From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marco Stornelli Subject: Re: [PATCH 1/4] fs: add SEEK_HOLE and SEEK_DATA flags Date: Sat, 20 Aug 2011 11:41:31 +0200 Message-ID: <4E4F814B.5070202@gmail.com> References: <1309275199-10801-1-git-send-email-josef@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, xfs@oss.sgi.com, viro@ZenIV.linux.org.uk To: Josef Bacik Return-path: In-Reply-To: <1309275199-10801-1-git-send-email-josef@redhat.com> Sender: linux-btrfs-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Hi, Il 28/06/2011 17:33, Josef Bacik ha scritto: > This just gets us ready to support the SEEK_HOLE and SEEK_DATA flags. Turns out > using fiemap in things like cp cause more problems than it solves, so lets try > and give userspace an interface that doesn't suck. We need to match solaris > here, and the definitions are > > *o* If /whence/ is SEEK_HOLE, the offset of the start of the > next hole greater than or equal to the supplied offset > is returned. The definition of a hole is provided near > the end of the DESCRIPTION. > > *o* If /whence/ is SEEK_DATA, the file pointer is set to the > start of the next non-hole file region greater than or > equal to the supplied offset. > I'm implementing the SEEK_DATA/SEEK_HOLE management for pramfs and I've got some doubts about the right behavior: 1) when we use SEEK_DATA/SEEK_HOLE, the offset used in lseek means always the offset from the start of the file, right? 2) in case of a file with hole at the beginning and data at the end, if I do lseek(fd, 0, SEEK_HOLE) I should receive the end of the file because the idea is to search the *next* hole and we have always a virtual hole at the end of the file, right? 3) about the last sentence of point 2), is it always true even if we have a case of block allocation beyond the end of file (fallocate with keep size option)? Thanks. Regards, Marco