fs: Add support FALLOC_FL_INSERT_RANGE for fallocate

FALLOC_FL_INSERT_RANGE command is the opposite command of
FALLOC_FL_COLLAPSE_RANGE that is needed for someone who wants to add
some data in the middle of file.

FALLOC_FL_INSERT_RANGE will create space for writing new data within
a file after shifting extents to right as given length. This command
also has same limitations as FALLOC_FL_COLLAPSE_RANGE in that
operations need to be filesystem block boundary aligned and cannot
cross the current EOF.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
index d1197ae3723c..3e445a760f14 100644
--- a/include/uapi/linux/falloc.h
+++ b/include/uapi/linux/falloc.h
@@ -41,4 +41,21 @@
  */
 #define FALLOC_FL_ZERO_RANGE		0x10
 
+/*
+ * FALLOC_FL_INSERT_RANGE is use to insert space within the file size without
+ * overwriting any existing data. The contents of the file beyond offset are
+ * shifted towards right by len bytes to create a hole.  As such, this
+ * operation will increase the size of the file by len bytes.
+ *
+ * Different filesystems may implement different limitations on the granularity
+ * of the operation. Most will limit operations to filesystem block size
+ * boundaries, but this boundary may be larger or smaller depending on
+ * the filesystem and/or the configuration of the filesystem or file.
+ *
+ * Attempting to insert space using this flag at OR beyond the end of
+ * the file is considered an illegal operation - just use ftruncate(2) or
+ * fallocate(2) with mode 0 for such type of operations.
+ */
+#define FALLOC_FL_INSERT_RANGE		0x20
+
 #endif /* _UAPI_FALLOC_H_ */