10  *  Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
31 	struct page *page = bio_first_page_all(bio);  in end_swap_bio_write()  local
34 		SetPageError(page);  in end_swap_bio_write()
36 		 * We failed to write the page out to swap-space.  in end_swap_bio_write()
37 		 * Re-dirty the page in order to avoid it being reclaimed.  in end_swap_bio_write()
43 		set_page_dirty(page);  in end_swap_bio_write()
47 		ClearPageReclaim(page);  in end_swap_bio_write()
49 	end_page_writeback(page);  in end_swap_bio_write()
53 static void swap_slot_free_notify(struct page *page)  in swap_slot_free_notify()  argument
60 	 * There is no guarantee that the page is in swap cache - the software  in swap_slot_free_notify()
62 	 * swapcache page.  So we must check PG_swapcache before proceeding with  in swap_slot_free_notify()
65 	if (unlikely(!PageSwapCache(page)))  in swap_slot_free_notify()
68 	sis = page_swap_info(page);  in swap_slot_free_notify()
74 	 * expecting that the page will be swapped out again.  in swap_slot_free_notify()
75 	 * So we can avoid an unnecessary write if the page  in swap_slot_free_notify()
84 	 * and make the VM-owned decompressed page *dirty*,  in swap_slot_free_notify()
85 	 * so the page should be swapped out somewhere again if  in swap_slot_free_notify()
89 	entry.val = page_private(page);  in swap_slot_free_notify()
95 		SetPageDirty(page);  in swap_slot_free_notify()
103 	struct page *page = bio_first_page_all(bio);  in end_swap_bio_read()  local
107 		SetPageError(page);  in end_swap_bio_read()
108 		ClearPageUptodate(page);  in end_swap_bio_read()
115 	SetPageUptodate(page);  in end_swap_bio_read()
116 	swap_slot_free_notify(page);  in end_swap_bio_read()
118 	unlock_page(page);  in end_swap_bio_read()
190 		if (page_no) {	/* exclude the header page */  in generic_swapfile_activate()
228 int swap_writepage(struct page *page, struct writeback_control *wbc)  in swap_writepage()  argument
232 	if (try_to_free_swap(page)) {  in swap_writepage()
233 		unlock_page(page);  in swap_writepage()
237 	 * Arch code may have to preserve more data than just the page  in swap_writepage()
240 	ret = arch_prepare_to_swap(page);  in swap_writepage()
242 		set_page_dirty(page);  in swap_writepage()
243 		unlock_page(page);  in swap_writepage()
246 	if (frontswap_store(page) == 0) {  in swap_writepage()
247 		set_page_writeback(page);  in swap_writepage()
248 		unlock_page(page);  in swap_writepage()
249 		end_page_writeback(page);  in swap_writepage()
252 	ret = __swap_writepage(page, wbc, end_swap_bio_write);  in swap_writepage()
257 static inline void count_swpout_vm_event(struct page *page)  in count_swpout_vm_event()  argument
260 	if (unlikely(PageTransHuge(page)))  in count_swpout_vm_event()
263 	count_vm_events(PSWPOUT, thp_nr_pages(page));  in count_swpout_vm_event()
267 static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)  in bio_associate_blkg_from_page()  argument
272 	memcg = page_memcg(page);  in bio_associate_blkg_from_page()
282 #define bio_associate_blkg_from_page(bio, page)		do { } while (0)  argument
285 int __swap_writepage(struct page *page, struct writeback_control *wbc,  in __swap_writepage()  argument
290 	struct swap_info_struct *sis = page_swap_info(page);  in __swap_writepage()
292 	VM_BUG_ON_PAGE(!PageSwapCache(page), page);  in __swap_writepage()
298 			.bv_page = page,  in __swap_writepage()
306 		kiocb.ki_pos = page_file_offset(page);  in __swap_writepage()
308 		set_page_writeback(page);  in __swap_writepage()
309 		unlock_page(page);  in __swap_writepage()
319 			 * Mark the page dirty and avoid  in __swap_writepage()
325 			set_page_dirty(page);  in __swap_writepage()
326 			ClearPageReclaim(page);  in __swap_writepage()
328 					   page_file_offset(page));  in __swap_writepage()
330 		end_page_writeback(page);  in __swap_writepage()
334 	ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);  in __swap_writepage()
336 		count_swpout_vm_event(page);  in __swap_writepage()
342 	bio->bi_iter.bi_sector = swap_page_sector(page);  in __swap_writepage()
345 	bio_add_page(bio, page, thp_size(page), 0);  in __swap_writepage()
347 	bio_associate_blkg_from_page(bio, page);  in __swap_writepage()
348 	count_swpout_vm_event(page);  in __swap_writepage()
349 	set_page_writeback(page);  in __swap_writepage()
350 	unlock_page(page);  in __swap_writepage()
356 int swap_readpage(struct page *page, bool synchronous)  in swap_readpage()  argument
360 	struct swap_info_struct *sis = page_swap_info(page);  in swap_readpage()
365 	VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);  in swap_readpage()
366 	VM_BUG_ON_PAGE(!PageLocked(page), page);  in swap_readpage()
367 	VM_BUG_ON_PAGE(PageUptodate(page), page);  in swap_readpage()
376 	if (frontswap_load(page) == 0) {  in swap_readpage()
377 		SetPageUptodate(page);  in swap_readpage()
378 		unlock_page(page);  in swap_readpage()
386 		ret = mapping->a_ops->readpage(swap_file, page);  in swap_readpage()
393 		ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);  in swap_readpage()
395 			if (trylock_page(page)) {  in swap_readpage()
396 				swap_slot_free_notify(page);  in swap_readpage()
397 				unlock_page(page);  in swap_readpage()
409 	bio->bi_iter.bi_sector = swap_page_sector(page);  in swap_readpage()
411 	bio_add_page(bio, page, thp_size(page), 0);  in swap_readpage()
416 	 * attempt to access it in the page fault retry time check.  in swap_readpage()
442 int swap_set_page_dirty(struct page *page)  in swap_set_page_dirty()  argument
444 	struct swap_info_struct *sis = page_swap_info(page);  in swap_set_page_dirty()
449 		VM_BUG_ON_PAGE(!PageSwapCache(page), page);  in swap_set_page_dirty()
450 		return mapping->a_ops->set_page_dirty(page);  in swap_set_page_dirty()
452 		return __set_page_dirty_no_writeback(page);  in swap_set_page_dirty()