The patch titled
Subject: mm/swapfile:__swap_duplicate: drop redundant WRITE_ONCE on swap_map for err cases
has been added to the -mm mm-unstable branch. Its filename is
mm-swapfile-__swap_duplicate-drop-redundant-write_once-on-swap_map-for-err-cases.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swapfile-__swap_duplicate-drop-redundant-write_once-on-swap_map-for-err-cases.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: Barry Song <21cnbao@xxxxxxxxx>
Subject: mm/swapfile:__swap_duplicate: drop redundant WRITE_ONCE on swap_map for err cases
Date: Wed, 21 Feb 2024 22:10:28 +1300
The code is quite hard to read, we are still writing swap_map after
errors happen. Though the written value is as before,
has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
[snipped]
WRITE_ONCE(p->swap_map[offset], count | has_cache);
It would be better to entirely drop the WRITE_ONCE for both
performance and readability.
Link: https://lkml.kernel.org/r/20240221091028.123122-1-21cnbao@xxxxxxxxx
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/swapfile.c~mm-swapfile-__swap_duplicate-drop-redundant-write_once-on-swap_map-for-err-cases
+++ a/mm/swapfile.c
@@ -3335,6 +3335,9 @@ static int __swap_duplicate(swp_entry_t
} else
err = -ENOENT; /* unused swap entry */
+ if (err)
+ goto unlock_out;
+
WRITE_ONCE(p->swap_map[offset], count | has_cache);
unlock_out:
_
Patches currently in -mm which might be from 21cnbao@xxxxxxxxx are
mm-swapfile-__swap_duplicate-drop-redundant-write_once-on-swap_map-for-err-cases.patch
