linux-kernel - Re: [RFC PATCH V3] iomap: add support to track dirty state of sub pages

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Date:   Wed, 19 Aug 2020 20:56:08 +0800
From:   Gao Xiang <hsiangkao@...hat.com>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     hch@...radead.org, darrick.wong@...cle.com, willy@...radead.org,
        david@...morbit.com, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com
Subject: Re: [RFC PATCH V3] iomap: add support to track dirty state of sub
 pages

On Wed, Aug 19, 2020 at 08:05:42PM +0800, Yu Kuai wrote:

...

> +static void
> +iomap_iop_set_range_dirty(struct page *page, unsigned int off,
> +		unsigned int len)
> +{
> +	struct iomap_page *iop = to_iomap_page(page);
> +	struct inode *inode = page->mapping->host;
> +	unsigned int first = DIRTY_BITS(off >> inode->i_blkbits);
> +	unsigned int last = DIRTY_BITS((off + len - 1) >> inode->i_blkbits);
> +	unsigned long flags;
> +	unsigned int i;
> +
> +	spin_lock_irqsave(&iop->state_lock, flags);
> +	for (i = first; i <= last; i++)
> +		set_bit(i, iop->state);
> +
> +	if (last >= first)
> +		iomap_set_page_dirty(page);

set_page_dirty() in the atomic context?

> +
> +	spin_unlock_irqrestore(&iop->state_lock, flags);
> +}
> +
> +static void
> +iomap_set_range_dirty(struct page *page, unsigned int off,
> +		unsigned int len)
> +{
> +	if (PageError(page))
> +		return;
> +
> +	if (page_has_private(page))
> +		iomap_iop_set_range_dirty(page, off, len);


I vaguely remembered iomap doesn't always set up PagePrivate.


@@ -705,7 +770,7 @@ __iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
 	if (unlikely(copied < len && !PageUptodate(page)))
 		return 0;
 	iomap_set_range_uptodate(page, offset_in_page(pos), len);
-	iomap_set_page_dirty(page);
+	iomap_set_range_dirty(page, offset_in_page(pos), len);
 	return copied;
 }

so here could be suspectable, but I might be wrong here since
I just take a quick look.

Thanks,
Gao Xiang