+ swap-remove-get-put_swap_device-in-__swap_duplicate.patch added to mm-unstable branch

+ swap-remove-get-put_swap_device-in-__swap_duplicate.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: swap: remove get/put_swap_device() in __swap_duplicate()
has been added to the -mm mm-unstable branch.  Its filename is
     swap-remove-get-put_swap_device-in-__swap_duplicate.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/swap-remove-get-put_swap_device-in-__swap_duplicate.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Huang Ying <ying.huang@intel.com>
Subject: swap: remove get/put_swap_device() in __swap_duplicate()
Date: Mon, 29 May 2023 14:13:54 +0800

__swap_duplicate() is called by

- swap_shmem_alloc(): the folio in swap cache is locked.

- copy_nonpresent_pte() -> swap_duplicate() and try_to_unmap_one() ->
  swap_duplicate(): the page table lock is held.

- __read_swap_cache_async() -> swapcache_prepare(): enclosed with
  get/put_swap_device() in __read_swap_cache_async() already.

So, it's safe to remove get/put_swap_device() in __swap_duplicate().

Link: https://lkml.kernel.org/r/20230529061355.125791-5-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Chris Li <chrisl@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/swapfile.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/mm/swapfile.c~swap-remove-get-put_swap_device-in-__swap_duplicate
+++ a/mm/swapfile.c
@@ -3265,9 +3265,7 @@ static int __swap_duplicate(swp_entry_t
 	unsigned char has_cache;
 	int err;
 
-	p = get_swap_device(entry);
-	if (!p)
-		return -EINVAL;
+	p = swp_swap_info(entry);
 
 	offset = swp_offset(entry);
 	ci = lock_cluster_or_swap_info(p, offset);
@@ -3314,7 +3312,6 @@ static int __swap_duplicate(swp_entry_t
 
 unlock_out:
 	unlock_cluster_or_swap_info(p, ci);
-	put_swap_device(p);
 	return err;
 }
 
_

Patches currently in -mm which might be from ying.huang@intel.com are

migrate_pages_batch-simplify-retrying-and-failure-counting-of-large-folios.patch
swap-remove-get-put_swap_device-in-__swap_count.patch
swap-__read_swap_cache_async-enlarge-get-put_swap_device-protection-range.patch
swap-remove-__swp_swapcount.patch
swap-remove-get-put_swap_device-in-__swap_duplicate.patch
swap-comments-get_swap_device-with-usage-rule.patch