Re: linux-next: manual merge of the vfs tree with the erofs tree

[Gao Xiang]

Hi Stephen,

On Mon, Dec 05, 2022 at 09:24:15AM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> Today's linux-next merge of the vfs tree got a conflict in:
> 
>   fs/erofs/fscache.c
> 
> between commits:
> 
>   89175ef1262d ("erofs: switch to prepare_ondemand_read() in fscache mode")
>   89175ef1262d ("erofs: switch to prepare_ondemand_read() in fscache mode")
> 
> from the erofs tree and commit:
> 
>   89175ef1262d ("erofs: switch to prepare_ondemand_read() in fscache mode")
> 
> from the vfs tree.

Is the commit from the vfs tree correct?

The conflict fix looks good to me (we tend to enable large folios in the
next cycle.)

Thanks,
Gao Xiang

> 
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging.  You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
> 
> -- 
> Cheers,
> Stephen Rothwell
> 
> diff --cc fs/erofs/fscache.c
> index f14886c479bd,4c837be3b6e3..000000000000
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@@ -126,28 -159,47 +126,28 @@@ static int erofs_fscache_read_folios_as
>   
>   	ret = fscache_begin_read_operation(cres, cookie);
>   	if (ret)
>  -		goto out;
>  +		return ret;
>   
>   	while (done < len) {
>  -		subreq = kzalloc(sizeof(struct netfs_io_subrequest),
>  -				 GFP_KERNEL);
>  -		if (subreq) {
>  -			INIT_LIST_HEAD(&subreq->rreq_link);
>  -			refcount_set(&subreq->ref, 2);
>  -			subreq->rreq = rreq;
>  -			refcount_inc(&rreq->ref);
>  -		} else {
>  -			ret = -ENOMEM;
>  -			goto out;
>  -		}
>  -
>  -		subreq->start = pstart + done;
>  -		subreq->len	=  len - done;
>  -		subreq->flags = 1 << NETFS_SREQ_ONDEMAND;
>  +		loff_t sstart = pstart + done;
>  +		size_t slen = len - done;
>  +		unsigned long flags = 1 << NETFS_SREQ_ONDEMAND;
>   
>  -		list_add_tail(&subreq->rreq_link, &rreq->subrequests);
>  -
>  -		source = cres->ops->prepare_read(subreq, LLONG_MAX);
>  -		if (WARN_ON(subreq->len == 0))
>  +		source = cres->ops->prepare_ondemand_read(cres,
>  +				sstart, &slen, LLONG_MAX, &flags, 0);
>  +		if (WARN_ON(slen == 0))
>   			source = NETFS_INVALID_READ;
>   		if (source != NETFS_READ_FROM_CACHE) {
>  -			erofs_err(sb, "failed to fscache prepare_read (source %d)",
>  -				  source);
>  -			ret = -EIO;
>  -			subreq->error = ret;
>  -			erofs_fscache_put_subrequest(subreq);
>  -			goto out;
>  +			erofs_err(sb, "failed to fscache prepare_read (source %d)", source);
>  +			return -EIO;
>   		}
>   
>  -		atomic_inc(&rreq->nr_outstanding);
>  +		refcount_inc(&req->ref);
> - 		iov_iter_xarray(&iter, READ, &req->mapping->i_pages,
> ++		iov_iter_xarray(&iter, ITER_DEST, &req->mapping->i_pages,
>  +				lstart + done, slen);
>   
>  -		iov_iter_xarray(&iter, ITER_DEST, &rreq->mapping->i_pages,
>  -				start + done, subreq->len);
>  -
>  -		ret = fscache_read(cres, subreq->start, &iter,
>  -				   NETFS_READ_HOLE_FAIL,
>  -				   erofc_fscache_subreq_complete, subreq);
>  +		ret = fscache_read(cres, sstart, &iter, NETFS_READ_HOLE_FAIL,
>  +				   erofs_fscache_subreq_complete, req);
>   		if (ret == -EIOCBQUEUED)
>   			ret = 0;
>   		if (ret) {
> @@@ -233,19 -297,17 +233,19 @@@ static int erofs_fscache_data_read_slic
>   		}
>   		iov_iter_zero(PAGE_SIZE - size, &iter);
>   		erofs_put_metabuf(&buf);
>  -		return PAGE_SIZE;
>  +		primary->submitted += PAGE_SIZE;
>  +		return 0;
>   	}
>   
>  +	count = primary->len - primary->submitted;
>   	if (!(map.m_flags & EROFS_MAP_MAPPED)) {
> - 		iov_iter_xarray(&iter, READ, &mapping->i_pages, pos, count);
>  -		count = len;
> + 		iov_iter_xarray(&iter, ITER_DEST, &mapping->i_pages, pos, count);
>   		iov_iter_zero(count, &iter);
>  -		return count;
>  +		primary->submitted += count;
>  +		return 0;
>   	}
>   
>  -	count = min_t(size_t, map.m_llen - (pos - map.m_la), len);
>  +	count = min_t(size_t, map.m_llen - (pos - map.m_la), count);
>   	DBG_BUGON(!count || count % PAGE_SIZE);
>   
>   	mdev = (struct erofs_map_dev) {