On Jun 20, 2018, at 9:32 AM, Arnd Bergmann 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 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 > --- > fs/ext4/sysfs.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c > index f34da0bb8f17..b970a200f20c 100644 > --- a/fs/ext4/sysfs.c > +++ b/fs/ext4/sysfs.c > @@ -274,8 +274,12 @@ static ssize_t ext4_attr_show(struct kobject *kobj, > case attr_pointer_ui: > if (!ptr) > return 0; > - return snprintf(buf, PAGE_SIZE, "%u\n", > - *((unsigned int *) ptr)); > + if (a->attr_ptr == ptr_ext4_super_block_offset) > + return snprintf(buf, PAGE_SIZE, "%u\n", > + le32_to_cpup(ptr)); > + else > + return snprintf(buf, PAGE_SIZE, "%u\n", > + *((unsigned int *) ptr)); > case attr_pointer_atomic: > if (!ptr) > return 0; > @@ -308,7 +312,10 @@ static ssize_t ext4_attr_store(struct kobject *kobj, > ret = kstrtoul(skip_spaces(buf), 0, &t); > if (ret) > return ret; > - *((unsigned int *) ptr) = t; > + if (a->attr_ptr == ptr_ext4_super_block_offset) > + *((__le32 *) ptr) = cpu_to_le32(t); > + else > + *((unsigned int *) ptr) = t; > return len; > case attr_inode_readahead: > return inode_readahead_blks_store(sbi, buf, len); > -- > 2.9.0 > Cheers, Andreas