linux-kernel - Re: [PATCH v14 128/138] iomap: Support multi-page folios in invalidatepage

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Message-ID: <20210715221018.GT22357@magnolia>
Date:   Thu, 15 Jul 2021 15:10:18 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v14 128/138] iomap: Support multi-page folios in
 invalidatepage

On Thu, Jul 15, 2021 at 04:36:54AM +0100, Matthew Wilcox (Oracle) wrote:
> If we're punching a hole in a multi-page folio, we need to remove the
> per-page iomap data as the folio is about to be split and each page will
> need its own.  This means that writepage can now come across a page with
> no iop allocated, so remove the assertion that there is already one,
> and just create one (with the uptodate bits set) if there isn't one.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>

Lol, Andreas already did the bottom half of the change for you.

Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D

> ---
>  fs/iomap/buffered-io.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 48de198c5603..7f78256fc0ba 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -474,13 +474,17 @@ iomap_invalidatepage(struct page *page, unsigned int offset, unsigned int len)
>  	trace_iomap_invalidatepage(folio->mapping->host, offset, len);
>  
>  	/*
> -	 * If we are invalidating the entire page, clear the dirty state from it
> -	 * and release it to avoid unnecessary buildup of the LRU.
> +	 * If we are invalidating the entire folio, clear the dirty state
> +	 * from it and release it to avoid unnecessary buildup of the LRU.
>  	 */
>  	if (offset == 0 && len == folio_size(folio)) {
>  		WARN_ON_ONCE(folio_test_writeback(folio));
>  		folio_cancel_dirty(folio);
>  		iomap_page_release(folio);
> +	} else if (folio_multi(folio)) {
> +		/* Must release the iop so the page can be split */
> +		WARN_ON_ONCE(!folio_test_uptodate(folio) && folio_test_dirty(folio));
> +		iomap_page_release(folio);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(iomap_invalidatepage);
> @@ -1300,7 +1304,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  		struct writeback_control *wbc, struct inode *inode,
>  		struct folio *folio, loff_t end_pos)
>  {
> -	struct iomap_page *iop = to_iomap_page(folio);
> +	struct iomap_page *iop = iomap_page_create(inode, folio);
>  	struct iomap_ioend *ioend, *next;
>  	unsigned len = i_blocksize(inode);
>  	unsigned nblocks = i_blocks_per_folio(inode, folio);
> @@ -1308,7 +1312,6 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  	int error = 0, count = 0, i;
>  	LIST_HEAD(submit_list);
>  
> -	WARN_ON_ONCE(nblocks > 1 && !iop);
>  	WARN_ON_ONCE(iop && atomic_read(&iop->write_bytes_pending) != 0);
>  
>  	/*
> -- 
> 2.30.2
>