FALLOC_FL_KEEP_SIZE

Allocates and initializes to zero the disk space within the specified range, but the file size will not be modified.

Deallocates space (i.e. creates a hole)

Newly allocated blocks will be marked as initialized.

Removes a byte range from a file, without leaving a hole

Zeroes space in the specified byte range

Increases the file space by inserting a hole without overwriting any existing data

Used to unshare shared blocks within the file size without overwriting any existing data