From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCH] Btrfs: use the normal checksumming infrastructure for free space cache Date: Mon, 13 Jun 2011 10:20:43 +0800 Message-ID: <4DF573FB.1080709@cn.fujitsu.com> References: <1307734827-10697-1-git-send-email-josef@redhat.com> <4DF56D60.4070208@cn.fujitsu.com> <1307929964-sup-6781@shiny> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Josef Bacik , linux-btrfs To: Chris Mason Return-path: In-Reply-To: <1307929964-sup-6781@shiny> List-ID: Chris Mason wrote: > Excerpts from Li Zefan's message of 2011-06-12 21:52:32 -0400: >> Josef Bacik wrote: >>> We used to store the checksums of the space cache directly in the space cache, >>> however that doesn't work out too well if we have more space than we can fit the >>> checksums into the first page. So instead use the normal checksumming >>> infrastructure. There were problems with doing this originally but those >>> problems don't exist now so this works out fine. Thanks, >>> >> >> This looks great, so I'll drop my patch that extends the original code to >> allow more than 1 crc page. > > I do like them a lot, but what happens when a special case crc kernel > mounts a free space cache created by this patch? > The generation number will be checked, and then we'll get this warning: "btrfs: space cache generation xx does not match inode yy" If xx happens to be equal to yy, crcs will be checked and this warning will pop up: "btrfs: crc mismatch for page zz" but it won't crash (not tested).