Re: [PATCH] f2fs: honor per-I/O write streams for direct writes

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 05/22, Wenjie Qi wrote:
> io_uring can pass a per-I/O write stream through kiocb->ki_write_stream,
> and block direct I/O propagates that value to bio->bi_write_stream.
> 
> F2FS added FDP stream mapping for DATA writes, but its direct write
> submit hook always rewrites bio->bi_write_stream from the inode write
> hint and F2FS temperature. As a result, a direct write with an explicit
> io_uring write_stream is submitted to the F2FS-selected stream instead
> of the user-requested stream.
> 
> Validate an explicit write stream before starting F2FS direct I/O, pass
> the kiocb through the iomap private pointer, and preserve the per-I/O
> stream in the direct write bio. When no per-I/O stream is supplied, keep
> using the existing F2FS temperature-to-stream mapping.
> 
> Fixes: 42f7a7a50a33 ("f2fs: map data writes to FDP streams")
> Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>
> ---
>  fs/f2fs/file.c | 30 +++++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 71385ca4163d..20d6e7ab7416 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -5074,17 +5074,36 @@ static int f2fs_dio_write_end_io(struct kiocb *iocb, ssize_t size, int error,
>  	return 0;
>  }
>  
> +static bool f2fs_valid_write_stream(struct f2fs_sb_info *sbi, u8 write_stream)
> +{
> +	int i;
> +
> +	if (!write_stream)
> +		return true;
> +	if (!f2fs_is_multi_device(sbi))
> +		return write_stream <= bdev_max_write_streams(sbi->sb->s_bdev);
> +
> +	for (i = 0; i < sbi->s_ndevs; i++)
> +		if (write_stream > bdev_max_write_streams(FDEV(i).bdev))
> +			return false;
> +	return true;
> +}
> +
>  static void f2fs_dio_write_submit_io(const struct iomap_iter *iter,
>  					struct bio *bio, loff_t file_offset)
>  {
>  	struct inode *inode = iter->inode;
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> +	struct kiocb *iocb = iter->private;
>  	enum log_type type = f2fs_rw_hint_to_seg_type(sbi, inode->i_write_hint);
>  	enum temp_type temp = f2fs_get_segment_temp(sbi, type);
>  
>  	bio->bi_write_hint = f2fs_io_type_to_rw_hint(sbi, DATA, temp);
> -	bio->bi_write_stream =
> -		f2fs_io_type_to_write_stream(bio->bi_bdev, DATA, temp);
> +	if (iocb->ki_write_stream)
> +		bio->bi_write_stream = iocb->ki_write_stream;
> +	else
> +		bio->bi_write_stream =
> +			f2fs_io_type_to_write_stream(bio->bi_bdev, DATA, temp);

Let me apply as below.

        bio->bi_write_stream =
+               iocb->ki_write_stream ? iocb->ki_write_stream :
                f2fs_io_type_to_write_stream(bio->bi_bdev, DATA, temp);


>  	blk_crypto_submit_bio(bio);
>  }
>  
> @@ -5122,6 +5141,11 @@ static ssize_t f2fs_dio_write_iter(struct kiocb *iocb, struct iov_iter *from,
>  
>  	trace_f2fs_direct_IO_enter(inode, iocb, count, WRITE);
>  
> +	if (!f2fs_valid_write_stream(sbi, iocb->ki_write_stream)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
>  	if (iocb->ki_flags & IOCB_NOWAIT) {
>  		/* f2fs_convert_inline_inode() and block allocation can block */
>  		if (f2fs_has_inline_data(inode) ||
> @@ -5159,7 +5183,7 @@ static ssize_t f2fs_dio_write_iter(struct kiocb *iocb, struct iov_iter *from,
>  	if (pos + count > inode->i_size)
>  		dio_flags |= IOMAP_DIO_FORCE_WAIT;
>  	dio = __iomap_dio_rw(iocb, from, &f2fs_iomap_ops,
> -			     &f2fs_iomap_dio_write_ops, dio_flags, NULL, 0);
> +			     &f2fs_iomap_dio_write_ops, dio_flags, iocb, 0);
>  	if (IS_ERR_OR_NULL(dio)) {
>  		ret = PTR_ERR_OR_ZERO(dio);
>  		if (ret == -ENOTBLK)
> 
> base-commit: 520760b9f9156bf9698de38dc44c614fad68a1f9
> -- 
> 2.43.0
>