com [10.72.12.155]) by smtp.corp.redhat.com (Postfix) with ESMTP id 197851121315; Tue, 13 Jun 2023 05:31:18 +0000 (UTC) From: xiubli@redhat.com To: idryomov@gmail.com, ceph-devel@vger.kernel.org Cc: jlayton@kernel.org, vshankar@redhat.com, mchangir@redhat.com, lhenriques@suse.de, Xiubo Li Subject: [PATCH v20 64/71] ceph: update documentation regarding snapshot naming limitations Date: Tue, 13 Jun 2023 13:24:17 +0800 Message-Id: <20230613052424.254540-65-xiubli@redhat.com> In-Reply-To: <20230613052424.254540-1-xiubli@redhat.com> References: <20230613052424.254540-1-xiubli@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org From: Luís Henriques Tested-by: Luís Henriques Tested-by: Venky Shankar 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