[PATCH] erofs: support STATX_DIOALIGN

[Hongbo Li]

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.

Thanks,
Hongbo

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