ext4: fix inode tree inconsistency caused by ENOMEM

commit 3f542479 upstream.

If ENOMEM fails when the extent is splitting, we need to restore the length
of the split extent.
In the ext4_split_extent_at function, only in ext4_ext_create_new_leaf will
it alloc memory and change the shape of the extent tree,even if an ENOMEM
is returned at this time, the extent tree is still self-consistent, Just
restore the split extent lens in the function ext4_split_extent_at.

ext4_split_extent_at
 ext4_ext_insert_extent
  ext4_ext_create_new_leaf
   1)ext4_ext_split
     ext4_find_extent
   2)ext4_ext_grow_indepth
     ext4_find_extent

Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230103022812.130603-1-zhanchengbin1@huawei.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>