[PATCH] erofs: support STATX_DIOALIGN

[Gao Xiang]

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.

Otherwise it looks good to me.

Thanks,
Gao Xiang