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

[Gao Xiang]

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