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

[yukuai (C)]

On 2020/8/19 20:56, Gao Xiang wrote:
> 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?

Hi,

You'are right, this shouldn't be inside spin_lock.

> > +
> > +	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.

If so, maybe I should move iomap_set_page_dirty() to
ioamp_set_range_dirty().

Thanks,
Yu Kuai

> @@ -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
>
>
> .