Re: [RFC PATCH] iomap: generalize IOMAP_INLINE to cover tail-packing case

[Chao Yu <yuchao0@huawei.com>]

Ping, any comments on this patch?

On 2019/7/3 15:55, Chao Yu wrote:
> Some filesystems like erofs/reiserfs have the ability to pack tail
> data into metadata, e.g.:
> IOMAP_MAPPED [0, 8192]
> IOMAP_INLINE [8192, 8200]
> 
> However current IOMAP_INLINE type has assumption that:
> - inline data should be locating at page #0.
> - inline size should equal to .i_size
> Those restriction fail to convert to use iomap IOMAP_INLINE in erofs,
> so this patch tries to relieve above limits to make IOMAP_INLINE more
> generic to cover tail-packing case.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  fs/iomap.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 12654c2e78f8..d1c16b692d31 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -264,13 +264,12 @@ static void
>  iomap_read_inline_data(struct inode *inode, struct page *page,
>  		struct iomap *iomap)
>  {
> -	size_t size = i_size_read(inode);
> +	size_t size = iomap->length;
>  	void *addr;
>  
>  	if (PageUptodate(page))
>  		return;
>  
> -	BUG_ON(page->index);
>  	BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data));
>  
>  	addr = kmap_atomic(page);
> @@ -293,7 +292,6 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>  	sector_t sector;
>  
>  	if (iomap->type == IOMAP_INLINE) {
> -		WARN_ON_ONCE(pos);
>  		iomap_read_inline_data(inode, page, iomap);
>  		return PAGE_SIZE;
>  	}
>