From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linda Walsh Subject: Re: max symlink = 5? ?bug? ?feature deficit? Date: Sun, 12 Feb 2006 16:54:23 -0800 Message-ID: <43EFD8BF.1040205@tlinx.org> References: <43ED5A7B.7040908@tlinx.org> <20060212180601.GU27946@ftp.linux.org.uk> <43EFA63B.30907@tlinx.org> <20060212212504.GX27946@ftp.linux.org.uk> <43EFBCA9.1090501@tlinx.org> <20060213000803.GY27946@ftp.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Linux-Kernel , linux-fsdevel@vger.kernel.org Return-path: Received: from ishtar.tlinx.org ([64.81.245.74]:23777 "EHLO ishtar.tlinx.org") by vger.kernel.org with ESMTP id S1751105AbWBMAy2 (ORCPT ); Sun, 12 Feb 2006 19:54:28 -0500 To: Al Viro In-Reply-To: <20060213000803.GY27946@ftp.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Al Viro wrote: > On Sun, Feb 12, 2006 at 02:54:33PM -0800, Linda Walsh wrote: > >> Al Viro wrote: >> >>> Care to RTFS? I mean, really - at least to the point of seeing what's >>> involved in that recursion. >>> >>> >> Hmmm...that's where I got the original parameter numbers, but >> I see it's not so straightforward. I tried a limit of >> 40, but I quickly get an OS hang when trying to reference a >> 13th link. Twelve works at the limit, but would take more testing >> to find out the bottleneck. >> > > Sigh... 12 works at the limit on your particular config, filesystems > being used and syscall being issued (hint: amount of stuff on stack > before we enter mutual recursion varies; so does the amount of stuff > on stack we get from function that are not part of mutual recursion, > but are called from the damn thing). > --- Yeah, I sorta figured that. Is there any easier way to remove the recursion? I dunno about you, but I was always taught that recursion, while elegant, was not always the most efficient in terms of time and space requirements and one could get similar functionality using iteration and a stack. The GNU libraries _seem_ to indicate a max of 20 links supported there. Googling around, I see I'm not the first person to be surprised by the low limit. I don't recall running into such a limit on any other Unixes, though I'm sure they had some limit. It can be useful for creating a shadow file-system where only root needs to point to a "target source", and the "symlink" overlay lies over the top of any real, underlying file. Why can't things just be easy sometimes...:-/ Linda