On Thu, Jun 21, 2018 at 7:49 PM, Andreas Dilger adilger@dilger.ca wrote:

On Jun 20, 2018, at 9:32 AM, Arnd Bergmann arnd@arndb.de wrote:

...

While working on extended rand for last_error/first_error timestamps, I noticed that the endianess is wrong, we access the little-endian fields in struct ext4_super_block as native-endian when we print them.

This adds a special case in ext4_attr_show() and ext4_attr_store() to byteswap the superblock fields if needed.

In older kernels, this code was part of super.c, it got moved to sysfs.c in linux-4.4.

Cc: stable@vger.kernel.org Fixes: 52c198c6820f ("ext4: add sysfs entry showing whether the fs contains errors") Signed-off-by: Arnd Bergmann arnd@arndb.de

I was wondering why this didn't just use le32_to_cpu() all the time, but I see that these functions are being used for both ext4_super_block (on-disk) fields, as well as ext4_sb_info (in-memory) fields. A bit ugly, but I don't think there is a better solution.

Reviewed-by: Andreas Dilger adilger@dilger.ca

One alternative that I considered was to just do away with helpers for the ext4_super_block structure and only use them for ext4_sb_info, especially after the last patch that changes this again. However, as a bugfix for stable backports it seemed best to keep the change as simple as possible.

Thanks for the review,

Arnd