From mboxrd@z Thu Jan 1 00:00:00 1970 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 0BA52C433F5 for ; Thu, 14 Apr 2022 15:20:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354744AbiDNPS1 (ORCPT ); Thu, 14 Apr 2022 11:18:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43372 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347662AbiDNN70 (ORCPT ); Thu, 14 Apr 2022 09:59:26 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 46BE24707A; Thu, 14 Apr 2022 06:51:02 -0700 (PDT) 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 D7A0E1F748; Thu, 14 Apr 2022 13:51:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1649944260; 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=8zj/qp1HcgBQX+/4vlQAgG9P0stPwQSdbGTrHMd1YsE=; b=bTcgkcf8ztn4CmqvW/jNOBLqNRtzRP+RDN6cNUaEQs/bH5zU27ADWbcilPDEAzR2Yz2fAD BZEM4XIC1h4TocI9fay50TaVF8su17gJWfB11TGgluQuLIyK0jwfzMkFttthzHNH2ckBTH qOrcpF4CY5APr2Fr01DyqqbKUg1/eo8= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1649944260; 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=8zj/qp1HcgBQX+/4vlQAgG9P0stPwQSdbGTrHMd1YsE=; b=1x3CnwOTKE5IX0W9CQhhgzPTP+mIgsHI7jW9usVyMLgN2LfoUmjieYzKPvIrYklIASKj03 nhUml7p89qGXefBg== 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 731A2132C0; Thu, 14 Apr 2022 13:51:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id UAcwGcQmWGJnTgAAMHmgww (envelope-from ); Thu, 14 Apr 2022 13:51:00 +0000 Received: from localhost (brahms.olymp [local]) by brahms.olymp (OpenSMTPD) with ESMTPA id c633f8db; Thu, 14 Apr 2022 13:51:24 +0000 (UTC) From: =?UTF-8?q?Lu=C3=ADs=20Henriques?= To: Jeff Layton , Xiubo Li , Ilya Dryomov Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, =?UTF-8?q?Lu=C3=ADs=20Henriques?= Subject: [PATCH v4 3/4] ceph: update documentation regarding snapshot naming limitations Date: Thu, 14 Apr 2022 14:51:21 +0100 Message-Id: <20220414135122.26821-4-lhenriques@suse.de> In-Reply-To: <20220414135122.26821-1-lhenriques@suse.de> References: <20220414135122.26821-1-lhenriques@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Luís Henriques --- Documentation/filesystems/ceph.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Documentation/filesystems/ceph.rst b/Documentation/filesystems/ceph.rst index 4942e018db85..d487cabe792d 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