On Mon, Feb 17, 2014 at 04:08:21PM +0100, Lukas Czerner wrote: > Introduce new FALLOC_FL_ZERO_RANGE flag for fallocate. This has the same > functionality as xfs ioctl XFS_IOC_ZERO_RANGE. > > It can be used to convert a range of file to zeros preferably without > issuing data IO. Blocks should be preallocated for the regions that span > holes in the file, and the entire range is preferable converted to > unwritten extents - even though file system may choose to zero out the > extent or do whatever which will result in reading zeros from the range > while the range remains allocated for the file. > > This can be also used to preallocate blocks past EOF in the same way as > with fallocate. Flag FALLOC_FL_KEEP_SIZE which should cause the inode > size to remain the same. > > Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx> > --- > fs/open.c | 7 ++++++- > include/uapi/linux/falloc.h | 1 + > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/open.c b/fs/open.c > index 4b3e1ed..6dc46c1 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -231,7 +231,12 @@ 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 & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)) > + if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | > + FALLOC_FL_ZERO_RANGE)) > + return -EOPNOTSUPP; > + > + /* Punch hole and zero range are mutually exclusive */ > + if (mode & FALLOC_FL_PUNCH_HOLE && mode & FALLOC_FL_ZERO_RANGE) I would have expected gcc to throw a warning on this. Even if it doesn't, it's so easy to mix up & an && and & it needs parenthesis around it to make it obvious what you actually meant and it doesn't have a && where an & should be or vice versa. Better, IMO, is this: /* Punch hole and zero range are mutually exclusive */ if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) == (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) return -EOPNOTSUPP; because it's obvious what the intent is and easy to spot typos. Cheers, Dave. -- 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
