From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Olenin Subject: Re: How to remount btrfs without compression? Date: Thu, 10 Nov 2011 16:04:33 +0900 Message-ID: <4EBB7781.7040907@parallels.com> References: <4EB72C1B.1030702@parallels.com> <201111071319.14493.Martin@lichtvoll.de> <4EB87E01.1040704@parallels.com> <4EB880A0.1030304@gmail.com> <4EB88BC9.7020509@gmail.com> <4EB88D4A.5050908@parallels.com> <20111108150151.GA4954@shiny> <20111108151208.GB4954@shiny> <4EB9D0D9.1000009@parallels.com> <4EBA33DB.2070409@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed To: Return-path: In-Reply-To: List-ID: On 11/10/2011 03:57 PM, Lubos Kolouch wrote: > Dmitry Olenin, Wed, 09 Nov 2011 17:03:39 +0900: > >> On 11/09/2011 04:48 PM, Lubos Kolouch wrote: >>> Sorry for possibly OT question - when I have historical btrfs system >>> mounted with zlib compression, >>> >>> can I remount it with lzo ? What will happen? Will the COW be broken >>> and the files taking duplicate space? Or will the Universe explode and >>> be replaced with something even more bizzare? >> >> Hello Lubos If you have a kernel that supports lzo (don't quite remember >> when it got in), why can't you? >> Absolutely nothing will happen, and only the new/updated files will be >> with lzo compression. You can remount on the fly switching b/w the two >> compression options without any problems. > > Hello Dmitry, > > By the way, this is interesting question to me - I mounted the filesystem > with -o compress=lzo, in dmesg showed btrfs: use lzo compression, > > but - the lzo module was not loaded (not shown in lsmod - and yes, I have > it as a module). > > When I do modprobe lzo, it shows there. > > Isn't it a bit strange? So btrfs is using lzo module that was not loaded? > (and says so in the dmesg output)? Hello Lubos Yes, I was wondering about this too when I started doing lzo. The lzo module you load most likely has nothing to do with btrfs. This is the only explanation. I would think that lzo for btrfs is built into kernel. Unfortunately I don't have my .config with me at the moment to check it.