On Mon, Nov 08, 2010 at 03:32:02PM -0500, Josef Bacik wrote: > Hole punching has already been implemented by XFS and OCFS2, and has the > potential to be implemented on both BTRFS and EXT4 so we need a generic way to > get to this feature. The simplest way in my mind is to add FALLOC_FL_PUNCH_HOLE > to fallocate() since it already looks like the normal fallocate() operation. > I've tested this patch with XFS and BTRFS to make sure XFS did what it's > supposed to do and that BTRFS failed like it was supposed to. Thank you, > > Signed-off-by: Josef Bacik <josef@xxxxxxxxxx> > --- > fs/open.c | 2 +- > include/linux/falloc.h | 1 + > 2 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index 4197b9e..ab8dedf 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -223,7 +223,7 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len) > return -EINVAL; > > /* Return error if mode is not supported */ > - if (mode && !(mode & FALLOC_FL_KEEP_SIZE)) > + if (mode && (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))) > return -EOPNOTSUPP; > > if (!(file->f_mode & FMODE_WRITE)) > diff --git a/include/linux/falloc.h b/include/linux/falloc.h > index 3c15510..851cba2 100644 > --- a/include/linux/falloc.h > +++ b/include/linux/falloc.h > @@ -2,6 +2,7 @@ > #define _FALLOC_H_ > > #define FALLOC_FL_KEEP_SIZE 0x01 /* default is extend size */ > +#define FALLOC_FL_PUNCH_HOLE 0X02 /* de-allocates range */ Hole punching was not included originally in fallocate() for a variety of reasons. IIRC, they were along the lines of: 1 de-allocating of blocks in an allocation syscall is wrong. People wanted a new syscall for this functionality. 2 no glibc interface needs it 3 at the time, only XFS supported punching holes, so there is not need to support it in a generic interface 4 the use cases presented were not considered compelling enough to justify the additional complexity (!) In the end, I gave up arguing for it to be included because just getting the FALLOC_FL_KEEP_SIZE functionality was a hard enough battle. Anyway, #3 isn't the case any more, #4 was just an excuse not to support anything ext4 couldn't do and lots of apps are calling fallocate directly (because glibc can't use FALLOC_FL_KEEP_SIZE) so #2 isn't an issue, either. I guess that leaves #1 to be debated; I don't think there is any problem with doing what you propose. What I will suggest is that this requires a generic xfstest to be written and support added to xfs_io to enable that test (and others) to issue hole punches. Something along the lines of test 242 which I wrote for testing all the edge case of XFS_IOC_ZERO_RANGE (*) would be good. Cheers, Dave. (*) fallocate() version: http://git.kernel.org/?p=linux/kernel/git/dgc/xfsdev.git;a=commitdiff;h=45f3e1831e3abc8bd12ec1e6c548f73a8dd9e36d -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
