From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx08.extmail.prod.ext.phx2.redhat.com [10.5.110.32]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u3RAoNh8013520 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Wed, 27 Apr 2016 06:50:23 -0400 Received: from smtp1.dds.nl (smtpgw.dds.nl [91.142.252.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6B8BBC00B8E5 for ; Wed, 27 Apr 2016 10:50:17 +0000 (UTC) Received: from webmail.dds.nl (app1.dds.nl [81.21.136.61]) by smtp1.dds.nl (Postfix) with ESMTP id 5EEA67FB8F for ; Wed, 27 Apr 2016 12:50:13 +0200 (CEST) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Date: Wed, 27 Apr 2016 10:50:13 +0000 From: Xen Message-ID: <29e7f847e1150949aa52c58fa33cf8cd@dds.nl> Subject: [linux-lvm] 2 questions on LVM cache Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Linux lvm 1. Does LVM cache support discards of the underlying blocks (in the cache) when the filesystem discards the blocks? I was reading https://lwn.net/Articles/293658/ which makes it clear that years ago kernel developers were introducing discard behaviour into Linux filesystems with respect to flash devices and their need to copy for wear leveling. I know so little about it, but I have seen the "discard" flag mentioned so much with respect to SSDs, that I must assume these discards are there. Are LVM cache blocks discarded when the filesystem layer discards these blocks? Where can I find this info? In https://www.redhat.com/archives/linux-lvm/2016-April/msg00030.html I mentioned that such a discard feature would be necessary in order for a filesystem to communicate to a block device layer which blocks are in use, and for a block device layer to communicate back a set of available blocks if these dynamically change. I forgot the other question lol. I'm interested in this solution to "https://bugzilla.redhat.com/show_bug.cgi?id=1189215" but I will respond in my other email (LVM Thin: Handle out of space conditions better).