linux-kernel - Re: [PATCH v2 15/25] iomap: Support large pages in iomap_adjust_read

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Date:   Wed, 12 Feb 2020 00:11:49 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 15/25] iomap: Support large pages in
 iomap_adjust_read_range

>  __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
>  		struct page *page, struct iomap *srcmap)
>  {
> -	struct iomap_page *iop = iomap_page_create(inode, page);
>  	loff_t block_size = i_blocksize(inode);
>  	loff_t block_start = pos & ~(block_size - 1);
>  	loff_t block_end = (pos + len + block_size - 1) & ~(block_size - 1);
> @@ -556,9 +557,10 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
>  
>  	if (PageUptodate(page))
>  		return 0;
> +	iomap_page_create(inode, page);

FYI, I have a similar change in a pending series that only creates
the iomap_page if a page isn't actually mapped by a contiguous extent.
Lets see which series goes in first, but the conflicts shouldn't be too
bad.

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 52269e56c514..b4bf86590096 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1387,6 +1387,8 @@ static inline void clear_page_pfmemalloc(struct page *page)
>  extern void pagefault_out_of_memory(void);
>  
>  #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
> +#define offset_in_this_page(page, p)	\
> +	((unsigned long)(p) & (thp_size(page) - 1))

I think this should go int oa separate patch.