mm: return the folio from __read_swap_cache_async()

Patch series "More swap folio conversions".

These all seem like fairly straightforward conversions to me.  A lot of
compound_head() calls get removed.  And page_swap_info(), which is nice.


This patch (of 13):

Move the folio->page conversion into the callers that actually want that. 
Most of the callers are happier with the folio anyway.  If the
page_allocated boolean is set, the folio allocated is of order-0, so it is
safe to pass the page directly to swap_readpage().

Link: https://lkml.kernel.org/r/20231213215842.671461-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20231213215842.671461-2-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/zswap.h

@@ -34,7 +34,7 @@ void zswap_swapon(int type);
 void zswap_swapoff(int type);
 void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg);
 void zswap_lruvec_state_init(struct lruvec *lruvec);
-void zswap_page_swapin(struct page *page);
+void zswap_folio_swapin(struct folio *folio);
 #else
 
 struct zswap_lruvec_state {};
@@ -54,7 +54,7 @@ static inline void zswap_swapon(int type) {}
 static inline void zswap_swapoff(int type) {}
 static inline void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg) {}
 static inline void zswap_lruvec_state_init(struct lruvec *lruvec) {}
-static inline void zswap_page_swapin(struct page *page) {}
+static inline void zswap_folio_swapin(struct folio *folio) {}
 #endif
 
 #endif /* _LINUX_ZSWAP_H */

mm/swap.h

@@ -49,10 +49,9 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 				   struct vm_area_struct *vma,
 				   unsigned long addr,
 				   struct swap_iocb **plug);
-struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
-				     struct mempolicy *mpol, pgoff_t ilx,
-				     bool *new_page_allocated,
-				     bool skip_if_exists);
+struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_flags,
+		struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated,
+		bool skip_if_exists);
 struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
 				    struct mempolicy *mpol, pgoff_t ilx);
 struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,

mm/swap_state.c

@@ -410,14 +410,12 @@ struct folio *filemap_get_incore_folio(struct address_space *mapping,
 	return folio;
 }
 
-struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
-				     struct mempolicy *mpol, pgoff_t ilx,
-				     bool *new_page_allocated,
-				     bool skip_if_exists)
+struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+		struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated,
+		bool skip_if_exists)
 {
 	struct swap_info_struct *si;
 	struct folio *folio;
-	struct page *page;
 	void *shadow = NULL;
 
 	*new_page_allocated = false;
@@ -434,10 +432,8 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 		 */
 		folio = filemap_get_folio(swap_address_space(entry),
 						swp_offset(entry));
-		if (!IS_ERR(folio)) {
-			page = folio_file_page(folio, swp_offset(entry));
-			goto got_page;
-		}
+		if (!IS_ERR(folio))
+			goto got_folio;
 
 		/*
 		 * Just skip read ahead for unused swap slot.
@@ -451,7 +447,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 			goto fail_put_swap;
 
 		/*
-		 * Get a new page to read into from swap.  Allocate it now,
+		 * Get a new folio to read into from swap.  Allocate it now,
 		 * before marking swap_map SWAP_HAS_CACHE, when -EEXIST will
 		 * cause any racers to loop around until we add it to cache.
 		 */
@@ -487,13 +483,13 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 		 * stumble across a swap_map entry whose SWAP_HAS_CACHE
 		 * has not yet been cleared.  Or race against another
 		 * __read_swap_cache_async(), which has set SWAP_HAS_CACHE
-		 * in swap_map, but not yet added its page to swap cache.
+		 * in swap_map, but not yet added its folio to swap cache.
 		 */
 		schedule_timeout_uninterruptible(1);
 	}
 
 	/*
-	 * The swap entry is ours to swap in. Prepare the new page.
+	 * The swap entry is ours to swap in. Prepare the new folio.
 	 */
 
 	__folio_set_locked(folio);
@@ -514,10 +510,9 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 	/* Caller will initiate read into locked folio */
 	folio_add_lru(folio);
 	*new_page_allocated = true;
-	page = &folio->page;
-got_page:
+got_folio:
 	put_swap_device(si);
-	return page;
+	return folio;
 
 fail_unlock:
 	put_swap_folio(folio, entry);
@@ -545,16 +540,16 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 	bool page_allocated;
 	struct mempolicy *mpol;
 	pgoff_t ilx;
-	struct page *page;
+	struct folio *folio;
 
 	mpol = get_vma_policy(vma, addr, 0, &ilx);
-	page = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
+	folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
 					&page_allocated, false);
 	mpol_cond_put(mpol);
 
 	if (page_allocated)
-		swap_readpage(page, false, plug);
-	return page;
+		swap_readpage(&folio->page, false, plug);
+	return folio_file_page(folio, swp_offset(entry));
 }
 
 static unsigned int __swapin_nr_pages(unsigned long prev_offset,
@@ -639,7 +634,7 @@ static unsigned long swapin_nr_pages(unsigned long offset)
 struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
 				    struct mempolicy *mpol, pgoff_t ilx)
 {
-	struct page *page;
+	struct folio *folio;
 	unsigned long entry_offset = swp_offset(entry);
 	unsigned long offset = entry_offset;
 	unsigned long start_offset, end_offset;
@@ -664,31 +659,31 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
 	blk_start_plug(&plug);
 	for (offset = start_offset; offset <= end_offset ; offset++) {
 		/* Ok, do the async read-ahead now */
-		page = __read_swap_cache_async(
+		folio = __read_swap_cache_async(
 				swp_entry(swp_type(entry), offset),
 				gfp_mask, mpol, ilx, &page_allocated, false);
-		if (!page)
+		if (!folio)
 			continue;
 		if (page_allocated) {
-			swap_readpage(page, false, &splug);
+			swap_readpage(&folio->page, false, &splug);
 			if (offset != entry_offset) {
-				SetPageReadahead(page);
+				folio_set_readahead(folio);
 				count_vm_event(SWAP_RA);
 			}
 		}
-		put_page(page);
+		folio_put(folio);
 	}
 	blk_finish_plug(&plug);
 	swap_read_unplug(splug);
 	lru_add_drain();	/* Push any new pages onto the LRU now */
 skip:
 	/* The page was likely read above, so no need for plugging here */
-	page = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
+	folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
 					&page_allocated, false);
 	if (unlikely(page_allocated))
-		swap_readpage(page, false, NULL);
-	zswap_page_swapin(page);
-	return page;
+		swap_readpage(&folio->page, false, NULL);
+	zswap_folio_swapin(folio);
+	return folio_file_page(folio, swp_offset(entry));
 }
 
 int init_swap_address_space(unsigned int type, unsigned long nr_pages)
@@ -806,7 +801,7 @@ static struct page *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
 {
 	struct blk_plug plug;
 	struct swap_iocb *splug = NULL;
-	struct page *page;
+	struct folio *folio;
 	pte_t *pte = NULL, pentry;
 	unsigned long addr;
 	swp_entry_t entry;
@@ -839,18 +834,18 @@ static struct page *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
 			continue;
 		pte_unmap(pte);
 		pte = NULL;
-		page = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
+		folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
 						&page_allocated, false);
-		if (!page)
+		if (!folio)
 			continue;
 		if (page_allocated) {
-			swap_readpage(page, false, &splug);
+			swap_readpage(&folio->page, false, &splug);
 			if (i != ra_info.offset) {
-				SetPageReadahead(page);
+				folio_set_readahead(folio);
 				count_vm_event(SWAP_RA);
 			}
 		}
-		put_page(page);
+		folio_put(folio);
 	}
 	if (pte)
 		pte_unmap(pte);
@@ -858,13 +853,13 @@ static struct page *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
 	swap_read_unplug(splug);
 	lru_add_drain();
 skip:
-	/* The page was likely read above, so no need for plugging here */
-	page = __read_swap_cache_async(targ_entry, gfp_mask, mpol, targ_ilx,
+	/* The folio was likely read above, so no need for plugging here */
+	folio = __read_swap_cache_async(targ_entry, gfp_mask, mpol, targ_ilx,
 					&page_allocated, false);
 	if (unlikely(page_allocated))
-		swap_readpage(page, false, NULL);
-	zswap_page_swapin(page);
-	return page;
+		swap_readpage(&folio->page, false, NULL);
+	zswap_folio_swapin(folio);
+	return folio_file_page(folio, swp_offset(entry));
 }
 
 /**

mm/zswap.c

@@ -368,12 +368,12 @@ void zswap_lruvec_state_init(struct lruvec *lruvec)
 	atomic_long_set(&lruvec->zswap_lruvec_state.nr_zswap_protected, 0);
 }
 
-void zswap_page_swapin(struct page *page)
+void zswap_folio_swapin(struct folio *folio)
 {
 	struct lruvec *lruvec;
 
-	if (page) {
-		lruvec = folio_lruvec(page_folio(page));
+	if (folio) {
+		lruvec = folio_lruvec(folio);
 		atomic_long_inc(&lruvec->zswap_lruvec_state.nr_zswap_protected);
 	}
 }
@@ -1383,14 +1383,14 @@ static void __zswap_load(struct zswap_entry *entry, struct page *page)
 * writeback code
 **********************************/
 /*
- * Attempts to free an entry by adding a page to the swap cache,
- * decompressing the entry data into the page, and issuing a
- * bio write to write the page back to the swap device.
+ * Attempts to free an entry by adding a folio to the swap cache,
+ * decompressing the entry data into the folio, and issuing a
+ * bio write to write the folio back to the swap device.
  *
- * This can be thought of as a "resumed writeback" of the page
+ * This can be thought of as a "resumed writeback" of the folio
  * to the swap device.  We are basically resuming the same swap
  * writeback path that was intercepted with the zswap_store()
- * in the first place.  After the page has been decompressed into
+ * in the first place.  After the folio has been decompressed into
  * the swap cache, the compressed version stored by zswap can be
  * freed.
  */
@@ -1398,56 +1398,56 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 				 struct zswap_tree *tree)
 {
 	swp_entry_t swpentry = entry->swpentry;
-	struct page *page;
+	struct folio *folio;
 	struct mempolicy *mpol;
-	bool page_was_allocated;
+	bool folio_was_allocated;
 	struct writeback_control wbc = {
 		.sync_mode = WB_SYNC_NONE,
 	};
 
-	/* try to allocate swap cache page */
+	/* try to allocate swap cache folio */
 	mpol = get_task_policy(current);
-	page = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
-				NO_INTERLEAVE_INDEX, &page_was_allocated, true);
-	if (!page)
+	folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
+				NO_INTERLEAVE_INDEX, &folio_was_allocated, true);
+	if (!folio)
 		return -ENOMEM;
 
 	/*
-	 * Found an existing page, we raced with load/swapin. We generally
-	 * writeback cold pages from zswap, and swapin means the page just
-	 * became hot. Skip this page and let the caller find another one.
+	 * Found an existing folio, we raced with load/swapin. We generally
+	 * writeback cold folios from zswap, and swapin means the folio just
+	 * became hot. Skip this folio and let the caller find another one.
 	 */
-	if (!page_was_allocated) {
-		put_page(page);
+	if (!folio_was_allocated) {
+		folio_put(folio);
 		return -EEXIST;
 	}
 
 	/*
-	 * Page is locked, and the swapcache is now secured against
+	 * folio is locked, and the swapcache is now secured against
 	 * concurrent swapping to and from the slot. Verify that the
 	 * swap entry hasn't been invalidated and recycled behind our
 	 * backs (our zswap_entry reference doesn't prevent that), to
-	 * avoid overwriting a new swap page with old compressed data.
+	 * avoid overwriting a new swap folio with old compressed data.
 	 */
 	spin_lock(&tree->lock);
 	if (zswap_rb_search(&tree->rbroot, swp_offset(entry->swpentry)) != entry) {
 		spin_unlock(&tree->lock);
-		delete_from_swap_cache(page_folio(page));
+		delete_from_swap_cache(folio);
 		return -ENOMEM;
 	}
 	spin_unlock(&tree->lock);
 
-	__zswap_load(entry, page);
+	__zswap_load(entry, &folio->page);
 
-	/* page is up to date */
-	SetPageUptodate(page);
+	/* folio is up to date */
+	folio_mark_uptodate(folio);
 
 	/* move it to the tail of the inactive list after end_writeback */
-	SetPageReclaim(page);
+	folio_set_reclaim(folio);
 
 	/* start writeback */
-	__swap_writepage(page, &wbc);
-	put_page(page);
+	__swap_writepage(&folio->page, &wbc);
+	folio_put(folio);
 
 	return 0;
 }
@@ -1593,7 +1593,7 @@ bool zswap_store(struct folio *folio)
 
 	dst = acomp_ctx->buffer;
 	sg_init_table(&input, 1);
-	sg_set_page(&input, page, PAGE_SIZE, 0);
+	sg_set_page(&input, &folio->page, PAGE_SIZE, 0);
 
 	/*
 	 * We need PAGE_SIZE * 2 here since there maybe over-compression case,