Date: Sun, 6 Mar 2011 09:54:45 +0100 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Attila Nagy <bra@fsn.hu> Cc: freebsd-fs@freebsd.org Subject: Re: Punching holes into (sparse) files - porting Solaris fcntl(F_FREESP) to FreeBSD? Message-ID: <20110306084217.GA9791@garage.freebsd.pl> In-Reply-To: <4D710154.90409@fsn.hu>
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[-- Attachment #1 --] On Fri, Mar 04, 2011 at 04:12:20PM +0100, Attila Nagy wrote: > Hi, > > Is it possible to make regions of files, with already written data > sparse? (I'm interested to do this on ZFS) > > All I could find in this topic is: > http://www.mail-archive.com/zfs-discuss@opensolaris.org/msg29047.html > > grepping through the source gives a match for VOP_SPACE in > cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_replay.c: > zfs_replay_truncate(zfsvfs_t *zfsvfs, lr_truncate_t *lr, boolean_t byteswap) > { > #ifdef sun > [...] > error = VOP_SPACE(ZTOV(zp), F_FREESP, &fl, FWRITE | FOFFMAX, > lr->lr_offset, kcred, NULL); > > And the relevant section from fcntl(2) in Solaris: > F_FREESP > > Free storage space associated with a section of the > ordinary file fildes. The section is specified by a > variable of data type struct flock pointed to by arg. > The data type struct flock is defined in the <fcntl.h> > header (see fcntl.h(3HEAD)) and is described below. Note > that all file systems might not support all possible > variations of F_FREESP arguments. In particular, many > file systems allow space to be freed only at the end of > a file. > > F_FREESP seems to be my friend, and it's implemented in Solaris's ZFS. > How hard would it be to complete the port and make it accessible from > FreeBSD? > I guess it was left out with a reason... Well, adding new VOP is important decision. We could eventually implement this via ioctl(2), I think... This is a nice feature after all. I don't know why do you need this, but note that when compression is enabled on a ZFS file system, all-zeros blocks are turned into holes, so if you do have compression enabled and you write all zeros in the place you want to punch a hole, the pool space should be reclaimed. -- Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://yomoli.com [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) iEUEARECAAYFAk1zS9QACgkQForvXbEpPzQE5QCYo51Ht4WXKSPPGLPXZj8lFyHn UACfTowvfEMJD7/s4NEYIR11T6zTH5Y= =q7p7 -----END PGP SIGNATURE-----help
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