[PATCH 23/28] mm, swap: remove no longer needed _swap_info_get

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

There is now only two users of _swap_info_get after consolidating these
callers, folio_try_reclaim_swap and swp_swapcount.

folio_try_reclaim_swap holds the folio lock and the folio is in swap
cache, _swap_info_get is redundant.

For swp_swapcount, _swap_info_get is insufficient as the swap entry is
no pinned so the device could be swapped off anytime, it should use
get_swap_device instead.

And after these change, _swap_info_get is no longer used, we can safely
remove it.

Signed-off-by: Kairui Song <kasong@tencent.com>
---
 mm/swapfile.c | 63 +++++++++++++--------------------------------------
 1 file changed, 16 insertions(+), 47 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c2154f19c21b..28bb0a74e4a6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1364,35 +1364,6 @@ void folio_free_swap_cache(struct folio *folio)
 	folio_ref_sub(folio, folio_nr_pages(folio));
 }
 
-static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
-{
-	struct swap_info_struct *si;
-	unsigned long offset;
-
-	if (!entry.val)
-		goto out;
-	si = swp_get_info(entry);
-	if (!si)
-		goto bad_nofile;
-	if (data_race(!(si->flags & SWP_USED)))
-		goto bad_device;
-	offset = swp_offset(entry);
-	if (offset >= si->max)
-		goto bad_offset;
-	return si;
-
-bad_offset:
-	pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
-	goto out;
-bad_device:
-	pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val);
-	goto out;
-bad_nofile:
-	pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
-out:
-	return NULL;
-}
-
 static unsigned char swap_put_entry_locked(struct swap_info_struct *si,
 					   struct swap_cluster_info *ci,
 					   swp_entry_t entry)
@@ -1549,7 +1520,7 @@ int swp_swapcount(swp_entry_t entry)
 	pgoff_t offset;
 	unsigned char *map;
 
-	si = _swap_info_get(entry);
+	si = get_swap_device(entry);
 	if (!si)
 		return 0;
 
@@ -1579,6 +1550,7 @@ int swp_swapcount(swp_entry_t entry)
 	} while (tmp_count & COUNT_CONTINUED);
 out:
 	swap_unlock_cluster(ci);
+	put_swap_device(si);
 	return count;
 }
 
@@ -1610,26 +1582,10 @@ static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
 	return ret;
 }
 
-static bool folio_swapped(struct folio *folio)
-{
-	swp_entry_t entry = folio->swap;
-	struct swap_info_struct *si = _swap_info_get(entry);
-
-	if (!si)
-		return false;
-
-	if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!folio_test_large(folio)))
-		return swap_entry_swapped(si, entry);
-
-	return swap_page_trans_huge_swapped(si, entry, folio_order(folio));
-}
-
 static bool folio_swapcache_freeable(struct folio *folio)
 {
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 
-	if (!folio_test_swapcache(folio))
-		return false;
 	if (folio_test_writeback(folio))
 		return false;
 
@@ -1665,9 +1621,22 @@ static bool folio_swapcache_freeable(struct folio *folio)
  */
 bool folio_free_swap(struct folio *folio)
 {
+	bool swapped;
+	struct swap_info_struct *si;
+	swp_entry_t entry = folio->swap;
+
+	if (!folio_test_swapcache(folio))
+		return false;
 	if (!folio_swapcache_freeable(folio))
 		return false;
-	if (folio_swapped(folio))
+
+	si = swp_info(entry);
+	if (!IS_ENABLED(CONFIG_THP_SWAP) || !folio_test_large(folio))
+		swapped = swap_entry_swapped(si, entry);
+	else
+		swapped = swap_page_trans_huge_swapped(si, entry,
+						       folio_order(folio));
+	if (swapped)
 		return false;
 
 	folio_free_swap_cache(folio);
-- 
2.49.0