2001-12-29 10:24:03

by alad

Subject: Mapped pages handling in shrink_cache()

Hi, In the following code from shrink_cache()

if (PageDirty(page) && is_page_cache_freeable(page) && page->mapping)
{
.
.
.

int (*writepage)(struct page *);

writepage = page->mapping->a_ops->writepage;
if ((gfp_mask & __GFP_FS) && writepage) {
ClearPageDirty(page);
SetPageLaunder(page);
page_cache_get(page);
spin_unlock(&pagemap_lru_lock);

writepage(page);
page_cache_release(page);

spin_lock(&pagemap_lru_lock);
continue; <<<<<<< shouldn't the page be unlocked before
continuing with the next page <<<<<
}

I am reading 2.4.16

-- Amol

2001-12-29 11:03:33

by Andrew Morton

Subject: Re: Mapped pages handling in shrink_cache()

[email protected] wrote:
>
> Hi, In the following code from shrink_cache()
>
> if (PageDirty(page) && is_page_cache_freeable(page) && page->mapping)
> {
> .
> .
> .
>
> int (*writepage)(struct page *);
>
> writepage = page->mapping->a_ops->writepage;
> if ((gfp_mask & __GFP_FS) && writepage) {
> ClearPageDirty(page);
> SetPageLaunder(page);
> page_cache_get(page);
> spin_unlock(&pagemap_lru_lock);
>
> writepage(page);
> page_cache_release(page);
>
> spin_lock(&pagemap_lru_lock);
> continue; <<<<<<< shouldn't the page be unlocked before
> continuing with the next page <<<<<
> }
>

The page is unlocked when IO completes, in interrupt context.
See end_buffer_io_async().