[PATCH] erofs: support STATX_DIOALIGN

[Hongbo Li]

On 2024/7/18 10:41, Gao Xiang wrote:
> 
> 
> 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.
> 
I'm working on ondemand direct io mode. This will affect the 
STATX_DIOALIGN result for erofs_is_fscache_mode case (.ie the 
dio_mem_align is i_blocksize(inode) in erofs over fscache). Should we 
apply this first and then modify it after the direct io is supported in 
ondemand erofs?

Thanks,
Hongbo

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