Re: migration cache, updated

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

On Fri, Jan 07, 2005 at 10:57:52AM -0600, Ray Bryant wrote:
> Marcello,
> 
> Attached is a patch which fixes some compiler warnings in mmigrate.c
> that I was getting with the migration cache code.  The only substantive
> change was to change:
> 
>         /* Wait for all operations against the page to finish. */
>         ret = migrate_fn(page, newpage, &vlist);
>         switch (ret) {
>         default:
>                 /* The page is busy. Try it later. */
>                 goto out_busy;
>         case -ENOENT:
>                 /* The file the page belongs to has been truncated. */
>                 page_cache_get(page);
>                 page_cache_release(newpage);
>                 newpage->mapping = NULL;
>                 /* fall thru */
>         case 0:
>                 /* fall thru */
>         }
> 
> in generic_migrate_page(), to:
> 
>         /* Wait for all operations against the page to finish. */
>         ret = migrate_fn(page, newpage, &vlist);
>         switch (ret) {
>         case -ENOENT:
>                 /* The file the page belongs to has been truncated. */
>                 page_cache_get(page);
>                 page_cache_release(newpage);
>                 newpage->mapping = NULL;
>                 /* fall thru */
>         case 0:
>                 break;
>         default:
>                 /* The page is busy. Try it later. */
>                 goto out_busy;
>         }
> 
> This change was made to get rid of the warning:
> 
> mm/mmigrate.c:500: warning: deprecated use of label at end of compound 
> statement
> 
> I suppose you used the previous order to eliminate an extra branch or
> some such.  Do you have any other suggestion on how to eliminate that
> warning?

Hi Ray,

No, I think your change is fine. I'll merge it to my tree (which currently
doesnt exist, yet).

> -- 
> Best Regards,
> Ray
> -----------------------------------------------
>                   Ray Bryant
> 512-453-9679 (work)         512-507-7807 (cell)
> raybry@sgi.com             raybry@austin.rr.com
> The box said: "Requires Windows 98 or better",
>            so I installed Linux.
> -----------------------------------------------

> Index: linux-2.6.10-rc2-mm4-page-migration-only/include/linux/swap.h
> ===================================================================
> --- linux-2.6.10-rc2-mm4-page-migration-only.orig/include/linux/swap.h	2005-01-04 07:55:22.000000000 -0800
> +++ linux-2.6.10-rc2-mm4-page-migration-only/include/linux/swap.h	2005-01-04 08:13:16.000000000 -0800
> @@ -258,7 +258,7 @@ static inline int remove_exclusive_swap_
>  {
>  	return __remove_exclusive_swap_page(p, 0);
>  }
> -extern int migration_remove_entry(swp_entry_t);
> +extern void migration_remove_entry(swp_entry_t);
>  struct backing_dev_info;
>  
>  extern struct swap_list_t swap_list;
> Index: linux-2.6.10-rc2-mm4-page-migration-only/mm/mmigrate.c
> ===================================================================
> --- linux-2.6.10-rc2-mm4-page-migration-only.orig/mm/mmigrate.c	2005-01-04 07:55:22.000000000 -0800
> +++ linux-2.6.10-rc2-mm4-page-migration-only/mm/mmigrate.c	2005-01-04 08:11:51.000000000 -0800
> @@ -79,7 +79,6 @@ struct page *lookup_migration_cache(int 
>  
>  void migration_duplicate(swp_entry_t entry)
>  {
> -	int offset;
>  	struct counter *cnt;
>  
>  	read_lock_irq(&migration_space.tree_lock);
> @@ -96,32 +95,11 @@ void remove_from_migration_cache(struct 
>          idr_remove(&migration_idr, id);
>  	radix_tree_delete(&migration_space.page_tree, id);
>  	ClearPageSwapCache(page);
> -	page->private = NULL;
> +	page->private = 0;
>  	write_unlock_irq(&migration_space.tree_lock);
>  }
>  
> -// FIXME: if the page is locked will it be correctly removed from migr cache?
> -// check races
> -
> -int migration_remove_entry(swp_entry_t entry)
> -{
> -	struct page *page;
> -	
> -	page = find_get_page(&migration_space, entry.val);
> -
> -	if (!page)
> -		BUG();
> -
> -	lock_page(page);	
> -
> -	migration_remove_reference(page, 1);
> -
> -	unlock_page(page);
> -
> -	page_cache_release(page);
> -}
> -
> -int migration_remove_reference(struct page *page, int dec)
> +void migration_remove_reference(struct page *page, int dec)
>  {
>  	struct counter *c;
>  	swp_entry_t entry;
> @@ -145,6 +123,28 @@ int migration_remove_reference(struct pa
>  	}
>  }
>  
> +
> +// FIXME: if the page is locked will it be correctly removed from migr cache?
> +// check races
> +
> +void migration_remove_entry(swp_entry_t entry)
> +{
> +	struct page *page;
> +	
> +	page = find_get_page(&migration_space, entry.val);
> +
> +	if (!page)
> +		BUG();
> +
> +	lock_page(page);	
> +
> +	migration_remove_reference(page, 1);
> +
> +	unlock_page(page);
> +
> +	page_cache_release(page);
> +}
> +
>  int detach_from_migration_cache(struct page *page)
>  {
>  	lock_page(page);	
> @@ -486,9 +486,6 @@ generic_migrate_page(struct page *page, 
>  	/* Wait for all operations against the page to finish. */
>  	ret = migrate_fn(page, newpage, &vlist);
>  	switch (ret) {
> -	default:
> -		/* The page is busy. Try it later. */
> -		goto out_busy;
>  	case -ENOENT:
>  		/* The file the page belongs to has been truncated. */
>  		page_cache_get(page);
> @@ -496,7 +493,10 @@ generic_migrate_page(struct page *page, 
>  		newpage->mapping = NULL;
>  		/* fall thru */
>  	case 0:
> -		/* fall thru */
> +		break;
> +	default:
> +		/* The page is busy. Try it later. */
> +		goto out_busy;
>  	}
>  
>  	arch_migrate_page(page, newpage);

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