On Tue, Nov 09, 2010 at 12:12:22PM +1100, Dave Chinner wrote: > 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. > So this was relatively simple, adding a flag to falloc for xfs_io and such. Got a test going and it worked great on XFS. Then I went to make sure it worked on non-XFS, and thats where I've run into pain. Turns out xfs_io -c "bmap" only works on XFS. So I thought to myself "well how hard could it be to make this thing use fiemap?", hahaha I'm an idiot. So I've been adding a xfs_io -c "fiemap" that spits things out similar to bmap, and it will probably be tomorrow when I finish it. So good news is my simple patches seem to work just fine for hole-punch, bad news is its going to take me another day to have all the infrastructure to test it on non-XFS filesystems. Also did you want me to rebase my patches on your fallocate() version of ZERO_RANGE? Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
