[PATCH] erofs: support STATX_DIOALIGN

[Gao Xiang]

On 2024/7/17 14:34, Hongbo Li wrote:
> 
> 
> On 2024/7/17 10:00, Gao Xiang wrote:
>> Hi,
>>
>> On 2024/7/16 20:45, Hongbo Li wrote:
>>> Add support for STATX_DIOALIGN to erofs, so that direct I/O
>>> alignment restrictions are exposed to userspace in a generic
>>> way.
>>>
>>> [Before]
>>> ```
>>> ./statx_test /mnt/erofs/testfile
>>> statx(/mnt/erofs/testfile) = 0
>>> dio mem align:0
>>> dio offset align:0
>>> ```
>>>
>>> [After]
>>> ```
>>> ./statx_test /mnt/erofs/testfile
>>> statx(/mnt/erofs/testfile) = 0
>>> dio mem align:512
>>> dio offset align:512
>>> ```
>>>
>>> Signed-off-by: Hongbo Li <lihongbo22 at huawei.com>
>>> ---
>>>   fs/erofs/inode.c | 19 +++++++++++++++++++
>>>   1 file changed, 19 insertions(+)
>>>
>>> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
>>> index 5f6439a63af7..9325a6f0058a 100644
>>> --- a/fs/erofs/inode.c
>>> +++ b/fs/erofs/inode.c
>>> @@ -342,6 +342,25 @@ int erofs_getattr(struct mnt_idmap *idmap, const struct path *path,
>>>       stat->attributes_mask |= (STATX_ATTR_COMPRESSED |
>>>                     STATX_ATTR_IMMUTABLE);
>>> +    /*
>>> +     * Return the DIO alignment restrictions if requested.
>>> +     *
>>> +     * In erofs, STATX_DIOALIGN is not supported in ondemand mode and
>>> +     * the compressed file, so in these cases we report no DIO support.
>>> +     */
>>> +    if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) {
>>> +        stat->result_mask |= STATX_DIOALIGN;
>>> +        if (!erofs_is_fscache_mode(inode->i_sb) &&
>>> + !erofs_inode_is_data_compressed(EROFS_I(inode)->datalayout)) {
>>> +            struct block_device *bdev = inode->i_sb->s_bdev;
>>> +            unsigned int bsize = (bdev) ? bdev_logical_block_size(bdev) :
>>> +                        i_blocksize(inode);
>>
>> I guess in this way you could always use
>>              stat->dio_mem_align = bdev_logical_block_size(bdev);
>>              stat->dio_offset_align = stat->dio_mem_align;
>> ? since bdev won't be NULL.
>>
> Yeah, only the EROFS_FS_ONDEMAND config is on, the s_bdev can be NULL.

Would you mind sending a v2 to fix this?  At least, s_bdev is always
non-NULL currently.

I could apply this for this cycle.

Thanks,
Gao Xiang

> 
> Thanks,
> Hongbo
> 
>> Otherwise it looks good to me.
>>
>> Thanks,
>> Gao Xiang