ext4: fix dx_map_entry to support 256k directory blocks
The dx_map_entry structure doesn't support over 64KB block size by current usage of its member("offs"). Because "offs" treats an offset of copies of the ext4_dir_entry_2 structure as is. This member size is 16 bits. But real offset for over 64KB(256KB) block size needs 18 bits. However, real offset keeps 4 byte boundary, so lower 2 bits is not used. Therefore, we do the following to fix this limitation: For "store": we divide the real offset by 4 and then store this result to "offs" member. For "use": we multiply "offs" member by 4 and then use this result as real offset. Signed-off-by: NToshiyuki Okajima <toshi.okajima@jp.fujitsu.com> Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
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