| Message ID | 20180620153322.54221-1-arnd@arndb.de |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/6] ext4: sysfs: print ext4_super_block fields as little-endian | expand |
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
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);
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> --- fs/ext4/sysfs.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) -- 2.9.0