From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: [PATCH -V7 5/9] vfs: Add freadlink syscall Date: Thu, 13 May 2010 18:09:53 +1000 Message-ID: <20100513180953.127df6c2@notabene.brown> References: <1273679444-14903-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1273679444-14903-6-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20100513114351.793caf70@notabene.brown> <87vdas1fnv.fsf@linux.vnet.ibm.com> <20100513165606.4bf57bd6@notabene.brown> <87mxw41chx.fsf@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: hch@infradead.org, viro@zeniv.linux.org.uk, adilger@sun.com, corbet@lwn.net, serue@us.ibm.com, linux-fsdevel@vger.kernel.org, sfrench@us.ibm.com, philippe.deniel@CEA.FR, linux-kernel@vger.kernel.org To: "Aneesh Kumar K. V" Return-path: In-Reply-To: <87mxw41chx.fsf@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Thu, 13 May 2010 13:04:18 +0530 "Aneesh Kumar K. V" wrote: > On Thu, 13 May 2010 16:56:06 +1000, Neil Brown wrote: > > On Thu, 13 May 2010 11:55:56 +0530 > > "Aneesh Kumar K. V" wrote: > > > > > On Thu, 13 May 2010 11:43:51 +1000, Neil Brown wrote: > > > > On Wed, 12 May 2010 21:20:40 +0530 > > > > "Aneesh Kumar K.V" wrote: > > > > > > > > > This enables to use open-by-handle and then get the link target > > > > > details of a symlink using the fd returned by handle > > > > > > > > > > > > > > > > > I find it very frustrating that a new syscall seems to be needed here. > > > > We have 'readlinkat', and it should be enough. > > > > How: the 'dfd' has to be a 'directory', and the path name as to be non-empty. > > > > > > > > The following patch allows 'path' to be NULL and in that case 'dfd' to be a > > > > non-directory. This allows readlinkat and faccessat (and probably others) > > > > to be used on an fd with not following path name. > > > > > > > > What do people think of this alternative? > > > > > > > > > > I will add this in the next iteration and drop the freadlink syscall. > > > > > > > I wouldn't be quite that hasty. It was only a proposal. It might not be > > appropriate to change all those syscalls.. > > > > An alternative that I don't think is a nice, but is a lot 'safer' is > > to just change readlinkat to accept a NULL path: > > That would mean only readlinkat now have a special case of accepting NULL path > and dirfd can point to objects other than directory. So from the > interface point of having the special case is confusing. But if you feel > strong enough to drop freadlink syscall i can do that. Just not sure > whether special case for only readlinkat is the right way considering we > have fstat/fchwon type calls for other file system operations. > > Not completely a special case. I modelled this code on utimesat. NeilBrown