ext4: add new online resize interface

This patch adds new online resize interface, whose input argument is a
64-bit integer indicating how many blocks there are in the resized fs.

In new resize impelmentation, all work like allocating group tables
are done by kernel side, so the new resize interface can support
flex_bg feature and prepares ground for suppoting resize with features
like bigalloc and exclude bitmap. Besides these, user-space tools just
passes in the new number of blocks.

We delay initializing the bitmaps and inode tables of added groups if
possible and add multi groups (a flex groups) each time, so new resize
is very fast like mkfs.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 4917cf24a5e0..10ec4639f152 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -581,6 +581,13 @@ Table of Ext4 specific ioctls
                               behaviour may change in the future as it is
                               not necessary and has been done this way only
                               for sake of simplicity.
+
+ EXT4_IOC_RESIZE_FS           Resize the filesystem to a new size.  The number
+                              of blocks of resized filesystem is passed in via
+                              64 bit integer argument.  The kernel allocates
+                              bitmaps and inode table, the userspace tool thus
+                              just passes the new number of blocks.
+
 ..............................................................................
 
 References