From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. R. Okajima" Subject: Re: [PATCH 0/9] overlay filesystem: request for inclusion (v17) Date: Sat, 16 Mar 2013 03:57:18 +0900 Message-ID: <29608.1363373838@jrobl> References: <1363184193-1796-1-git-send-email-miklos@szeredi.hu> <20130313160854.54ac0491044371b4db214698@linux-foundation.org> <20130315012541.GU21522@ZenIV.linux.org.uk> <19058.1363320936@jrobl> <20130315044411.GW21522@ZenIV.linux.org.uk> <20079.1363324154@jrobl> <20130315051322.GX21522@ZenIV.linux.org.uk> <1363335318.2459.4.camel@dabdike> <20130315121220.GY21522@ZenIV.linux.org.uk> Cc: James Bottomley , Miklos Szeredi , Andrew Morton , torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, apw@canonical.com, nbd@openwrt.org, neilb@suse.de, jordipujolp@gmail.com, ezk@fsl.cs.sunysb.edu, dhowells@redhat.com, sedat.dilek@googlemail.com, mszeredi@suse.cz To: Al Viro Return-path: In-Reply-To: <20130315121220.GY21522@ZenIV.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Al Viro: > The trouble with such mechanisms is that they tend to end up depending on > fairly non-trivial properties of underlying fs. Try aufs one on btrfs, > see how soon you spot the problem. It's nice when a method turns out > to be really redundant and implementable in uniform way via other methods > present; see fh_to_dentry history for example of situation where it hadn't... Hmm, I could not see problem around aufs using btrfs as the upper RW branch, tested on linux-3.9-rc2. Would you describe more specifically? Some of my local tests didn't pass due to an error return from btrfs. For example, repeat "ln fileA $very_loooong_filename", then btrfs returns EMLINK so soon. And aufs refers the common set of inode attribute. I mean attrs declared in VFS. Also I know some filesystems don't maintain attrs on each operation. For such fs, aufs calls vfs_getattr() internally. J. R. Okajima