Commit bdb0ed54 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

mm/swapfile: convert try_to_free_swap() to folio_free_swap() 

Add kernel-doc for folio_free_swap() and make it return bool.  Add a
try_to_free_swap() compatibility wrapper.

Link: https://lkml.kernel.org/r/20220902194653.1739778-11-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 14d01ee9

include/linux/swap.h

+6 −0
Original line number Diff line number Diff line
@@ -490,6 +490,7 @@ static inline long get_nr_swap_pages(void) 


extern void si_swapinfo(struct sysinfo *);

swp_entry_t folio_alloc_swap(struct folio *folio);

bool folio_free_swap(struct folio *folio);

extern void put_swap_page(struct page *page, swp_entry_t entry);

extern swp_entry_t get_swap_page_of_type(int);

extern int get_swap_pages(int n, swp_entry_t swp_entries[], int entry_size);
@@ -606,6 +607,11 @@ static inline swp_entry_t folio_alloc_swap(struct folio *folio) 
	return entry;

}



static inline bool folio_free_swap(struct folio *folio)

{

	return false;

}



static inline int add_swap_extent(struct swap_info_struct *sis,

				  unsigned long start_page,

				  unsigned long nr_pages, sector_t start_block)

mm/folio-compat.c

+7 −0
Original line number Diff line number Diff line
@@ -146,3 +146,10 @@ void putback_lru_page(struct page *page) 
{

	folio_putback_lru(page_folio(page));

}



#ifdef CONFIG_SWAP

int try_to_free_swap(struct page *page)

{

	return folio_free_swap(page_folio(page));

}

#endif

mm/swapfile.c

+18 −14
Original line number Diff line number Diff line
@@ -1567,43 +1567,47 @@ static bool folio_swapped(struct folio *folio) 
	return swap_page_trans_huge_swapped(si, entry);

}



/*

 * If swap is getting full, or if there are no more mappings of this page,

 * then try_to_free_swap is called to free its swap space.

/**

 * folio_free_swap() - Free the swap space used for this folio.

 * @folio: The folio to remove.

 *

 * If swap is getting full, or if there are no more mappings of this folio,

 * then call folio_free_swap to free its swap space.

 *

 * Return: true if we were able to release the swap space.

 */

int try_to_free_swap(struct page *page)

bool folio_free_swap(struct folio *folio)

{

	struct folio *folio = page_folio(page);

	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);



	if (!folio_test_swapcache(folio))

		return 0;

		return false;

	if (folio_test_writeback(folio))

		return 0;

		return false;

	if (folio_swapped(folio))

		return 0;

		return false;



	/*

	 * Once hibernation has begun to create its image of memory,

	 * there's a danger that one of the calls to try_to_free_swap()

	 * there's a danger that one of the calls to folio_free_swap()

	 * - most probably a call from __try_to_reclaim_swap() while

	 * hibernation is allocating its own swap pages for the image,

	 * but conceivably even a call from memory reclaim - will free

	 * the swap from a page which has already been recorded in the

	 * image as a clean swapcache page, and then reuse its swap for

	 * the swap from a folio which has already been recorded in the

	 * image as a clean swapcache folio, and then reuse its swap for

	 * another page of the image.  On waking from hibernation, the

	 * original page might be freed under memory pressure, then

	 * original folio might be freed under memory pressure, then

	 * later read back in from swap, now with the wrong data.

	 *

	 * Hibernation suspends storage while it is writing the image

	 * to disk so check that here.

	 */

	if (pm_suspended_storage())

		return 0;

		return false;



	delete_from_swap_cache(folio);

	folio_set_dirty(folio);

	return 1;

	return true;

}



/*

mm/vmscan.c

+1 −1
Original line number Diff line number Diff line
@@ -2049,7 +2049,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, 
		if (folio_test_swapcache(folio) &&

		    (mem_cgroup_swap_full(&folio->page) ||

		     folio_test_mlocked(folio)))

			try_to_free_swap(&folio->page);

			folio_free_swap(folio);

		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);

		if (!folio_test_mlocked(folio)) {

			int type = folio_is_file_lru(folio);