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Mon, 11 Mar 2024 16:14:35 -0700 (PDT) MIME-Version: 1.0 References: <20240221210845.13488-1-21cnbao@gmail.com> <3439a693-753e-4293-a0fe-eefd7b3cdf53@redhat.com> In-Reply-To: <3439a693-753e-4293-a0fe-eefd7b3cdf53@redhat.com> From: Barry Song <21cnbao@gmail.com> Date: Tue, 12 Mar 2024 07:14:24 +0800 Message-ID: Subject: Re: [PATCH v2] mm/swapfile:__swap_duplicate: drop redundant WRITE_ONCE on swap_map for err cases To: David Hildenbrand Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4D71C180003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: kq1or5ky4tzen8uwddpqkhy7t6wr6po5 X-HE-Tag: 1710198876-185369 X-HE-Meta: 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 zW1u3W5Z 2YS9S4DY+CNMJe9YprGez6r9Dxsxn3/ZpmzgggWPPNkFqW21yfjuugwHP2yaf6iQALaQoaQtLE2+JZMwPQBTOHV93jXRpBbJXFaoZ2LgetDW8kYbr8EstWbqfeMXxGqVyZTB78R9FonxTLGxq5LzXluTZSlYLArarUUekUkM6J/5ul3B3y7Dy+pNBDctAOrLOpS6YVTJcFkfeuFkGNSE6SDUEe2ogq9Q50HOEkjhHaYYQ69lEGkdAYhD2SvhR4jnJSJ3gqN+23rfQVMs7bFO3jitVFEky7nwlN86TKS+j2Gq6UBsIJj8QeZrDnTSW5W+MZZmI8XboiBoL9re8eUYA1UyZ80zpx5EOdX1DiP9L629DLNh/6w8bOPwNkNVAod/ahKpxLoRAVOjUlblaYVAdQtmbgQDz2NAU5KSwERkdqHVh2VvJ6SG35mPCTHS2Ia0IBqdB9i7eI6WwJqNo+syjOpHFNPIS96HLaGi0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 11, 2024 at 10:37=E2=80=AFPM David Hildenbrand wrote: > > On 21.02.24 22:08, Barry Song wrote: > > From: Barry Song > > > > 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 =3D count & SWAP_HAS_CACHE; > > count &=3D ~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. > > > > Signed-off-by: Barry Song > > --- > > -v2: drop goto according to Andrew, Thanks! > > > > mm/swapfile.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 556ff7347d5f..7cb6d9a2d51d 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -3320,7 +3320,8 @@ static int __swap_duplicate(swp_entry_t entry, un= signed char usage) > > } else > > err =3D -ENOENT; /* unused swap entry */ > > > > - WRITE_ONCE(p->swap_map[offset], count | has_cache); > > + if (!err) > > + WRITE_ONCE(p->swap_map[offset], count | has_cache); > > > > unlock_out: > > unlock_cluster_or_swap_info(p, ci); > > Maybe too late, but LGTM > > Reviewed-by: David Hildenbrand David, thanks! Though it is probably too late as this one has been in mm-stable for a long time. > > -- > Cheers, > > David / dhildenb Thanks Barry