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AJvYcCX5Nm+Ud65d+oGu8jMWBb2gN27ouInBmg2/cPthSEu8M4KQxwu36Ml1Au5e9lTx9pePRjDzEMpIdA==@kvack.org X-Gm-Message-State: AOJu0YyE5SBK+sofc3E0RT2pPKTNlPjlzJF5e8G9qbAmtapYg6Pxa2im mdDz91996iQ1ZVGGKemLPjz9Uj0H71Ko9qp3UQZ82tshxdQZYpir7wu6dZ8A0d3Mh5h5bqydpsQ B42WQ/q4e3z9Fr4T8wEILZwCCQtk= X-Google-Smtp-Source: AGHT+IFPConTEKWbPY2PEn82yByECOm2rh2w2jvpgsowhvmXet489QmnAkLlx/4vZ1J4vXNx0p+2G45N0VKcPkRQKe4= X-Received: by 2002:a05:6214:4388:b0:6cb:3b9b:1673 with SMTP id 6a1803df08f44-6cbf0105d01mr32723146d6.49.1728662173048; Fri, 11 Oct 2024 08:56:13 -0700 (PDT) MIME-Version: 1.0 References: <20241002012042.2753174-1-nphamcs@gmail.com> <20241002012042.2753174-2-nphamcs@gmail.com> <87cyk79mes.fsf@yhuang6-desk2.ccr.corp.intel.com> In-Reply-To: <87cyk79mes.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Nhat Pham Date: Fri, 11 Oct 2024 11:56:02 -0400 Message-ID: Subject: Re: [PATCH v2 1/1] swap: shmem: remove SWAP_MAP_SHMEM To: "Huang, Ying" Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, yosryahmed@google.com, hughd@google.com, shakeel.butt@linux.dev, ryan.roberts@arm.com, chrisl@kernel.org, david@redhat.com, kasong@tencent.com, willy@infradead.org, viro@zeniv.linux.org.uk, baohua@kernel.org, chengming.zhou@linux.dev, v-songbaohua@oppo.com, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: ckt6mebkyt5oqsh3zuwau87dcp5chqtd X-Rspamd-Queue-Id: 4846D1C001D X-Rspamd-Server: rspam02 X-HE-Tag: 1728662171-138974 X-HE-Meta: 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 C1zROb3Q x22iuCFFun2oI50PLpHwWqhojwEQhopUb+0vMWRG59bdB3gmAUfi7wYgQndqdMQk/ZNvWQBKGCYosV7g1S5B9nKBm5nLMexOH4zY+OYUX0tkgRmXyWJDIUaEt4DoZeO4yCQRaUxi7lVQVCwumTvqMYQrV+wosaTlFM2wVNmMSJyhOerHEA/AKb47s/hvC/ZZgNZAkNf205w1UwH+uoHG979v1m1cKt8YUKPkRF9Pz55xggv5QNQUfR9qiR8Tj3j4IsOR/dX23ELtSzOWCzz7LHNDisn6fX0LbgqTOVkSzc4g0Ce9G4n+gNp9gklYdiXf/DpaNzepR0A5a4VHP0CUi4Q0FHlyf8Z/urCsKoMvCnaVjHe0vH6BFJux2WUOwxwM54mLLwW5doaV+bfDYcze+wFIWTWzaiDU0zdwh X-Bogosity: Ham, tests=bogofilter, spamicity=0.016644, 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 Fri, Oct 11, 2024 at 2:39=E2=80=AFAM Huang, Ying = wrote: > > Nhat Pham writes: > > [snip] > > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 0cded32414a1..9bb94e618914 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -1381,12 +1381,6 @@ static unsigned char __swap_entry_free_locked(st= ruct swap_info_struct *si, > > if (usage =3D=3D SWAP_HAS_CACHE) { > > VM_BUG_ON(!has_cache); > > has_cache =3D 0; > > - } else if (count =3D=3D SWAP_MAP_SHMEM) { > > - /* > > - * Or we could insist on shmem.c using a special > > - * swap_shmem_free() and free_shmem_swap_and_cache()... > > - */ > > - count =3D 0; > > } else if ((count & ~COUNT_CONTINUED) <=3D SWAP_MAP_MAX) { > > if (count =3D=3D COUNT_CONTINUED) { > > if (swap_count_continued(si, offset, count)) > > @@ -3626,7 +3620,6 @@ static int __swap_duplicate(swp_entry_t entry, un= signed char usage, int nr) > > > > offset =3D swp_offset(entry); > > VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER); > > - VM_WARN_ON(usage =3D=3D 1 && nr > 1); > > ci =3D lock_cluster_or_swap_info(si, offset); > > > > err =3D 0; > > @@ -3652,6 +3645,13 @@ static int __swap_duplicate(swp_entry_t entry, u= nsigned char usage, int nr) > > err =3D -EEXIST; > > } else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) { > > err =3D -EINVAL; > > + } else { > > + /* > > + * The only swap_duplicate_nr() caller that passe= s nr > 1 is shmem, > > + * who never re-duplicates any swap entry it owns= . So this should > > + * not happen. > > + */ > > + VM_WARN_ON(nr > 1 && (count & ~COUNT_CONTINUED) = =3D=3D SWAP_MAP_MAX); > > Why not > > VM_WARN_ON_ONCE(nr > 1 && count); > > ? > > IIUC, count =3D=3D 0 is always true for shmem swap entry allocation. The= n > developers who use __swap_duplicate() with nr > 1 without noticing the > unsupported feature can get warning during development immediately. > "(count & ~COUNT_CONTINUED) =3D=3D SWAP_MAP_MAX" is hard to be triggered > during common swap test. Yeah honestly, I agree with this. Let's not try to be smart and make provision for things that can't happen (and make it harder to catch issues in the future). Thanks for the suggestion, Ying. I'll just do this in next version. > > > } > > > > if (err) > > @@ -3686,27 +3686,28 @@ static int __swap_duplicate(swp_entry_t entry, = unsigned char usage, int nr) > > return err; > > } > > [snip] > > -- > Best Regards, > Huang, Ying